ahmad ramezanzadeh

Bit wear is one of the fundamental challenges affecting the performance and cost of drilling operations in oil, gas, and geothermal wells. Since identifying the factors influencing bit wear rate (BWR) is essential, and the ability to predict its variations during drilling operations is influenced by environmental and operational factors, this study aims to develop an Adaptive Bit Wear Rate Predictor (ABWRP) algorithm for estimating the BWR during drilling operations for new wells. The structure of this algorithm consists of a data transmitter, data processor, deep learning-based bit wear rate estimator, and a bit wear updating module. To develop a model for the BWR estimation module, data from two wells in an oil field in southwest Iran were collected and analyzed, including petrophysical data, drilling data, and bit wear and run records. Both studied wells were drilled using PDC bits with a diameter of 8.5 inches. After preprocessing the data, the key factors affecting the bit wear rate were identified using the Wrapper method, including depth, confined compressive strength, maximum horizontal stress, bit wear percentage, weight on bit, bit rotational speed, and pump flow rate. Subsequently, seven machine learning (ML) and deep learning (DL) algorithms were used to develop the bit wear rate estimation module within the ABWRP algorithm. Among them, the convolutional neural network (CNN) model demonstrated the best performance, with Root Mean Square Error (RMSE) values of 0.0011 and 0.0017 and R-square (R²) values of 0.96 and 0.92 for the training and testing datasets, respectively. Therefore, the CNN model was selected as the most efficient model among the evaluated models. Finally, a simulation-based experiment was designed to evaluate the performance of the ABWRP algorithm. In this experiment, unseen data from one of the studied wells were used as data from a newly drilled well. The results demonstrated that the ABWRP algorithm could estimate final bit wear with a 14% error. Thus, the algorithm developed in this study can play a significant role in the design and planning of new wells, particularly in optimizing drilling parameters while considering bit wear effects.

Shear Wave Slowness Log (DTSM) is one of the most important petrophysical logs applicable for studying reservoirs, especially geomechanical studying of the oil and gas fields. However, lack of this parameter in wellbore logging can import great sources of uncertainty into geomechanical studies. This study aims to provide solutions for decreasing the uncertainty of geomechanical models with estimation of the DTSM log using the high accurate deep machine learning models. The main idea is using data from offset fields for extending the range of training data and improving the estimation ability and generalizability of machine learning models. For this purpose, petrophysical data from 8 wells of 4 Iranian oil fields were collected. In the first stage, data preprocessing was performed for reducing the effects of wrong data, missing value, noises, and outliers. Then, machine learning (regression learning-based and deep neural network-based) and analytical models implemented for estimating DTSM. The results indicated that the Gated Recurrent Unit (GRU) model with the values of 1.9 and 2.14 for RMSE and 0.99 for R-square had the most exact answers, for training and test data, respectively. Meanwhile, evaluation of the accuracy of the models on the validation well data indicated that GRU model with the values of 2.43 and 0.93 had been the most accurate model for RMSE and R-square, respectively. Accordingly, using a multi-field comprehensive data bank and applying machine learning methods are strongly recommended to estimate the DTSM, for the cases where limited offset data is available.

Optimization is one of the branches of applied mathematics used in various decision-making fields such as engineering, mathematics, and computer science. The classical method is one of the branches of optimization that can be used to make decisions in various problems. Accurate knowledge of pore pressure and minimum horizontal stress is necessary for the drilling, stability, and completion stages of the wellbore. The estimation of the mentioned parameters is generally obtained using empirical and analytical relationships. The answer to these equations is suitable when the constant coefficients chosen for each equation are correct. The computation of coefficients is usually done experimentally and even manually. Now, accurate and automatic computation of parameters can be a progressive step for using these equations. Therefore, the purpose of this research is presented in three parts. First, the pore pressure is estimated based on Eaton's relationship. To accurately estimate the pore pressure, the constant coefficients of the Eaton equation are automatically calibrated and calculated through the gradient-based Newton classical optimization method. Second, the minimum horizontal stress is obtained using the Blanton equation. To estimate properly the minimum horizontal stress, the constant coefficient of Blanton’s method is computed automatically via the Newton classical optimization method. Finally, the values of pore pressure and minimum horizontal stress are compared with the measured data to evaluate the accuracy of the results. These results show the ability of the proposed optimization method to determine accurately the pore pressure and the minimum horizontal stress.

The Cased, Cemented, and Perforated (CCP) completion method is considered one of the superior well completion methods in sand-prone reservoirs due to its execution safety and cost-effectiveness compared to alternative techniques. In the design of perforation configurations, the number of shots aligns with the requisite hydrocarbon production volume. Consequently, the optimization of the phase angle (phasing) emerges as a critical design parameter, typically deployed to forestall overlap within the impacted zones surrounding neighboring perforations and curtail their interaction. In light of the absence of constraints and the ease of establishing a single helical perforation pattern compared to alternatives, this study is dedicated to exploring the optimal phase angles within this pattern using a pythonic brute-force search approach. Moreover, emphasis is placed on achieving the minimum spacing between adjacent perforations, and the analysis is geared towards identifying the most optimal phase angles for 6, 9, and 12 shots per foot across three common wellbore diameters. Innovations of this study include the consideration of more than three consecutive wraps of perforations in determining the optimal phasing, as well as the simultaneous impact of perforation stability and uniform flow distribution around the wellbore in reducing the likelihood of sand production. The uniform distribution of perforations has been achieved by introducing a parameter known as the Equilateral Likeness Score (ELS), where its minimum value signifies the most uniform arrangement of adjacent perforations. The optimal phasing angles are determined by drawing inspiration from two distinct perspectives: maximizing the spacing between adjacent perforations and achieving the highest possible phasing values. A comparative analysis of the outcomes derived from the presented theory and existing ones underscores the potential for significant variations in the determined phasing values for certain shot densities. Ultimately, the optimal phase angles for the aforementioned shot densities are projected as 127, 130, and 97 degrees for a 41/8-inch wellbore, 130, 97, and 143 degrees for a 61/8-inch wellbore, and 97, 143, and 77 degrees for an 81/2-inch wellbore.

Due to the significance of the sand production (SP) issue in sandstone hydrocarbon reservoirs, the main objective of this study is to evaluate the Asmari formation layers along well No. 469 in the Ahwaz hydrocarbon field in terms of SP causes and its potential capacity to provide suitable solutions for its reduction from a geomechanical perspective. The evaluation was carried out using the Techlog software. The required parameters for constructing a one-dimensional geomechanical reservoir model were estimated from available data. The Mohr-Coulomb failure criterion was adopted considering the scale effect for perforated cavities under non-hydrostatic stress conditions. After constructing the one-dimensional model, the Critical DrawDown Pressure (CDDP) curve was plotted for both open hole and perforation completions, and the susceptible SP zones were identified. The M2 layer was selected as one of the most susceptible zones for SP sensitivity analysis due to its low strength, porosity, and permeability compared to other layers. The sensitivity analysis was conducted based on well geometry, formation rock properties, field stress conditions, and perforated cavity characteristics. The analysis was performed at depths of 2822 and 2837 meters in the open hole and the perforation completions, respectively, with a dominant sand diameter of 200 microns in the potential SP zone. The Critical Bottom Hole Pressure (CBHP) and the Critical Reservoir Pressure (CRP) were estimated to be 1898 and 2735 pounds per square inch, respectively, in the maximum horizontal stress direction with a 0.4-inch perforation diameter and 861 and 2115 pounds per square inch, respectively, in the direction perpendicular to the maximum horizontal stress direction with a 0.3-inch perforation diameter. By defining and determining Transitional Deviation Angle (TDA), Minimum Safe Deviation Angle (MSDA), and Critical Perforation Orientation Angle (CPOA) based on sensitivity analyses, a novel design approach for perforation operations in sand-prone reservoirs has been introduced.

Geometry of fractures including orientation, spacing, aperture and etc. are the influential parameters on permeability in rocks. In order to investigate the effect of spacing and orientation of fractures on permeability in laboratory scale, selecting proper sample is essential in terms of physical and mechanical properties. Therefore, in this study, two types of samples (concrete and fibrous fiber) were selected. Then, physical and mechanical parameters, which consist of density, water absorption, porosity, wave velocity, uniaxial compressive strength and permeability, were measured. The test results showed that the concrete sample is not appropriate sample for studying effect of fracture parameters on permeability due to high porosity, water absorption, permeability and brittle behavior of sample. However, the sample of fibrous fiber not only possesses the favorable physical and mechanical properties but also is suitable to create the fractures with different spacing and orientations as well as the same aperture owing to flexibility and ductile behavior.

Nowadays, Tunnel Boring Machines (TBM) are widely used around the world on account of their high rate of excavation, little impact on the surrounding rock and their high safety standards. The rock mass boreability is considered as one of the main parameters in evaluating the TBMs performance in jointed rock masses .Boreability is a parameter reflecting the interaction between the rock mass and cutting tools. This paper aims to render an account of the effect of Joints Geometrical Parameters on the boreability by use of a database prepared utilizing the data (TBM operation and geological parameters) collected from Kerman Water Conveyance Tunnel projects in Iran. For this purpose, the joint parameters (orientation, spacing, persistence) affecting the boreability have initially been investigated. Then, the total fracturing factors (Bruland) and Persistence classification were used to investigate the effects of all three parameters on the borability. The results showed that the boreability is also increased by increasing the joint persistency. Besides, the effect of fracturing factor ( ) on boreability increases by increasing the joint persistency. In this paper, a new parameter called "Rock Joint Index"(RJI) is also presented according to the analysis performed on the database. The boreability value estimated based on the RJI shows a good agreement with the actual penetration rates.

Summary:

Increasing population and urban development highlight the role of tunnels as a suitable solution to meet various needs, especially transportation and reducing traffic in cities. The control and estimation of settlement of ground in tunneling is one of the most important challenges. In this study, tunnel is modeled in the FLAC3D software and Deformation due to drilling operations in both coupled and uncoupled modes is investigated.  Results shows that the coupled method is in more agreement with the instrumentation data than the uncoupled method.

Direct hydromechanical interactions in the Earth's crust have been known since the late 1800s. an example of studies conducted in this field is given below:Yoo et al. (2012) and (2008) using ABAQUS software examined the effect of groundwater drawdown on subsidence and displacements around the excavation. Zhou et al. (2018) and Lee et al. (2008) using FLAC3D software, the amplitude of excavation effect on deformation and pore pressure change was investigated. A review of studies shows that in most modeling have been carried out with simplifications such as not considering the drilling sequence, ignoring groundwater level and Pore pressure changes. These simplifications lead to far-fetched results.Therefore, after selecting numerical software in accordance with the problem conditions, the three-dimensional model of the case study tunnel is modeled in the FLAC3D software. Based on the results, the coupled method is in more agreement with the instrumentation data than the uncoupled method. Also, the deformation around the excavation space is heavily dependent on the drainage and the groundwater level condition, so that the displacement and expansion of the plastic zone around the excavation space, in drained mode, is more than undrained. The long-term behavior of the tunnel in both drained and undrained mode shows that the deformation caused by drained does not change over time. Furthermore, in the drained condition, the displacement increases around the excavation space with over time.

Methodology and Approaches:

Using FLAC3D software, the complete association between a porous deformable solid and a viscous fluid flowing through its pores can be modeled. The modeling of the study area has been done in two phases, mechanical and hydraulic. For modeling the mechanical phase, the soil is considered homogeneous and isotropic with full elastoplastic behavior and horizontal layering. The Mohr-Coulomb behavior model is used for the tunnel media, and the elastic behavioral model is used for the boring machine and lining.

The most important results obtained from this study are as follows:The parameters of in situ stress conditions, groundwater level and environmental drainage conditions have a great impact on the results of numerical modeling.Comparison of the results with the instrument data shows that the amount of settlement created in the couple mode is more consistent with the instrument data.Water outflow from excavation operations reduces the pore pressure and increases the effective stress around the excavation space.
Pore pressure changes indicate the importance of studying long-term behavior.

Rate production and final recycling rates are heavily influenced by permeability as a dynamic parameter, but this parameter is low in some carbonate reservoirs and requires an appropriate solution to increase it. The purpose of this study was to investigate the effect of injection and confining pressure in a laboratory study of the permeability of reservoir rocks during acid-bed corrosive operations. Considering this approach, 6 samples of carbonate reservoir rock from one of Iran’s oil fields have been prepared. After determining the physical and mechanical properties of the samples, the effect of the confining pressure and the injection pressure on permeability variations and optimal flow rates were studied. Examination of the results of the experiments as well as the CT scans of the samples after acidizing operation showed that permeability increased to an acceptable level in all samples. In lower injection rates, the acid has enough time to react with the rock, wormholes are well-formed, and the rest of the sample space retains its density to a large extent, but by increasing acid injection rates, there are wormholes changing themselves with the complete destruction of the primary core section, and the remaining density has been reduced. This is accompanied by a combination of the two above-mentioned behaviors, by increasing the rate to a maximum. This has led to an increase in over 530 times permeability over the initial value of the sample. However, there is a slight difference between the formation time of the formation of wormholes in the injected sample with maximum discharge and the sample injected with a minimum. However, there is a slight difference between the formation time of wormholes in the injected sample with maximum rate and the sample injected with a minimum.

Well integrity is defined as the application of technical and operational solutions to reduce the uncontrollable risk of fluids leakage in the well lifetime. In any drilling and production operation, lack of knowledge about geomechanical behavior of the surrounding formations is considered as a major risk. Therefore, in-situ stress conditions and mechanical properties of formations are important factors in well integrity studies. In this paper, a 3D finite element model was built to simulate the integrity of wells. An FEM analysis was used to investigate the plastic deformation in cement and the Von Mises failure criterion inside the casings under different stress conditions, and to study the mechanical properties of the formation. A clear increase in plastic strain in the cement and Von Mises stress inside the casings was observed with increasing the ratio of horizontal to vertical stress in orthotropic and isotropic conditions as well as with increasing the difference between horizontal stresses in anisotropic conditions. When conducting the translation error sensitivity analysis, the impact of major mechanical parameters of the formation was evaluated as well. The results showed that by increasing Young's modulus, cement became hard and brittle. Meanwhile, an increase in the Poisson ratio led to plastic behavior. The maximum plastic strain was found at the cement-casing boundary due to the presence of a lower cement-formation friction value. The highest Von Mises stress value in the casings was also produced parallel toward the minimum horizontal stress. Additionally, with an increase in the cohesion and friction angle of formation, the cement became harder, and consequently, the safety factor for the casings increased.

It is neccecery to use numerical methods in prediction the long-term behavior of structures with considering different conditions, because of presentation general and quick response of problems. Creep behavior of salt, as a time-dependent behavior, has always caused problems such as shear failure and convergence of oil wells casings. Thus, it is important to study of long-term behavior of these formations and the effect of creep behavior on well stability. In addition to time, salt layer thickness, stress distribution conditions and mechanical characteristic of salt rock are geomechanical factors which affecting on creep behavior of salt formations. Thus, in this paper, 3D numerical simulation using FLAC3D software is being performed to evaluate the effect of salt formation’s geomechanical properties (e.g. salt layer thickness, stress distribution and mechanical parameters of salt rock) on casing collapse of oil wells by considering data from one oil well in Kupal oilfield. For this purpose, at the first, Uniaxial creep test have been simulated similar to real conditions. Then by comparing between experimental and numerical results, constitutive model has been validated. Burgers creep model has been chosen as constitutive model for salt formation based on this validation. To be very close to real condition and also avoiding from simplifications as much as possible, Drilling rate, Drilling mud pressure, cement injection and casing installation have been considered in modeling. Then, three dimensional model has been solved for several period of time. Based on the results, stress distribution conditions have a major role in the creep behavior of salt formation among geomechanical properties. The effect of salt layer thickness on the amount of damage imposed to the casing is negligible. Also, studying the behavior of salt with different elastic modulus has shown that this parameter is an important factor to cause casing collapse of oil wells.

There has been little interest in the application of hydraulic fracture treatment in Iranian oil fields, thanks to the primarily suitable production rates of the vast oil fields. In this paper, hydraulic fracturing treatment was simulated by different models for a carbonate reservoir in the southwest of Iran. Suitable pay zones were nominated based on the lithology, water-oil saturation, geomechanical properties, and finally in-situ stress conditions – with the optimum option chosen based on a pseudo three-dimensional (P3D) model. In this work, modeling with P3D, finite different method (FDM), and the methods proposed by Perkins, Kern, and Nordgren (PKN) and Khristianovic, Geertsma, and de Klerk (KGD) were performed in order to determine and compare fracture growth geometrical aspects and the required pressure. Comparison of the above-mentioned models confirmed that P3D and FDM provides more reasonable results, while neither of PKN and KGD models was suitable for such a complex condition. Eventually, sensitivity analysis of input data, such as in-situ stress, injection rates, and reservoir geomechanical properties, was performed to evaluate the variation influence of these factors on fracture growth aspects, such as required pressures and geometrical specifications. The results showed that successful hydraulic fracturing treatment not only depended on the controllable parameters like fluid and proppant specifications, but also uncontrollable parameters such as reservoir properties and in-situ stress had to be taken into account. This study can help to select the optimum model in future hydraulic fracture design and implement it in carbonate reservoirs with similar conditions.

Drillability of rock is defined in terms of a large number of parameters. However, in most drilling rate models uniaxial compressive strength (UCS) was used as rock drillability. There is a paucity of researches to combine rock drillability with the penetration rate model. Thus, in this study, rock drillability will be calculated based on the penetration rate. BYM was chosen as drilling rate mathematical model to normalize the penetration rate into operational parameters. After eliminating effects of drilling parameters, regression method will be used to evaluate relationships of rock paramters (such as Confined Compressive Strength (CCS), UCS, porosity, clay content, density, Poisson’s ratio, and internal friction angle) with drilling rate. Then, the best parameters of rock based on determination of coefficient will be selected to compute rock drillability. To define coefficients of this model, multiple non-linear regression will be used. The comparison between the modified version of BYM with rock dirllability index and the prior BYM will be done to validate the proposed method. For this research data were gathered from one vertical well in Karanj oilfield. Results indicated that rock parameters significantly affect the penetration rate. Evaluating relationships of understudied rock parameters with drilling rate revealed that UCS, CCS, porosity and shale content have high determination coefficients. The comparison between modified BYM and original BYM showed that applying computed rock drillability using three rock parameters (i.e. CCS, friction angle, density and Poisson’s ratio clay content) in BYM improves accuracy of prediction.

Enjoying the twelfth largest coal reserve in the world، only one percent of Iran’s energy consumption basket is supplied by coal. Now، Iran’s energy economy is under the influence of natural oil and gas resources، causing other more profitable energy resources to be neglected. The Underground Coal Gasification (UCG) technology is a procedure to transform the underground coal into gas، resulting in improving the recovery of coal layers with different thicknesses and depths. This technology may be considered as a strategy to feed the domestic gas network with the synthetic gas of UCG. Therefore، Iran’s gas export capacity will be improved، helping domestic and foreign economy of energy. Implementing and using the UCG technology in Iran will help us take a leap toward the goals of upstream documents and orders of the Supreme Leader in the fields of oil and gas.

Water flow in tunnel projects is one of the main issues that can affect the plan and tunneling activity. Therefore، it is necessary to predict the location and the amount of water flowing into the tunnel. The experience has shown that the accurate prediction of water flow in excavated tunnels due to the lack of consideration all influencing factors، especially the properties and condition of discontinuity is not possible. In this paper، In order to investigate the effect of discontinuities properties on the rate of water flow، the cross section of Koohrang 3 (1+897 - 1+950) with the UDEC software has been modeled. By variation of the properties of discontinuity، the flow rate into the tunnel has been assessed. Results of this study have shown that the variation of the properties of discontinuity has significant influence on the steady state flow of water. Among these properties، the aperture of joint has the most significant effect on flow rate in the tunnel. Analysis of water flow is necessary for construction of underground structures. In this analysis، the possibility of any kind of change in the ground water behavior and flow rate should be considered. In this paper by using numerical model، the effect of discontinuity properties on the water flow rate were studied. Methodology and Approaches: The discontinuity properties have great influence on the water flow rate into tunnels. In order to investigate the effect of discontinuities characteristics on the flow rate of water، the cross section of Koohrang 3 with the UDEC software has been modeled. By variation of the properties of discontinuity، the rate of flow to the tunnel has been assessed. Finally، The water flow rate calculated by numerical modeling were compared with the values obtained from the analytical methods. Results and Results of this study have shown that the increase of the joint spacing reduced the rate of water flow into the tunnel due to the increase of formed blocks’ size. In addition، increase of the joint aperture has substantially increased the amount of water flow to the tunnel. Moreover، by increasing the joint orientation from 30 to 120 degree، the maximum water flow occurred at an angle between 50 and 70 degree. According to results of the investigation among the discontinuities properties، the joint aperture had the greatest effect on the flow rate of water to the tunnel.

This study aims at presenting a numerical model for predicting grout flow and penetration length into the jointed rock mass using Universal Distinct Element Code (UDEC). The numerical model is validated using practical data and analytical method for grouting process. Input data for the modeling, including geomechanical parameters along with grout properties, were obtained from a case study. The effect of rock mass properties such as joint hydraulic aperture, spacing, trace length, orientation and grout properties as yield stress and water to cement, w/c ratio was considered on grout flow rate and penetration length. To illustrate the effect of aforementioned properties, models were constructed with dimensions of 40×20m. A vertical borehole with diameter of 60mm and 10m depth was drilled in a jointed rock media. The results were in a good agreement with analytical method. It was observed that by increasing joint hydraulic aperture, grouting flow increases using a power law function. The optimum grout penetration observed with joint sets intersection of 40°-60° as experienced in practice. With an increase in joint spacing grout penetration increases around borehole when spacing exceeds two meters it decreases, gradually.