Abstract

When a high temperature deep well carbonate reservoir is stimulated with conventional acid fluid, some unfavorable behaviors often occur, such as high acid-rock reaction rate, short effective reaction distance of live acid, failure of acid etching in the acid fracture front, and serious corrosion to downhole string. This paper presents a new acid fracturing fluid system. This system consists of the acid-generator SGA-E, the optimized polymeric thickener CHJ-1 and the cross-linking agent SJL-1. With the performance of water-based fracturing fluid, this system can be used as prepad during acid fracturing. Moreover, this system has weak or no acidity at low temperature and slow release of H+at high temperature (120-150°C) in fractures, Its ultimate effective acid concentration is about 8% which is capable of effective acid etching. During pumping, this system shows less corrosion to the string, so few corrosion inhibitor is required. This new acid fracturing fluid system can achieve effective acid etching of a whole fracture, so as to increase the stimulated reservoir volume.

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