煤层气压裂井固相产出机理与防治技术研究进展OA

[Background]The effective coalbed methane(CBM)exploitation using hydraulic fracturing wells is severely constrained by two major solid-phase production issues:coal fines blockage and proppant flowback.The mechanisms behind both issues are associated with complex interplays between geological conditions and engineering disturbances.This study presents a systematic review of the current status of domestic and international research on the mechanisms of the solid-phase production,as well as relevant prevention and control methods.Furthermore,future research directions are proposed.[Advances]The solid-phase production in hydraulically fractured CBM wells essentially arises from flow-solid-chemical multi-field coupling processes under interplays between geological conditions and engineering disturb-ances.Specifically,coal fines generation is attributed to the synergistic effect between intrinsic factors(i.e.,coal proper-ties)and extrinsic factors(e.g.,coal seam abrasion by drilling tools,fracturing impact,and CBM production-induced pressure differences).The coal fines migration is jointly governed by the critical flow velocity,particle-size distribution,and fracture geometry,with coal fines undergoing a dynamic evolutionary process from banded to blocky morphologies.Coal fines blockage results from geometric straining(e.g.,the"one-sixth rule")and physicochemical adsorption within proppant packs.Additionally,proppant flowback occurs when the hydrodynamic drag force exceeds the particle reten-tion force and is comprehensively governed by the fracture closure pressure,the ratio of the fracture width to proppant particle diameter(i.e.,the w/d ratio,a ratio of greater than 3 leads to lower proppant stability),and fracturing fluid flow-back velocity.Regarding technologies for the prevention and control of solid-phase production,a multi-tiered technical framework has been developed,covering source control,process control,and end treatment.In this framework,the pre-ventive and control measures against coal fines blockage include coal surface modification using chemicals,proppant optimization,the application of fracturing fluid additives,and the fine-scale control of drilling and production paramet-ers.Meanwhile,primary preventive and control measures against proppant flowback include fracturing fluid infilling by fiber,proppant modification,and the optimization of fracturing parameters.[Prospects]There is an urgent need to ad-dress several critical challenges,including poorly understood microdynamic mechanisms underlying solid-phase produc-tion,a lack of mechanisms controlling coal-proppant-fracturing fluid multi-phase interfaces,and less complete geologic-al-engineering integrated technologies for the prevention and control of solid-phase production.Future research should focus on(1)the exploration of mechanisms behind coal fines migration and retention using multi-scale dynamic ima-ging combined with intelligent algorithms;(2)the R&D of coal rank-specific interfacial modifiers for coordinated mul-tiphase control;and(3)the construction of geology-engineering integrated intelligent prevention and control systems based on digital twin and real-time monitoring.These efforts will facilitate the shift from passive response to proactive control,thereby ensuring safe and efficient CBM production.