Co‐optimization of CO₂‐EOR and storage processes in mature oil reservoirs

Abstract

This paper presents an optimization methodology for CO2 enhanced oil recovery in partially depleted reservoirs. A field‐scale compositional reservoir flow model was developed for assessing the performance history of an active CO2 flood and for optimizing both oil production and CO2 storage in the Farnsworth Unit (FWU), Ochiltree County, Texas. A geological framework model constructed from geophysical, geological, and engineering data acquired from the FWU was the basis for all reservoir simulations and the optimization method. An equation of state was calibrated with laboratory fluid analyses and subsequently used to predict the thermodynamic minimum miscible pressure (MMP). Initial history calibrations of primary, secondary and tertiary recovery were conducted as the basis for the study. After a good match was achieved, an optimization approach consisting of a proxy or surrogate model was constructed with a polynomial response surface method (PRSM). The PRSM utilized an objective function that maximized both oil recovery and CO2 storage. Experimental design was used to link uncertain parameters to the objective function. Control variables considered in this study included: water alternating gas cycle and ratio, production rates and bottom‐hole pressure of injectors and producers. Other key parameters considered in the modeling process were CO2 purchase, gas recycle and addition of infill wells and/or patterns. The PRSM proxy model was ‘trained’ or calibrated with a series of training simulations. This involved an iterative process until the surrogate model reached a specific validation criterion. A sensitivity analysis was first conducted to ascertain which of these control variables to retain in the surrogate model. A genetic algorithm with a mixed‐integer capability optimization approach was employed to determine the optimum developmental strategy to maximize both oil recovery and CO2 storage. The proxy model reduced the computational cost significantly. The validation criteria of the reduced order model ensured accuracy in the dynamic modeling results. The prediction outcome suggested robustness and reliability of the genetic algorithm for optimizing both oil recovery and CO2 storage. The reservoir modeling approach used in this study illustrates an improved approach to optimizing oil production and CO2 storage within partially depleted oil reservoirs such as FWU. This study may serve as a benchmark for potential CO2–EOR projects in the Anadarko basin and/or geologically similar basins throughout the world. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.

Two risk metrics for CO2storage reservoirs with varying domain size, heterogeneity, and injection rate

“…Even though it is expected that most real-world CO 2 storage sites would have a larger effective flow region, such small sites have been used to sequester CO 2 in nonpower plant projects, especially in mature small-to medium-sized enhanced oil/gas recovery projects [53][54][55][56] such as Farnsworth field 57 in Texas, Ketzin 58 in Germany, and other fields 59 from around the world.…”

The Performance of Polymer Flooding in Heterogeneous Type II Reservoirs—An Experimental and Field Investigation

“…At present, the fall in oil prices has contributed to the fact that many EOR projects are facing cancellation or delay, but the tertiary techniques including CO 2 -EOR for improving the production of partially depleted reservoirs is still an attractive option. A survey in 2014 showed that miscible CO 2 floods yielded 292,735 bbls per day, which accounted for 38% of oil production for EOR processes in the USA [5][6][7][8][9][10]. The EOR potential evaluation, which assessed more than 200 onshore oilfields of 17 different worldwide oil reserved districts, indicates that China has great EOR potential [11].…”

Simulation and 4D seismic studies of pressure management and CO2 plume control by means of brine extraction and monitoring at the Devine Test Site, South Texas, USA

“…Therefore, monitoring and controlling pressure build‐up are crucially important for environmentally safe and efficient implementation of GCS projects . Furthermore, in CO 2 EOR and storage processes, it is important to monitor reservoir pressure to operate within miscibility for avoiding excessive gas production and improving storage . The sensitivity analysis and Monte Carlo sampling results illustrated that porosity, reservoir thickness, and permeability are the key parameters to control CO 2 /water injection and oil production rates in an active CO 2 ‐EOR field …”

“…12 Furthermore, in CO 2 EOR and storage processes, it is important to monitor reservoir pressure to operate within miscibility for avoiding excessive gas production and improving storage. [13][14][15] The sensitivity analysis and Monte Carlo sampling results illustrated that porosity, reservoir thickness, and permeability are the key parameters to control CO 2 /water injection and oil production rates in an active CO 2 -EOR field. 16,17 Extraction of native brine during GCS operations as a pressure management approach has been proposed and can increase storage capacity and effectively diminish the risk of environmental impacts.…”