Experimental Study On Stress Sensitivity Of Mahu Conglomerate Tight Reservoir And The Influence Of Gravel

Stress sensitivity has an important influence on oil and gas flow.The conglomerate tight reservoir in Mahu is a conglomerate reservoir with deep burial,huge reserves,strong heterogeneity,and difficult development.Its stress sensitivity is different from that of a typical tight reservoir.It is of great significance to study the stress sensitivity of conglomerate reservoir and explore the influence of gravel for understanding the characteristics of Mahu conglomerate reservoir and improving the development effect of Mahu conglomerate reservoir.Three kinds of displacement media are selected to carry out permeability stress sensitivity experiments on conglomerate samples of two scales cored from Baikouquan formation of Mahu conglomerate reservoir,.The influencing factors and changing rules of stress sensitivity of conglomerate reservoir are analyzed.The influence of gravel content on stress sensitivity is emphatically analyzed.The stress sensitivity is evaluated by logarithmic model.Combined with the results of water sensitive experiment,CST experiment,mineral composition analysis,scanning electron microscope and numerical simulation,the Mahu conglomerate reservoir stress sensitive characteristics,control factors and the effect on production are obtained.The experimental results show that Mahu conglomerate reservoir has strong stress sensitivity and is greatly influenced by gravel content.The main influence factors includes the size and content of gravel,mechanical properties of gravel and matrix,types of cemented minerals and cementation strength.With the difference of gravel content,conglomerate can be divided into two types: matrix support and gravel particle support.The stress sensitivity of matrix support conglomerate is stronger,which is due to the permeability mainly provided by the matrix and the matrix stress is different under the two support conditions.The stress sensitivity curve of liquid displacement stress measurement shows in two groups: matrix control and particle control,and the irreversible damage degree of permeability is higher for matrix control group.Under the action of stress,the contact stress concentration of gravel particles can induce microcracks around the gravel edge,increase the permeability and reduce the permeability hysteresis effect.For conglomerate samples with artificial fractures,the presence of gravel increases the fracture tortuosity and the roughness of fracture surface,and reduces the stress sensitivity of reservoir.This study provides a reference for the study of stress sensitivity and production of conglomerate reservoir.