Experimental Study On The Change Rule Of Multilayer Combined-production Wellhead In Coal Measure Gas Reservoir

The gas reservoir has many thin upper layers in the vertical direction with large original gas content and low stratified production yield.The multilayer combined-production with the wellbore is often adopted for production,which can increase the production per well and reduce the development cost.However,due to the difference of gas production rate and pressure in the reservoir,the gas production rate loss and even reservoir damage are caused by the interlayer interference.At present,the research of experts and scholars on the combined-production of gas reservoir is mainly focused on the physical parameters of the production layer,the replacement time of co-production and the tube flow and pressure drop in the wellbore.There are few studies on the change rule of gas production during stable production period after interlayer interference.In this paper,the influence of the gas production rate and the pressure of each production layer on the gas production rate of coalbed production in gas reservoirs after interlayer interference is studied as follows: Firstly,the physical model of gas reservoir multilayer combined-production is established,and the formula of multilayer gas production rate in gas reservoir is derived;Then,according to the physical model,the simulation experiments of single-layer,double-layer and three-layer combined-production in gas reservoir are carried out,and the gas production rate,pressure and wellhead gas production rate of each production layer are measured;Finally,the value range of the formula coefficient of multilayer combined-production gas production rate is determined by using the experimental data fitting.This paper mainly made the following three achievements:(1)Established a set of physical simulation model and experimental method of multilayer combined-production of gas reservoir;(2)The formula of multilayer combined-production gas production rate was established,and the value range of undetermined coefficient was determined;(3)The law of multilayer combined-production and development of gas reservoir is revealed,and the conditions of combined-production and development are defined,which lays a theoretical foundation for multilayer combined-production and development of gas reservoir.