--> Determination of the Laminar, Structural and Disperse Shale Volumes Using a Joint Inversion of Conventional Logs
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Determination of the Laminar, Structural and Disperse Shale Volumes Using a Joint Inversion of Conventional Logs

Abstract

Abstract

The determination of the volumes of disperse, structural and laminar shale is a challenging problem in the clastic-rock characterization. For this purpose, we have developed a technology to estimate spatial shale distribution to improve the assessment of hydrocarbon saturation and permeability prediction. This technology includes the simulation of physical properties of clastic rocks by introducing a unified hierarchical petrophysical model for shaly-sands and the joint petrophysical inversion of conventional well logs.

We consider clastic formations as a sequence of laminar-shale and sand layers. Sand layers are treated as porous composite materials containing: solid grains of quartz, structural shale, and pores filled with a mixture of oil, water, and disperse shale. For calculating the Previous HiteffectiveNext Hit physical properties of this composite, we apply the self-consistent Previous HiteffectiveNext Hit media method. We simulate the Previous HiteffectiveNext Hit physical properties of shaly-sand formations by applying three-step homogenization. Firstly, we calculate the Previous HiteffectiveNext Hit properties of pores composed of water, oil, and disperse shale. Then, the properties of sand layers are determined by using the pore Previous HiteffectiveNext Hit properties obtained in the first step. Finally, the formation Previous HiteffectiveTop physical properties can be calculated.

The determination of physical properties in the second step requires information about shapes of grains and pores that was determined by inversion procedure taking into account a set of experimental data. We have shown that the acoustic and electrical logs depend significantly on the volumes and spatial distribution of shales. Layered formations are transverse isotropic media and the elastic moduli and electrical resistivity are represented by tensors.

We have validated the proposed technology on synthetic models with different levels of a random noise and experimental data. Application of this technology allows us to add new shale characteristics to the conventional evaluation parameters such as volumes and porosities of laminar, structural, and disperse shales. These characteristics improve the assessment of hydrocarbon saturations and permeability of clastic formations.