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Minimization of disparities between welltest and log-derived average permeabilities has always been an issue, particularly in carbonates where complex pore structures add on challenges to permeability estimation from wireline log data. The disagreement between permeability averages from logs and well tests originates from the combined effects of measurement-scale of static porosity components for permeability models, dual flow system of fractures and matrix, tensorial nature of permeability and the averaging techniques used. The proposed workflow exploits rock-physics templates to identify and to quantify secondary porosity. Rock-physics templates employ conventionally derived total porosity and shear modulus as inputs. Fracture and vug porosity identified by the proposed workflow through rock-physics agree with other qualitative and quantitative evidences of non-primary porosity obtained from NMR, Image logs and core data1. Matrix and connected-vug permeabilities are computed, calibrated and integrated via "Chen-Jacobi" connectivity-driven model2 by using NMR and acoustic log data. Fracture permeability is estimated from "fracture aperture" and fracture-porosity by using image log data and rock-physics algorithms. The final permeability profile is computed with a selective-replacement step. This step ensures that in co-presence of matrix, connected vugs and fracture permeabilities at a given discrete depth level, the greater one would dominate and replace the lesser one. The final step in efforts of lessening the disparity between averages of wireline-driven and well test/DST permeabilities for a given interval is the usage of proposed averaging technique for the integrated wireline-driven permeability profile. The rock-physics templates used in this study combine Kuster and Toksoz3 "inclusions" theory with the Dvorkin-Nur4 granular media model (1996). We have observed appreciable correlations between secondary porosity driven from shear velocities against the secondary porosity determined from NMR and Image logs and core data. These correlations further provide routes for newer permeability models that can be solely based on the rock-physics. Comparisons of permeability averages computed from wireline-driven permeability profiles against DST or welltest permeability showed significant improvements toward parity via proposed methodology and averaging technique. The workflow presented in this study is to guide the reader through numerous steps of the proposed algorithm in detail.

The document presents a consistent method to build 3D Mechanical Earth Models (3D MEM). It is based on a rock physics study to derive field specific correlations between mechanical properties and interpreted petrophysical quantities. The 3D MEMs built using this methodology yield robustness and consistency when matching to the measured minimum stress. They also display good predictive capabilities making them valuable for operational design. This method consists of conducting a preliminary rock physics study in order to obtain correlations between the mechanical properties (elastic moduli and strength), of the various formations that are considered, and basic interpreted quantities which are readily available in most 3D geological models (porosity or mineralogy). The correlations are used to build a 3D MEM which is consistent with both the 3D geological model and the 1D geomechanical interpretation. It is also possible to extend the correlations by linking raw log data to rock mechanical properties. The model was tested against field case study to verify its predictiveness. Minimum stresses calculated by the 3D MEM matched well to the measured values obtained from mini-frac tests performed at various locations. Ultimately it permits to better forecast the material properties (in 3D) as well as the effective stress tensor (in 4D). The 3D MEMs were used to evaluate the risks for infill drilling, and for completion purposes. Performing this type of preliminary rock physics study has a number of benefits. Firstly, to help identify which logging suite should be run to characterize the geomechanical properties of a given formation, and secondly it can be used to derive correlations between raw log data and geomechanical properties. These correlations can be applied during operations for real time decision making purposes when there is not yet a petrophysical interpretation available. The novelty of the method introduced lies in the systematic and coherent integration of data to build a consistent geomechanical model (3D or 1D), that exhibits a robust predictive capability and shows the value of 3D MEM for the design of drilling and completion operations.

Biot's coefficient is one of the key parameters in estimating effective stresses, leading to understanding of the three stresses spatial distribution, namely vertical, minimum and maximum horizontal. Ultimately, these stresses shape up the behavior of a geomechanics model (either in 3D or in 1D). Thus, the robustness of any geomechanics model significantly depends on the precision of Biot's coefficient estimation. The proposed technique allows evaluating isotropic and anisotropic Biot's coefficients based on the log responses independent of the geological environment. The methodology is based on elastic moduli-minimization. In isotropic case, Bulk rock frame and Bulk rock grain moduli minimization produce the best fit to the measured Density, DTP and DTS. Then, isotropic Biot's coefficient can be computed directly. In the case of anisotropy, additional control on lamination is required. This can be achieved by comparing estimated laminated and dispersed clay volumes based on the anisotropic rock-physics model and derived from the Thomas-Stieber plot or any alternative lamination analysis technique. Anisotropy modeling allows to produce five independent VTI elastic moduli and as a result to compute anisotropic Biot's coefficient. The methodology has been tested in several fields: clastic (Western Siberia, Norwegian offshore, Argentina unconventional) and carbonates (Brazil, Middle East, North Sea chalks). It produces reliable results in all cases. This study shows good agreement of the Biot's coefficient computed from the proposed methodology with measurements of core-based Biot's coefficients. In practice, core-based Biot's coefficient measurements are rarely available and quite often done on a few samples, taken in the reservoir section only. The proposed methodology allows reliable estimates of Biot's coefficient for the entire wellbore section, where density and sonic logs are available. It utilizes a minimization technique instead of using geomechanics correlations. Thus, it is applicable for any rocks and geological settings and is not bounded to the area or formation compared to correlations specific to the particular formation. The novelty of the method is in the process of elastic-moduli minimization based on logs and allows direct extraction of the Biot's coefficient. Previous works were either concentrating on principles of the laboratory Biot's coefficient measurements or focusing on the correlations derived from core tests. Correlation derivation requires a significant number of core tests conducted for the same geological settings. However, the proposed methodology requires a few core samples for Q.C. purposes only.