Development of a Smart Fracturing Fluid for Tight and Unconventional Reservoirs

Abstract

Abstract Massive hydraulic fracturing is the only method to have economic production from unconventional resources (i.e. tight sandstone and shale gas reservoirs, etc.). Tight permeability reservoirs represent around 60% of global unconventional resources, they have large quantities of hydrocarbon, and with their impaired permeabilities, hydraulic fracturing is the most promising technique dealing with those types of reservoirs. A typical fracturing fluid usually consists of a cross-linked gel system, buffer, clay and gel stabilizers, biocide, and a breaker among many other constituents, all to prevent damage resulting from such operations, or better yet, enhancing the formation beyond the aim of a fracturing operation. This paper introduces a new zero leak-off, smart fracturing fluid system for tight formations and conventional resources as well. The fluid system consists of GLDA chelating agent that has the abilities of a cross-linker, breaker, biocide, clay stabilizer, replacing those constituents in one simple fluid, GLDA is also a low IFT fluid which will reduce the IFT eliminating the water blockage problems due to the capillarity effect in tight reservoirs. It is also stable in high temperature reservoirs (up to 300°F), environmentally friendly and readily biodegradable. The effect of temperature, pH, shear rate, polymer concentration and GLDA concentration on the rheological properties of the new fluid system has been studied, as well as the thickening-breaking time and efficiency, thermal stability of the developed fluid system. The new fracturing fluid formulation can withstand up to 200°F of formation temperature and stable for about 6 hours under high shearing rates (511s−1), with polymer concentration ranging from 20 to 70 pptg with the optimum being 45 pptg at pH 12, the viscosity building and breaking time can be controlled by the concentrations of the constituents. Coreflooding experiments were conducted using Scioto and Berea sandstone cores to evaluate the effect of the developed fluid on the core permeability and to investigate the zero leak-off property. The flooding experiments were in conformance with the rheological properties of the developed fluid regarding the thickening and breaking time as well as yielding high return permeability (85-89%).