Effects of Adsorption and Confinement on Shale Gas Production Behavior

Abstract

Abstract Shale gas becomes an important natural gas supplier in recent years. The technologies including horizontal wells and hydraulic fracturing drive the booming of shale gas industry. Gas in shale reservoirs is stored as free gas in both mineral pores and natural fractures, as well as absorbed gas on pores surface. The effect of gas adsorption is generally ignored in conventional reservoirs. However, the absorbed gas has to be taken into consideration for shale gas production because of its huge amount in nanoscale porous media. The smaller the pore throat radius, the more significant is the effect of confinement. Therefore, production behavior can be altered by the effects of adsorption and confinement in shale gas reservoirs. On the basis of Montney shale gas reservoir modeling, effects of adsorption and confinement on shale gas production behavior are investigated in this paper. Results show that total gas production increases with the consideration of adsorption and confinement effects. As gas density and viscosity decreases prior to condensation occur with the effect of confinement caused by nanoscale pore throat, incremental of density difference between free gas and absorbed gas will delay the production of absorbed gas. Moreover, the difference between the amount of free gas produced and absorbed gas produced become larger with the effect of confinement during reservoir depletion.