A Comparative Thermal IOR Simulation Study with Experimental Design for Optimal Future Performance of a Heterogeneous Light Oil Reservoir

Abstract

AbstractSteamflooding has been widely used to improve oil recovery in heavy and light oil reservoirs. It has proved its efficiency to thrive the oil displacement and enhance the sweep efficiency by changing the reservoir and fluid properties, especially in heterogeneous formation. The reservoir under study is the main pay/upper sandstone member in South Rumaila oil field located in Iraq. This field, with a 58-year production history, has 40 production wells and is surrounded by an infinite active edge water aquifer from the east and the west flanks. Since the east flank is much less effective than the west one, twenty injection wells have been drilled at the east flank over the last 35 years. The formation depth is 10350 ft. sub-sea with a maximum vertical oil column of 350 ft. The average bubble point pressure of 2660 psi and the average reservoir temperature is 210°F while oil density is 34°API. In this study, a comparative thermodynamic simulation study has been done in conjugation with experimental design to investigate the main factors controlling the Steamflooding feasibility in improve oil recovery and to determine the optimal future Steamflooding scenario that has the maximum cumulative oil Production in a future production period.Firstly, the thermodynamic reservoir simulator (CMG-STARS) has been applied to demonstrate the impact of steam flooding to enhance the sweep efficiency through this heterogeneous reservoir. A full factorial approach considering full interaction terms has been adopted to determine the optimal Steamflooding scenario considering four main factors to be changed in two-levels. The response in this approach is the cumulative oil production in twelve future production years. The factors are steam quality, steam injection rate, number of steam injection wells, and the steam temperature. For two levels of four factors in full factorial design, sixteen observations have been done according to the (2^k factorial design). The entire analysis of the current designed experiments have been performed by R statistical software packages. The regression model has been tested by ANOVA table, p-value, R Squared & R adjusted, and basic diagnostic plots and it has shown reliable evaluation. The results have shown that the steam quality, injection rate, and no. of wells have the most influence factor on the cumulative oil production in addition to some interaction rate that have no temperature. There is very limited effect of the temperature.Among these runs, the optimal scenario, which has distinct target, has low levels of steam quality, flow rate, steam injectors, and temperature. The rationale behind these results is that the reservoir under study is light oil and has high heterogeneity at the east flank that lead to high steam distortion and spread. The optimal scenario has been compared with the base case without injection and has distinct different in cumulative oil production.