Volume 51

Production Prediction and Optimization Combination in Multilayer Commingled CBM System in Eastern Yunnan and Western Guizhou Anna Dai, Zhiming Wang, Tianhao Huang, Xianlu Cai

Abstract

The coalbed methane (CBM) reservoirs in eastern Yunnan and western Guizhou have the characteristics of
multiple seams superposed, which are commonly exploited by multilayer commingled methods. It is observed that there is crossflow within the reservoir during the development, which impacts the production. To
accurately describe the fluid flow law of multilayer CBM co-production, according to the flow mechanism of
CBM in composite reservoirs, establish a multilayer combined fluid flow model including crossflow. A numerical simulator based on a fully implicit finite difference solution was developed to analyze the effect of
permeability ratio and interlayer pressure differences on production. The results indicate that the numerical
simulation results of the established model have a high compliance rate with the fitting results of the field
production data, which confirms the validity of the model production prediction in this paper; With the
increase of permeability ratio and interlayer pressure difference, the phenomenon of interlayer interference is
intensified, the single well production is low, and the degree of reservoir utilization is poor. Differences in the
above major influencing factors have resulted in interlayer conflicts and disturbances during combined
production. Therefore, the development of CBM reservoirs should select homogeneous multiple coal seams
under the same pressure system for co?production as far as possible. The research results provide a theoretical basis for the rational and efficient development of the CBM reservoir, realize quantitative evaluation of multilayered parameters, and have a certain guiding significance for CBM co-production of the reservoir.

Keywords coalbed methane, multilayer commingled production, production prediction, interlayer crossflow