مجله ژئومکانیک نفت
سال ششم شماره 1 (بهار 1402)

This research examines and presents the mechanisms of achieving a competitive advantage in the field of petroleum geomechanics of first-level industrial universities of Tehran, the purpose of the research is to use its results to achieve a competitive advantage of the field of geomechanics of first-level universities of Tehran at the national level. And it is international. The approach used in this research was mixed (with a sequential exploratory design that started with the review of articles and books related to competitive intelligence and competitive advantage and interviews and then continued with quantitative work). Also, in terms of strategy, this research was of a survey type in the qualitative part, content analysis, and in the quantitative part, a comparison. Achieving competitive advantage mechanisms was implemented in two qualitative and quantitative stages. In the qualitative part, in addition to the review of related texts and articles, interviews were also conducted with faculty members related to petroleum geomechanics and related trends. The interviewees were selected in a purposeful way, and the mechanisms were identified.The identified mechanisms include education and information mechanisms, research mechanisms, market research mechanisms, executive mechanisms, monitoring and evaluation mechanisms. Next, to determine the importance of each of the mechanisms, a questionnaire was prepared and distributed using an online questionnaire among faculty members related to petroleum geomechanics, managers and experts of the petroleum industry, and students and graduates of the orientation, finally 53 questionnaires were obtained. which was analyzed using fuzzy Delphi statistical methods and t-test. The results of the research showed that among the proposed mechanisms, the mechanisms of compiling and implementing educational programs; The development of intra- and extra-academic communication and the holding of joint and continuous meetings with industry representatives are of the highest importance.

As a result of extraction from underground oil reservoirs, the pore pressure in the reservoir decreases and the effective stress increases accordingly. Field measurements in the past two decades have shown that in addition to the change of effective stress, the total horizontal and vertical stress field can also change in and around the reservoir. As a result of the settlement that occurs at the upper part of the reservoir due to the consolidation phenomenon, the stability of this area is reduced and it causes “Stress Redistribution” inside and around the reservoir. The mechanism of stress redistribution is attributed to the “Stress Arching” phenomenon. By the stability reduction at the roof of the reservoir due to the compaction, this area will no longer bear the whole over-burden weight. A part of the over-burden is transferred to more stable areas such as the sides of the reservoir. The current research aims to investigate how the total stresses change around oil and gas reservoirs due to the extraction by a fully-coupled hydro-mechanical (HM) simulation. In order to simulate the process of fluid extraction from the reservoir and to consider the effect of production operations on the geo-mechanical properties of the depleting zone, a Non-linear elastic constitutive model has been used. In this research, a comparison is made between the amounts of the total stresses in the surrounding rock of three different reservoirs in terms of width. In addition, the effects of the difference between the initial stiffness of the reservoir rock and the surrounding medium on the intensity of the stress arching phenomenon are investigated by considering three different stiffness ratios. The conducted studies show that the changes in the total stresses are significant and it is necessary to consider their effect on aspects of the production and the development of field.

Elastic properties (Young's modulus and Poisson's ratio) are considered to represent important parameters in geomechanical investigations of reservoirs and hydrocarbon fields. These parameters can be calculated using common geomechanical tests in the laboratory. However, due to the lack of access to suitable samples, laboratory equipment and high costs, in many cases, empirical equations, statistical and mathematical methods have been used to estimate these characteristics. We present a Digital Rock Simulation (DRS) approach using high-resolution CT-images to estimate Young's Modulus and Poisson's ratio of carbonate samples following a non-destructive approach. In the numerical simulations we use a voxel model of reconstructed 3D geometry that is evaluated using Finite Element Method (FEM). We extract Representative Volume Elements (REV) of Kangan carbonates with different porosity and mineralogy. In laboratory experiments, we quantified the modulus based on Axial Stress-Axial Strain Curve that was obtained from Triaxial Compression Tests. Finally, we compare the simulation results and laboratory measurements. Our analysis shows that obtained Young's Modulus of modeling are between 4.3% and 18.9% higher than compared to the results of laboratory tests. The highest error is related to the samples with the more porous, which are mainly dolomite. The assumptions about solid fraction properties regarding to mineralogy differences remains challenging

The three main factors affecting formation breakdown pressure (PB) include rock mechanical and petrophysical properties, fluid properties and in-situ stress fields. Boreholes in different reservoir sections within the same rock type and reservoir and even under the same stress fields may exhibit different PB behaviors due to differences in pore water chemistry (different ionic composition and ionic strength) and geochemical interactions between pore water and rock. The PB can be estimated based on different theoretical and empirical models. However, in these models, the geochemical effect is not directly captured. Besides, the accuracy of PB estimation using these relations is still unknown. In this study, the accuracy of PB estimation using the conventional models and the effects of pore water chemistry on PB were investigated using published data from literature. Also, a new model was developed based on the concept of effective stress, disjoining pressure and the superposition principle for stress distribution around well-bore. The results indicate that most of the conventional models are unsuccessful in PB prediction for hydraulic fracturing operations. As an example, the popular Hubert-Willis model has an average error of 34.7%. Our study indicates that pore water chemistry has a substantial effect on rock wettability and PB due to the change of inter-granular forces, based on the DLVO theory, affecting the rock strength. The results of the new conceptual model show a decrease in the PB of chalkstone with an increase in the concentration of the sulfate ions in the pore water.

It is very important to know the rock creep behavior in the evaporitic cap rocks in order to investigate the convergence in oil wells. In general, among evaporitic rocks, the creep behavior of gypsum and anhydrite has been less investigated compared to halite, which are investigated in this research. Since accessibg to the cores of oil wells drilled in Gachsaran Formation is very difficult and expensive, in this research, sampling was done from the surface outcrops of section 1 of Gachsaran formation. For this purpose, blocks were prepared from gypsum and anhydrite and then cored from them in the laboratory. First, unconfined compressive strength (UCS) tests were performed on cores to determine the amount of initial load for uniaxial multi-stage creep test. Next, based on the UCS results and the approximate temperature conditions of cap rock, creep tests were performed at two temperature conditions of the laboratory and cap rock environment. Then, based on the data obtained from the creep tests, fitting the exponential and Powerlaw creep equations was done on gypsum and anhydrite. The results show the creep yield stress of 12 MPa for gypsum and 20 MPa for anhydrite. Also the creep tests was performed at two levels of initial stress 0.1 yield stress and 0.75 yield stress in UCS test. Based on these tests, the linear viscous limit for creep of gypsum and anhydrite was obtained as 5.5 to 6.7 MPa and 9.8 to 15.15 MPa, respectively. In addition, gypsum shows more uniform plasticity and creep under temperature compared to anhydrite. This is while in the anhydrite, the threshold of accelerated creep is lowered and the creep time is reduced.

Although groundwater withdrawal is considered to be the main and most common cause of land subsidence, extraction of oil and gas, or minerals from beneath the earth's surface also results in land subsidence. Land subsidence over oil and gas fields leads to several natural and manufactured disasters such as critical and strategic infrastructure destruction. In addition, it imposes significant costs on the oil industry, which indicates the need to control and monitor land subsidence in oil fields. Due to irrecoverable damage caused by this phenomenon, it is necessary to regularly monitor areas subject to subduction in oil and gas fields. There are different ways to measure crustal deformation in Geomatics engineering based on geodetic and remote sensing technologies. Despite high accuracy, the use of geodetic techniques such as Global Navigation Satellite System (GNSS) to regularly monitor crustal deformation in a wide coverage is limited by some disadvantages like discontinuous data collection, the need for installation of the equipment on the ground or direct contact with the ground which is time- and cost-consuming. InSAR technology has been widely used in recent decades to monitor crustal deformations with high spatiotemporal resolution and lower cost and time. This study aims to present a new methodology based on the Persistent Scatterer-InSAR (PS-InSAR) method to investigate the correlation between land subsidence and petroleum extraction in the southwestern region of Iran with active oil and gas fields during two periods from 2017/04 to 2017/10 and from 2019/04 to 2019/10, respectively with the highest and lowest petroleum extraction. The results showed that subductions of 10 to 30 cm during the period of 2017/04 to 2017/10 with an annual rate of 20 to 50 cm have occurred in southwestern Iran around the active oil fields which might be due to the significant petroleum extraction since 2016.