A Classification and Evaluation Method for Complex Carbonate Reservoir Based on Weight Analysis

The Kenkiyak Carboniferous oil reservoir under the salt is a complex carbonate reservoir with low porosity and ultra-low permeability. The distribution of favorable reservoirs is influenced by various factors such as sedimentary facies, karstification, degree of fracture development, and formation pressure. When identifying favorable reservoirs, previous researchers often used seismic attribute maps, fracture development areas, and pressure maps to overlap and search for favorable areas. This method mainly focuses on qualitative identification and cannot distinguish the weight coefficients of various influencing factors. It is difficult to consider multiple influencing factors when dividing favorable areas, resulting in biased range of favorable reservoirs when deploying well locations. In order to realize quantitative evaluation of the weight coefficient of each influencing factor, the weight analysis method in mathematical statistics is introduced to systematically analyze the weight coefficient of each influencing factor. By calculating and dividing favorable reservoirs, the multifactor quantitative evaluation of complex reservoirs is realized. This method first selects cumulative oil production as the parent factor, and the four parameters of formation pressure, fracture density, reservoir thickness, and porosity as sub factors to measure the quality of carbonate reservoirs. Then, by calculating the weight coefficients of each evaluation parameter, the reservoir types are classified based on the comprehensive evaluation criteria of the reservoir. This method achieves the qualitative to quantitative division of favorable reservoirs under multiple factors, improves prediction accuracy, and provides geological basis for oilfield well deployment.