Upscaling of Foam Mobility Control to Three Dimensions

1. Upscaling of Foam Mobility Control to Three Dimensions Busheng Li George Hirasaki Clarence Miller Rice University, Houston, TX

2. continuous gas discontinuous gas (flowing) discontinuous gas (trapped) Foam in Porous Media Foam in Porous Media • Dispersion of gas in liquid • liquid phase is continuous • gas phase is discontinuous • Stabilized from coalescence by the presence of surfactants Effects of Foam on Gas Flow • Trapped foam reduces gas permeability • Flowing “bubble-trains” increase effective gas viscosity

3. Gas Injection Well Gas Flow Unswept Area Unswept Area Application of Foam on Gas Sparging Without foam, gravity force dominates the gas flow and gas sweep is poor Foam can be used to control gas mobility and increase gas sweep efficiency Problem: • Foam mobility is larger in 3-D than in 1-D; Results from laboratory 1-D column experiments cannot represent foam behavior in 3-D • Previous foam simulators which based on 1-D results cannot be used to design a 3-D field application

4. Objectives • Study 3-D foam behavior • Build a simulation model to simulate 1-D and 3-D foam flow

5. 2 ft Sand 2 ft 2 ft Base of the tank Four sampling points in each tube Perforated plate 6 inch Injection well Injection well and sample tubes Production wells Nine sample tubes Layout of the 3-D Tank

6. Pressure transducer P2 P3 P1 Air Flow controller 0.1~10LPM Homogeneous Sand pack 40 darcy Heterogeneous Sand pack 40 & 200 darcy Air flow in from air pump P1 P2 P3 Three way valve Air flow controller 1~100 LPM Experimental Description Surfactant: 0.05%CS330+0.05%C13-4PO

7. 6 PV, : 23% : 35% : 66% : 80% 0.37PV, 1 PV, 2 PV, Foam Increases Gas Sweep Efficiency and Gas Saturation Homogeneous Tank Results Air/Water Diagonal cross section Gas fractional flow contour plots Poor displacement of liquid at the base of the tank In situ generated foam Good displacement of liquid at the base of the tank

8. : 39% : 92% : 84% : 20% : 37% 0.37PV, 1 PV, 6 PV, 2 PV, 1 PV, Foam Increases Gas Sweep Efficiency and Gas Saturation Heterogeneous Tank Results Air/Water Diagonal cross section Gas fractional flow contour plots Poor displacement of liquid at the base of the tank In situ generated foam Good displacement of liquid at the base of the tank

9. ~ 37% ~ 66% ~ 73% Different Injection Strategies Homogeneous Pack, Bottom sampling layer, 1 PV gas injected Constant injection pressure ~0.8 psi Constant Injection Rate 0.39 LPM (injection pressure < 0.4 psi) Intermittent Gas injection Continuous Gas injection • The injection pressure should be high enough to generate strong foam and get better gas sweep efficiency. • For a constant injection pressure, the intermittent injection method provides better gas sweep efficiency and higher total gas saturation than the continuous injection method.

10. Comparison of Injection Rate Experimental condition: Homogeneous sand pack, ~0.8 psi constant injection pressure Air/Water Case In foam case, at steady state, gas injection rate is ~1/30 lower than in air/water case Foam Case In 1-D, foam mobility is much lower

11. P2,P3 P3 P2 P1 P1 P2 P3 6 inch Diagonal Cross Section Pressure Profileheterogeneous sand pack Injection pressure Air/ Water Injection pressure In air/water case: P1 > P2 In foam case: P1 < P2 Foam

12. Foam Stability Heterogeneous Pack, Constant injection pressure ~0.8 psi 1 PV gas was injected and then gas injection was stopped Gas bubbles flow up Water flows down Heterogeneous tank with foam after 1PV gas injection Gas saturation in the tank is high and remains almost the same 20 days after stopping gas flow.

13. 1-D 3-D Simulation Approach Observation: Foam mobility Larger scale 3-D field application 3-D tank experiments (Expensive, Time consuming) 1-D Experiments (Easy to perform in lab) Obtain parameters Simulate & predict Foam model ?

14. Foam Changed Two Gas Flow Properties Darcy’s law governs gas flow in porous media: No foam: Two gas properties are changed when foam is present: Gas relative permeability With foam: Gas apparent viscosity

15. Foam increases gas residual saturation Effect of shear thinning Geometry factor Effect of gas saturation Details of the Model Parameters: Represents difference between 1-D and 3-D Can be determined from 1-D column experiments

16. Flow out Syringe pump 1-D sand pack Pressure Control Parameter Determination from 1-D Column

17. Foam, 1-D Column, Simulation Results 40 darcy sand, (0.4psi/ft) Grid block:20x1x1 Average gas saturation after 1 PV gas injection: Exp: 82% Simu: 84%

18. = 0.21 Simu Exp Foam, 3-D tank history match simulationHomogeneous sand pack, (0.4 psi/ft) Grid block: 9x9x9 Gas Injection Rate Pressure Profile Cross section gas fraction flow contour plots Other parameters are the same as in the 1-D simulation, except:

19. 1-D 3-D = 1 = 0.21 Gas apparent viscosity Comparison of 1-D and 3-D In the homogeneous sand tank, under our experimental condition, 3-D foam flow is about 5 times weaker than 1-D foam.

20. z propagation of gas front y gas front Injection well P x 2 ft Scaling Up Criteria for Larger Scale Assumption: The pressure drop is mainly within the gas front Criteria: Use the overall pressure gradient in the gas front when it reaches the edge of a 2x2x2 ft region (NWR) as the comparison standard to choose corresponding simulation parameters from 1-D i.e. Injection pressure: 8 psi over hydrostatic pressure The overall pressure gradient when gas front reaches the NWR is 4 psi/ft Simulation parameters will then be chosen from a corresponding 4 psi/ft 1-D column experiments.

21. Conclusions • Foam increases lateral gas distribution and gas saturation in the 3-D sand tank • To generate foam and get good sweep efficiency, a critical injection pressure must be exceeded. • For the same injection pressure, the stabilized injection rate with foam is about 1/30 of that with surfactant-free water. • The foam is stable. Most of the injected gas remains in the tank for more than 3 weeks. • A foam model is proposed. Parameters can be determined from 1-D column experiments and applied to 3-D simulation. In the homogeneous sand tank, under our experimental condition, 3-D foam flow is about 5 times weaker than 1-D foam.