Study On Reservoir Classification And Evaluation Of An Onshore Oil Reservoir In Middle East UAE

Zone D of X-Y oilfield in UAE is an important development horizon in this area.Zone D is a typical porous carbonate reservoir,but there are some problems in this layer,such as complex pore structure,strong heterogeneity,obvious differences in vertical and horizontal physical properties.Therefore,it is necessary to carry out reservoir classification and evaluation in the study area.In this study,the experimental data such as petrographic analysis,cast thin section,nuclear magnetic resonance,capillary pressure and core physical property analysis were used to describe the lithology of the reservoir in a single well,quantitatively characterize the pore structure of the reservoir,and divide the reservoir types according to the pore structure.In multiple wells,the IPSOM(self-organizing feature map)module of techlog software is used to realize the petrophysical classification of Zone D in the whole work area and fine division of good and bad reservoirs.At last,we make thickness statistics of the good and bad reservoirs of 18 wells in the work area,and make a comprehensive evaluation of the reservoir.The following understanding has been achieved:1)According to the sedimentary structure,structure and diagenesis,the core and thin section data can be divided into three types: wackestone,packstone and grainstone.On the thin section scale,dissolution pores and mold pores are developed in the wackestone,with a few intergranular pores;Intergranular pores are developed in both packstone and grainstone.The most common bioclastic species are bivalves and occasionally monodiallel foraminifera.2)According to the data of nuclear magnetic resonance,capillary pressure and core physical property analysis of 39 core samples from a single well,the pore structure of the reservoir can be quantitatively characterized,and the reservoir can be divided into four types: type I reservoir with good physical property and strong seepage capacity is high porosity and high permeability reservoir;Type II reservoir has high porosity and good seepage capacity,which is high porosity and medium permeability reservoir;The physical properties and seepage capacity of type III reservoir are general,which is medium porosity and low permeability reservoir;Type IV reservoir only develops micro pores and is non reservoir.3)In multiple wells,the IPSOM(self-organizing neural network)module of techlog software is used to divide the mercury injection data and physical property data of rock samples into six categories,and the results are better in the cross plot of porosity and permeability;Then the 18 wells in the work area are classified on the logging domain,and the D reservoir is comprehensively evaluated by counting the thickness ratio of each type of reservoir,and the structural plane map shows that the oil and gas enrichment zones are concentrated in the structural high point.