No.1 Drilling Engineering Company of CNPC Bohai Drilling Engineering Limited Company, BHDC, Dagang, Tianjin, 300280, China.
Chang 8 oil deposit, developed in Hohe and Jihe oil fields at the southern Yi-Shan Slop of Ordos Basin, is regarded as a kind of typical sand reservoir formation with super-low porosity, poor permeability, strong anisotropy as well as locally natural faults and fractures. The previous studies believed that matrix reservoir has a good permeability, whereas fracture reservoir has a reverse manner. In the past years, there have been fewer researches on studying matrix-fracture type oil reservoir; therefore, up to now, it has been still difficult to identify whether network hydraulic fracturing can be effectively exploited in low permeable matrix-fracture type reservoir. In this paper, the author tries to analyze the feasibility of network hydraulic fracturing application in Chang 8 oil deposit from aspects such as mineral component, rock brittleness index, and development status of natural fractures, ground stress, and net press during hydraulic fracturing. The statistical results indicate that the geological condition of the research object is confirmed to meet the standard of hydraulic fracturing with a quartz content of about 40.0% to 41.6%, a brittleness index of 42.6% to 54.6%, a high angle or bevel fracture with a fracture density of 0.03 to 2.6 crack per meter, a mean of 0.38 crack per meter of developed natural fracture and horizontal layers, and the difference of two principal horizontal stresses of 2.8 to 5.5 MPa. Therefore, a certain degree of complex fractures can be built by the methods of segmental perforation, interference between multiple clusters, and the increased net pressure. Finally, we concluded that it is an important treatment to effectively develop this type of oil reservoirs by network hydraulic fracture technology in horizontal wells.
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