Enhancing the reliability of core analysis

• Main Authors: Ivan S. Putilov, Irina P. Gurbatova, Nikita А. Popov, Denis B. Chizhov, Aleksander V. Yuriev
• Format: Article
• Language: English
• Published: Perm National Research Polytechnic University 2019-09-01
• Series: Perm Journal of Petroleum and Mining Engineering
• Subjects: whole core; complex carbonate reservoir; permeability and porosity properties; water flood displacement efficiency; hypothesis statistical check method
• Online Access: http://vestnik.pstu.ru/get/_res/fs/file2.pdf/8926/Enhancing+the+reliability+of+core+analysisfile2.pdf

The selection of a representative collection of samples is one of the main problems during the performance of the analysis of core material. Such collection should reflect physical and hydrodynamic processes in the layer in question as accurately as possible. In the case of complex carbonate reservoirs, it is particularly important to cover the maximum range of variation of permeability and porosity properties. It is important to analyze processes occurring in the matrix of rock, as well as in the cavernous and fractured constituent of a rock. The methodology is not sufficiently elaborated; therefore, at the moment of studying a reservoir of a particular field, the task is to develop a method to select a representative collection of samples to perform core analysis. So, using the information obtained on the waterflood displacement efficiency, it is possible to make a sufficiently reliable estimation of reserves and obtain a more accurate oil recovery factor. Taking the Tedinskoye field as an example, the recommendations have been developed on how to select a representative collection of samples to conduct core analysis, and the need to use a full-diameter core to determine water flood displacement efficiencies has been established. To evaluate the representativity of a selected collection of samples, a statistical analysis was performed; the hypothesis (statistical criteria) statistical check method was applied based on Student's distribution. It has been found that the selection of a representative collection of samples for analysis should be made for all types of reservoirs representing a section in question, thus covering a full range of permeability and porosity properties. A collection of samples should include whole core samples, as well as standard size samples, as they help to define the processes occurring in different parts of a formation.