Research On The Influence Of Pore Structure On The Electrical Resistivity In Carbonate Rocks

Carbonate reservoirs are widely distributed in the world and have large oil and gas reserves,which have very high exploitation value.Resistivity logging is one of the most important logging methods,which is widely used in oil and gas reservoir evaluation.Because the pore structure of carbonate reservoir is very complex,the interpretation of resistivity log data often appears deviation.At present,the influence of pore structure on resistivity of carbonate reservoir lacks quantitative characterization.Therefore,based on the preparation of artificial cores with specific pore structure,the effect of pore structure on resistivity of carbonate reservoir is studied experimentally.At the same time,numerical simulation is used to verify and improve the law of influence of resistivity of carbonate rock.Through literature research and experimental research,the preparation method of artificial core and the testing method of core rock physical parameters are optimized.By measuring the resistivity and porosity of artificial cores,the effects of porosity,size of dissolved cores,porosity of artificial cores with cracks,aspect ratio of cracks and dip angle of cracks on the resistivity of carbonate rocks are studied.The results show that the resistivity decreases with the increase of porosity of artificial cores with dissolved holes,and the size of dissolved holes decreases with the increase of porosity of artificial cores with the same porosity.The larger the resistivity is,the smaller the resistivity decreases with the increase of porosity;the larger the fracture aspect ratio is,the smaller the resistivity decreases with the increase of porosity under the same conditions of fracture porosity and fracture dip angle;when the fracture aspect ratio is fixed,the influence of fracture dip angle on the resistivity is small,and the main influence is the tendency of resistivity decreasing with the increase of porosity.In addition,the geometric model and numerical simulation method of artificial core are established through literature research.The influence of pore throat ratio and coordination number on the resistivity of carbonate rock is analyzed.The results show that when the porosity is the same,the resistivity increases with the increase of pore throat ratio and decreases with the increase of coordination number.Based on the results of petrophysical experiment and numerical simulation,an empirical model between resistivity and pore structure parameters of carbonate rocks is established.The validation of carbonate cores proves that the model can accurately predict the resistivity of carbonate rocks with specific pore structure and improve the accuracy of interpretation of resistivity logging data of carbonate rocks.