Energy & Fuels, Vol.33, No.8, 6904-6920, 2019
Surfactant-Assisted Spontaneous Imbibition to Improve Oil Recovery on the Eagle Ford and Wolfcamp Shale Oil Reservoir: Laboratory to Field Analysis
Abundant resources being left behind at the end of the short production life of an unconventional liquid-rich reservoir (ULR) well has inspired many to investigate methods to improve the recovery. One eminent method is through the addition of surfactant during the completion stage of the well. Through numerous published laboratory studies, it can be concluded that this process possesses a promising potential in improving overall well productivity. Several field-scale results gathered from public data sources also confirmed the laboratory-scale study by correlating the effect of surfactants to the improvement of the estimated ultimate recovery (EUR). However, the absence of independency on those field-scale results often casts doubt on the actual efficacy of the method. The lack of field-scale information in the realm of scientific publications contributes to the limited understanding of surfactant application. This study is to fulfill the obvious need of field-scale studies on the application of surfactant by surfactant-assisted spontaneous imbibition (SASI) during completion of wells in the ULR. Numerical-based upscaling through modification of capillary pressure and relative permeability of the laboratory-scale experimental results provides a view on the effectiveness of this method on the field scale. Comparison is performed between the initial oil production rate, cumulative oil, and cumulative water production. A complete set of the laboratory-scale experimental studies is also included and consists of interfacial tension, contact angle, zeta potential, adsorption isotherm, and CT-assisted spontaneous imbibition. CT-scan technology is incorporated as well in the construction of a core-scale numerical grid model to model the heterogeneity of the shale core plug sample. In the end, sensitivity analysis is also executed to analyze the effect of different reservoir properties and SASI-related completion parameters on the efficiency of the method. There are four main takeaways of this comprehensive study. First, a complete and robust workflow on investigating SASI performance is compiled and tested. This workflow consists of a laboratory-scale experimental study as well as a numerical-based field-scale investigation and can be applied to different shale reservoirs as well as different surfactants. Second, three different surfactants are tested in this study with significant well production improvement observed, thus confirming the increment of production observed in the laboratory-scale study. These results are also compared to other lab-scale experiments conducted with different ULR samples to verify and strengthen the effectiveness of SASI. Third, sensitivity analysis shows that SASI improves well productivity for a variety of fracture and matrix properties. We observed a range of matrix and fracture properties where SASI performs optimally, and last, an independent field data study is provided. This actual case study is done carefully to isolate the effect of SASI on the well production. An agreement on the range of production improvement by SASI between the field data analysis and the numerical field-scale model is also observed.