The Evaluation and Application of Engineering Sweet Spots in a Horizontal Well in the Fuling Shale Gas Reservoir

Due to the fact that shale gas reservoirs possess heterogeneity, sectional perforation and multi-stage fracturing in horizontal wells in the reservoir may generate very different effects. The engineering sweet spot parameter can affect the crack initiation, extension and reconstruction of hydraulic fractures. Accordingly, the parameter can be used to guide the sectional perforation of shale gas horizontal wells, which can be helpful in improving the reservoir and productivity. With the P-wave transit time and density logging data, the calculation model of S-wave transit time was established for the Fuling shale gas reservoir, and the calculation method of determining the engineering sweet spot was defined for the Fuling shale gas reservoir based on the experimental results of rock mechanics. Combined with the test results for 73 gas production sections in six wells, including Well Jiaoye 7-1HF, the evaluation indicators for the engineering sweet spot in the Fuling shale gas reservoir were summarized, namely, that the horizontal stress difference was less than 8MPa, and the brittleness index ranged from 45% to 50%. Optimum design for fracturing the Well Jiaoye 30-1HF was conducted based on the engineering sweet spot data, and then total liquid volume and total sand content were matched well with stable operation pressure. Post-frac open flow was 88.54×104 m3/d, and better stimulation results were achieved.