Rock Physics Modeling And Reservoir Properties Prediction For Shale Reservoir

Shale is the most common sedimentary rock.It is a multi-mineral heterogeneous natural complex composed of different clay minerals,organic matter,quartz,calcite,feldspar and other minerals with different contents.Shale is usually considered as a very important unconventional oil and gas reservoir because of the characteristics of organic matter enrichment,fracture development and low permeability.It is a huge potential energy source and has great industrial exploitation value.Therefore,it is necessary to further understand the relationship between mineral component content and microstructures of shale reservoirs and their macro-seismic responses,and to obtain accurate and valuable reservoir evaluation parameters.Petrophysical modeling plays a fundamental and most important role in the process of reservoir identification and evaluationShale reservoirs have complex and changeable mineral components and pore space microstructures,and usually show VTI anisotropy.The factors that determine the elasticity,mechanical properties and anisotropy of shale reservoir mainly include the content of organic matter and the degree of pore development of organic matter,the content of clay mixture,the micro-structure and the micro-characteristics of pore space.In this paper,the effects of the above three factors on the macroscopic properties of shale,such as P-wave velocity V_p,S-wave velocity V_s,and the corresponding anisotropic parametersεandγ,are mainly considered in the process of rock physical modeling.For organic-rich shale reservoirs,the influence of organic matter properties on shale properties is fully considered in the process of petrophysical modeling,in which the properties of organic matter are mainly determined by the porosity of organic matter and the morphology of organic matter mixture.Based on Kuster-Toks?z formula,the effects of porosity of organic matter and pore fluid on organic matter mixtures were quantitatively analyzed during the modeling process.The self-consistent approximate equivalent theory is applied to quantify the effect of the aspect ratio of organic mixtures on the elastic properties of shale.The prediction results of shear wave velocity based on rock physical model verify the applicability of the model to shale reservoirs in the study area.Develop inversion process based on rock physical model to obtain important reservoir evaluation parameters such as organic porosity and aspect ratio of organic matter mixture.The effects of kerogen content and porosity of organic matter on the elasticity and mechanical properties of shale are clarified by forward analysis of rock physics.For shale reservoirs,clay micro-characteristics and pore space morphology are the main controlling factors of shale elasticity and anisotropy.In the process of petrophysical modeling,Chapman multi-scale fracture model is used to quantitatively describe the pore space and horizontal fracture of shale reservoir.Development of model-based in-well inversion method to obtain horizontal fracture density in wells and provide information for evaluation of fracture system in shale reservoirs.Under the assumption that the orientation of clay mineral particles is the main controlling factor of shale elastic anisotropy,Clay Lamination CL is introduced to quantitatively describe the orientation of clay particles in the Backus theory of rock physics modeling.The in-well inversion method based on rock physical model is developed to predict clay compaction index CL and shale anisotropy parameters.Based on the Anisotropic Effective Field Theory,the micro-structure and physical properties of clay mixtures composed of illite,montmorillonite and intergranular soft matter are considered in petrophysical modeling,It is explained that the P-S wave velocity of shale reservoir is higher than that of V_p/V_s..Inversion of illite,montmorillonite and intergranular soft matter ratio in clay mixtures based on rock physical model.The anisotropic parameters of clay mixture,solid matrix and shale reservoir are further calculated to provide basis for reservoir Mechanics Evaluation and velocity model for seismic forward and inversion...