Evaluation of rock void space structure based on hydraulic reservoir type concept

UDK: 622.276.031.011.431.2

DOI: 10.24887/0028-2448-2026-7-18-23

Key words: lithotypes of carbonate sediments, secondary transformations, hydraulic flow units, effective pore space size, Flow Zone Indicator (FZI) parameter

Authors: A.A. Makhmutov (World-Class Research Center “Efficient Development of the Global Liquid Hydrocarbon Reserves" of Ufa State Petroleum Technological University, RF, Ufa; Academy of Sciences of the Republic of Bashkortostan, RF, Ufa); Sh.Kh. Sultanov (World-Class Research Center “Efficient Development of the Global Liquid Hydrocarbon Reserves" of Ufa State Petroleum Technological University, RF, Ufa; Academy of Sciences of the Republic of Bashkortostan, RF, Ufa); A.A. Lutfullin (TATNEFT PJSC, RF, Almetyevsk; Almetyevsk State Technological University «Petroleum Higher School», RF, Almetyevsk); K.D. Shumatbaev (TATNEFT PJSC, RF, Almetyevsk; Almetyevsk State Technological University «Petroleum Higher School», RF, Almetyevsk); R.F. Khusainov (TATNEFT PJSC, RF, Almetyevsk); A.R. Sharafutdinov (World-Class Research Center “Efficient Development of the Global Liquid Hydrocarbon Reserves" of Ufa State Petroleum Technological University, RF, Ufa); V.M. Chilikin (World-Class Research Center “Efficient Development of the Global Liquid Hydrocarbon Reserves" of Ufa State Petroleum Technological University, RF, Ufa)

The paper presents a method for evaluation of void space structure of terrigenous and carbonate rocks based on the concept of hydraulic reservoir types. The study aims to determine the effective pore size distribution, which influences the anisotropy of reservoir properties. Results of laboratory studies and layer-by-layer description of core samples from the South Tatar Arch were used to determine the regularities in the distribution of pore space structure (equivalent diameter) with secondary transformations (dolomitization, recrystallization, leaching, fracturing, stylolization, etc.) and lithological features (Dunham lithotypes) for Kizelovian carbonate reservoirs. To gain the understanding of effective pore throat sizeт distribution, an approach relying on estimation of average equivalent pore and pore throat size using porosity factor and Flow Zone Indicator is proposed. Histogram analysis enabled determination of cut-off values for equivalent pore throat size for Tournaisian carbonate reservoirs. The resultant cut-off values and identified dependencies enabled generation of three-dimensional distribution models of secondary transformations to reflect anticipated void space alteration zones in carbonate reservoirs. Application of updated and
detailed geological model improved the history matching process of reservoir simulation model and, thus, increased the accuracy of simulated forecast data. It is demonstrated that the concept of hydraulic flow units combined with
lithotypes distribution and secondary transformations, provides an efficient tool for a more detailed description and differentiation of the void space in carbonate reservoirs.