Research on heterogeneous deflagration enhancement effects and key parameter optimization in methane in-situ deflagration fracturing
CAI Chengzheng
ZHAI Cheng
WANG Bo
SUN Weifu
CHI Huanpeng
LIU Ting
ZHU Zhengchao
WANG Yu
Abstract：Methane in-situ deflagration fracturing technology creates complex fracture networks through high-temperature,high-pressure shock waves from the ignition of a mixture of reser-voir-desorbed methane and combustion-assisting agent.To investigate the characteristics of non-uniform mixed methane deflagration within the wellbore,a three-dimensional model for confined non-uniform methane deflagration was established.This model,based on a pre-charged agent delivery method,couples the Arrhenius kinetics with the eddy dissipation con-cept.The pressure characteristics of the wellbore deflagration were examined.The effects of wellbore pressure,temperature,methane volume fraction,and ignition method on the defla-gration pressure were analyzed.The results show that pre-charged injection creates distinct methane concentration zones along the wellbore.Centered at the injection tool,symmetrical regions are formed:low-concentration weak deflagration zones(5％—14％),intense deflagra-tion zones(15％—55％),and high-concentration weak deflagration zones(55％—92％)are formed.Compared to homogeneous combustion condition,heterogeneous mixing increases peak pressure at the wellbore bottom while reducing shock pressure at the upper sealed section by 12％—15％,establishing an optimized fracturing safety window.Parametric analysis indi-cates that increasing the initial pressure from 5 MPa to 15 MPa raises the peak deflagration pressure by 39.3 MPa,although the pressure rise rate decays with increasing pressure.At a constant initial pressure,every 40 K temperature increase causes a 10.4％attenuation in peak pressure.Heterogeneous mixing lowers the optimal methane combustion volume fraction from 33.3％to 26.8％,considerably reducing sensitivity to the mixing ratio.High-temperature ig-nition increases the peak pressure in the upper wellbore by 30％and effectively eliminates igni-tion delay observed in spark ignition systems.The findings reveal the deflagration enhance-ment effect under non-uniform mixing conditions and provide a theoretical basis for field appli-cations.
Keywords：methanecombustion-assisting agent injectionnon-uniform deflagrationwellbore pressurefracturing
Publication Date：2025-09-30
Online Publishing Date：2025-10-31(First online date of this platform, not the publication date of the document)
Pages：14( 1082-1095 )