The Fracturing Effect Evaluation In Multiple Fractured Horizontal Wells: Research And Application

Multiple fractured horizontal well (MFHW) is a key technology to stimulate reservoirs and enhance oil and gas recovery, which plays a significant role in large-scale development of tight gas, shale gas, tight oil and other unconventional oil/gas resources. Currently, horizontal well staged fracturing has gained remarkable progress in instrument manufacture, liquid exploit as well as construction organization, but how to evaluate the hydraulic fracture condition, post-fracturing production and other fracture evaluation techniques is in urgent need. This paper focused on the fracture simulation, production forecast and micro-seismic monitoring technology of multiple fractured horizontal wells to conduct a deep study, then formed a more practical and systematic evaluation method of horizontal wells, which improved the reliability of effect evaluation technology. Then a real case application was successfully implemented. Through the test of a block in Jilin Oilfield, the design level of horizontal well staged fracturing has been improved, providing important technical support for the development of low permeability oil/gas resources in China.The main research contents and innovative achievements are as follows:1.The mutual interference between hydraulic fractures and the impact of natural fractures have been considered in the establishment of the calculation model of fracture pressure in multistage horizontal wells which have multiple successive initial fracture points. Then the influence law of mechanic properties of rock, in-situ stress of reservoir, perforation intervals between clusters upon initial fracture pressure and its variation rule influenced by hydraulic fracture clusters has been obtained.2.Based on the boundary element method and fracture mechanics theory, a fracture propagation model of multiple fractured horizontal well coupled fluid and structure was created, the influence of fracture net pressure, fracture interval, reservoir stress difference and other factors upon propagation path and fracture size were researched. A numerical analysis of the effect of fracturing fluid viscosity, cluster interval design, construction flow rate, total fracturing fluid and other engineering parameters in horizontal well staged fracturing has been done to guide the field fracturing design.3.In the basis of Warren and Root’s model, the author combined complex potential theory, superposition principle and dual-medium gas reservoir seepage theory together to derive a productivity calculation model of multiple fractured horizontal wells, where the complex fracture geometry and mutual interference between hydraulic fractures were considered. Then the variables-separation method and Bessel function were applied to solve this model and a analytical solution was obtained. According to this model, the impact of fracture number, fracture length, fracture conductivity and fracture orientation upon productivity were obtained, which is applicable to guide the parameter optimization of multiple fractured horizontal wells.4.The spread path of micro-seismic released in fracture propagation was analyzed by using the ray tracing method, and its application in layered homogeneous model was discussed. Then the simulated annealing method was adopted to invert the hypo-center, so as to determine the source coordinate of initial fracture point, analyze the fracture propagation direction and choose a preferred algorithm model. Several trials have been done in propagation source of multiple fractures to ensure a high accuracy of the inversion of source coordinate.5.A real case application in a low permeability block of Jilin oilfield was implemented, where the adaptability evaluation of horizontal well staged fracturing and the optimization of fracturing parameters aimed at optimum effective fracture length were conducted. The design level of multiple fractured horizontal wells in Jilin oilfield has been improved to some degree through the field application.During the study period focusing on the theory and application of multiple fractured horizontal wells, the author published 2 papers on SCI,1 paper on El, and 1 patent has been authorized,2 progress rewards of provincial and ministerial in science and technology have been obtained.