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

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 continuous gasdiscontinuous gas (flowing) discontinuous gas (trapped) Foam in Porous Media

Application of Foam on Gas Sparging Without foam, gravity force dominates the gas flow and gas sweep is poor Gas Injection Well Unswept Area Gas Flow 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

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

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

P1 P3P2 Air flow in from air pump Air Flow controller 0.1~10LPM Air flow controller 1~100 LPM Three way valve P1P2P3 Pressure transducer Experimental Description Homogeneous Sand pack 40 darcy Heterogeneous Sand pack 40 & 200 darcy Surfactant: 0.05%CS %C13-4PO

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

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

Constant Injection Rate 0.39 LPM (injection pressure < 0.4 psi) Intermittent Gas injection Continuous Gas injection Constant injection pressure ~0.8 psi 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. Homogeneous Pack, Bottom sampling layer, 1 PV gas injected Different Injection Strategies ~ 37% ~ 66% ~ 73%

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

In air/water case: P1 > P2 In foam case: P1 < P2 Diagonal Cross Section Pressure Profile heterogeneous sand pack Air/ Water Foam P2,P3 P1 P3 P2 6 inch P1 P3P2 Injection pressure

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

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

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

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

Injection pressure ft/day 40 darcy sand column 0.2 psi/ft , psi/ft , psi/ft , psi/ft , darcy sand column 0.2 psi/ft psi/ft , psi/ft , psi/ft ,1501 Parameter Determination from 1-D Column Pressure Control 1-D sand pack Flow out Syringe pump

Foam, 1-D Column, Simulation Results ft/day ,5001 Average gas saturation after 1 PV gas injection: Exp: 82% Simu: 84% 40 darcy sand, (0.4psi/ft) Grid block:20x1x1

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

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

x z y gas front propagation of gas front 2 ft P Injection well 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.

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.