A Research Of Carbonate Reservoirs Classification In Block H

With the deepening of exploration and development,a large number of porous carbonate reservoirs have been found in Block H of the Middle East.Porous carbonate reservoirs are controlled by various diagenesis,with complex pore structure and strong heterogeneity which makes it difficult to find high-quality reservoirs.Therefore,it is necessary to study the classification of porous carbonate reservoirs.In this paper,the lithology,physical properties and pore structure characteristics of carbonate reservoirs in the study area are analyzed based on the thin sections,mercury injection experiment and physical property analysis.On this basis,the pore structure characteristics were studied in depth.The pore structure of the reservoir is divided into four types by capillary pressure curve shape,pore throat distribution frequency and pore structure parameters.The shape of capillary pressure curve is studied,and the morphological parameters which can accurately describe the shape of capillary pressure curve are obtained by fitting.It is proposed to classify the reservoir by combining the morphological parameters b and c.In order to evaluate the whole well section,according to the theory of pseudo-capillary pressure curve,the applicability of the linear scale method and the power function scale method to construct the pseudo-capillary pressure curve in this area is discussed.Based on this,the pore structure parameters and morphological parameters are calculated and reservoir types are classified by the established classification criteria.Aiming at the accuracy problem of pseudo-capillary pressure curve by linear scale method and power function scale method,the pore throat system parameters were constructed based on NMR T₂ spectrum to characterize the pore structure.The pore throat system parameter and flow porosity calculated from NMR logging data are used as variables,and carbonate reservoirs is divided into four types by using the K-means clustering method in combination with core experimental data.Then a reservoir classification model based on NMR logging is established by Fisher discriminant method,and the classification results are consistent with logging response and production data.Based on the classification result of reservoirs by NMR logging,reservoir classification studies are carried out based on conventional logging data.Optimizing conventional logging curves,a reservoir classification model is established by Rotation Forest algorithm for the problem that the conventional logging has low resolution,strong multi-solution,and the reservoir type is linearly inseparable.The established model has a coincidence rate of 86.3%in the study area,which verifies the reliability of the algorithm and model.