Applied Research Of Cracked Porous Theory In Oil And Gas Identification

With the increasing demand of oil and gas,as well as the improvement of exploration and development technology,the exploration and development of unconventional oil and gas reservoirs have been paid more and more attention.The important characteristics of unconventional oil and gas reservoirs(such as tight sandstone reservoirs)are low porosity and low permeability,but there are usually considerable oil and gas shows in these reservoirs,indicating that there are developmental fissures in reservoir rocks.The conventional logging technology can't accurately identify the properties of fluid in the reservoir.In order to solve this problem,this paper uses the cracked porous medium elastic wave theory to study identification of oil and gas.Firstly,we analyzed the squirt flow model in the rocks which contain pores and crack on the basis of the above theory.At the same time,we study the effect of the parameters-crack density,aspect ratio and gas saturation on the dispersion and attenuation of the mode waves in the infinite stratum.Then we apply this theory to the dense formation,and study the acoustic field response of borehole as well.The simulation results show that the tight rocks containing gas with a lot of cracks can improve the recognition ability of tight gas reservoirs.After the above analysis,first of all the experimental data by using acoustic logging was used to calculate the longitudinal and rotational wave speed ratio,Poisson's ratio,volume compression coefficient,and then we analyzed the relationship between these parameters and the gas saturation.Uses of Poisson's ratio-volume compression cross plot and longitudinal and rotational wave speed ratio-P-wave slowness-time cross plot can help us identify fluids qualitatively.Secondly,based on the Bire model,we compared the longitudinal wave velocity-gas saturation calculated by the model with the measured longitudinal velocity-gas saturation,and found that the calculation of gas saturation can be carried out quantitatively through the way.Finally,I used this method to process the actual data on the spot,as a result,the calculation result is the same as that of gas test.At the same time,The gas layer and water layer that can not be identified by the resistivity-Porosity conventional log can also be well divided by the method presented above.Therefore,the identification of oil and gas using cracked porous medium elastic wave theory can accurately identify the properties of fluid in tight reservoirs,and better guide the interpretation and processing of well logging.