pg. 106

Contents lists available at

Journal homepage: http://twasp.info/journal/home

Edwin Robert Faustini*, Guan Zhenliang, Esther Donald and Xie Congjiao

Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences),

Ministry of Education, Wuhan 430074, Hubei, P.R. China

*Corresponding Author:

Email: edwinjepro@gmail.com

Published online : 19 November, 2018

Abstract: The most important tasks of the reservoir engineer is to predict future production

rates from a given reservoir. The general approach taken in predicting production rates is

through the calculations of the production rates from a period, engineer already has the

production information. If the calculated rates match the actual rates, the calculation is

assumed to be correct and can then be used to make future predictions. If the calculated

rates do not match the existing production data, some of the process parameters are modified

and the calculation need to be repeated.

The main task of this research paper is to squeeze all layers in ZH86 block reservoir which

contribute to the high water cut greater than 90% to the particular wells in order to avoid

uneconomical operation (High water production) within ZH86 block of ZHAOZHOUQIOA

Oil Field. It was also necessary to identify the quantity of remaining oil saturation into

different layers, and results point out that layer 35 to 48 of ZH86 block of ZHAOZHOUQIOA

Oil Field has 69.8% remaining oil saturation which was the most candidates for the

perforation consideration during oil production forecasting. An estimate of the amount of

crude oil remained in ZH86 block of ZHAOZHOUQIOA Oil Field in China was calculated

and the results shows that the remains reserve oil was 1.088 M m3 (81.4% of OOIP) within a

production scheduled July 01, 1998 to Dec 1, 2011.

The historical matching of oil production data was done by using simulation model created

by Petrel 2014. The main reason for history matching is not just to match historical data, but

to enable the prediction of future performance of the reservoir and thus production

optimization with regards to oil recovery by improved or enhanced methods. Future

performance of ZH86 block of ZHAOZHOUQIOA Oil Field in terms of Oil production

forecasting was done by using reservoir model which has matched with oil production rate

from the oil field. The input values to the simulation runs are the production/injection rate,

from known reservoir parameters (reservoir temperature, initial reservoir pressure, oil

water-contact, and reservoir fluid properties). Parameters that are optimized in most history

matching techniques are primarily permeability, and other flow related parameters. The

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pg. 107

history-matched model was then used to confidently check the production and injection field

performance. Simulation was also carried out to investigate the total oil production, amount

of water should be injected into the reservoir for the displacement of crude oil and

maintenance of the pressure of the reservoir.

Three (3) prediction cases was created named Case_01, Case_02 and Case_03, the results of

Simulations shows that, Case_03 has high prediction of oil recovery about 23.13 % of OOIP,

and this implies that Case_03 was the best case compared to Case_01 (predicted oil recovery

was about 6.83%) and Case_02 (predicted oil recovery was about 17.32 %) in terms of oil

production , However the ratio of injection water to the oil production was 2.15 for Case_03,

1.29 for Case_01 and 2.3 for Case_02 which means Case_03 was the best case compared to

others in terms of injected water to oil production ratio.

Keywords: History matching, Reservoir performance, Production Prediction, Zh86 block

1 Introduction

Oilfield is located in HEBEI Zhaoxian arch bridge, structural position belongs to Shanxi

Jizhong Depression, Bohai Bay Basin south Zhaoxian County anticline, depression is the

depression scale, shape integrity, the highest elevation amplitude (1000m) in NNW trending

anticline. The overall structure of the ZHAOZHOUQIAO oilfield NNW trending anticline.

Anticline morphological integrity, north and south wings asymmetry, East West steep relief,

top thin blade thickness, uplifted by nearly 1000m. The main development in this area to the

NE and NW fault groups, mainly to NE trending faults, NW trending faults formed earlier,

was the late NE-trending faults cutting, forming a series of north-east elongated block traps.

The oil producing layer Es4+Ek1 of ZH86 Block in ZHAOZHOUQIAO Oilfield, China is a

lithologic reservoir under the control of the tectonic setting. According to previous studies,

the original oil in place (OOIP) of ZH86 block is approximately to be 1.38 × 106 m3 (1.38

Million m3) = 1,380,000 m3 and the average density is approximately to be 868 kg/m3. The

average permeability and porosity of the reservoir rock in this block are 42.8mD and 14.6%,

respectively. Figure 1-1 and Figure 1-2 show the locations of the ZH86 block in HEBEI

Province and ZHAOZHOUQIAO fields, respectively (Strategy, December 2004). ZH86

block started primary oil recovery in July 01, 1998 using a single well ZH86. After three (3)

years of operation with maximum oil production rate of 111.3m3/day (700.06 bbl/day), the

reservoir oil exploitation declined that was due to depletion of reservoir pressure (energy).

This shows that, primary drive (natural energy of the reservoir) mechanism has no longer

sufficient to provide enough energy as before which can be used to transport/push oil towards

and out of the production wells. So, in order to rise and maintaining of the reservoir pressure

for the purpose of increasing oil recovery, secondary oil recovery by water-flooding started

on May 01, 2001 (Strategies, Dec 2004).

pg. 108

Figure 1-1: Location of ZHAOZHOUQIAO Oilfield in Hebei, Province Sources: (Strategies,

Dec 2004)

Figure 1-2: Location of ZH86 Block in ZHAOZHOUQIAO Oilfield (Strategies, Dec 2004)

After the block reported the reserves, the number of drilling wells in the block increased

greatly, and there was no major change in the structural pattern and oil-bearing area, but the

thickness of the oil layer changed greatly..

pg. 109

Figure 1-3: Location of ZH86 Block in ZHAOZHOUQIAO Oilfield showing different wells

drilled from 1998 to 2004 (Strategies, Dec 2004)

1.2Primary Recovery Drive Mechanism for ZH86 Block

According to the ZH86 block field development strategy report that developed in December

2004, it is believed that the ZH86 block’s driven primary energy source is the under-saturated

solution gas driving mechanism, which means that the block does not initially contain free

gas, but develops free gas as the pressure drop during production. As reservoir pressure

decreases during oil production, the expansion of oil and its dissolved gas (dissolved gas 83

m3/m3) provides the majority of the reservoir's main driving energy, and also derives

additional energy from rock contraction and water influx. (Oilfield ZH86 block development

plan, January 1999). If the reservoir pressure may drop below the bubble point pressure of 9.7

bar, the ZH86 block may generate free gas. About 51,142.80 cubic meters of oil are produced

by the primary drive mechanism. The dissolved gas drives 44% of the oil produced, 30% of

the water influx, and 26% of the rock shrinkage.

pg. 110

Figure 1-4: Oil Produced by Primary Drive Mechanisms of ZH86 Block Source: Researcher,

2016

1.3Oil Production History of ZH86 Block

Field development strategies report of ZHAOZHAQIAO Oil Field, pointed out that

commercial extraction of crude oil within ZH86 block dates back to July 01, 1998 involved

Primary and Secondary Oil recovery methods (Strategies, Dec 2004).

1.3.1 Primary Oil Recovery within ZH86 Block

The block started primary oil recovery in July 01, 1998 using a single well Zh86. After three

(3) years of operation with maximum oil production rate of 111.3m3/day (700.06bbl/day), the

reservoir oil exploitation declined that was due to depletion of reservoir pressure. This shows

that, primary drive (natural energy of the reservoir) mechanism has no longer sufficient to

provide enough energy as before which can be used to push oil towards out of the production

wells. So, in order to rise and maintain the reservoir pressure for the purpose of increasing oil

recovery, secondary oil recovery by water-flooding started on May 01, 2001 (Strategies, Dec

2004). At that time only 51142.80 m3 (44391.95 tones, 3.71 % OOIP) of the oil has been

produced for the period of 35 months as the first stage of oil exploitation. Figure 3-6 below

and Table 1-1 show the variation of field oil production rate with time for the thirteen (13)

primary production wells.

pg. 111

Figure 1-5: Primary Field Oil Production rate of ZH86 Block Source: ZH86 Block report,

2004

Table 1-1: Schedule of Primary Oil Production Well (Source: ZH86 report, 2004)

After reporting a significant drop in reservoir pressure for the economic primary oil recovery

method within the ZH86 Block in ZHAOZHOUQIAO Oilfield, secondary oil recovery by

water injection began on May 1, 2001. Two injection wells was used which include Zh57-84

X and Zh57-87 wells.

1.3.2 Secondary Oil Recovery within a ZH86 Block

pg. 112

The initial phase of oil production in an oil field is commonly termed as the primary phase.

Primary production is oil initially recovered from a field either from wells flowing under

natural pressure, or wells that produce by means of pumps that carry oil from the well bore to

tanks at the ground surface (Congjiao. Xie, 2014). Secondary production is the initial phase

of Enhanced oil Recovery in the petroleum field. Secondary production within ZH86 block

started on May 01, 2001, it involved waterflooding an oil reservoir (injecting water in some

wells to push more oil through the reservoir toward other producing wells). ZH86 block has

been explored and developed for secondary Oil recovery about 11 years from May 01, 2001

to Dec 31, 2011, lead to the additional oil recovery of 206079.3 m3 (14.9% OOIP) by 25

operated well (16 production wells while 9 were injection wells) (Strategies, Dec 2004).

Figure 1-6: Oil Produced by Primary Drive Mechanisms and Secondary Recovery Source

Researcher, 2016

2.0 Research methodology

This study was carried out over several steps, where the first step was building up a 3D static

geological model of Zh86 block, then volume calculation which was therefore used to check

the validity of the constructed model, and the final step is to create a simulation case. Then

export the Simulation Case created from Petrel software to the Eclipse software for

simulation. These tools was used to run reservoir simulations by using processed petro-

physical properties, PVT and production data obtained from ZH86 Block in

ZHAOZHOUQIAO oil field. Software used in this study is as shown below;

pg. 113

Table 2-0: Software used for successful 3D geological model and creation of simulation case

in Zh86 block

2.1 The static model of Zh86 block

The static model of the reservoir can be considered as the final product of structural,

stratigraphic and lithological simulation activities (Luca Cosentino, 2001). The workflow for

building a static model always begins by building a structural model that includes

reproducing top and bottom maps of the reservoir and all the geophysical, geologic, and well

information needed to identify the fault. The final part of the static modeling workflow is to

assign each block the appropriate lithology and petrophysical properties. Fluid saturations

and porosity are the most important parameters that control the amount of the hydrocarbons

stored inside the reservoir where as permeability dictates the ease with which they can flow

and thus eventually be produced. The values of the petrophysical parameters are usually

derived from well and core data but their distribution in the model is controlled by

deterministic or statistical methods.

2.2 Data collection within Zh86 block in Zhaozhouqiao Oilfield

In this section the main tasks is the collection of raw data of all wells including log, core,

water and oil PVT analyses data, Field production and Injection data.

2.2.1 Well head data

Content including Wells, ground location coordinates (X, Y), ground bushing elevation and

the target depth of the hole. Fig 4.1 below shows a display of the well heads on the Zh86

block in ZHAOZHOUQIAO Oilfield.

2.2.2 Well deviation data

Drift data can be used to reflect the status of single well deviation of various data

combination, such as depth angle and azimuth angle combination or depth, X direction and Y

direction displacement combination, and other forms of combination can skew the data as

well. Drift data file main role is to carry on the deviation correction.

2.2.3 Well log data

pg. 114

Logging data includes the depth and logging value derived from two kinds of information.

Depth values can reflect any logging data points in three dimensional spaces and Logging

value refers to the different logging curves which represent the corresponding log value at a

particular depth or point location. With respect to this study, variety of logs data were

deployed which includes the lithology logs, saturation logs, porosity, etc.

2.2.4 Well top data

Including Wells, layer number, type, stratification point/depth information, etc.

Table 2-1: Imported well data for ZH86 Block of ZHAOZHOUQIAO oil field

Geological Model of Zh86 block in ZHAOZHOUQIAO oilfield

The Petrel modeling domain is divided into several main process groups this include:

structural framework, corner point gridding and property modeling. These helps to build a

reliable subsurface model containing faults, horizons, and properties. The 3D model can then

be used for volume calculations, well design etc. Petrel software was used to build a 3D

geological Model of ZH86 Block of ZHAOZHOUQIAO oil field. Figure 2.1 below, shows

the imported 25 well and wellheads for ZH86 Block of ZHAOZHOUQIAO oil field.

pg. 115

Figure 2-1: All Wells and Wellhead of ZH86 Block in ZHAOZHOUQIAO oil field

Figure 2-2: All Well tops within ZH86 Block in ZHAOZHOUQIAO oil field

pg. 116

Figure 2-3: Zones (hierarchy) of for ZH86 Block in ZHAOZHOUQIAO oil field

Figure 2-4:ZH86 Block reservoir wells location

Well correlation in ZH86 Block

Well correlation of Zh86 Block consists of a number of steps aimed at finding similarities in

well data across a reservoir in order to capture the lateral continuity of rock properties. Well

pg. 117

correlation in Petrel makes it possible to bring up multiple wells in a well section, create well

tops and bring up new wells to compare with already correlated wells. Also, as new wells are

drilled they can easily be zoned. Figure 2-5 show a well correlation of zh57-79x, zh57-76 and

zh57-75 wells based on lithology SP, gamma ray and AC log

Figure 2-5: Well section with well tops correlation surfaces

2.2.5Structure modeling Zh86 Block

Zh86 Block of ZHAOZHOUQIAO oil field structural model built from well data (heads, tops

and deviations), contour, and fault polygons data. In Petrel, structural modeling is divided

into three processes: fault modeling, pillanr gridding, and vertical layering (make horizons).

The process begins with the fault modeling, in which fault sticks where used as bases for the

fault modeling. Using the Petrel Software, the faulting pattern of Zhao 86, V oil group was

reproduces. Under this process Main and Minor faults where identified, Zh86 Block of

ZHAOZHOUQIAO oil field has only four main faults that were identified and modeled.

Major faults shows a wider range coverage of reservoir blocks, while Minor faults are the

ones which vary in a very short distance.

pg. 118

Figure 2-6: Zh86 Block structural surfaces (arrow pointing south)

2.2.6 Fault model

Grid vertical layering starts with creation of the 3D grid from fault model. Zh86 Block of

ZHAOZHOUQIAO oil field reservoir grid was created by 20m pillar increment in the X and

Y directions. To preserve geological features direction of the reservoir, the grid was oriented

according to the main faults direction. The gridding process results in a set of pillars along

faults and between faults. Fault key pillars created by digitizing pillars on the top and bottom

structure surfaces using add pillar by 2 points function in Petrel, pillars form the fault model

figure 2.7. Fault Model the basis for the generation of the 3D grid.

pg. 119

Figure 2-7: Fault model of Zh86 Block (arrow pointing south)

Structures horizons used as inputs in pillar gridding process (make horizons) well tops and

contour lines used as second and third data inputs. In Petrel make horizons is the first step of

creating vertical layering of the 3D grid. Structure model of Zh86 Block of

ZHAOZHOUQIAO oil field reservoir.

Figure 2-8: Structural model

of Zh86 Block reservoir

(arrow pointing south)

Zh86 fault block is trending

from northwest to the

southeast gradually falling

off, the order of its reservoir

structure is very complex,

within a certain number of

micro structure, mainly for

some little nose-like

structure of low margin.

pg. 120

2.2.7Property model for ZH86 Block

Property modeling processes are used for filling the cells of the grid with discrete (facies) or

continuous (petrophysical) properties. Petrel assumes that the layer geometry given to the

grid follows the geological layering in the model area. The modeling process is dependent on

the geometry of the existing grid. When interpolating between data points, Petrel will

propagate property values along the grid layers. Property modeling in Petrel is divided into

several separate processes:

Geometrical modeling

Facies modeling

Petrophysical modeling

The reservoir property model is set up by displaying the reservoir permeable layer thickness

model, the porosity model and permeability model with reference to the developed structural

frame work. The main objective of doing Property modeling is to allow the distributing of

properties with the available wells data, the process involve showing how the well data are

matching to each other as well as heterogeneity of the reservoir.

Figure 2-9: Geometrical model of ZH86 Block showing Bulk volume

The above represent a Geometrical modeling of ZH86 Block showing Bulk volume which

has positive value of volumes 13 as shown in table below; hence it implies the model was

good and ready for property modeling.

Table 2-2: Statistics for Bulk volume

pg. 121

Property modeling process are description involve main three steps followed: First scale up

well logs this process was done by scale up the available well data, with the intension to

distribute the available well data to nearby grid cell where the well penetrate, but for the far

away cells property modeling was done to show the distribution of a specific property to the

whole reservoir grid cell. Second, Data analysis where under this modeling process different

variogram was set according to the modeled property. Data analysis process is essentially

used to check up and interpret data based on their similarities and flow trend of the given well

logs. Third, Specific property modeling process. The input distribution of the data is honored

during the modeling process, the input data were interpreted on how much their variation

were distributed.

2.2.8Porosity model in Zh86 Block

Determining the probability distribution at each node and then drawing a number at random

from this distribution, simulated value at each node is generated. In many cases, the

properties being modeled are likely to be related to one another, permeability is often high in

areas of high porosity, etc. In addition, certain properties may have much better control than

others, like a porosity model built from logs in all the wells for this reason, it may be

desirable to model fewer well controlled properties based on better controlled ones.

Table 2-3: Statistics for Porosity

pg. 122

Porosity model filter (arrow pointing south) of Zh86 block of ZHAOZHOUQIAO oil field is

shown in figure 4-11, ZH86 Block of ZHAOZHOUQIAO oil field Statistics shows that

porosity changes are small for each layer, mainly distributed between 10 ~ 18%, average

14.6%.

Figure 2-10: Porosity model filter (arrow pointing south) of Zh86 block

Figure 2-11: Porosity model (arrow pointing south) of Zh86 block

pg. 123

According to Levorsen (1967); the porosity of reservoir can be classified in to five categories,

and the category is used to determine a reservoir prominence. Porosity range was categorized

into different range for determine its prominence. Below are the five porosity categories

range:

Table 2-4: Qualitative Evaluation of porosity According to (Levorsen, 1967)

From the porosity model on it shows clear there is high porosity value flow from north to

south, the trend follows the way facies model where distributed. Areas where there is Sand

and conglomerate together with fine sand from facies model. Hence from the top north side

towards south of the field shows there is high porosity distribution. This implies that the pore

spaces possess enough space for reservoir fluid to be accommodated, from lithology

identification a reservoir contain Sand and conglomerate together with fine sand, hence it’s

possible for the reservoir to encounter high porosity distribution in some areas. Finally, since

a mean porosity value of a modeled porosity properties was 0.03% According to Levorsen,

the reservoir has very good porosity, which allow further development stages to be done.

2.2.9 The Permeability model in Zh86 Block

Correlation between porosity and permeability was calculated. Results obtained indicate that

porosity and permeability exhibit good relationship (Figure 4.14), so porosity used as

secondary property in modeling permeability. Reliable permeability data is rarely available,

not to the extent that porosity data is available. Therefore, it is often a relationship between

these two properties and it is common practice to base the permeability model directly upon

the porosity model. The simplest method of generating a permeability model from aporosity

model is to use a straightforward transformation from a porosity vs. permeability cross plot.

pg. 124

Figure 2-12: Porosity vs. Permeability crossplot

Sequential Gaussian Simulation (SGS) was used to model permeability. Permeability model

is shown by Figure 2-13. Variability in permeability values indicate severe reservoir

heterogeneity.

Figure 2-15: Permeability model (arrow pointing south) of Zh86 block

pg. 125

Table 2-5: Qualitative evaluation of permeability According to (Levorsen, 1967)

From the 3D geological model of permeability distribution results, it shows that. Permeability

value range between of 0 mD to 5756.38 mD, while the mean permeability value is 42.4558

mD for the modeled Zh86 block in ZHAOZHOUQIAO Oil field in China. Permeability

concentration vary from North to south as it is the same way as in a lithology model flow,

where the area with high permeability is the same with where there is Sand and conglomerate

together with fine sand facies rock type. According to Levosen an average permeability value

of when compared with the given categorized permeability range provided in table, the

permeability model reflects to have a very good extent of reservoir rock that allow the flow of

fluids within it.

2.2.10Oil water contact model

Oil water contact is the surface separating oil deposit or gas deposit oil rim from contacting

confined strata water in the reservoir. There is no clear-cut boundary between water and oil;

there is always a transitional zone or inter-penetration zone in OWC. It may be of different

thickness (from parts of meter up to 10–15 meters) depending on the height of water capillary

rise, on collecting properties of water-bearing and oil-bearing deposits, as well as on physical

and chemical parameters of water and oil (Gazprom, 2003). In Zh86 Block of

ZHAOZHOUQIAO oil field Water Oil contact was set using resistivity logs to differentiate

areas where is water zone and hydrocarbon zone.

pg. 126

Figure 2-16: Oil Water contact of ZH86 Block in ZHAOZHOUQIAO oil field

The ZH86 Block Reservoir Model is a black oil model with a strong aquifer, the blocks

consist of 10164 Number of Plane Grid with dimensions of approximately 132m in the X

direction and 77m in the Y direction. ZH86 Block has two oil water contact (OWC) is at

2760m and 3030m and a reference depth of 3300m with a pressure of 291.2 bars at that

depth.

2.2.11Net to Gross (NTG) Property Model

The main purpose of net-pay model, was to calculate the quantity of a reservoir rock and

eliminate non-reservoir rock, based on well data as shown in the figure 2.16, a resulting 3D

NTG model of a Zh86 block in ZHAOZHOUQIAO Oil field in China and provided much

information on the quantity of the hydrocarbons in place.

pg. 127

Figure 2-17: NtG Log of Zh86 block in ZHAOZHOUQIAO Oil field

The method used to construct the NTG model was Sequential Gaussian Simulation (SGS)

under stochastic modeling method, since there were few well information to construct the

model. Only 25 well data were used.

Figure 2-18: NtG Model of Zh86 block in ZHAOZHOUQIAO Oil field

pg. 128

A model shows the most paying zone which has great probability of accommodating

hydrocarbons in a reservoir. The figure 4.17 shows the distribution of net to gross value with

an average value of 0.2.

2.2.12 Water Saturation model of ZH86 Block

A resulting constructed 3D model of Water saturation, shows the distribution of water in

Zh86 block in ZHAOZHOUQIAO Oil field in China. Has an average value of 0.90. A model

was created using 24 well logs data as secondary interpretation data. Since Water

saturation=1-Oil saturation (Sw = 1-So), hence areas where water saturation is high there is a

probability of having low content of oil and it’s vice versa is true. From the model Oil

saturation as dragged out from the water saturation model the flow was high from north part

to south of the model. Where middle part and first part from north showed to have high

concentration of oil.

Figure 2-19: Water saturation presented in 3D model of Zh86 block in ZHAOZHOUQIAO

Oil field

3.0Reserve Calculation of ZH86 Block

Oil and gas reserves include original oil in place (geological reserves) and recoverable

reserves. According to information of oil-gas reservoir obtained in the stage of exploration

and development, oil and gas reserves can be classified into three types: proved reserves,

controlled reserves and predicted reserves. Determination of the Original Hydrocarbon in

pg. 129

Place (OHIP) is typically the representation of the amounts of oil initially in place in the

reservoir. Reserves or recoverable reserves of ZH86 Block are the volume of hydrocarbons

that can be profitably extracted from a ZH86 Block reservoir using existing technology.

Volumetric estimates of Original Oil in Place (OOIP) were based on a geological model that

geometrically describes the volume of hydrocarbons in the reservoir which lead to the

Original Oil in Place of 1.36 million m3 （ 1.358 M m3） within ZH86 Block with an average

reservoir pressure 250.48 bars. The reserve estimation was done by using Petrel2014, Table

4-14, shows the Oil reserve distribution for each layer within a ZH86 Block. Calculation of

hydrocarbon-in-place from the geologic, reservoir, and production data requires a clear

understanding of the behavior of oil and gas under various reservoir and surface operating

conditions. Volume calculation often considered as one of the last phases of a reservoir

investigation when detailed property modeling completed. The Volume calculation process is

used to estimate the initial hydrocarbons volumes in place (before any production has taken

place), it accurately calculates the volumes in a 3D grid (bulk, pore and fluid).

Table 3-1: Oil reserve distribution for each layer within zh86 block in ZHAOZHOUQIAO

oilfield

Since the reserve contained in zh86 block in ZHAOZHOUQIAO oil field is economical

feasible and since the model reserve results are relating to the original geological reserve

(1.38 × 106 m3 (1.38 Million m3) = 1,380,000 m3), it is clear indicating that the calculated

pg. 130

hydrocarbon of commercial value thus; the reservoir model could be used for further

production plan of a reservoir so as to solve different production challenges facing the field.

4.0 Historical Matching of Zh86 Block

Simulation of petroleum reservoir performance refers to the construction and operation of a

model whose behavior similates actual behavior. The model itself is either physical or

mathematical. A mathematical model is simply a set of equations that subject to certain

assumptions, describes the physical process active in the reservoir. Such mathematical

models are widely used to predict field behavior. Their use requires that the reservoir rock

properties, such as porosity and permeability, be specified throughout the reservoir. The usual

procedure is to estimate these parameters, compute the past field history and then compare

the computed results with the observed behavior of the field. If the comparison is not

satisfactory, the estimates are repeatedly modified until an acceptable match is obtained. It is

then assumed that the rock properties are adequate for future predictions. Recently effort has

been devoted to the development of various techniques in order to minimize the differences

between actual and predicted performance (S. A. Ghoniem, 1983).

History matching, within the context of oil reservoir simulation, entails the adjustment of the

geological description, or other model parameters, in order to achieve conformity between

simulation results and actual/observed production data.

In Zh86 Block in ZHAOZHOUQIAO Oil Field Production history data were history matched

to determine the reservoir description parameters from the given performance. These

parameters were found to have excellent match between the observed data and calculated

values.

pg. 131

Figure 4-1: Zh86 Block Historical Matching steps

4.1 Creation of base case of the ZH86 Block

A base case of ZH86 block was created from a Geological Model, a case have a 16 and 9

Production and injection wells respectively. This was a starting point from which multiple

realizations are created to analyze the model response with the variability in model

parameters. During historical matching the following; Field Oil Production rate, Field water

Production rate and Field water injection rate were set as the objective functions for the

assessment between simulated results and the actual/observed data

pg. 132

Figure 4-2:Zh86 Case Block for Historical Matching

History matching is a model validation procedure, which consists in simulating the past

performance of the reservoir and comparing the results with actual historical data. When

differences are found, modifications are made to the input data in order to improve the match

(Luca Cosentino, 2001). Therefore, historical matching is an iterative process whose ultimate

goal is to reconcile all the different static and dynamic data into a coherent framework that

represents a certain degree of actual reservoir behavior.

4.2 Running the Prediction Cases

Running the production forecast cases is, in general, a less difficult process than the history

match phase. Switching the model from history match to forecast very often results in

discontinuities in the individual well rates, pressures and activities. (Luca Cosentino, 2001).

In fact, switching the model from history match to forecast very often results in

discontinuities in the individual well rates and pressures (Fig. 4.25). As mentioned in the

previous section, this is related to the fact that the Production Index calculated in the model

are not generally calibrated with the actual field Production index. This difference is

transparent in the history match phase, where wells work under imposed rate conditions, but

becomes obvious in the prediction phase, where computed Production index actually

determine well productivities.

pg. 133

Figure 4-2: Well Production Index calibration (Luca Cosentino, 2001)

5.0 Results and Discussion

the objectives of this research were to Optimize Field Development Strategy with Historical

Matching Approach, Second objectives is to build a three Simulation Cases of ZH86 Block in

ZHAOZHOUQIAO Oilfield using field and well data from ZH86 Block Model and to

compare the observed oil production obtained from historical oil production data with the

simulated oil production results obtained after running our simulation. Static 3D-geological

model was used to calculate the ultimate reserve potential of Zh86 block in

ZHAOZHOUQIAO Oil field in China and validate it with the original geological reserve

estimations. The rest of the data nst. The simulation case was exported from Petrel software

and the simulation proeeded to carry out the simulation was gathered and input in the

software to build the simulation case for the forecacess carried out in Eclipse software. After

run Simulations by using processed petro-physical and production data obtained from ZH86

Block of ZHAOZHOUQIAO oil field, the historical match was performed, production

prediction strategies were developed and compared in which Production index like water cut,

water production rate, oil production rate, Oil production total and Water production total of

field. Results of the indexes were presented against time and analyzed. The results portrayed

that ZHAOZHOUQIAO oil field is still very promising in terms of production.

5.1 Overall Life Cycle of Zh86 Block

Reservoir engineer must become familiar with production performance. Normally, this

includes such things as water cut, reservoir pressure, and gas-to-oil ratio (GOR) trends.

Combined with some PVT data, the potential drive mechanisms should be identified at this

stage. Then during Data gathering, Relative permeability and capillary pressure data are

pg. 134

normally screened. PVT data is similarly screened. This also means digitizing reservoir maps

of structure, net pay, porosity, and permeability. Under reservoir Initialization phase, the

basic data deck is built. An initial run is made in which the model calculates original oil,

water in place and mobile oil with respect to water (OOIP, OWIP and MOwrtW

respectively).

Table 5.1: Field Initial in place for ZH86 Block of ZHAOZHOUQIAO oil field

The model is run with the historical base production specified usually oil. The idea is to

match GORs, water cuts, and pressures predicted by the model to actual performance (M. R.

Carlson, 2006). At the end of the history-matching phase prediction will be conducted, the

prediction results are stored in a special restart file. With this, it is possible for the reservoir

simulation to be continued without rerunning the problem through the history match. After

completing the history match, various predictions are made using different production, well,

and injection Cases. The results can be interpreted and ranked according to acceptability. (M.

Carlson, 2006).

5.2 Historical Matching Results of Zh86 Block

In order to confirm that the results of the simulation were accurate, a history match was

carried out. One way to evaluate the history match is to compare observed and calculated

parameters. Typically, observed and calculated parameters are compared by making plots of

the parameters versus time, such as production (or injection) rates versus time, cumulative

production (or injection) versus time. The general approach taken to predict production rates

is first to calculate producing rates for a period for which the engineer already has production

information. If the calculated rates match the actual rates, the calculation is assumed to be

correct and can then be used to make future predictions (Z. Guan, C. Xie, and G. Luo, 2012).

The usual procedure is to estimate some parameters, compute the past field history and then

compare the computed results with the observed behavior of the field. If the comparison is

not satisfactory, the estimates are repeatedly modified until an acceptable match is obtained.

It is then assumed that the rock properties are adequate for future predictions (S. A. Ghoniem,

1983). For the match to be satisfactory the difference between calculated and observed values

should be very small. If there is a big difference between the two, the input data in the model

is adjusted until there is a minimum difference between the performance of the model and the

pg. 135

history of the reservoir. For the history matching, the key parameters that can be adjusted are

Relative Permeability, permeability property and Transmissibility factor. The obtained results

were plotted against the observed values to determine the accuracy of the simulation. A few

adjustments were made in the relative permeability to give a satisfactory history match.

Figure 5-1:History match curves (Base Case) of Zh86 block oilfield (FOPR– simulated oil

rate, SM3/Day; FOPRH– actual oil rate, SM3/Day; FWCT– simulated water cut; FWCTH–

actual water cut)

The values of FOPT simulated Field oil production total, FOPTH Actual Field oil production

total, FOPR simulated Field oil production ratio and FOPRH Actual Field oil production rate

were compared to see the difference in the uncertainty between the two values. From the

above plot, both indexes have the same trend indicating that the results can be relied on.

History matching was done on all vectors using their observed and calculated values, the field

and well portrayed similar trends. This results can be termed as reliable. Therefore the above

case named Figure 5.8 History match curves (Base Case) of Zh86 block oilfield (FOPR–

simulated oil rate, SM3/Day; FOPRH– actual oil rate, SM3/Day; FWCT– simulated water

cut; FWCTH– actual water cut) was the Selected for Prediction Simulation within Zh86

block in ZHAOZHOUQIAO Oil field.

5.3Basics of Reservoir Performance Prediction

A fundamental task of the reservoir engineer is to adopt techniques to predict future

production rates for a given reservoir, the objective of history matching is to build a reservoir

model that integrates available data and yields production forecasts that are accurate. For

these forecasts to be as reliable as possible, a necessary condition is to ensure that the model

encompasses all available data and information.

pg. 136

After History Matching the Zh86 block in ZHAOZHOUQIAO Oil field in China, a basis for

predicting future production and further development of the field is now available. Three

prediction scenarios are analyzed here:

Producing the field for another nine 9 years from (2011-2020) year’s using the present

development strategy and the wells currently in place.

Placing a new well and producing from there while shutting in the present production

wells.

Running production forecasts is usually the concluding phase of an integrated reservoir study.

In its essence, the objective of this work is to visualize the future performance of the field

under different operating strategies and to generate the production profiles needed for the

economic evaluation of the project. Whether a simple or complex method is used, the general

approach taken to predict production rates is first to calculate producing rates for a period for

which the engineer already has production information. If the calculated rates match the

actual rates, the calculation is assumed to be correct and can then be used to make future

predictions. If the calculated rates do not match the existing production data, some of the

process parameters are modified and the calculation repeated (Z. Guan, C. Xie, and G. Luo,

2012). This production prediction method was successfully applied in Zh86 block in

ZHAOZHOUQIAO Oil field adjustment development. At the end of our simulation run in

December 2020 production well control was ZH57-75, ZH57-78,ZH57-77X,ZH57-85,ZH57-

71,ZH57-83 and ZH57-93 this wells are still open for production in the Zh86 block in

ZHAOZHOUQIAO Oil field in China while pressure support is achieved using the injectors

ZH57-73, ZH57-73F, ZH57-78, ZH57-78F, ZH57-80X, ZH57-80F, ZH57-84X, ZH57-84F,

ZH57-87 and ZH57-87F. The field has been simulated another 9 years from 2011 Dec 1st to

2020 Dec 31st prediction of the recovery from the Zh86 block in ZHAOZHOUQIAO Oil

field in 2020, table 5.2 below shows the details of the development strategy used.

pg. 137

Table 5-2: Development Strategy for Case_01 and Case_02 Zh86 block in

ZHAOZHOUQIAO Oil field

This section discusses the 3 Simulation Cases that was defined in the simulation model before

running production forecasts. The first step is always the definition of the cases to be run.

Prediction cases are usually designed at the start of the forecast phase. This Simulation was

carried out to investigate the location and number of production/injection well(s) should be

used for the economic oil production process within ZH86 block, which involved three (3)

simulation prediction cases. The cases were named as Case_01, Case_02 and Case_03

respectively

Figure 5-2: Curves of development index of Zh86 block in ZHAOZHOUQIAO Oil field

(FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut)

pg. 138

From the above curves of development index of Zh86 block in ZHAOZHOUQIAO Oil field

(FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut) for the first

proposed development strategy of Case_01 and Case_02 in Zh86 block in

ZHAOZHOUQIAO Oil field, results shows no changes for both field oil production rate and

Water Cut. This make us to rethink about the designing of new development strategy named

Development Strategy Case_03, simulation results of this new case makes tremendous

change in Oil production rate and water cut as compared to Case_01 and Case_02 results.

Below table describe the new Development Strategy, Case_03 of Zh86 block in

ZHAOZHOUQIAO Oil field, with this new case simulation result we can have the

confidence in our strategy since the analyzed makes better result. Oil production rate and

Water cut were used as key criteria during data and results analysis.

Table 5-1: Development Strategy Zh86 block in ZHAOZHOUQIAO Oil field

Below figure shows the curves of development index of Zh86 block in ZHAOZHOUQIAO

Oil field (FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut). The

amount of detailed input and the type of simulation model depends upon the issues to be

investigated, and the amount of data available. It is in view of this development that three

Cases were designed and the development index was predicted to optimize the Zh86 block in

ZHAOZHOUQIAO Oil field development. As expected, the simulated results rely on skills

and experience of the engineer. One will need to be careful with prediction results if they rely

on parameters that have not been validated in the history match. Different reservoir

descriptions can produce the same history match but provide different forecasts (Z. Guan, C.

pg. 139

Xie, and G. Luo, 2012). If data are incomplete or suspect, simulators may be used only to

compare semi-quantitatively the results of different ways of operating the reservoir. In either

case, the accuracy of the simulator can be improved by history matching (A. S. Odeh, 1981).

Figure 5-1: Curves of development index of Zh86 block in ZHAOZHOUQIAO Oil field

(FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut)

In fact, the reasons for plotting curves of development index of Zh86 block in

ZHAOZHOUQIAO Oil field for (FOPR– simulated oil rate, SM3/DAY and FWCT–

simulated water cut) is to have a good degree of confidence in our proposed Development

Strategy before we proceed with details study. The quality of the results, as observed above,

gives confidence in the reliability of data in our new strategy and confirm that this additional

information can be used to optimize the Zh86 block in ZHAOZHOUQIAO Oil field

development. The results got were plotted alongside the observed values to determine the

accuracy of the simulation. A few adjustments were made in the relative permeability to give

a satisfactory history match. The values of (FOPR SM3/DAY) simulated oil production rate

and (FWCT)simulated water cut were compared to see if the difference in the uncertainty

between the two values. From the above plot, both indexes have the same trend indicating

that the results can be relied on. History matching was done using the observed and

calculated values, for both the field and the wells. The field and well portrayed similar trends.

The results can be termed as a reliable result.

5.4Reservoir Performance Prediction Cases

Simulation results of ZH86 Block of ZHAOZHOUQIAO oil field shows that more than 63%

Remaining oil saturation in Zh86 Block by 01 December 2011, Maybe this was caused by Oil

contained in pores, poor pore throat connectivity, and heterogeneity in pore size distribution

pg. 140

at the end this cause major impact on poor oil displacement. Determination of Residual Oil

Saturation is very important since it is a crucial step in the accurate evaluation of sweep

efficiency and oil recovery factors. However, one should know that the essential aim of most

of these processes is the recovery of additional oil by reducing the residual oil saturation (M.

Carlson, 2006). Three production prediction cases were proposed during this study named

Case_01, Case_02 and Case_03.

5.5Reservoir Performance Prediction for Case_01

For the first case named Case_01 we have two injection well was involved these are ZH57-73

and ZH57-84X. Water Injection was maintained at field injection rate of 43m3 /day and

17.888 m3 /day respectively. This injection was done for the period of nine years from 2012

to 2020. The number and type of Prediction cases obviously depends on the particular study

and the available time, however it is common practice to define a base case, which

corresponds to the continuation of the field exploitation under the prevailing operating

conditions. All the prediction results from Case_01, Case_02 and Case_03 are compared to

this base case, which can therefore be considered as a standard for alternative development

options. For Case_01 the production prediction was set to begin 1st Dec 2011 to 31st Dec

2020 and all the available Historical production well data was set as shown in table below.

Table 5-2:Case_01 Historical production well data

By using those data successful Simulation study was conducted which means Case_01 was

the first Production prediction case designed in Zh86 Block of ZHAOZHOUQIAO oil field.

Then later the simulation results obtained under this Case_01 will be compared with the

obtained simulation results of Base Case in order to judge the Recovery percentage among

each other (Case_01 and Base Case results)

pg. 141

Figure 5-4 (A) Shows a Residual Oil saturation for Layer 42 of ZH86 Block of

ZHAOZHOUQIAO oil field by 01 Jan 2012; (B) shows Predicted ZH86 Block simulation

results after applying the development strategy related to Case_01 by 31 Dec 2020

Figure 5-5: Curves of Case_01 development index of Zh86 block in ZHAOZHOUQIAO Oil

field (FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut)

5.6Reservoir Performance Prediction for Case_02

For the second case named Case_02 we restart the development strategy of Case_01 which

started 1st Dec 2011 and later on January 2012 we introduce new development strategy as

shown below. This new development strategy of Case_02 has seven injection wells, these are

ZH57-73(Existing Well), ZH57-73F (New Well), ZH57-78F (New Well), ZH57-80X

(Existing Well), ZH57-84X ZH57-87(Existing Well) and ZH57-87F (New Well). Average

Water Injection rate was maintained at field injection rate of 20.21 m3 /day, 39.64 m3 /day,

pg. 142

39.64 m3 /day, 39.64 m3 /day, 10.07 m3 /day, 19.94 m3 /day and 19.82 m3 /day

respectively. This injection was done for the period of nine years from 2012 to 2020. Average

Pressure (Bottom hole pressure) from 2011-2020 was maintained at 636.68 Bars, 622.31

Bars, 584.91 Bars, 600.41 Bars, 593.97 Bars, 624.07 Bars and 584.28 Bars. The number and

type of Prediction cases obviously depends on the particular study and the available time,

however it is vital to define a base case, which corresponds to the continuation of the field

exploitation under the prevailing operating conditions.

Table 5-5: Development Strategy for Case_02 Zh86 block in ZHAOZHOUQIAO Oil field

Case_02 we have 7 Production well control named ZH57-71, ZH57-75, ZH57-77 X, ZH57-

78, ZH57-83, ZH57-85 and ZH57-93 production process in Case_02 was controlled by

Liquid rate (LRAT) of 20 m3 /day for each well. The obtained Simulation results are shown

below. As shown from the table 5.5 Development Strategy for Case_02 Zh86 block in

ZHAOZHOUQIAO Oil field above the average well production rate within Zh86 block in

ZHAOZHOUQIAO Oil field for all production wells used in Case_02 was 0.43 m3 /day,

3.10 m3 /day, 0.61 m3 /day, 3.40 m3 /day, 1.19 m3 /day, 1.69 m3 /day and 0.75 m3 /day

respectively. Figure 5.4 below (A) Shows a Residual Oil saturation for Layer 42 of ZH86

Block of ZHAOZHOUQIAO oil field by 01 Jan 2012; (B) shows Predicted ZH86 Block

simulation results after applying the development strategy related to Case_02 by 31 Dec

2020.We can observe huge changes in oil displacement (Sweep efficiency) compared to the

results obtained in Case_01.We can confirm this by having a look on Figure 5.5 Curves of

Case_02 development index of Zh86 block in ZHAOZHOUQIAO Oil field (FOPR–

simulated oil rate, SM3/DAY and FWCT– simulated water cut).

pg. 143

Figure 5-6 (A) Shows a Residual Oil saturation for Layer 42 of ZH86 Block of

ZHAOZHOUQIAO oil field by 01 Jan 2012; (B) shows Predicted ZH86 Block simulation

results after applying the development strategy related to Case_01 by 31 Dec 2020

Figure 5-7 Curves of Case_02 development index of Zh86 block in ZHAOZHOUQIAO Oil

field (FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut)

5.7Reservoir Performance Prediction for Case_03

For the third case named Case_03 in Dec 1st 2011 we modify the Case_01 and use two

injection well was involved in it wells used for injection includes ZH57-73 and ZH57-84X.

Water Injection was maintained at field injection rate of 84 m3 /day and 40 m3 /day

respectively. This injection was done for the period of nine years from 2011 to 2020. The

number and type of Prediction cases obviously depends on the particular study and the

available time, however it is common practice to define a base case, which corresponds to the

pg. 144

continuation of the field exploitation under the prevailing operating conditions. Prediction

results from Case_03 are compared to base case, which can therefore be considered as a

standard for alternative development options if they meet conditions of field operations. This

new development strategy of Case_03 has ten (10) injection wells, these are Zh57-

73(Existing Well), Zh57-73F (New Well), Zh57-78 (Existing Well),Zh57 78F (New

Well),Zh57-80F (New Well),Zh57-80X(Existing Well),Zh57-84F (New Well),Zh57-

84X(Existing Well), Zh57-87 (Existing Well) and Zh57-87F (New Well) Average Water

Injection rate was maintained at field injection rate of 19.82 m3 /day, 0.09 m3 /day, 19.82m3

/day ,19.82 m3 /day,9.91 m3 /day,4.95 m3 /day20.18 m3 /day, 10.03 m3 /day and 9.91 m3

/day respectively. This injection was done for the period of nine years from 2011 to 2020.

Average Pressure (Bottom hole pressure) from 2011-2020 was maintained at 537.59 Bars,

314.61 Bars, 509.83 Bars, 516.37 Bars, 722.07 Bars, 518.84 Bars, 598.04 Bars, 577.08 Bars

and 509.80 Bars. It is vital to define a base case, which corresponds to the continuation of the

field exploitation under the prevailing operating conditions. For Case_03 the production

prediction data was set as shown in table below.

Table 5-3: Development Strategy Case_03 Zh86 block in ZHAOZHOUQIAO Oil field

Case_03 we have 7 Production well control named ZH57-71, ZH57-75, ZH57-77 X, ZH57-

78, ZH57-83, ZH57-85 and ZH57-93 production process in Case_03 was controlled by

Liquid rate (LRAT) of 20 m3 /day for each well. The obtained Simulation results are shown

below. As shown from the table 5.6 Development Strategy Case_03 Zh86 block in

ZHAOZHOUQIAO Oil field above the average well production rate within Zh86 block in

pg. 145

ZHAOZHOUQIAO Oil field for all production wells used in Case_03 was 0.65 m3 /day,

4.52 m3 /day, 1.21 m3 /day, 4.31 m3 /day, 1.70 m3 /day, 2.03 m3 /day and 0.83 m3 /day

respectively. Figure 5.6 below (A) Shows a Residual Oil saturation for Layer 42 of ZH86

Block of ZHAOZHOUQIAO oil field by 01 Jan 2012; (B) shows Predicted ZH86 Block

simulation results after applying the development strategy related to Case_03 by 31 Dec

2020.We can observe huge changes in oil displacement (Sweep efficiency) compared to the

results obtained in Case_01 and Case_02.We can confirm this by having a look on Figure 5.7

Curves of Case_03 development index of Zh86 block in ZHAOZHOUQIAO Oil field

(FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut).

Figure 5-8 Below (A) Shows a Residual Oil saturation for Layer 42 of ZH86 Block of

ZHAOZHOUQIAO oil field by 01 Jan 2012; (B) shows Predicted ZH86 Block simulation

results after applying the development strategy related to Case_03 by 31 Dec 2020

pg. 146

Figure 5-9 Curves of Case_03 development index of Zh86 block in ZHAOZHOUQIAO Oil

field (FOPR– simulated oil rate, SM3/DAY and FWCT– simulated water cut)

Evaluation of Oil Recovery within Zh86 block

Primary recovery drive mechanisms these are natural energies that can be used to move oil

from reservoir towards the production well. Drive mechanisms of Zh86 block were

determined by the analysis results generated by results from Figure 5.8 History match curves

(Base Case) of Zh86 block oilfield (FOPR– simulated oil rate, SM3/Day; FOPRH– actual oil

rate, SM3/Day; FWCT– simulated water cut; FWCTH– actual water cut) after running a

simulation of the historical oil production data from July 01, 1998 to December 1, 2011,

primarily reservoir pressure data and fluid production. It was found that, the main driving

energy of ZH86 block was Solution Gas (solution gas expansion/undersaturated solution gas)

driving mechanisms associated with others water influx and rock contraction. Table 5.7 and

figure 5.9, shows driving mechanisms and percentage of oil produced by each drive during a

primary production.

pg. 147

Figure 5-10 Primary Recovery Drive Mechanisms of ZH86 Block

Table 5-7 Oil recovered by Primary Recovery Drive Mechanisms

Calculation of the remain reserve into ZH86 Block

An estimate of the amount of crude oil remained in ZH86 Block was calculated by using a

material balance within a Base case which shows that the remains reserve oil was 1.088 M

m3 (81.4% of OOIP) within a production scheduled July 01, 1998 to Dec 1, 2011. Generally

crude oil remain is the different between the estimated OOIP and the produced oil within the

time period. Figure 5.10 below show remains oil reserve of ZH86_block with the associated

produced oil by drive mechanisms.

pg. 148

Figure 5-11: Remaining Oil reserves of ZH86 Block

Closing perforation which contributes water-cut to the Production well

It is not necessary, nor desirable, to completely shut off the coproduced water. The logic here

is the distinction between “good” (necessary) and “bad” (excess) water (Bailey, B. 2000)

“Good” water is that water produced at a rate below the water/oil economic limit (i.e., the oil

produced can pay for the water produced). “Good” water, then, is that water that cannot be

shut off without reducing oil production. The fractional water flow is dictated by the natural

mixing behavior that gradually increases water/oil ratio (WOR).

“Bad” water is water produced into the wellbore that produces no oil or insufficient oil to pay

for the cost of handling the water. The remainder of this discussion deals with “bad” water.

All layers which contribute to the high water cut greater than 90% to the particular well were

squeezed in order to avoid uneconomical operation within ZH86 block. The figure 5.11

below shows a squeezed layer 37-38, for the production well number ZH57-72.

pg. 149

Figure 5-12 Closing perforation which contributes water-cut

Figure 5-13 Oil Saturation Distribution of the Layer 37-38

Selection of the Candidate perforation layer(s)

This part is vital during for Oil Production Prediction. Oil production within a layers/zones

varies in according to the lithological properties of the particular i.e.; Porosity, pressure and

interconnected pores which will permit the movement of oil either within the given layer or

crosscut to another subsequent layer. So it necessary to identify the quantity of remaining oil

saturation oil into different layer. Figure 5.12, point out that layer 35-48 of ZH86 block has

69.8% remaining oil saturation which was the most candidates for the perforation

consideration during oil production forecasting.

pg. 150

Figure 5-16 Remaining oil saturation Distribution of Layers for ZH86 Block

6.0 Crude Oil Production Forecasting and water injection strategies

Accurate and reliable production forecasting is certainly a significant step for the

management and planning of the petroleum reservoirs. The prediction the performance of

the ZH86 Block from January 1, 2012 to Dec 1, 2020 in terms of Crude Oil production rate

and water injection rate were conducted by varying the location of the injection and

production wells. Also the perforations of the selected zones which have reserve greater than

10% of the Remaining oil saturation were taken into consideration. Figure 5.13, presents a

combined graph of historical and predicted field oil production total for all three (3)

prediction cases generated during prediction simulation.

pg. 151

Figure 6-1 Field Oil Production Forecasting of four cases

6.1 Oil Recovery forecastingfor different Cases in Zh86 block

This Simulation was carried out to investigate the total Oil production, amount of water

should be injected into the reservoir for the displacement of Crude Oil and maintenance of

the pressure of the reservoir. It involved three (3) simulation prediction cases, the results of

Simulations show that, Case_03 has high prediction oil recovery about 23.13 % of OOIP, and

this implies that Case_03 could be more economic viable project since the ratio of injection

water to the oil production is 2.15. Table 5.3 and figure 5.1 below show addition predicted

Oil recovery from ZH86 by the three (3) cases.

Table 6-1 Below show addition predicted Oil recovery from ZH86 by the three cases

It indicated that the Case_03 was much better than the Case_01 and Case_02 in three

parameters like oil rate, cumulative oil rate and water cut. The of Zh86 block in

ZHAOZHOUQIAO oilfield was developed in 1998. It went through many stages, such as

development with natural energy. The Case_03 was used to enhance oil recovery in the Zh86

block in ZHAOZHOUQIAO oilfield since the water cut reached 79% in Dec 31st 2011. The

pg. 152

total oil production was 305643.47 t, with a recovery factor of 23.13%. With 9 years of water

injection, the field increased its recover factor from 17.32% to 23.13%, enhanced oil recovery

is 3.8%.

Oil and gas development projects need production forecasts for planning purposes and to

understand the economic viability of each project. Sometimes, especially in the exploration

and appraisal stages, it is necessary to develop a range of production forecasts for a project

based on very limited data, often in the absence of flow information for that particular field

(Baker R. O, 2015). The purpose of conducting this analysis was to forecast how much oil

can be produced in ZH86 Block of ZHAOZHOUQIAO oil field from 2012-2020. The

forecasting results will be useful during planning for domestic energy. The oil production

forecasts were produced using separate time series data and models for ZH86 Block of

ZHAOZHOUQIAO oil field as a whole.

Figure 6-2 Oil recovery forecasting for ZH86 Block of ZHAOZHOUQIAO oil field

Field Performance Analysis results shows that Case_03 the best case to be considered

Compared to Case_01 and Case_02 in in terms of Field oil production rate, cumulative oil

production rate and water cut. The Case_03 was used to enhance oil recovery in the Zh86

block in ZHAOZHOUQIAO oilfield since the water cut reached 79% in Dec 31st 2020. The

total oil production was 305643.47 t, with a recovery factor of 23.13%. With 9 years of water

injection, the field increased its recover factor from 17.32% to 23.13%, enhanced oil recovery

is 3.8%.

pg. 153

Figure 6-3 Oil recovery level comparison for all cases in terms of Water cut

Conclusion

The aim of the project was to Optimize Field Development Strategy with a History Matching

Approach a case study Of ZH86 Block in ZHAOZHOUQIAO Oilfield, China simulation to

predict the production of an oil field. Predicting the performance of ZH86 Block from

January 1st, 2012 to Dec 1, 2020 in terms of Oil production rate and water injection rate was

successful conducted by varying the location of the new injection and production wells.

ZH86 Block in ZHAOZHOUQIAO Oilfield, China was adopted as a case study and its

production predicted for the next nine years. Production indexes oil production, oil rate, water

pg. 154

cut and water production were successfully predicted. The aim of the study was hence

achieved. The results produced had to be tested for accuracy and reliability. The accuracy of

the results was confirmed using history matching process. In the history matching process,

modifying the shape of the relative permeability curve helped to minimize the difference

between actual and the simulation results data.

The closely matched model was an indication of the accuracy and reliability of the results.

Also the perforations of the selected zones which have reserve greater than 40% of the

remaining oil saturation were taken into consideration. The historical matching of oil

production data was done by using simulation model created by Petrel 2014. The main

reason for history matching is was to enable the prediction of future performance of the

reservoir and thus production optimization with regards to oil recovery by improved or

enhanced methods. Future performance of ZH86 block in terms of Oil production forecasting

was done by using reservoir model which has matched with oil production rate from the oil

field. Simulation was also carried out to investigate the total oil production, amount of water

should be injected into the reservoir for the displacement of crude oil and maintenance of the

pressure of the reservoir In the history matching process, modifying the shape of the relative

permeability curve helped to minimize the difference between actual and the simulation

results data. The closely matched model was an indication of the accuracy and reliability of

the results. The history-matched model was then used to confidently check the production

and injection field performance. Simulation was also carried out to investigate the total oil

production, amount of water should be injected into the reservoir for the displacement of

crude oil and maintenance of the pressure of the reservoir.

Drawing up of a future development strategy for ZHAOZHOUQIAO oil field involve three

(3) simulation prediction cases named Case_01, Case_02 and Case_03, the results of

Simulations show that, Case_03 has high prediction oil recovery about 23.13 % of OOIP, and

this implies that Case_03 could be viable project since the ratio of injection water to the oil

production is 2.15. Petroleum industry must investigate more on improving oil recovery from

the operating oilfields and improve technology of discovery of the new reservoirs.

pg. 155

Recommendations

Figure 6-4: Remaining oil saturation (78%) distribution within ZH86 block

According to the simulation study there is huge remaining oil saturation distribution within

ZH86 block as shown above. For this case we recommend more advanced technology of oil

recovery should be performed in ZH86 block in ZHAOZHOUQIAO Oilfield in China, the

method like Polymer flooding should be considered since Polymer flooding can increase oil

recovery 10 to 20% over conventional waterflooding technology which is the current main

technology of oil recovery in Zh86 block in ZHAOZHOUQIAO Oilfield in China.

Due to the complexity and heterogeneity of Reservoirs, uncertainty analysis should be

done on reservoir models to determine the impact parameters have on simulation

results.

Pressure history data for the wells should be made available to improve the history

match done on the field.

To appreciate more the functionalities of PETREL more geological and reservoir data

is needed to enable a more representative model be built on PETREL

pg. 156

Figure 6-5:ZH86 Base Block remaining oil distribution for layer 44

Polymer flooding is a significant method in which the mobility of the displacing phase can be

reduced effectively by the addition of small amounts of water-soluble polymers. Polymer

flooding will enhance oil recovery by increasing the water phase viscosity, improving the

water/oil mobility ratio and improving sweep efficiency. (Zhenliang, G).

Acknowledgement

We are grateful to the Department of Petroleum Engineering (China University of

Geosciences) Ministry of Education, Wuhan, Hubei, and P.R. Chinafor providing us with the

ZH86 block in ZHAOZHOUQIAO Oilfielddata used in this work and for financial support.

These contributions are gratefully acknowledged. We would also like to thank our colleagues

from China University of Geosciences for their guidance and suggestions for this paper.

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