مجله ژئومکانیک نفت
سال ششم شماره 2 (تابستان 1402)

In this study, the distribution of the fracture intensity in the Sarvak carbonate Formation in an oilfield located in the Dezful embayment and its relationship with geomechanical parameters were investigated. Therefore, fracture intensity data, reservoir data such as porosity, along with rock elastic properties were imported into Petrel software. In this software, after providing several seismic attributes, such as variance attributes, they were merged together using the neural network approach and converted to one driver (representative attribute) to be applied for fracture intensity modeling. After constructing the 3D grid, the imported data such as fracture intensity, porosity, and geomechanical parameters were scaled up and prepared for modeling. Therefore, all related logs including porosity, Young’s modulus, Poisson's ratio, and uniaxial compressive strength along with the fracture intensity logs were distributed in three dimensions using geostatistical algorithms, in order to investigate the relationship between geomechanical parameters and fracture network distribution. Based on this study, there is a notable relationship between geomechanical parameters and porosity while there is no logical relationship between geomechanical parameters and fracture intensity. Also, the parts with high fracture intensity in the upper and lower Sarvak do not show a clear relationship with the effective porosity distribution, indicating the effect of diagenesis processes in porosity variation during the geological time.

Seismic wave propagation modeling, one of the key steps in seismic imaging, plays an important role in oil geomechanics studies based on subsurface non-destructive imaging. Two of the most accurate non-destructive seismic imaging methods are full waveform inversion (FWI), and least squares reverse time migration (LSRTM). Since the general approach of these methods to recover geomechanical properties is based on minimization of data residuals, an accurate forward modeling operator makes the inversion results independent from the modeling errors. Seismic modeling is based on the numerical solution of the partial differential equation of wave propagation using methods such as finite difference or finite element. In the simplest case, this equation is solved under conditions of constant density and for an acoustic medium. Different methods have been conducted to develop modeling methods by considering real conditions. One of these considerations, which has a significant impact in geomechanics onshore studies, is the topography. In this research, we used the immersion boundary method to solve the wave equation in the time domain in environments with complex topography, and we developed this method for wave propagation in a visco-acoustic medium with variable density. In visco-acoustic environments, including the effect of absorption (dispersion and dissipation) in modeling, requires the complex wave equation, which is challenging to solve in the time domain. In this study, a novel method is used to incorporate the effect of absorption in wave propagation in the time domain. Finally, the performance of the proposed method is investigated by modeling the wave propagation in visco-acoustic models with complex topography and variable density.

Identifying faults and fractures in hydrocarbon reservoirs is of particular importance in the stages of enhanced recovering and development of oil fields. The correct description and drawing of faults and fractures can enable the implementation of development projects in the oil industry. One of the methods of describing the discontinuity in the layers is the use of seismic indicators. In this study, the algorithm developed by Hardap [1] was used along with the application of the latest methods of seismic markers in one of Iran's oil fields to evaluate its ability to identify faults and fractures. The results of this study for the reservoirs revealed that the thinned fault likelihood as well as fault likelihood show good consistency regarding to the quality and accuracy of discontinuities in the field. In this regard, the use of information on the slope and azimuth of layers plays an important role in increasing the accuracy of interpretation of discontinuities, especially fractures. Finally, the evaluation of these indicators shows that the main extension of the faults and fractures in the studied reservoir is in the north-south and northwest-southeast direction, which is consistent with the data of pictorial diagrams (Rose diagram) corresponds to the wells drilled in this field. Based on the distribution of the density of fractures at the location of the drilled wells, it can be concluded that in addition to the diagenesis phenomena, the fracture networks and their connection with each other can control the production of field wells.

This study addresses the numerical simulation of cohesive crack propagation and the problem of normal contact in porous media. Penalty method is used to inforce essential boundary conditions. The strong discontinuity in the deformation field is effectively modeled by exploiting the partition of unity property of element-free Galerkin shape functions and employing an external enrichment strategy. To account for the crack initiation and propagation behavior in mode I, which occurs under tensile stresses, as well as the compressive behavior at the edges of a closed crack in compression, the cohesive crack theory and the penalty method are incorporated into the existing computer program prepared for the simulation of porous media using the enriched element-free Galerkin method. The resulting algebraic system of equations are strongly non-linear. So, a suitable approach must be utilized to linearize and solve the equations. Newton-Raphson technique is utilized in this study for this purpose. The results obtained from solving the problems of tensile cracks and cracks under compression (i.e., the contact of two crack edges) indicate the capabilities of the numerical formulation and the prepared computer program. Expanding the prepared numerical model allows for the modeling of crack growth problems in porous media in the presence of fluids, as seen in processes like hydraulic fracturing.

Compressional and shear wave velocities (Vp and Vs respectively) are basic and essential parameters for any geomechanical modelling in deep ground conditions. However, both are complex parameters that are strongly influenced by other rock properties such as porosity, in situ stress, pore filling, clay content, etc. Therefore, detailed information about the contribution of each of these attributes can improve the results obtained in geomechanical models. Especially when the wave velocity in the surface conditions is estimated based on in situ data such as geophysical logs from wells or core samples or drilling chips, the importance of this matter becomes much significant. In this research, experimental data for more than 180 shaly rock samples were analysed. Clearly, porosity was the most critical parameter affecting shear wave velocity. Accordingly, increasing porosity leads to a dramatic decrease in wave velocity. Nevertheless, it was noticed that for a certain porosity value, a relatively wide range of wave velocities may be observed. Further investigation revealed that, clay content was also a significant contributing parameter. Based on explicit statistical analysis, a predictive equation was introduced with which shear wave velocity can be estimated with high certainty. Accordingly, for samples with the same porosity, variation in clay content would result in different wave velocities

Geoenergy has a significant effect in optimizing the analysis of mechanical phenomena during drilling, exploration, production and even release of an oil field. Identifying the technological capabilities of geomechanics in Iran's oil and gas industry is effective in improving the exploration and production process. Therefore, the current research has extracted, categorized and interpreted the basic, organizing and inclusive themes using a multi-method qualitative approach (theme analysis and gray Delphi). Therefore, first, semi-structured interviews were conducted with 14 industrial and academic managers and experts, and using the theme analysis approach based on the inductive strategy, technological capabilities in the field of oil and gas geomechanics were identified and categorized into 7 organizing themes and 34 basic themes. . The themes of the organizer include investment capability with 4 basic themes, linking/networking capability with 5 basic themes, learning capability with 6 basic themes, human resources capability with 4 basic themes, management and strategic capability with 7 basic themes, technical and executive capability with 4 themes Basic, complementary capability is formed by 4 basic themes. Then, by doing gray Delphi, these themes were classified into five classes in order of importance. Credibility in senior managers, the existence of a strategic plan and access to sufficient credit resources were of the highest importance.