Coalbed Methane Drainage Warning Parameter Study In Southern Qinshui Basin

In this paper, CBM geology, and numerical simulation are combined to research coalbedmethane enrichment regularity, characteristic of gas production wells curves, well productivitydifferences, wells dynamic recovery, well drainage factors, and gas warning parameters in thesouthern Qinshui basin coalbed methane field, which are based on plenty of CBM wells producedynamic monitoring data. The following conclusions:(1)southern Qinshui Basin CBM preserv-ation condition is better, coalbed methane enrichment type is constructed with groundwatercoupling control type.coalbed gas content is10-24m3/t,while gas saturation is60%-90%.coalreservoir permeability is higher, but the adsorption ability of CBM, CBM wells critical desorptionpressure and the critical desorption pressure and reservoir pressure ratio is high.(2) gas productioncurves of coalbed methane wells in southern Qinshui Basin reveals drop funnel formation andexpansion of the law of methane drainage and gas pressure.Gas production curves of coal bedmethane gas production wells showed the characteristics of earlier peak time and long duration andcoal gas well production can be basically stable at2000m3/d.(3) CBM well gas production type inthe southern Qinshui Basin is divided into five types such as smooth gas production type, steady lifting-type production, gas production declined sharply volatile type, the initial high yield andfluctuating late and low-yielding type.(4)fluctuation of the bottomhole pressure fluctuations andconcentration of coal bed methane drainage are made as early warning parameters. Bottomholepressure fluctuations warning indicators: bottomhole pressure fluctuation value is0.05MPa/d orless, which is less damage to the reservoir; bottomhole pressure fluctuations is0.05MPa/d-0.1MPa/d, have some damage to the reservoir; wells bottom pressure fluctuationexceeds0.1MPa/d, which is big damage to the reservoir. Warning indicators pulverized coalconcentration: concentration of pulverized coal in safety production wells should be less than1%;coal concentration production wells existing Card pump danger is1%to3%; and an increased riskof production wells pump block will arise when pulverized coal concentration is greater than3%.