Laboratory Development and Successful Field Application of a Conformance Polymer System for Low-, Medium-, and High-Temperature Applications

Abstract

Abstract This paper presents the laboratory development of an organically crosslinked polymer (OCP) system with a wide temperature range of execution (60 to 350°F). The OCP system is targeted to address conformance problems (water and gas shutoff) to ultimately improve hydrocarbon recovery. This paper presents an overview of case histories in which the OCP system was implemented in various regions of the world in onshore and offshore hydrocarbon-producing wells. The OCP system has been successfully applied to sandstone, carbonate, and shale formations needing a conformance treatment. The OCP system has proven to be resistant to acid and stable in CO2 and H2S environments. In addition, the activation time and gel strength of the system is not affected by lithology, formation fluids, or heavy metals. The OCP system is acceptable to be used in some areas of the North Sea (including UK and Netherlands). Recently, a base polymer (for low temperatures) and a retarder (for high temperatures) have been introduced to the system to allow a wider temperature range of applicability without compromising its effectiveness or thermal stability. With the new base polymer, reasonable gelation times (~4 to 6 hours) can be achieved at 60°F with low crosslinker loadings. In addition, the new retarder allows reasonable placement times up to 350°F, without the need of cooling down the formation to obtain enough pumping time. Neither the new base polymer nor the retarder are detrimental to the thermal stability or gel strength of the system. To date, more than 600 jobs have been performed with the OCP system around the world to address conformance problems, such as water coning/cresting, high-permeability streaks, gravel-pack isolation, fracture shutoff, and/or casing leak repair. Because of the capability of the OCP system to withstand pressure, workover operations have been successfully performed in previously treated wells, including acid stimulation, sand control, and frac-pack treatments, among others. Case histories are presented for onshore and offshore applications.