Influence Of Pore Networks On Spontaneous Imbibition In Shale And Related Application

Shale plays has relatively low permeability and connectivity.Hydraulic fracturing is commonly used to enhance shale gas production.The influence of large volume of pumped water remained in formation is still in debate.Shale has abundant micro-nano pore networks,which will lead strong imbibition effect.These special networks make the diffuse ability in shale stronger than normal ones.The diffuse ability is influenced by many parameters and it is not widely researched.In this work,the influence of pore networks on spontaneous imbibition is focused.Firstly,an asymmetric branch-like structure is established to represent the basic structure of pore networks.Additionally,fractal pore structure network is developed.Within these structures,some newly established mathematical imbibition models are used to examine factors,such as porosity,reservoir wettability,viscosity of fracturing fluid,surface tension,pore-throat tortuosity,and pore size distribution on the spontaneous imbibition process.And dimension less diffuse ability is expressed based on pore structure parameters.Secondly,some imbibition experimental methods are used to discuss imbibition features of Baojing shale samples.The imbibition speed and imbibition index are developed to present the diffuse ability and connectivity of pore networks based on imbibition curve.Some comparisons with other samples are made.Finally,by the analysis of nano-CT images,the pore structures are rebuilt and pore networks are extracted to discuss the imbibition features of shales and other samples.The models and experiments built in this work are relatively useful to analysis the influence of pore networks on spontaneous imbibition process.Some abundant micro-nano pore networks may give shale stronger diffuse ability and water-unblock potential for fracturing fluids.These features are helpful to diffuse the blocked water in main flowing pass for shale gas.Compared with other core samples,Baojing shale sample has some imbibition ability,but not very strong,which means some part of injected fracturing fluids can be absorbed in matrix.This work is helpful to investigate the interaction of fracturing fluid and shale reservoir.