Impact of gas desorption on production behavior of shale gas.

摘要

Ultimate recovery in an unconventional gas reservoirs is typically less than conventional gas reservoirs because the adsorbed gas is not consistently taken into consideration. As a result, it is important to study the effect of desorption on production behavior to improve the recovery of hydraulically fractured horizontal wells in shale gas reservoirs.;This dissertation summarizes the results of modeling study to evaluate the impact of gas desorption on production behavior of multi-fracture horizontal well completed in a shale formation. A numerical simulator was utilized to model a multi-layer dual porosity shale gas reservoir. The impact of the formation properties, hydraulic fracture characteristics, and desorption characteristics on adsorbed gas recovery were studied and analyzed. These parameters included matrix and fissure porosity and permeability as well as langmuir concentration and diffusivity coefficient. Subsequently, the impact of gas desorption on flow regimes associated with hydraulically fractured horizontal wells and production decline behavior were studied.;Based on the result of this study, the number hydraulic fracture and the fissure permeability were found to have significant impact on the recovery of adsorbed gas in the shale gas reservoirs. In addition, the average recovery of adsorbed gas is about 25%. Furthermore, for 13 fracture stages, the additional gas can be recovered due to desorption is 18%. Therefore, adsorption should be taken into consideration for more reliable recovery estimation. Moreover, gas desorption causes linear and interference flow periods to appear longer and masks the boundary effects.