Hydraulic, acid, and proppant-carrying acid fracturing stimulation of volcanic reservoirs in Sichuan Basin, China: an experimental study

Abstract

Nowadays, volcanic reservoirs show great development potential. However, the stimulation mechanism of volcanic reservoir is yet unclear. In this article, hydraulic fracturing, acid fracturing, and proppant-carrying acid fracturing of volcanic rock were analyzed by the laboratory tests. The average acid etching and proppant-embedded depths were assessed. The effect of different proppant sizes and acid types on fracture conductivity was studied. The results indicate that acid fracturing is failed to produce high-conductivity fractures. Large-sized proppants had larger embedded depths. For the hydraulic fracturing, the average depth of the 30/50 mesh proppant (5 kg/m2, 60 MPa) embedded in the volcanic rock is 33 μm, and the conductivity is 45.27 D·cm, which is 1.5 times that of the 40/70 mesh proppant. Embedded depth of proppant in the proppant-carrying acid fracturing (347 μm) was ten times larger than that in hydraulic fracturing (33 μm), but in terms of conductivity, hydraulic fracturing is only 20% better than proppant-carrying acid fracturing. This study is helpful to elucidate the mechanism of different stimulation methods and provide scientific means for the efficient development of volcanic reservoirs. Highlights In this article, experimental study is made on the stimulation mode of volcanic reservoir. There are few studies on volcanic. This study is helpful to elucidate the mechanism of different stimulation methods and provide scientific means for the efficient development of volcanic reservoirs. Based on the three-dimensional (3D) surface data of the rock, the average acid etching depth and the average embedding depth of proppant are accurately calculated by a new method. The experimental results can provide a good basis for the selection of volcanic reservoir stimulation. The embedded depth and etching depth have an intuitive image display.