Enhanced-Oil-Recovery Pilot-Testing Best Practices

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 118055, "Enhanced- Oil-Recovery Pilot-Testing Best Practices," by G.F. Teletzke, SPE, R.C. Wattenbarger, SPE, and J.R. Wilkinson, SPE, ExxonMobil, prepared for the 2008 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, UAE, 3-6 November. The paper has not been peer reviewed. Enhanced-oil-recovery (EOR) implementation is complex, and successful applications must be tailored to each reservoir. A systematic staged evaluation and development process is required to screen, evaluate, pilot test, and apply EOR processes for particular applications. Pilot testing can play a key role in this process. Before field testing, pilot objectives must be defined clearly and well spacing, pattern configuration, and injectant volumes determined. Staged Process for EOR-Project Evaluation and Development The EOR evaluation begins with screening-level-data collection, candidate-process selection, injectant-source identification, and screening economics. If favorable, EOR-project design and implementation require in-depth analysis of the most-promising processes. In addition to standard laboratory tests, specialized fluid characterization and reservoir-conditions coreflood tests with in-situ fluids and a range of injectants are performed to customize a process for each reservoir. Reservoir-characterization studies are conducted concurrently to identify key geological controls on field-scale sweep efficiency. Results from the studies then are used as input to geological and dynamic reservoir-simulation modeling of the process at various scales to evaluate options, define a preferred process design, and provide input to screening-level development and facilities planning. If anticipated rates, recoveries, and economics are favorable, pilot testing in the target field often is undertaken to resolve uncertainties and fine-tune operational and execution details. Additional laboratory, reservoir-characterization, and simulation work may be undertaken after pilot testing to resolve uncertainties further. If the technical and commercial outlook is still positive, commercial-scale implementation takes place. Stakeholder reviews are held after each stage of this process. This process is illustrated in Fig. 1 of the full-length paper. The example used in the paper is a CO2 water-alternating-gas (WAG) process. Pilot Objectives Care should be taken when developing pilot objectives to ensure that the pilot is used appropriately as part of a long-term field-development strategy. Pilot tests should field test recovery processes that have been evaluated technically and economically beforehand. Also, the recovery process to be field tested should be optimized through both laboratory and reservoir-simulation studies to maximize oil recovery at the lowest possible cost. Before field testing, the most appropriate well spacing, pattern configuration, length and orientation of wells, injectant, and injection strategy should be defined. Considerations for Pilot Design Adequate time spent on pilot design and optimization can lead to earlier full-field implementation. A poorly designed and executed pilot may lead to condemning an appropriate EOR process incorrectly or promoting an inappropriate EOR process.