基于分布式光纤传感的毕节试验区煤层气井产出剖面评价OA

Coalbed methane serves as a vital component of clean energy,and its efficient development encounters technical bottlenecks in the dynamic monitoring of production profiles.To tackle the difficulties in monitoring the production profiles during commingled drainage of low-pressure,thin-interbedded coalbed methane wells,as well as the insufficient accuracy of conventional methods and restricted instrument running,this paper takes well A1 in the Bijie pilot area of Guizhou province as the research object and proposes an evaluation method for coalbed methane well production profiles based on distributed optical fiber sensing.The study adopts a fixed-point optical fiber binding process outside the tubing to realize synchronous acquisition of full-wellbore temperature and acoustic signals under multiple working systems in well A1.A production profile interpretation framework is established based on the Ramey wellbore heat exchange model,Joule-Thomson effect and two-phase flow drift model.A coupled interpretation strategy is put forward,which uses the steady-state frequency band energy(FBE)analysis of distributed acoustic sensing(DAS)to constrain the temperature field inversion of distributed temperature sensing(DTS).Specifically,the steady-state frequency band energy of DAS in characteristic frequency bands is used to extract the water production rate information of each layer,so as to constrain the gas-liquid ratio parameters in the DTS temperature forward model.This strategy solves the strong multi-solution problem of traditional single DTS interpretation under gas-liquid two-phase flow conditions and realizes the fine quantitative allocation of gas and water production rates of each coal seam.Monitoring data clearly indicate the main gas-producing and water-producing layers,and the optical fiber interpretation results show good consistency with open-hole logging conclusions and fracturing operation parameters,which verifies the reliability of optical fiber monitoring in coalbed methane wells.This study provides a reliable dynamic monitoring method for the development of low-pressure,thin-interbedded coalbed methane and offers scientific guidance for the optimization and adjustment of production technologies in the process of coalbed methane development.