An Effective Whole Fracture Acid Etching Technology for High Temperature Deep Carbonate Reservoir

Abstract

When high temperature and deep carbonate reservoirs are stimulated with conventional acid fracturing fluids, some unfavourable behaviors often occur, such as quick acid-rock reaction, serious damage to downhole string, failure of acid etching in a whole fracture using existing technology whether with prepad or acid system. This paper describes two kinds of new acid fracturing fluid systems which can achieve effective acid etching of a whole fracture, and provides associated fracturing processes. For these acid fracturing systems, SGA-E, an acid generator resistant to high-temperature and friendly to environment, is selected, and supporting high-temperature thickener and cross-linking agent have been developed. The non-crosslinked acid fracturing fluid system with degradable filtrate reducer is applied for tight and low-filtrate loss reservoirs; the cross-linking weak acidic fracturing fluid system stable at high temperature and shear force is applied for reservoirs with developed natural fractures and high filtrate loss. These systems have the advantages of fracturing and acidizing fluids, suitable for reservoirs at 120-160 °C, and can work as prepad for creating fractures.