SUDAPETDeveloping The Andalusia Field and Improving Its Recovery Factor Using Eclipse and Pipesim Engineering SoftwareAuthors : Bayu Dwi F.P. (113120058), I Kadek Gerardave D.U (113120027), Rachmat Kurniawan D.U (113120016)SUDAPETCopyright 2015, Development Project of Andalusia Field to SKK MigasThis paper was prepared for presentation at the 2015, Development Project of Andalusia Field to SUDAPET held in UPN Veteran Yogyakarta, Yogyakarta, Indonesia, 3 July 2015.

AbstractIn physiographic, Andalusia Field, precisely Barito basin covers an area of 70,000 square kilometers in the southeast part of South Kalimantan and is located along the southeast limit of the Sunda Plate Micro. Barito basin is a basin-type Foreland the Tertiary, dealing directly with Meratus (Satyana and Silitonga, 1994). Barito basin basement rocks are rocks Pre-Tertiary igneous rocks are composed of andesitic and granitic and metamorphic rocks consisting of crossing siltstone with fine to coarse sandstones with conglomerates and breccias inserts. Pre-Tertiary rocks above is deposited Tertiary sedimentary rocks consisting of old to young, namely: Tanjung Formation, Berai Formation, Warukin Formation, Dahor Formation, Quaternary Deposition (Alluvium). Andalusia Field model is devided into 3 layer in Eclipse software. The current recovery factor (2009) is 0.204 %, and RF prediction until 2029 is 1.473%, with OOIP volumetric is 33.56 MMSTB.Sudapet make a field development plan for 20 years that aiming for recovery factor as much as possible in accordance with the data of reservoir simulation using Eclipse software without considering of economic aspect. The simulation is based on reservoir aspect and production using six different field devoelopement scenarios.As Sudapet analysis that Andalusia field has water drive mechanism, this drive is potential to be developed until the RF around (35% - 75%). Finally, the result from the scenarios Sudapet made have different recovery factor, they are : 1st Scenario (20.30 %), 2nd Scenario (22.54%), 3rd Scenario (22.87%), 4th Scenario (21.92 %), 5th Scenario (24.17%), 6th Scenario (25.97%). The best is 6th Scenario (existing well, 5 infill wells, 2 injection wells and 2 pressure maintenance well). The recomendation to Andalusia Field is 6th Scenario by adding injection wells and some infiil well.2SUDAPET3SUDAPET

I. Field ReviewAndalusia Field is located in Barito Basin. Regional stratigraphic in this basin in order from old to young, are Tanjung Formation, Berai Formation, Warukin Formation, Dahor Formation, Quarter Sediment (Alluvium)By the stratigraphic data, Berai Formation is a productive formation. Berai Formation is deposited above Tanjung Formation during Oligosen until Lower Miosen Times, compiled by Lower Berai which are composed by marl, siltstone, limestone and coal as the insert, Central Berai which are characterized by massive limestne with marl interklas, and the Upper Berai which are composed by limestone flakes with marl as the isert, claystone with napal inline and a bit of coal. This formation is neritik depositional environment with thickness of about 1000 m. The major production is located in this formation which is a reservoir formation with a thickness varying between 3900-4500 ft. Andalusia Field has a petroleum system as follows. Tanjung Formation is use as source rock, Berai Formation is use as reservoir rock , Warukin Formation as Cap Rock, And the Trap is Structural Trap ( Faults & Folds).

Cap RockReservoir RockSource Rock

III. Data PreparationThe data used in the simulation process can be divided into two principal categories, static data and dynamic DataStatic DataStatic data is the fixed data, where the data is not changed during the simulation process executed. Static Data consist of reservoir geological data, reservoir data (rock properties, SCAL data, PVT data) and well completion data (Table A until Table J).

Geological Data The prospect layer of Andalusia field is provided in Berai formation. Members scattered composed by shale with limestone inserts alternating with silt, silty claystone and a little coal. This formation is deposited in the environment neritik with a thickness of about 1000 m. The main production is located in this formation which is a reservoir formation with a thickness varying between 3900-4500 ft. Geological data consist of Top Structure Map, Bottom Structure Map, Net to Gross Map, Isoporosity Map, and Isopermeability Map (Picture A until Picture E)

Reservoir DataIn this case, reservoir data used consist of rock properties, PVT data, SCAL data, and completion data (Table A until Table J).IV. Reservoir SimulationStages to perform reservoir simulation are:1. Reservoir simulation modeling2. Initialization and equilibration3. History Matching4. Prediction

1. Reservoir Simulation ModelingReservoir simulation model is is the combination of the geological model with reservoir data, production, drilling and other into the reservoir simulation software, in this case, the reservoir is simulated by Eclipse software. Results of geological modeling used in reservoir simulation are depth of the structure map (top and bottom), porosity distribution maps, facies distribution maps, permeability distribution map, saturation distribution map (when Pc = 0), rock region map and amount of in place (OOIP and or OGIP).

2. Initialization After reservoir simulation modeling is done, the next step is initializing, this step purposed to equalize the initial reservoir conditions (inplace and pressure) with the model.

Reservoir Model Intialization Step In theory to get the good initialization, the initialization stages needs to be done, as follows:1. Do initial initialization process, by comparing amount of inplace (OOIP or OGIP) of volumetric simulation, If the difference is more than 10%, then consult back models geological or do price changes Net To Gross (NTG). But in the development of this field, the difference between OOIP actual and OOIP models should be less than 0.01%2. In theory if the first initialization process has resulted in a difference of less inplace of 10% (in theory) or 0.01% (in this case), then the next step are:-Change the capillary pressure data of model. -Change the PVT data (Pb, Bo, Rs), the data affect the amount of PVP is inplace (OOIP and OGIP), the data is usually obtained from the PVT fluid analysis or using correlations.-Change gas cap thickness. gas cap thickness will affect the amount of inplace (OOIP and OGIP), the data obtained from log interpretation. Change thickness of the gas cap is very rarely done, except if the data we have not provide good accuracy on the thickness.-WOC and GOC depth will affect the amount of inplace (OOIP and OGIP), the data is obtained from the interpretation or logs and RFT. WOC and GOC depth generally very rare done, but the results are still doubting the depth of log interpretation.But in this case we change only the capillary pressure of model.

Reservoir Model Intialization Using Eclipse SoftwareIn this case, the base case is only using single well called Well A. Provided data to intialize the reservoir with the model are as following Table K. Before initialization, we get the difference of OOIP model and OOIP actual is still 6.34 %. It means that the initialization have to be continue. In this case we change the capillary pressure of model. After the capillary pressure of model changed, the result of initialization are as following Table K. The difference of OOIP model and OOIP actual is 0.00105 %. It means that the initialization is done that the percent of difference is less than 0.01%.

3. History MatchingHistory matching is the process of modifying parameters used in the modeling, in order to create harmony between models with real conditions, which are based on the data parameters measured over a specific time period. This stage is crucial in conducting reservoir simulations. The purpose of matching process is validating the reservoir simulation model with actual reservoir conditions.Performance parameter are aligned in the process of history matching include production Performance Matching (fluid production rate, gas-oil ratio and water cut)

Production Performance MatchingSimulator will calculate the flow rate of gas or oil after the actual pressure is inserted. If the obtained graph of gas or oil flow rate does not match with the actual flow rate graph, do the matching. This matcing is done by changing the WI (Well Index) value of each well to obtain alignment between models and actual production. In this project, the base case is only using single well called Well A. Oil, gas and water rate match by change the relative permeability of oil (Kro), relative permeability of gas (Krg) and relative permeability of water (Kro). The relative permeability of oil (Kro) and relative permeability of water (Krw) curve will be determine the wettability of this reservoir. If we look at the curve (Picture G) the cross over between Kro line and Krw line located in Sw < 0.5. It means the wettability of this reservoir is oil wet.The data after history matching process is shows as following Table L and Table M.

4. PredictionBefore predict reservoir simulation, parameter limits must first inserted into the simulation model. The purpose of inserting parameter limit is to match simulation results to the field conditions. Limitation consists of the rate of oil production, gas production rate, water cut, WGR (water gas ratio), BHP and WHP. The limit value is calculated based on the economic value of a well or field, while BHP based on operations and artificial lift equipment eg WHP based on operational gas supply / facility.By using single Well A, the performance of well productivity from 2009 to 2029 (20 years), the production cumulative is 494.35 MSTB. By this prediction, we can develop the field by using various scenario.

V. Development ScenarioBased on the actual data production until 2009, with Current Recovery Factor (CRF) is 0.264 %. Sudapet proudly made great scenario to improve its CRF by setting 6 scenario of development, because of Tanjung Formation still has big oil saturation left in productive zone of reservoir. Development scenarion built by adding infil well, injection well (pressure maintenance) or both of them in certain time periodically. Sudapet Development project of Bujang field consists of 6 scenarios as follows (More details shown at Table P): Scenario 1 : Basecase + 3 infill wells Scenario 2 : Scenario 1 + 1 infill well + 1 water injection well + 1 pressure maintenance well Scenario 3 : Scenario 2 + 1 infill well Scenario 4 : Scenario 1 + 2 infill wells Scenario 5 : Scenario 2 + 1 water injection well + 1 pressure maintenance well Scenario 6 : Scenario 5 + 1 infill well

The Reservoir Aspect Development of Andalusia FieldThe scenarios above has been planned, first observe the prediction of the Basecase. This field has water drive mechanism, this case is observed in the curve of GOR, WOR, and pressure at picture R, S, T. Where before prediction of basecase until 2009 the number of WOR increasing greater than GOR which is stable with low rate, and the pressure could be said constant enough until 2009. In theory, this drive mechanism has recovery factor between 35% - 75%. And then we analize maximum recovery factor use JJ. Arps method, we have recovery factor maximum is 86.9%.The Sudapet action in constructing the scenario considering many actual data based on model and production data during certain time of prediction. Will be describe as follows:1. Oil Saturation, this parameter as the important think must be review before locate the infill well location. As an example, the infill 1 well is placed at layer 1 and 2 which has 0.81866 oil saturation (So) at grid coordinat 24 33 1. Hence this could bring more oil saturation left if we set the infil 1.2. Pressure, this pressure as the second one, where the the greater pressure give the big drive to fluid flow. The well block pressure at grid coordinat 24 33 1 is 2227.3 psi, hence the infil 1 properly to be set.3. Permeability, this parameter as consideration to know the capable of formation to flow the fluid. As an example, infil 1 again, the permeability is 171.9 md and it was great enough to flow the oil saturation left in thet layer.4. Porosity, this parameter will give another consideration to set where the infil well must be. The greater porosity in number 0.25. In grid coordinat 24 33 1 the porosity is 0.2726. 5. Fault, the fault will cause some problems when we put infill well near to it. For example their would be a problem during drilling for making the well.

The Production Aspect Production aspect involves determining the oil rate optimum that applied on infil well based on oil rate of the previous or the nearest existing well. Sudapet using Pipesim Software in analyzing Productivity Analysis which can be seen on Table O.

Completion DesignTable N has shown the completion for each well. The all well are cased hole, because in this formation there are claystone dan siltstone can make sloughing problem. Sudapet team know from the stratigraphy correlation review, formation Dahor and Warukin consist of any siltstone and claystone, hence the completion is cased hole for all well.

Injection Well Injection well in this scenario we used is as Pressure Maintenance, because the water injected at depth under WOC that means water enter to the water zone (aquifer) in order to maintain the pressure of reservoir high, eventhough finally the pressure exactly will decrease during the production time, but here the pressure maintenance could benefit its pressure enough, hence the oil saturaion could be swept more by the water injected. Besides, the water injected into oil zone that serves as a water flooding. water injection using the water produced from production wells.

VI. Result The result of those all scenario could be seen on Table P. Here the cummulative production of oil (Np), gas (GP), water (WP) and recovery factor (RF) resulting from each scenario, they are:1. Basecase: Np = 494.35063 MSTB, GP = 219.94 MMSCF, WP = 72.9 MSTB, RF = 1.47 %2. 1st Scenario: Np = 6815.1175 MMSTB, GP = 9448.552 MMSCF, WP = 37.19 MMSTB, RF = 20.3 %3. 2nd Scenario: Np = 7565.814 MSTB, GP = 914.44 MMSCF, WP = 42.3 MMSTB, RF = 22.54 %4. 3rd Scenario : Np = 7676.8595 MSTB, GP = 9313 MMSCF, WP = 42.5 MMSTB, RF = 22.87 %5. 4th Scenario : 7359.481 Np MSTB, GP = 9839.3 MSCF, WP = 37.2 MMSTB, RF = 21.92 %6. 5th Scenario: Np = 8114.6745 MSTB, GP = 8800.6MSCF, WP = 45.02 MMSTB, RF = 24.17 %7. 6th Scenario : Np = . 8717.515 MSTB, GP = 9454.1 MMSCF, WP = 45.5 MMSTB, RF = 25.97 %

VII. ConclusionFinally Sudapet could gain some points tobe concluded based on scenarios using Eclipse and Pipesim Engineering Software, namely :1.The driving force of Andalusia Field reservoir is Water Drive Mechanism. 2.Andalusia Field recovery factor (Well-A) from the start of production until the year 2029 amounted to 1.473%, so need for development to increase the recovery factor suited by ability of Water Drive, that is around 35% - 75% 3. Andalusia Field development is done by reconstructing several scenarios and simulated the Eclipse program. 4. Scenarios such as the addition of infill wells and injection wells. Determination of the location of infill wells and injection wells considering: (a) oil and water saturation, (b) pressure, (c) permeability, (d) porosity, and (e) flow rate of water production.5. Based on Recovery Factors resulting from scenarios, the biggest RF is 6th Scenario that is 25.97 %VIII. Recommendation1.From the six of scenarios that have been proposed, it is recommended to develope a Andalusia Field using Scenario 6 (existing well, 5 infill wells, 2 injection wells and 2 pressure maintenance well), with a recovery factor for the next 20 years by 25.97%. 2.For 20 years, the management of the production wells can be done with re-completion and installation of chokes to regulate the production flow rate. 3.After the next 20 years, the development of the field can be done by adding injection wells (operating pressure maintenance) or EOR for optimizing of residual oil recovery.

IX. References1. Kristanto, Deddy, Diktat Kuliah Teknik Pengurasan Reservoir Tahap Lanjut, Universitas Pembangunan Nasinal Veteran, Yogyakarta, 1997.2. Pamungkas, Joko, Simulasi Reservoir, UPN Veteran Yogyakarta.