Abstract
Deep volcanic reservoir in Xinjiang Zhungeer basin is buried over 4000m, the elastic modulus of reservoir rocks is high, hence it is difficult to initiate hydraulic fracture during fracturing operation; fracturing fluid filtration is serious and hard to be controlled due to the massive natural fractures in reservoir. Because of the serious heterogeneity along both horizontal and vertical direction, the optimum targets of design fracturing for different well layers are not the same. 4 out of 12 fracturing wells have not achieved the target amount of proppant. Ultimately, fracturing success rate is low and the production increase after fracturing shows a big difference among different wells. In order to improve the success rate and efficiency of deep volcanic reservoir fracturing, based on the analysis of the difficulties in previous fracturing operation, combined with the geological characteristics of reservoir, we optimized the key engineering parameters of deep volcanic rock fracturing, including perforation parameters, filtration parameters, fracture parameters and operation parameters. Results of fracturing design optimization bear an important guiding significance for improving the fracturing success rate and efficiency of deep volcanic reservoir in Zhungeer basin, Xinjiang province.
Highlights
Deep volcanic reservoir is characterized by great burial depth and low matrix permeability
Due to the volcanic reservoir develop a large number of natural fractures and dissolved pores, which has serious impact on the opening and expansion of hydraulic fractures, the existence and extension of multiple fractures limit the width of the opening hydraulic fracture [2,3,4,5], raised the risk of sand plug[6]
Fluid filtration is mainly controlled by natural fracture, and the natural fractures network will change the propagating direction of hydraulic fractures, which will distort and intersect with each other, and turn into artificial fractures network [7,8,9,10,11]
Summary
Deep volcanic reservoir is characterized by great burial depth and low matrix permeability. According to the characteristics of volcanic rock reservoir, Vermani et al proposed the slug sand schedule, small diameter proppant, high viscosity fracturing fluid and other measures to improve the operation success rate of volcanic rocks fracturing [13]. Buried depth of volcanic reservoir leads to the high closure stress, and makes the proppant vulnerable under the. According to the indoor rock mechanics experiments, the elastic modulus of volcanic rock in Jinlong 2 reservoir is 30152MPa, poisson ratio is 0.186, the direction of maximum principal stress is 118°, with value of 82MPa, the minimum principal stress is 68MPa. In view of the geological characteristics of deep volcanic reservoir in the Zhungeer basin, the key fracturing parameters are optimized based on the analysis of the previous fracturing operation
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