CO2-Foam EOR Field Pilots

1The National IOR Centre of Norway, 2University of Stavanger (UiS), Norway, 3University of Bergen (UiB), Norway

References: Aarra, M. G. and Skauge, A. 1994. A Foam Pilot in a North Sea Oil Reservoir: Preparation for a Production Well Treatment. Paper SPE 28599 presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 25-28 September · Alvarez, J. M., Rivas, H. J. and Rossen, W. R. 1999. Unified Model for Steady-State Foam Behavior at High and LowFoam Qualities. Paper SPE 56825 presented at the SPE Annual Technical Conference and Exhibition, Houston, Texas, 3-6 October · Barenblatt, G. I. 2003. Scaling. Cambridge University Press · Chang, S.-H. and Grigg, R. B. 1998. Effects of Foam Quality on Flow Rate on CO2-Foam Behavior at Reservoir Conditions. Paper SPE 39679 presented at the SPE/DOE Improved Oil Recovery Symposium, Tulsa, Oklahoma, 19-22 April · Falls, A. H., Hirasaki, G. J., Patzek, T. W., Gauglitz, D. A., Miller, D. D. and Ratulowski, T. 1988. Development of a Mechanistic Foam Simulator: The Population Balance and Generation by Snap-Off. SPE Res Eng 3 (3) , 884-892. SPE-14961-PA · Hirasaki, G. J. and Lawson, J. B. 1985. Mechanisms of Foam Flow in Porous Media: Apparent Viscosity in Smooth Capillaries. SPE J 25 (2), 176-190. SPE-12129-PA · Holm, L. W., Josendal V. A. 1974. Mechanisms of Oil Displacement By Carbon Dioxide. J Pet Technol 26 (12), 1427-1438. SPE-4736-PA · Kovscek, A. R., Patzek, T. W. and Radke, C. J. 1993. Simulation of Foam Transport in Porous Media. Paper SPE 26402 presented at the SPE Annual Technical Conference and Exhibition, Houston, Texas 3-6 October · Lake, L. W. 1989. Enhanced Oil Recovery. Prentice Hall Incorporated, New Jersey · Rossen, W. R., Zhou, Z. H. and Mamun, C. K. 1995. Modeling Foam Mobility in Porous Media. SPE Advanced Technology Series 3 (1), 146-153. SPE-22627-PA · Rossen, W. R. 1996. Foams - Theory, Measurements and Application, Chapter 11: Foams in Enhanced Oil Recovery · Skauge, A., Aarra, M. G., Surguchev, L., Martinsen, H. A. and Rasmussen, L. 2002. Foam-Assisted WAG: Experience from the Snorre Field. Paper SPE 75157 presented at the SPE/DOE Improved Oil Recovery Symposium, Tulsa, Oklahoma, 13-17 April · Wang, F. P., Lucia, F. J. and Kerans, C.1998. Integrated Reservoir Characterization Studyof a Carbonate Ramp Reservoir: Seminole San Anders Unit, Gaines County, Texas. SPE Res Eval & Eng 1 (2), 105-113. SPE-36515-PA

Mohan Sharma1,2 (mohan.sharma@uis.no), PhD Candidate,Martin Fernø1,3 , Arne Graue1,3 , Svein M. Skjæveland1,2

Introduction

Carbon dioxide has been successfully used in fields as EOR agent, especially in the USA due to access to CO2 from natural sources,which is relatively inexpensive compared to other processed solvents. Because CO2 forms a dense phase at typical reservoirconditions, it exhibits higher density and viscosity compared to other gases, thus making it favourable for gas flood. Under a specificcombination of reservoir pressure, reservoir temperature and oil composition, CO2 may become mutually soluble with the residual oilleading to miscible displacement. The residual oil saturation is then reduced nearly to zero resulting in high ultimate oil recovery.However, below some pressure called Minimum Miscibility Pressure, CO2 and reservoir oil are no longer miscible. CO2 may still forceout additional volume of oil owing to oil swelling and viscosity reduction under immiscible displacement but considerable residual oilsaturation can remain, often leading to unfavourable project economics. Nevertheless, despite its high local displacement efficiency, theprocess suffers from poor sweep efficiency due to viscous fingering caused by unfavourable mobility ratio, and gravity segregationcaused by density difference between injected and displaced phases.

Increase in global energy demand and maturing oil fields has resulted in pushing recoveries to higher levels through integrated andinnovative solutions. Application of foam (generated by using surfactants) has been found to reduce gas mobility in laboratory corefloodexperiments, and to establish favourable mobility conditions. The impact of various parameters like rock wettability, capillary pressure,fluid saturations, flow rates, adsorption etc. on foam flood have been studied extensively at lab scale.

Research Objectives

• Understand large scale CO2 mobility control using foam in heterogeneous reservoirs from field pilots• Develop a framework to scale-up the mechanisms that are observed at lab scale and are required to describe flow at reservoir scale

Ongoing Work

Lab-scale Studies

• Experiment Design: Based upon the information available about thereservoir's petrophysical properties, reservoir condition and rock-fluid/surfactant interactions, several different scenarios will be tested through1D numerical scoping study. This would ensure lab experiments areconducted under conditions favorable to generate foam during coreflooding.

• Lab Experiments: The experiments using representative core and fluidsystem will be carried out under in-situ conditions at UiB.

• Data Analysis: 1D numerical modelling will be used to simulate corefloodexperiments. Parameters relevant to foam modelling will be tuned to get amatch on pressure drop across core, breakthrough time, oil recovery trendand water-cut/GOR trends.

Field-scale Studies

• Pilot Design: A few fields have been identified onshore in Texas, USA to conduct pilot studies. This includes a sandstonereservoir, a heterogeneous carbonate reservoir and a fractured carbonate reservoir. The project involves reservoircharacterization for pilot area suitable for CO2 EOR, by integrating data available from various sources and scales. Surfaceoil, gas and water samples are being collected for fluid characterization studies. It is planned to use historical production andinjection data to calibrate the model, which would form the basis for pilot design. Numerical modelling and sensitivity studiesunder uncertainty will be carried to decide on the well pattern, well spacing and injection strategy.

• Pilot Execution: Appropriate data required to understand the displacement process will be acquired prior to, during and postpilot execution. This includes well logs and cores from planned infill wells; well pressure, rates and fluid samples; pressurebuild-up and fall-off tests; production logging; tracer studies; and base and repeat seismic surveys post feasibility study.

• Data Analysis: The data gathered during and post pilot would be analysed using appropriate tools. The interpreted resultswould be used for pilot model re-calibration and to understand the production mechanisms at larger scale.

Process Scale-up

The behaviour of foam in porous media is controlled by the behaviour of individual films between bubbles in the foam.Because foams are at best metastable, the research so far has focused to understand processes involved in dynamicbreak-and-reform mechanisms at small scale, and to capture them via numerical models. However, laboratory results areoften used unscaled, or are only partially scaled-up, for field studies. Starting with the governing component flowequations, different scaling groups are currently being studied using Inspectional Analysis. The results from pilot will beused to validate the scale-up approach and identify any relaxation required on similarity groups under certain situations.

Summary

The results from the pilot studies will be used to understand the flow mechanisms at larger scale, and to establish a link between relevant processes observed at lab scale and pilot scale. To date, commercial CO2value chain does not exist to support field-scale CO2 EOR on the NCS. Knowledge and experience gained from pilots carried out as part of this work can be used for effective pilot design on NCS.

Acknowledgement

The authors acknowledge the Research Council of Norway and the industry partners; ConocoPhillips Skandinavia AS, BP Norge AS, Det Norske Oljeselskap AS, Eni Norge AS, Maersk Oil Norway AS, DONGEnergy A/S, Denmark, Statoil Petroleum AS, ENGIE E&P NORGE AS, Lundin Norway AS, Halliburton AS, Schlumberger Norge AS, Wintershall Norge AS of The National IOR Centre of Norway for support.

Figure 1: Components of Foam

Figure 2: Gas mobility control with foam(Numerical simulation for co-injection into a reservoir)

Figure 3: Lab-scale studies to derive inputs for field scale numerical modelling Figure 4: Integrated numerical modelling and data acquisition for field-trials

Figure 5: Microscopic to macroscopic scales involved during foam flow in porous media

Interface(1 nm)

Lamellae(10–100 nm)

Grid Block(1–10 m)

Pilot(10-100 m)

Core(1–10 cm)

Pore(10–100 μm)

WG W G

SurfactantWater

Gas

Trapped Gas

Flowing Gas