Strength Properties, Elastic Modules and Compressibility Factors of Rocks from Oil Fields OOO LUKOIL–Western Siberia

Abstract

Abstract The purpose of our work – is to show our version of determining the strength properties, elastic modules and compressibility factors at reservoir conditions on the example of rock fields OOO "LUKOIL–Western Siberia". This paper briefly shows a method of measurement and processing of the results. The paper also shows some results of the determination of dynamic and static elastic moduli of rocks (Poisson's ratio, Young's modulus, shear modulus, compressibility, ultimate strength, elastic limits). This article also shows some results of a comparison of dynamic and elastic Young's modulus. Static deformation and strength characteristics of the rock were determined by direct measurements of the longitudinal and transverse strains. All measurements were made at reservoir conditions by increasing the axial load until destruction of the sample. The rate of deformation changes was no more than 1.5 • 10-6 s-1, reservoir pressure and temperature were maintained automatically with a high degree of accuracy. Static deformation and strength characteristics are the most reliable, and reflect real properties of both homogeneous and heterogeneous anisotropic rocks. In our laboratory, on by our optimized measurement method were performed investigations of dynamic and static strength properties of more than 500 rock samples from different oilfields of OOO "LUKOIL–Western Siberia". Our Company has received a very valuable information about the rocks in the form of diagrams "Stress–Strain," of Mohr's circles, elastic limits, ultimate strengths, elastic modulus, graphs of compressibility factor and Biot's coefficients depending on the pressures. It should also be noted that we have not been able to find any general and uniform dependence (laws) in all studied formations and fields, between dynamic and static elastic moduli. For solving of some specific tasks (for example, a field development, design of hydraulic fracturing) and for obtaining high–quality and reliable results on the rock mechanics we need use only static strength characteristics of rocks identified at true reservoir conditions. Our methodology is based on the American Standard ASTM D 3148–93, and the results of our experimental work and the measurement procedure (Owner's Manual) for our equipment, taking into account the specific properties of sedimentary rocks of OOO "LUKOIL–Western Siberia". For concrete oil formations studied fields of OOO "LUKOIL–Western Siberia" we had found quite close links between the dynamic and static Young's modulus. Such petrophysical links is possible to use for obtaining more important information from the results of rocks research by dynamic method.