Large-Scale High-Throughput Sensitivity Analysis of CO2 MMP to Optimize Gas Injection EOR Processes

Abstract

Abstract Performance of CO2 injection relies on accurate CO2 MMP/miscibility data at reservoir conditions. The CO2 stream typically contains gas impurities, and in most cases CO2 is combined with recycled gasses, which in either case the MMP changes – imposing additional uncertainties to deviate from expected CO2-MMP. Slim-tube is the most reliable tool; however, it is very time- and capital-intensive, making it impossible to provide high-throughput data to assess the impact of other gasses. Throughout a case study, we present a very efficient microfluidic platform to measure high-quality MMP data of CO2 with various impurities significantly faster and easier. In this work, a microfluidic platform was designed and used to determine the MMP/miscibility condition of CO2 in pure state and with several impurities (i.e., hydrocarbon mixtures, CH4, H2S, H2, N2, Ar) for an EOR operation in a depleted reservoir. 18 miscibility tests were conducted over ∼4 weeks to provide detailed data on how the MMP or miscibility of CO2 changes due to gas impurities – possibly the largest and fastest empirical study of MMP sensitivity ever. A high-resolution fluorescence microscopy along with an automated image analysis algorithm were employed to assess the miscibility condition. The MMP of a few gasses were also measured using the slim-tube to verify the validity of the microfluidic measurements, showing a tight agreement between the data. The results have demonstrated a reliable, accurate, and quick method to conduct a thorough CO2-MMP sensitivity analysis for gas injection processes. While each impurity may have a clear impact on the MMP, either in an increasing or decreasing manner, the interconnection between multiple impurities is generally unknown and differs as a function of impurity composition and reservoir conditions. The outcome of this work, eventually, gave a roadmap to provide a boundary of a miscible zone, in which the level of impurities is acceptable and not adversely affecting miscibility performance of injection, and while beyond this boundary, the impurities may negatively impact the recovery from performance of gas injection by increasing the MMP above the current reservoir pressure. Given the very small volume of oil sample, easier operations, and faster run-time required for this microfluidic approach, the miscibility/MMP study of a testing oil with various gas compositions can be determined in days – not obtainable with the slim-tube approach. The microfluidic platform utilized here provides accurate and quick gas injection related miscibility information, that can potentially open a new opportunity to better develop the current resources, improve the production efficacy, and mitigate uncertainties associated with gas injection plannings and operations. The benefits can be further extended for facility design, regulatory requirements, land acquisition strategy, workflow modifications, and reserve estimates.