Enhanced gelled hydrocarbon well treatment fluids

Abstract

Abstract Compared with water-based well treatment fluid systems, hydrocarbon-based fluids possess advantages such as better fluid compatibility and lower formation damage, especially in water-sensitive formations. Hydrocarbon-based fluids are therefore often used in oilfield operations including hydraulic fracturing, sand control, and coiled tubing cleanout. The metal-crosslinked, phosphate ester-based gelled hydrocarbon (or gelled oil) fluids have been the preferred choice among hydrocarbon-based fluids since they are cost effective, robust at elevated temperatures, and operationally simple as only a couple of fluid additives are involved. Functioning as the gelling agent in gelled oil fluids, phosphate ester could cause fouling in refinery equipment. It is therefore desirable to lower the dosage of the phosphate ester-based gelling agent as much as possible, but without adversely affecting the fluid performance. A number of materials have been identified that could enhance the gelled oil viscosity and stability, which in turn translates into the reduction of the phosphate ester needed in the gelled oil. Among these enhancing materials, a type of aluminum pillared montmorillonite clay (the additive) was found to enhance the gelled oil viscosity to the largest extent. In laboratory tests, 30 ppt (30 pounds per thousand gallons) of the additive increased the gelled oil viscosity by 84% (± 5%) at 250 °F when compared with the baseline gelled oil without the additive. With the additive dosage at 30 ppt, the amount of the phosphate ester in the gelled oil could be reduced by 25% without decreasing the fluid viscosity. The additive was successfully applied to the crude oil-based gelled fluid, resulting in multiple times of viscosity increase in the study. In addition to the gelled oil viscosity enhancement, the additive also increased the regained permeability in the coreflow tests to near 3 times.