Imbibition Characteristics and Its Influencing Factors of Shale Gas Reservoirs: A Case Study of the Longmaxi Shale in Southeast Chongqing.

For the purpose of estimating the influence of reservoir pore structure, composition, imbibition fluid type, and fluid pressure on imbibition fluid amount and imbibition rate, parallel subsamples of Longmaxi Shale in southeast Chongqing were selected to carry out imbibition experiments on five kinds of solutions under pressures of 10 and 0.1 MPa. The amount of imbibition fluid entering the reservoir sample is closely related to the porosity. With the increase in imbibition time, the saturation of imbibition fluid in large pores first increases rapidly, then increases slowly, and finally tends to stabilize. The imbibition fluid amounts decrease with the increase in clay and carbonate mineral contents and increase with the increase of felsic mineral content. The trend lines of imbibition saturation in micro, medium, and macropores of the same sample with imbibition time under the five types of imbibition solutions are the same or similar. The rate and amount of imbibition fluid have little correlation with the type of imbibition solution. The higher the fluid pressure, the faster the imbibition fluid enters the sample and the larger the amount of imbibition fluid.