Fifty-eight District Gas Reservoir Fracturing Technology Research

Block 58 of Xinjiang oilfield is located in the footwall of Karamay fault of northwestern margin of Zhunger Basin, west slope of Mahu sag and North Slope of Zhongguai bulge. The overall tectonic framework is southeast monocline. The main gas source of block 58 is Jia-Mu River Group which has the characters of low porosity and permeability. Furthermore, the drilling fluid has damaged the formation, so the natural production of the wells in block 58 is low. Hence, the hydraulic fracturing is the necessary stimulation measure. But there is large difficulty for fracturing in the district because of the complex lithology, abundant fractures and strong water sensitivity. Though the hydraulic fracturing has been applied successfully in block 58 through fracture height control technology, mini-fracturing test, liquid nitrogen flowback, proppant slug technology and so on, the stimulation effects after fracturing are bad because of the bad pertinence. Hereby it's necessary to do some researches into the systematic hydraulic fracturing technologies for black 58. Based on the actual situation of this area, this paper has done the research into the follow ways and gotten some conclusions:(1)Through the analysis of geologic characteristics and statistical datum of the fracturing before, find the key factors affecting the fracturing effects, and propose the fracturing technology countermeasures for block 58.(2)Combined with the permeability difference of gas formations, this paper simulated the effects of some factors to the stimulation effects, and optimized the fracture parameters. The key factor is permeability for fracture parameters design. When permeability is 0.5mDc-1.0mDc, the designed fracture length is 150-180m and the conductivity is 20-24Dc.cm.(3)Based on the situation of formation physical property and the demand of fracturing technology, this paper proposed the fracturing fluid characters of low damage, low friction and so on for this area, and formed the fracturing fluid system for block 58 through indoor experiments.(4)Analyzed the effecting factors of conductivity such as proppant embedding extend, assemblage of grain size, fracturing fluid residue and so on, and select the proppant suitable for block 58.(5)In view of the excessive extension of fracture height, the fracture height control technology and relevant technique have been studied, and selected the material of artificial interlayer.(6)Analyzed the mechanism of multiple fractures, evaluated the effects of fluid loss additives, and formed the systematic technology of decreasing fluid loss and preventing multiple fractures.(7)Analyzed the fracturing flowback technologies, done some research into the theories of fracturing fluid flowback, and optimized the coactions flowback procedure. The combined application of choke size optimization and fiber flowback technology is suitable for Block 58 to raise the fracturing fluid flowback efficiency.Through the research, the systematic fracturing technologies for Block 58 have been formed, which has significant guidance for the effective development of 2500×108 m3 prognostic reserves in 550Km2 of Jia-Mu River Group.