Experimental Study On The Petrophysical Properties And Seismic Rock Phyhsics Properties Of Carbonate Rocks In Gucheng Area Of Eastern Tarim Basin

Carbonate reservoirs are important reservoir types for onshore oil and gas exploration in China.Carbonate reservoirs in different regions have significant differences on sedimentation and diagenesis.The factors that affect petrophysical properties and seismic rock physics properties are also different.Therefore,it is especially important to compare the seismic rock physics properties and petrophysical properties of carbonate rocks in different regions.In this paper,seismic rock physics experiments were carried out on the carbonate rock samples of the Yingshan formation in Gucheng of Tarim Basin and the Ordovician Majiagou formation in Daniudi of Ordos Basin.According to the petrological characteristics and microstructure characteristics of the samples,the experimental relationship between petrophysical properties and seismic elasticity properties of the reservoir were established.The seismic rock physics empirical model were also constructed.Comparing the rock samples of four different regions,including the third member of Ordovician Yingshan formation in Halahatang of Tarim Basin and the fourth member of paleogene Shahejie formation in Dongying depression,the factors that affect the seismic elastic properties and petrophysical properties of the samples were analyzed.The results indicate that the seismic rock physics properties and petrophysical properties of rock samples are controlled by the calcite micrite microtextures.The carbonate rock-typing method on rock microstructure and pore structure can not fully reflect the variation of the above characteristics.According to the morphological characteristics,the micrite microtextures of the rock samples can be classfied into three types: porous micrite,compact micrite and tight micrite.According to this classfication method,the pore throat radius is gradually reduced,which also reflects the boundary mechanical properties and elastic uniformity of the calcite particles are gradually enhanced.Consequently the seismic elastic properties such as compressional and shear wave velocity will decrease when the porosity increase.For low-porosity samples with tight micrite(porosity ?<5%),the contribution of micrite pores is small,and the elastic properties of micrite are close to the rock matrix.And the effect of cracks and dissolution pores on petrophysical properties and seismic elastic properties is more obvious.The variation of seismic rock physics properties and petrophysical properties is manifested by the control of pore structure.The pore aspect ratio also has a good indication of the pore type.The aspect ratio of the dissolution pores is higher than 0.2,and the aspect ratio of intergranular pore is between 0.1 and 0.2.The porous micrite and compact micrite aspect ratio is less than 0.15.And the aspect ratio of the tight micrite is close to 0.2.The difference on the samples pore structure uniformity will affect the fluid-related velocity dispersion.The apparent velocity dispersion of most compact micrite and porous micrite samples is less than 5%,which indicate that the pore structure is more uniform.The tight micrite samples have a wide range of velocity dispersion,which reflects the feature of the particle-supporting structure and the coexistence of multiple pore types.The results can provide a basis for the classfication of carbonate reservoir and the hydrocarbon detecting.