Abstract
The occurrence characteristics of hydrates in the Shenhu area reflect a typical inhomogeneity in terms of spatial distribution. It is difficult to accurately describe the petrophysical properties of a reservoir using a petrophysical model considering a single cementation factor parameter. According to the analysis of a mathematical model and the estimation results of V p and V s , the unique structure of foraminiferal sediment particles provides opportunities for forming a diversified hydrate occurrence in the foraminiferal area. In areas where hydrates are thin and interbedded, hydrate reservoirs are generally three-phase media, with obvious thermoelastic properties. Therefore, the parameters of the three characteristic models of the pore-filling model, particle cementation model, and thermodynamic elastic model are all included in the correction model. The weights of the influence factors are then changed to realize an accurate description of the petrophysical characteristics of the correction model in different drilling areas and at different formation depths, reducing the limitations of using a single petrophysical model to describe the petrophysical characteristics of heterogeneous regions under the influence of multiple factors.
Highlights
A petrophysical model is an equivalent model that describes the microscopic characteristics of rock
This type of model assumes an average internal stress in the rock and is suitable for static isotropy; it can be used to constrain upper and lower limits of the model physical property parameters to improve the inversion accuracy, but it is difficult to apply to the inversion of physical property parameters in complex reservoirs [5, 6]; (2) equivalent models based on self-adaptation, differentiation, and scattering theory, such as the Kuster-Toksoz (KT) model and Differential Equivalent Medium (DEM) model
Based on the above analysis, this paper constructs a unified petrophysical model to address the following problems: (1) the hydrate occurrence state and the reservoir structure in the model must be similar to the patchy distribution in the background stratum, with strong horizontal and vertical heterogeneity; (2) there are diversified cementation modes in the hydrate reservoir in the foraminifera-controlled area; and (3) due to the structural characteristics of the target area, the abnormal heat flow value affects the thermoelastic properties of the study area
Summary
A petrophysical model is an equivalent model that describes the microscopic characteristics of rock. The currently applicable rock physics models are mainly divided into three types: (1) equivalent volume-average models, such as the Voigt-Reuss-Hill (VRH) model and Hashin-Shtrikman (HS) model This type of model assumes an average internal stress in the rock and is suitable for static isotropy; it can be used to constrain upper and lower limits of the model physical property parameters to improve the inversion accuracy, but it is difficult to apply to the inversion of physical property parameters in complex reservoirs [5, 6]; (2) equivalent models based on self-adaptation, differentiation, and scattering theory, such as the Kuster-Toksoz (KT) model and Differential Equivalent Medium (DEM) model. This type of model is mainly used to study the internal pore structure of the rock and the influence of pore filling on the rock
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