This paper is the result of oil and gas exploration engineering.

Objective The second member of Xujiahe formation of the HC area in the Sichuan Basin has great potential for exploration and development, but it is a typical low-porosity and low-permeability tight gas reservoir, which requires in-situ stress refined evaluation to recommend the optimal selection of engineering sweet spots for later vertical fracturing and plane fracturing to increase production.

Methods Based on experimental test analysis such as 25 groups of acoustic emission and 13 groups of differential strain, combined with hydraulic fracturing, conventional and special logging data, we analyze the applicability of different experimental test methods in tight sandstone reservoirs by performing a fine-scale evaluation of in-situ stress and identified layers and sweet spots conducive to engineering modifications.

Results The results of the experimental tests of the second member of Xujiahe formation in the HC area showed that the maximum horizontal principal stress values ranged from 50.77 to 75.65 MPa, with a mean value of 59.71 MPa; the minimum horizontal principal stress values ranged from 45.37 to 54.31 MPa, with a mean value of 49.31 MPa; and the vertical stress values ranged from 48.11 to 65.62 MPa, with a mean value of 56.53 MPa. The simulation results show that the smaller the thickness of the stress barrier within the reservoir and the differential coefficient of in-situ stress in both directions, the more favorable the fracture modification. The comparison of the three-dimensional stress relationships between the minor layers indicates that the second member of Xujiahe Formation is in a strike-slip stress state. The dense sandstone in the second member of the Xujiahe Formation is more homogeneous, the acoustic emission test results are more inaccurate. The results of the differential strain test are in better agreement with the results of the in-situ stress magnitude interpretation, making the test method more suitable for more homogeneous sandstone formations.

Conclusions In combination with the magnitude of in-situ stress, it is recommended vertically that the more favorable combination of compartments, upper middle of the second subsection of Xu-Ⅱ, be selected as the target layer for fracturing. To achieve a better volume fracturing network, it is recommended to avoid areas near faults with a large differential coefficient of two-dimensional stress. The area of HC102-HC111 well in the central part of the HC area, where high-quality reservoirs are developed and two-dimensional stress difference factor is relatively small, should be selected.