Determination of shale stiffness tensor from standard logs

Abstract

A B S T R A C TA technique allowing inversion of the shale stiffness tensor from standard logging data: sonic velocities, density, porosity and clay content is developed. The inversion is based on the effective medium theory. The testing of the technique on laboratory measurements of the elastic wave velocities in shale samples shows that the inversion makes it possible to predict the elastic wave velocities V P , V S1 and V S2 in any direction within an error of a few per cent.The technique has been applied for the stiffness tensor inversion along a well penetrating a shale formation of the Mississippian age altered by thin layers of limestone. It is demonstrated that the symmetry of a stiffness tensor inverted at the sonic frequency (2 kHz) is slightly orthorhombic and taking into account the experimental errors, can be related to the vertical transverse isotropy symmetry. For the productive interval of the shale formation, the Thomsen parameters ε, γ , and δ average, respectively, 0.32, 0.25 and 0.21, which indicate anelliptic behaviour of the velocities in this shale. The coefficients of anisotropy of this shale interval are around 24% and 20% for the compressional and shear waves, respectively. The values of the inverted velocities in the bedding plane for this interval are in good agreement with the laboratory measurements. The technique also allows inversion of the water saturation of the formation (Sw) and the inverted values are in agreement with the Sw values available for this formation.A Backus-like upscaling of the inverted stiffness tensors is carried out for the lower and upper bounds of the frequency band used in the crosswell tomography (100 Hz and 500 Hz). These results can serve as an initial velocity model for the microearthquake location during hydrofracking of the shale formation.

Problems of Multiscale Brittleness Estimation for Hydrocarbon Reservoir Exploration and Development

“…, where α is the aspect ratio and  is the void's volume concentration. The crystalline matrix is an isotropic polycrystal of calcite characterizing by the elastic wave velocities, compressional (Vp) and shear (Vs), equal to 6.54 and 3.35 km/s and density 2.71 g/cm 3 [54]. The properties of formation water are Vp is 1.6 km/s and density is 1.1 g/cm 3 .…”

“…Figure 4 shows aspect ratios inverted from log data (2371 depth points) of a well penetrating carbonate reservoir rocks (limestones) of West Siberia (Russia). Another set of aspect ratios shown in Figure 4 is derived from well logs of limestone layers within a shale formation [54]. We select only the depths where calcite volume concentration is at least 90% (17 depth points).…”

Critical analysis of theoretical basics of displacement discontinuity model for media with oriented fractures.

“…Показано, что такой подход позволяет получать более детальные сведения о физических характеристиках коллекторов, чем при использовании других известных моделей [Баюк, 2011, 2013]. Детально разработаны методы применения предложенного подхода к таким важным для добычи углеводородов типам пород, как сланцы, песчаники, карбонатные коллекторы, в рабо-тах [Баюк, Рыжков, 2010;Баюк, Дьяур, 2012;Баюк и др., 2012;Chesnokov et al, 2009Chesnokov et al, , 2010и др.]. Найдены возможности определения "неизмеряемых" физических свойств пород, электропроводности и теплопровод-ности, по упругим свойствам.…”