| Author's Name: CUI Zhe, YANG Wei, WANG Qianyou, ZUO Rusi, CAI Jianfeng, CUI Zhengjie, XU Liang, LI Lan, GU Xiaomin |
| Based on the high pressure mercury-injection analysis, displacement pressure test and breakthrough pressure test of 6 groups of roof and floor samples from 6 outcrops, the sealing properties of the roof and floor of Wufeng Formation-Longmaxi Formation in Sichuan Basin and its surrounding areas and its influence on the shale gas differential enrichment are studied. The results show that: (1) The rocks of the roof and floor of Wufeng Formation-Longmaxi Formation are dense, showing the characteristics of low porosity and low permeability. (2) The displacement pressure of roof samples ranges from 11.027 MPa to 16.677 MPa, with an average of 13.637 MPa; most of the displacement pressures of floor samples range from 13.766 MPa to 13.798 MPa. (3) The breakthrough pressure of roof samples ranges from 5 to 33 MPa, and the difference in different areas is obvious; the floor breakthrough pressure ranges from 21 to 42 MPa, which is generally greater than that of the roof, showing good sealing property of the floor. (4) The displacement pressure and breakthrough pressure have good negative correlation with the porosity and permeability; shale gas content has a good positive correlation with micro sealing parameters of roof, and has a certain positive correlation with that of the floor. (5) Compared with the floor, the micro sealing ability of roof can more affect the vertical loss of shale gas, and the difference of micro sealing ability of roof leads to the shale gas differential enrichment in different areas. The evaluation index system of roof and floor sealing of three categories and nine parameters of Lower Paleozoic marine shale gas in the study area is preliminarily established, which can be used to make a more accurate and reasonable evaluation on the sealing of roof and floor. |
