Experimental Evaluation of Using Treated Produced Water for IOR/EOR: A New Sustainability Frontier

Abstract

Abstract Huge volumes of produced water are being generated from oil & gas fields worldwide. If this produced water can be treated for reuse as low salinity injection water, it becomes a real game changer to promote sustainability in IOR/EOR projects. In this study, the low salinity treated produced water obtained from zero liquid discharge (ZLD) technology has been used to evaluate the potential of recycled produced water in polymer flooding, gel- and foam-based mobility control processes. Both static and dynamic tests were conducted at ambient and elevated temperatures using high salinity injection water (HSIW) and treated produced water (TPW). Rheometer was used to determine the viscosity characteristics of sulfonated polyacrylamide polymer solutions at 25oC and 75oC. Static glass bottles tests were conducted with gel solutions formulated using 3,000 ppm sulfonated polyacrylamide and 150 ppm Cr(III) crosslinker at 95oC to determine the gel strength. Foam half-life times were measured to assess the foam stability. Finally, a core flood was conducted to evaluate the incremental oil recovery potential of using treated produced water in polymer flooding. The results demonstrated that the polymer concentrations are reduced by about 8-times (from 2000 ppm to 250 ppm) to achieve the same viscosity in TPW as HSIW to significantly lower the polymer consumption requirements. The gelation times of the gel in HSIW was one to two hours, while that of the gel in TPW was one to two days. Such considerable elongation of gelation time obtained with treated produced water would favorably deliver the gel deep into reservoir to achieve more efficient conformance improvement. The foam generated using the treated produced water showed at least 10-times longer foam half-life than that produced using the high salinity injection water. The core flood results conducted using 250 ppm polymer in treated produced water showed about 18% total incremental oil recovery after high salinity water injection. These findings clearly demonstrate the promising potential of treated produced water in different IOR/EOR processes to lower chemical concentrations and achieve better mobility control/conformance improvement for higher oil recovery. This work, for the first time, evaluates the beneficial impact of treated produced water in different mobility control processes involving polymer, gels, and foams. The promising experimental results obtained suggest that the proposed method of using low salinity treated produced water not only increases oil recovery due to synergistic effects, but also establishes a new sustainability frontier in IOR/EOR projects due to produced water recycle/reuse.