Abstract
Deep shale gas exploration and production in Fuling (Sichuan Basin, SW China) are confronted with hydraulic fracturing challenges owing to high stress, high fracture pressure, low pump rate and proppant concentration, as well as high closing pressure in deep strata. This study focused on the mechanical properties of shale core samples from Fuling through high-temperature triaxial rock mechanical tests and in-situ stress tests based on the Kessel effect of acoustic emission. Their mechanical property variations with depth were delineated using brittleness index calculated via simulating different depths and different confining pressures for the samples. The results showed that several parameters of deep shale reservoirs, i.e. brittleness index, fracture density, performance of self-propping, and flow conductivity, are lower than that of shale reservoirs with moderate burial depth. Thus, the current operating pressure in deep shale reservoir stimulation should be taken full advantage of, rather than channeling the focus on the propagation of fracture length. The objective is to increase the complexity of the near-hole fracture network for enhancing self-propping and flow conductivity of the fractures. This can be achieved by reducing the number of perforation clusters and cluster spacing, adopting variable-rate fracturing, decreasing proppant size, increasing sand volume, and optimizing the fracturing parameters. A field application showed that, compared with the neighboring wells, the test well had larger drainage area, doubling the gas yield.
论文详情