Numerical simulation of multistage deflagration fracturing and composite fracturing
To improve the efficiency of shale gas development,we conduct a study on fracture propagation during deflagration fracturing in shale gas reservoirs.Using the continuous-discontinuous method,we develop a deflagration fracture propagation model by integrating the fracture seepage model and the explosion source model.An evaluation system of deflagration fracturing performance is constructed with fracture range and fracture degree as evaluation indexes.Based on the established deflagration fracture propagation model,the single and multiple deflagration fracture propagation simulations are carried out,and the transformation effect under the combined fracturing is explored.The results indicate that deflagration fracturing can break through the stress concentration at the bottom of the well,forming initial radial fractures along the well circumference under the action of stress impact,followed by a significant increase in fracture length under the drive of high-pressure explosive gas.Compared with the single stage pulse,the fracture degree and fracture range under multistage blasting pulse(tertiary)are greatly improved,i.e.,the fracture degree is increased by 14.5%,and the fracture length is increased over 10.7%.Multiple fractures can be formed when the in-situ stress difference is 10 MPa by the composite fracturing process.The results can provide guidance for the development of shale gas reservoirs.
oil and gas field developmentshale gasdeflagration fracturingcomposite fracturingcontinuous-discontinuous methodnumerical simulation
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