An Integrated Variable Viscosity Acidizing and Fracturing Dual-Use System

Abstract

Abstract At present, carbonate reservoirs are becoming more and more complex, and multi-stage alternating injection acidification and acid fracturing process is required. Therefore, we have developed an integrated variable viscosity thickener based on a copolymer of a series of designed functional monomers and acrylamide. With this thickener, six liquid systems including slick water, linear glue, glue liquid, drag-reducing acid, gelling acid, and high-viscosity gelling acid could be prepared online in one dose. The viscosity of fracturing fluid could reach 195 mPa·s at a concentration of 6.0 wt% without any cross-linking agent. At the same concentration, the viscosity of the acidizing fluid was 150 mPa·s, with only a 23% decrease in viscosity compared to the fracturing fluid. And by changing the length hydrophobic chain, the thickening time in hydrochloric acid could reach 2 to 8min adjustable. Both fracturing fluid and acid fluids showed a good temperature resistance and shear resistance. Under high temperature and high-speed shear conditions, the viscosity retention rate was above 65%. And the lower reaction level of variable viscous acid indicated that the liquid performance was more stable when reacting in the formation. In a word, the suspension-type thickener could prepare six types of fluids with one agent with convenient construction, high time efficiency, and high temperature resistance and superior retardation performance, which could meet the demand of complex and variable fracturing and acidizing transformation process of deep and ultra-deep carbonate reservoirs in real time.