A New Fracturing Fluid for HP/HT Applications

Abstract

Abstract Hydraulic fracturing is used extensively to develop oil and gas wells in both high and low-permeability formations. Biopolymer-based fluids, including guar or guar derivatives, constitute the majority of polymers in fracturing fluids. These polymers cause formation damage, which is a serious problem on production enhancement. Therefore, the search for an alternative to guar is meaningful to the oil industry. In this paper, a novel viscosifier (V1) was developed to prepare fracturing fluids. The rheological properties and proppant suspending ability of V1-based fluid have been studied with the effects of viscosifier concentration, temperature, and salts. Formation damage of the new type of hydraulic fracturing fluid in sandstone has been evaluated and compared to guar, hydroxypropyl guar (HPG), and viscoelastic surfactant (VES) fluids. The effects of temperature, viscosifier type, concentration, and formation permeability were investigated. The regained permeability of sandstone cores (expressed as a percentage of the initial permeability) was used to quantify the damage degree in coreflood tests. The viscosity measurements have shown that V1-based fluids were stable up to 350°F with a high tolerance to KCl and CaCl2. Moreover, V1-based fluids had a good proppant suspending ability at 75 and 250°F, which out-performanced guar-based fluids. Coreflood tests were run using Berea and Bandera sandstone cores. As for V1 fluids, the regained permeabilities of the cores were 88% or higher of the initial permeabilities, suggesting that V1 caused a slight damage. However, guar and HPG fluids caused much more damage than V1 fluids under same conditions. The effects of temperature, viscosifier concentration, and formation type were different for guar-based fluids from V1 fluids. The external filter cake was formed when the V1 fluid was injected; however, no external filter cake was found for guar, HPG, or VES. The filter cake could be removed by injecting 5 wt% KCl brine in the opposite direction. It was the first time to use this new cellulosic viscosifier in hydraulic fracturing fluids. The new type of fracturing fluid has better thermal stability and proppant suspending ability than guar-based fluids under the same conditions. Moreover, high regained permeability of sandstone cores can be maintained when treated by the new fracturing fluid.