Specified staged acid fracturing of horizontal well for strong-heterogeneity carbonate gas reservoirs: A case study on the gas reservoir of the fourth member of Upper Sinian Dengying Formation in Gaoshiti-Moxi area of the central Sichuan Basin

The carbonate gas reservoir of the fourth Member of Upper Sinian Dengying Formation (hereinafter referred as “Deng 4 Member”) is characterized by deep burial, high temperature, low porosity, low permeability and strong heterogeneity in the Gaoshiti-Moxi area of the central Sichuan Basin. In order to effectively enhance the well productivity and gas reservoir development benefits, this paper defines the reservoir stimulation factor by comprehensively considering the drilling, logging and well type characteristic parameters, to carry out quantitative reservoir evaluation. Then, the refined segmentation method was developed by fully considering the reservoir stimulation factor, in-situ stress and borehole condition. In addition, the differential acid fracturing technology was prepared for different types of reservoirs. On this basis, the specified staged acid fracturing technology of horizontal well for strong-heterogeneity carbonate reservoirs was developed and then applied in the field. And the following research results were obtained. First, the reservoir stimulation factor (y) can be used to accurately evaluate the reservoir characteristics. The high quality reservoir has y ≥ 1.0, the moderate reservoir has 0.5 ≤ y