Study On The Structure And Sealing Of Fault Fractured Zone In Graben Basin

Fault sealing has always been one of the hot topics in petroleum geology of fault basins.Previous researchers have done a lot of static work in mudstone smearing and mudstone confrontation sealing.However,there is still a lack of in-depth dynamic and static analysis on the sealing of different types of fault fracture zones,which affects the understanding of fault sealing mechanism.The author describes the macroscopic and microscopic features through field fault investigation,core and thin section observation: Fault-induced cracks(high angles,low angles)are often multi-stage and multi-group development,partially filled with calcite and shale,resulting in reduced sealing;the section fillings are argillaceous,sandy,gray matter hybrids,containing fault breccia.The crack is not developed,resulting in enhanced sealing.The above results were calibrated on logging data and seismic profiles,and the relationship between the second-and fifth-order faults and the fracture zone was identified.It was also found that different types of faults developed different types of secondary faults.These secondary faults make faults.The structure of the fracture zone is complicated,and the sealing property of the fault fracture zone changes with its structure.For the first time,mercury intrusion analysis of different structural samples of fault fracture zone was carried out.It was found that the breakthrough pressure of the section filling was 14.5 MPa and the breakthrough pressure of the fracture zone was 0.15-0.17 MPa.The closed mode of fault fracture zone with different structures was established,and hydrothermal fluid was also found.The filling effect enhances the sealing ability of the fault fracture zone.The authors conducted four water injection simulation experiments on three structural fault fracture zones.It was found that the permeability of the fracture zone changed the most before and after water injection,the increase rate was above 600%,and the permeability change of the section fill was the smallest,with an increase rate of 366-466%.This indicates that the water-injection development has the greatest effect on the modification of the fracture zone,while the transformation effect on the fracture filler is minimal.The author calculated the heights of the second,fourth and fifth fault-sealed oil,natural gas and nitrogen in the study area.The oil sealing height was 411-1427 m,the natural gas sealing height was 295-1006 m,and the natural gas sealing height was 184-623 m.The closed height is large,and it generally does not break through the fault.It has reference significance for the double-drive experiment in the fault block oilfield.Through the calculation and evaluation of the displacement pressure of different levels of fault fracture zone in He 68-8 fault block and Xin 48 fault block,it is found that the displacement pressure of the filling section in the fault fracture zone is 3.5-27.6 MPa,which plays a major sealing role;The displacement pressure is 0.06-0.18 MPa,which basically does not seal.Selecting Four wells with different structural fault fracture zones and subjected to water-driven simulation experiments.The rate of change of the late flow pressure of the section fillings in the water injection was 32.4-42%,which was difficult to break through.The rate is at most around 35%.The authors carried out a calculation on the fault sealing ability of the 68-8 fault block and the Xin 48 fault block,and obtained the fault height of the fault for oil,natural gas and nitrogen.The fault height of the oil and gas fluid is different at different junction levels.The fault has a high sealing height for natural gas and nitrogen,up to 1006 m,which is difficult to break through the fault.