论煤层气有效开发双甜点评价特殊内涵OA

[Objective]In China,the exploitation of deep and shallow coalbed methane(CBM)still relies on the evalu-ation approach oriented to the geological-engineering dual sweet spots of unconventional hydrocarbons.However,exem-plary CBM production technologies delivered unsatisfactory performance in other blocks and failed to find wide applica-tion even in zones with overlapping geological and engineering sweet spots.This issue represents the principal theoretic-al and technical challenge confronting the comprehensive development of the CBM industry in China.[Methods]This study aims to elucidate the causes of this issue and provide corresponding solutions,as well as clarifying the conditions for the effective linkage between geological and engineering sweet spots.Based on the unique chain-like CBM mass transfer pattern consisting of desorption from pore walls,diffusion in matrix,seepage into cleats,and flow in fractures with high hydraulic conductivity,this study explored the coupling relationship between the fluid and solid mineral attrib-utes of CBM reservoirs.Then,based on the CBM flow rate from matrix to cleats,this study analyzed the conditions for the linkage between geological and engineering sweet spots and revealed the unique connotation of geological-engineer-ing dual sweet spot evaluation tailored to effective CBM exploitation.[Results and Conclusions]Different from other unconventional gas reservoirs,CBM reservoirs are characterized by distinct solid and fluid mineral attributes.The recov-erability assessment of fluid mineral resources necessitates the assessment of reservoir physical properties,while the re-serve recoverability of solid mineral resources should involve the physical properties of surrounding rocks.In the case where the CBM flow rate from matrix to cleats is inherently high or can be significantly enhanced using engineering measures,the fluid mineral attribute of CBM predominates.In this case,the high production of CBM wells can be achieved only when geological and engineering sweet spots overlap in space.Therefore,in addition to existing paramet-ers for geological-engineering dual sweet spot evaluation,the recoverability evaluation of CBM reservoirs should high-light the CBM flow rate from matrix to cleats.To investigate the geological sweet spots of CBM,the saturation and abundance indices of free gas in cleats should be supplemented.For the engineering sweet spot evaluation of CBM,greater emphasis should be placed on the coupling effect between coal seams and surrounding rocks' physical properties in the solid mineral attribute of CBM.