Enhanced Oil Recovery through Steam Assisted Gravity DrainageA Comparative study of Continuous and Cyclic Steam Injection

with Trapping of Oil Phase

Muhammad Adil JavedWAREM Generation 2011

apl. Prof. Dr.-Ing. Holger ClassIWS - Dept. of Hydromechanics and Modelling of Hydrosystems

Advisor

Agenda

• Introduction to SAGD technique

• Why Cyclic SAGD?

• Model Description• Mass Balance, Energy Balance• Oil Production Well Equation• Relative Permeability Relation• Trapping Model• Heavy Oil Thermo-physical Properties

• Problem Setup

• Results

• Conclusion and Remarks

Introduction to SAGD technique - I

SAGD Schematic (after ClydeUnion Industry)

Introduction to SAGD technique - II

Typical SAGD setup and the simulated section of reservoir used in this study

Why Cyclic SAGD? - I

● SAGD is not so energy efficient technique. It consumes roughly one-third of barrel for production of barrel of oil.

● Replacing the energy required for steam generation by renewables like solar energy could be of economic and environmental interest.

● Assuming reservoir as large thermal accumulator, Birrell et al., 2005suggests, that the effect of daily and seasonal variations on the average bitumen production is negligible.

Why Cyclic SAGD? - II

● The motivation of this study is to investigate the influence of cyclic behavior of steam injection due to fluctuations in the availability of solar thermal energy.

● To simplify the problem in this study, these fluctuations were depicted with 12 hours of injection and 12 hours of production in a day.

Model Description – I [Mass Balance, Energy Balance]

● This model implements three-phase two-component (3p2c) flow of up to three fluid phases 𝛼 𝜖 𝑤𝑎𝑡𝑒𝑟, 𝑜𝑖𝑙, 𝑔𝑎𝑠 , composed of two components 𝜅 𝜖 𝑤𝑎𝑡𝑒𝑟, 𝑜𝑖𝑙

Mass Balance Eq.

Energy Balance Eq.

Model Description – II [Oil Production Eq.]

Butler, 1985

Zhangxin, 2008

Model Description – III [Relative Permeability Relation]

• In this study, (Parker et al., 1987) approach has been used to estimate three phase relative permeability. It is a parametric model based on (Van Genuchten, 1980) capillary pressure saturation curves and relative permeability curves by (Mualem, 1976).

• This model is different from most relative permeability models because it does not require two-phase relative permeability data.

• Capillary Pressure is neglected in this study.

Parker et al., 1987

Model Description – III [Trapping Model - I]

• In this study, the hysteresis effect of non-wetting phase is incorporated into (Parker et al., 1987) relative permeability relation by putting a trapped saturation term in the effective saturation eq.

• A simple history-dependent non-wetting-phase trapping model was proposed by (Patterson and Falta, 2012) which is based on Land’s Trapping Model (Land, 1968).

• It requires a new variable which stores the maximum saturation of oil phase 𝑆𝑛𝑀𝑎𝑥 in the history of the scenario.

Model Description – III [Trapping Model - II]

𝑆𝑛𝑡,𝑀𝑎𝑥 is the maximum possible trapped saturation of phase n , achieved during non-wetting phase evacuation. It is a static parameter used for the characteristic curve.

Land, 1968

Patterson and Falta, 2012

Heavy Oil and Thermo-Physical Properties

● This study has also a focus on the implementation of the thermo-physical relations of a heavy oil which is not a Newtonian fluid.

● Relative permeability of the oil phase is dependent on temperatureconditions since the oil viscosity changes strongly.

● Most important parameters in phase equilibrium and physicalproperty calculations are vapor pressure, critical constants, andviscosity-temperature relations.

Perturbation Expansion for Physical Properties of Heavy Oil• If we have a reference system which

is based on quite reliable data setsthen one can make other bettermodels by adding a perturbation orcorrection factor to the referencesystem.

Riazi, 2005

Problem Setup - I

Model Setup and Boundary Conditions

Problem Setup - II

Average Reservoir Properties

Steam Injection Rates

Results – I [Temperature Plume Growth]

Case – ICont. Injection

Case – IICyclic Injection

Case – IIICyclic Injection with

Trapping of Oil Phase

Results – II [Sw, Sn, Sg]

Results – III [Mobility of Oil]

Case – ICont. Injection

Case – IICyclic Injection

Case – IIICyclic Injection with

Trapping of Oil Phase

Results – IV [Trapping of Oil]

After 1 Year After 2 Year

Results – V [Production of Oil]

Cumulative Production of Oil on simulated section

Results – VI [Mobility of Oil]

Viscosity of Heavy Oil vs Time(at 1.5m to the left from

Injection Well)

Relative Permeability of Oil (at 1.5m to the left from

Injection Well)

Mobility of Oil vs Distance from Injection Well

Results –VII [Pressure Fluctuations]

Pressure near Injection Well (at 1.5m to the left from Injection Well)

Conclusion and Remarks

• Cyclic injection leads to higher production rates than in the continuous injection case.

• Relative permeability is strongly influenced by the fluctuations in saturation in the cyclic scenarios and strongly dependent on the increased retention due to the trapping in the hysteresis scenario.

• It would be interesting to see the effect of more distinct collapsing and reappearing steam chambers during intervals longer than 12 hours. In particular the effect of buoyancy becomes more important then. While oil and steam have a strong density difference, which drives the oil down towards the production well, the density difference between oil and hot water is negligible. This issue should be addressed in further studies.

• The effect of hysteresis is implemented here in a simplified approach only for the oil phase. One could investigate the influence of three-phase hysteric effects, including also capillary pressure, although our hypothesis was that oil relative permeability is the most important process. Therefore, it would be important to have experimental evidence and measurements for determining values for the applied parameterization of hysteresis.

𝑇ℎ𝑎𝑛𝑘𝑠!