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Bottom-like flowing pressure (BHFP) prediction for multi-stage fractured horizontal shale gas with constant rate production is a key problem of stable production period estimation. Based on the transient linear flow theory of multi-stage fractured horizontal shale gas, the rate-time superposition function (Qg・t0.5)sup is proposed, a type curve identification charts of pseudopressure difference [m(pi)-m(pwf)]-rate-time superposition function (Qg・t0.5)sup is established, a parameter group of m which could reflect reservoir properties and fractured effect is determined, an BHFP prediction analytical solution function for constant rate production shale gas well is constructed. This method is applied in constant rate production and variable rate production shale gas wells, the results show that there is an excellent coincidence rate between predicted BHFP and monitored BHFP, which is above 95%, and the forecasting precision of stable production period is above 90%. This BHFP prediction method has an important guiding significance for stable production period prediction, rational proration of multi-stage fractured horizontal shale gas well with constant rate production. [ABSTRACT FROM AUTHOR]

Gas content is a key parameter for shale reserves estimation，production prediction and gas rate decline analysis. The storage mechanisms in shale is contained free and adsorption，and there are many different gas content testing methods such as gravimetric isotherm method，volume isotherm method and traditional testing method in field. In this study，a new shale gas content lab testing method is proposed based on measuring the gas volume changes during shale gas desorption. In this new method，cylindrical shale cores are used for simulating the influences of temperature，pressure，moisture content，real pore structure on total gas content，negative adsorption anomalies are eliminated by using this method. The experimental results revealed that adsorption gas content increased with pressure and the volume of adsorption gas content is at equilibrium and does not increase while the pressure is up to 12MPa. There is a positive relationship between adsorption gas content and TOC，and a negative relationship between adsorption gas content and temperature and moisture content. Adsorption of methane is higher than the nitrogen adsorption in shale. At a temperature of 20℃，under pressure of 30MPa，the adsorption gas content of Longmaxi shale in Jiaoshiba is 1.8-3.1m3/t and total gas content is 5.1-6.5m3/t，and about 40% of the total volume is adsorbed gas. [ABSTRACT FROM AUTHOR]