摘要：Shale reservoirs are widely developed with microfracture systems,which are the passages between reservoir pores and artificial fractures,and play an important role in shale gas storage and seepage.How to identify and characterize shale microfractures and predict the scale of microfracture development is of great significance for the efficient development of shale gas.In this paper,based on a systematic study of microfracture structure characteristics,we have established a method for predicting the scale of microfracture development in shale reservoirs.Microfracture structure characteristics were analyzed by high-power scanning electron microscope and high-pressure mercury intrusion tests.A quantitative parameter suitable for characterizing the scale of microfracture development is proposed,namely the microfracture pore volume.Furthermore,the control law of shale mineral composition and organic matter content on the development of microfractures was studied,and a mathematical model was used to establish a prediction model of shale microfracture development scale.Using this method,the development scale of microfractures in the Longmaxi Formation shale in the southern Sichuan Basin was predicted.The average predicted microfracture volume is 0.000543 mL/g.Clay minerals contribute the most to microfracture volumes,accounting for 70%; followed by organic matter,which accounts for 24%; and brittle minerals contribute the least,which accounts for 6%.There is a good match between the scale of shale microfractures predicted by the model and the porosity and permeability of the reservoir.
