bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calibration of Rockmass Failure Criteria for Mines Using Seismic Monitoring Data
Authors: Malovichko D. A. , Rigby A. 
Published: August 2024

ABSTRACT:
A method is proposed for the calibration of a mine-scale numerical stress models using seismic monitoring data. The method is based on comparing the gridded observed and modelled seismic potency of slip-type seismic events according to a misfit/cost function. Expressions are derived for the gradients of this misfit function with respect to the parameters of Mohr-Coulomb failure criteria defining the intact and post-peak behaviour of the rockmass. Determining these gradients requires a single modelling simulation regardless of the number of model parameters; this affords a significant reduction in runtime compared to a simple finite-difference approximation, which requires a number of simulations equal to twice the number of model parameters. The gradient of the misfit function is used in an optimization algorithm (nonlinear conjugate gradient method) to update the failure criteria. The performance of the optimization is demonstrated using synthetic and real data. The proposed method makes it possible to promptly reconcile the numerical model of mines with recent seismic data, which is important for operational forecast of seismic and ground motion hazards for planned mining. An example of the effect of updating the stress model to the assessment of ground motion hazard is presented.

1 INTRODUCTION
Numerical stress models are used extensively in mine engineering practice. The models make it possible to assess the deformations and stresses in the rockmass, which have been disturbed by excavations (shafts, tunnels, stopes, caves, etc.). This helps to ensure that planned design of the excavations is safe. Modern numerical stress modelling algorithms are powerful. They can describe complex 3D geometry of mining and geology with high resolutions. Various constitutive relations are available to represent the behavior of the rockmass before and after the failure. One of the main challenges in modelling is the reliability and completeness of input information about rockmass properties. For example, the properties of rocks can be assessed for small samples (few centimeters size) extracted from boreholes and these need to be extrapolated to larger volumes (meters and tens of meters). Some parts of the rockmass may have sparse coverage by exploration drilling and, therefore, knowledge of their properties is approximate.
Evaluation of Mechanical Properties of Heavy Oil Injection and Production Pipelines in Multi-Component Thermal Fluid Corrosive Environment
Authors: Weng Jintao , Tian Shouceng , Tian Kangjian , Wang Tianyu , Tan Yawen , Zhang Wenhong 
Published: August 2024

ABSTRACT:
Aiming at the problem of dynamic changes in mechanical properties of oil pipes (N80 steel), casings (J55, TP90H, P110 steel) and surface gathering and transportation pipelines (20#) in the multi-component thermal fluid corrosion environment during the thermal recovery of heavy oil. Based on high-temperature and high-pressure corrosion experiments and tensile experiments, this article analyzes the mechanical properties of five types of steels containing corrosion damage. The experimental results show that all five types of steel are severely corroded in this environment, Among them, P110 steel and TP90H steel have the highest corrosion rates, which are 7.83mm/a and 5.78mm/a respectively. Combining the scanning results of SEM, EDS and XRD, it was found that the corrosion products are mainly composed of FeCO3, Fe2O3, Fe3O4 and FeOOH, and these iron oxides formed a double-layer film structure on the steel surface, the outer film is loose and porous, and the inner film is relatively dense. Due to differences in the corrosion products of the inner and outer film layers, there are obvious corrosion pits at the clamp end of the corroded specimens. Tensile tests revealed that the yield strength and tensile strength of steel decrease as corrosion damage increases.

1. INTRODUCTION
Heavy oil resources are abundant and have significant reserves, and are currently a hot spot for oil and gas exploration and development, both domestically and internationally(Omoregbe & Hart, 2022; Yao et al., 2023) Multi-component thermal fluid thermal recovery technology is a highly efficient method for the recovery of heavy oil. This is achieved by injecting high-temperature and high-pressure thermal fluids, such as steam, hot water, N2, and CO2, which reduce viscosity and aid in the recovery process. N2 is not easily soluble in water and has good compressibility. It also has a high volume expansion coefficient and a certain lifting effect on the fluid. On the other hand, CO2 gas dissolves and reduces viscosity when in contact with heavy oil, which can improve the extraction effect and reduce the interfacial tension of crude oil, ultimately improving its fluidity (Dong et al., 2015).
The Influence of Burial History and Capillary Suction on Geomechanical Properties of Clay Shales
Authors: Winhausen L. , Gaus G. , Jalali M. , Amann F. 
Published: August 2024

ABSTRACT:
Geomechanical properties of clay shales significantly depend on mineralogical composition, saturation, and burial history. In this contribution, we provide insights into a unique opportunity to study the influence of burial history on geomechanical parameters of a rock unit in a distinctive area in Northern Germany where clay shales were retrieved at shallow depths. In this area, the mineralogical composition is relatively homogeneous, but thermal maturity increases substantially over a lateral distance of approximately 50 km. Using an empirical correlation between vitrinite reflectance and temperature, and assuming a geothermal gradient of 30 °C/km, initial estimates suggest that maximum burial depths range between 1300 m and 3600 m.
Systematic uniaxial compression tests and consolidated undrained triaxial tests under well-defined saturation conditions suggest a major impact of thermal maturity on geomechanical properties. Although peak strength and stiffness are functions of porosity, which is the main parameter influenced by maximum burial, the general hydro-mechanical behavior remains similar. While comparing the first results from two degrees of thermal maturity in this contribution, the overall goal of this systematic analysis is to develop functions that allow predicting geomechanical properties for a clay shale formation that has undergone different burial histories.

1 INTRODUCTION
Shales and similar clay-rich rocks have increasingly attracted attention for utilization as host rocks for the final disposal of radioactive waste in deep repositories. A precise characterization of such rocks in terms of their (thermo-)hydro-mechanical behavior is therefore fundamental for evaluating their suitability as a geological barrier. This task is, however, challenging since the properties of clay-rich rocks are highly influenced by, for instance, structural and mineralogical heterogeneities. They exhibit state-dependent properties, meaning that mechanical strength or permeability are functions of saturation.
Another important factor influencing the geomechanical properties of shales is their geological burial history, i.e., thermal maturity. During burial, the rock experiences different diagenetic processes such as compaction or cementation as a result of elevated stresses and temperatures.
Prediction of Formation Pressure Relief by Using Neural Network
Authors: Li Yanchao , Gao Yanfang , Shen Shijie , Li Dengke , Chen Zupeng , Liang Xuelin 
Published: August 2024

ABSTRACT:
Accurate formation pressure relief prediction is crucial, especially in drilling operations technically and economically. Its prediction will save costs and time, and even the right decisions can be taken before problems occur. The available correlations for pore pressure prediction depend on logging data, formation characteristics, and a combination of logging and drilling parameters. The objective of this work is to apply BP neural networks (BPNN) models to estimate the formation pressure relief through the available drilling data. The used parameters include Gama (Gr), interval transit time (Dt), wave velocity, and resistivity(R10). A data set obtained from some vertical wells was utilized to develop the predictive model. A different set of data was utilized for validating the proposed artificial intelligence (AI) models. The models forecasted the output with a good correlation coefficient (R) for training and testing. Moreover, the mean relative Error (MRE) did not exceed 15.9%. By comparing and analyzing the formation pressure predicted by the traditional model Bowers, the BPNN model has better performance. The predicted results of the BPNN model are closer to the true pressure coefficient and have smaller errors. This study proves the reliability of the proposed models in estimating the formation pressure relief while drilling using drilling data.

1. INTRODUCTION
Pore pressure prediction is very important for drilling operations. Pore pressure influences drilling efficiency and well operation costs, such as well designing, wellbore stability analysis, casing design, mud program designs, drilling operations, and structural optimization (Lee B Y et al., 1998). Accurate pore pressure determination is important for selective production and injection.
The abnormal pressure is divided according to the size of the formation pressure coefficient (SONG Xianzhi et al., 2022), which is defined as the ratio of the measured formation pressure to the hydrostatic pressure at the same depth, which is a dimensionless quantity, which reflects the relative level of the formation pressure (LUO Ming et al., 2021). When the pressure coefficient is less than 0.8, it is abnormal low pressure, and when the pressure coefficient is between 0.8∼1.2, it is normal pressure. When the pressure coefficient is less than 0.8 or greater than 1.2, it is abnormal pressure. The normal pressure of pore pressure usually does not cause any drilling problems. Abnormal pressures need to be considered in the design of oil wells; Tubing, slurry density, cement planning, and casing solidification depth are all included in this. Many problems, such as kicking and bursting, shale uplifting, and differential pressure pipe adhesion, are thought to be the result of pressure abnormalities (Rock Mechanics, 1995).
Experimental Investigation of Chalk Influx in a Depleted Reservoir
Authors: Bhuiyan M. H. , Papamichos E. 
Published: August 2024

ABSTRACT:
Chalk is generally a weak reservoir rock with high porosity and moderately low permeability compared to sandstone reservoir rock. Chalk production and chalk influx events are a challenge that operators encounter during the production of hydrocarbons from chalk reservoirs. Appropriate completion of the well is therefore crucial for long term optimal production. The challenges are bigger when producing from a depleted reservoir. To avoid problems during production and increase the lifetime of the producing reservoir, it is crucial to comprehend the behavior of chalk production and/or chalk influx in a depleted reservoir. A series of experiments has been undertaken to investigate this behavior in simulated depleted reservoirs using outcrop Mons chalk as testing material in laboratory experiments. The tests were conducted in two phases. The first phase involved simulation of depletion at two different stress levels followed by re-pressurization and the second phase replicated production by increasing the applied drawdown. The results indicate a reduction in drawdown stress within a depleted reservoir compared to a non-depleted one. It was also found that the critical drawdown is independent of the effective stress amplitude.

1. INTRODUCTION
Weak chalk has a strong tendency to compact when the hydrocarbon is produced due to an increase in effective stresses. The compaction observed in the high porosity chalk reservoir can be extended to the sea floor surface; one well-known example of this phenomenon is the surface subsidence observed in the Ekofisk Field in the North Sea. Oil companies employ several reservoir management systems to prevent such situations. One strategy involves increasing the pore pressure in the reservoir to prevent reservoir compaction and enhance oil recovery. However, the high porosity and compressible nature of the reservoir pose significant challenges (Omdal, 2010). Drilling new wells to produce from such depleted and re-pressurized reservoirs is technically demanding in terms of borehole stability. Production of hydrocarbons from depleted and re-pressurized reservoirs adds another level of complication to an already challenging reservoir management system.
Chalk influx or liquefaction in the form of toothpaste like material involves a significant part of chalk formation near the borehole which eventually fills the well, tubing and destroys the flow (Kristiansen and Meling 1996). It is important to understand the behavior and mechanisms of chalk influx to avoid or effectively manage chalk influx events to ensure uninterrupted production and maximize recovery.
3D Fracture Propagation Simulation of Shale Oil Reservoirs with Bedding Planes and Natural Fractures Development
Authors: Wang H. Y. , Guo T. K. , Chen M. , Zhang B. , Wang J. W. 
Published: August 2024

ABSTRACT:
The development of shale oil reservoirs has received extensive attention from countries around the world. Shale oil reservoirs are often distributed with a large number of horizontal bedding planes (BPs) and natural fractures (NFs), the presence of both have a greater impact on the propagation of hydraulic fractures. The continuous-discontinuous element method (CDEM) integrates the advantages of the finite element method and discrete element method, which is very suitable for the numerical simulation of complex fracture propagation in shale oil reservoirs. According to the geological characteristics of shale oil reservoirs in Longdong area of Ordos Basin, a three-dimensional fracture propagation model of double BPs and a three-dimensional mine-scale fracture propagation model considering the BPs and NFs were established based on CDEM, the width and range of the opening of BP under the influence of different factors were analyzed, and the fracture propagation law under different factors was clarified. The results show that (1) With the increase of difference between vertical stress and minimum horizontal stress, the BP opening width and the BP opening range both decreases; With the increase of BP cohesion, the BP opening range is reduced. (2) Increased displacement, increased BP opening width and opening range. As viscosity increases, the maximun BP opening width increases but the BP opening range decreases significantly. (3) Under the combined influence of BPs and NFs, the asymmetry of the two wings of hydraulic fracture is significant at low displacement, while the spread non-uniformity of the two wings decreases at high displacement; when the viscosity is high, the NF opening range is small, and the spread of the two wings is non-uniform. (4) At NF approach angles &gt;60°, hydraulic fractures tend to cross through NF, and NF opening range is small. This study provides theoretical guidance for realizing efficient development of target shale oil reservoirs.

1. INTRODUCTION
At present, conventional oil and gas resources are difficult to meet the increasing energy demand of human beings. The shale oil and gas revolution, represented by breakthroughs in the exploration and development technology of unconventional oil and gas resources, has triggered a major change in the international energy landscape (Feng et al. 2020; Tong et al. 2018; Wang et al. 2016). In 2022, China's shale oil production exceeds 300×104 t, a nearly three-fold increase compared to 2018, strongly contributing to the growth of shale oil production, which is currently an important part of China's oil and gas energy mix.
Exploring Ground Penetrating Radar (GPR) Simulation for Imaging and Determining Electromagnetic Wave Velocity in Volcanogenic Massive Sulfide (VMS) Deposits
Authors: Abbasian L. , Butt S. D. 
Published: August 2024

ABSTRACT:
Ground-Penetrating Radar (GPR) simulation plays a pivotal role in geophysical methods, aiding in survey design, understanding physical behaviour, and quantifying responses. This study employs the gprMax software to simulate the propagation of electromagnetic waves through different Volcanogenic Massive Sulfide (VMS) deposits, each with unique electrical properties. The fundamentals of GPR modeling and factors influencing survey design (operating frequency, recording time window, temporal and spatial sampling interval) are outlined. Careful consideration of these parameters is essential for effective GPR surveys. In addition, results from the simulations of EM wave propagation through VMS minerals such as Galena, Bornite, Magnetite, Pyrite, Sphalerite and Hematite, and their host rocks were utilized to calculate wave velocities in each mineral, rendering it possible to determine the location of Boundaries of VMS veins within the host rock using this method. Some deposits with lower electrical conductivities, showed possibility of being imaged successfully using Electromagnetic (EM) methods. In contrast, some other deposits, having higher electrical conductivities, tended to weaken electromagnetic signals, especially within the frequency range used in GPR applications. This study enhances our comprehension of GPR simulation and its possible uses in geophysics, specifically in the characterization of diverse geophysical materials that possess distinct electrical properties.

1 INTRODUCTION
Volcanogenic massive sulfide (VMS) deposits, are key sources of metals like Zn, Cu, Pb, Ag, and Au. Also, there is a substantial proportion of pyrite, or iron sulphide (FeS2) that is frequently connected to VMS occurrences. The economic importance of these deposits is underscored by their contribution to metal production. Most VMS deposits consist of massive (&gt;40 percent) sulphide (typically pyrite, pyrrhotite, chalcopyrite, sphalerite, and galena as well as magnetite) (Best, 2015). These minerals and their associated economic minerals are listed in Table 1. GPR simulation is a powerful tool in delineating VMS deposits, crucial for optimizing GPR survey parameters and understanding mineral-host rock interactions. This approach facilitates accurate mapping and exploration of VMS deposits, enhancing the effectiveness of geophysical surveys by allowing for precise adjustments in survey design based on the simulation outcomes.
Study on the Damage Mechanism of Rock Around Wells Subjected to Impact Loading
Authors: Huang T. , Liu Q. Y. , Zhu H. Y. , Dai X. W. , Ji R. , He X. , She C. Y. , Zheng M. J. 
Published: August 2024

ABSTRACT:
To investigate the rock damage characteristics in the vicinity of a wellbore under mid-to-high temperature reservoirs with varying impact parameters, this study conducts bit impact rock-breaking experiments under high-temperature and high-pressure conditions. Standard core samples are drilled at different positions on the wellbore wall to test and obtain the distribution pattern of microcracks in the surrounding rock and to characterize their microdamage attributes. Numerical simulations are then carried out to further analyze the damage patterns to rocks near the wellbore caused by impact drilling. The results demonstrate that impact drilling can cause damage to rocks near the wellbore, with the damage becoming more severe and the microcracks more densely packed as one approaches the wellbore wall. The temperature of the reservoir significantly influences the effectiveness of impact drilling. Different phases of impact also affect the stress state and damage characteristics of the rocks, particularly during the unloading phase, where the bottomhole and surrounding rocks generate more fissures.

1. INTRODUCTION
As an important clean and renewable energy source, geothermal energy has the characteristics of low carbon, environmental protection, stability and high efficiency. It is one of the most competitive renewable and clean energy sources (Yu et al., 2018). Geothermal resources are mainly divided into open heat extraction and closed heat extraction according to different development methods. Studies have shown that the former is superior to the latter in terms of economy and heat extraction efficiency (Wang et al., 2019). For open heat extraction, formation permeability is an important factor to determine the efficiency of heat extraction. On the one hand, the higher the formation permeability, the greater the flow rate of the fluid, the more heat it can carry, and the higher the convective heat transfer intensity, so the thermal efficiency is significantly increased. On the other hand, the currently under construction and completed water-intaking geothermal systems require tail water recharge to ensure the sustainability of heat extraction and prevent environmental pollution and land subsidence. It can be seen that improving the formation permeability has become a key link to strengthen the heat extraction effect.
Numerical Investigation on the Rock Breaking Performance of Special-Shaped PDC Cutters Combination
Authors: Jin Ming , Chen Xuyue , Li Gengchen , Cao Xiaohua , Wang Rong , Zhu Mingchi 
Published: August 2024

ABSTRACT:
The special-shaped polycrystalline diamond compact (PDC) cutter has good rock breaking performance. This paper adopts the finite element method to conduct research on the rock-breaking capabilities of special-shaped PDC cutters. The results show that: with the increase of the spacing between the front row of cutters, the cutting force on the back row of cutters gradually increases and then tends to be stable. The optimum spacing of cutters in the combination of ‘axe-shaped and triple-ridged cutters' is 11mm, the optimum spacing of cutters in the combination of ‘axe-shaped and conical cutters’ is 14mm, the optimum spacing of cutters in the combination of ‘conical and triple-ridged cutters’ is 13mm. In transverse vibration, the combination type of ‘conical and triple-ridged cutters’ has the smallest vibration condition. In the axial vibration, the combination of ‘axe-shaped and conical cutters’ has the lowest vibration. The results of the study can provide a basis for the selection of cutter combinations and the optimal design of drilling tools for PDC drills.

1. INTRODUCTION
With the increasing global demand for energy, the exploitation of deep formation oil and gas resources has become one of the focuses of attention in the energy industry (Sun et al., 2013). Deep formation oil and gas resources are rich in reserves and high in quality, however, the characteristics of deep formations such as high rock hardness, strong heterogeneity of formations and high geostress severely limit the drilling efficiency in deep formations (Chen et al., 2024; Guo et al., 2019; Wu et al., 2020). How to efficiently crush rocks in deep hard-to-drill formations and improve rate of penetration has become a key problem to be solved. Conventional rock-breaking techniques are often ineffective when facing deep formations, and it is difficult to meet the industrial demand for efficient, safe, and low-cost drilling (K. Abbas, 2018). Special-shaped Polycrystalline Diamond Compact (PDC) cutter combination rock-breaking technology, as an innovative tool and method, offers a novel solution to overcome the limitations of traditional techniques.
Special-shaped PDC cutters not only efficiently crush a wide range of rock types, but also remain stable and wear-resistant over long periods of high-load operation (Che & Ehmann, 2014). In the combined rock-breaking technology of special-shaped PDC cutters, cutters of different shapes and sizes work in concert with each other to maximize crushing efficiency and reduce energy waste.