bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessing the Effect of In-Situ Stress Conditions in Back-Analysis of Rock Mass Parameters of Tunnels Using Machine Learning Techniques
Authors: Khetwal A. , Gutierrez M. 
Published: October 2022

ABSTRACT:
One approach to improve the reliability of predicting the response of tunnels is the "design as you go" method, where tunnel response is monitored during tunneling using field instrumentation. In the present study, various machine learning (ML) techniques are evaluated, and the best approach is proposed for the back-analysis of tunnel response. Incorporating in-situ stress conditions in back analysis is also essential as these are responsible for short- and long-term deformations. The study aims at predicting the cohesion and friction angle for a tunnel by setting the monitoring data and in-situ stress conditions. The ML techniques are combined with the results obtained from the commercially available finite difference code FLAC, widely used in geotechnical modeling. The ML algorithm with maximum accuracy is then used to determine the input parameters using the synthetic monitoring data. The present study evaluates a single tunnel with an overburden of 1000 m and an in-situ stress ratio ranging from 0.25 to 3 to prepare a training and validation set. The results show that with an acceptable 0.1% error, the Levenberg-Marquardt Back-Propagation Method (LMBP) of Artificial Neural Network (ANN) is found to be the most suitable ML algorithm.

1. INTRODUCTION
The key to the meticulous design of the underground structure is the careful assessment of ground parameters. Evaluation of rock mass behavior is crucial in determining the necessary support measure design that ultimately defines the safety of underground structures. This assessment is based on the results obtained from the numerical models with rock mass parameters as input data prior to construction. Bertuzzi (2017) pointed out that the elastic modulus of rock mass is often calculated using the correlations obtained from the rock mass classification system. Many researchers have expressed difficulty in interpreting the rock mass parameters using the in-situ testing as high variability in the results can be obtained, and the average behavior can be assessed by performing a large number of tests (Vibert and Ianos, 2015). Back-analysis of the rock mass parameters using the monitoring data is another approach that has proven to be helpful in optimizing underground structures’ overall design and is the aim of the present study. The back-analysis aims to validate the model parameters and improve the forward modeling of subsequent excavations. Re-calibration of the back-calculated parameters optimizes the design and overall project. Callisto and Ricci (2019) studied the tunnel damage response under seismic loading. It was found that back analysis contributed to assessing the primary causes of damage: geometry and dynamic response of lining. The crucial point for performing the back analysis is identifying the parameters that affect its accuracy.
A Simplified Hydro-Mechanical Model for Sanding from Hollow Cylinder Tests
Authors: Gravanis E. , Sarris E. , Patruno S. 
Published: October 2022

ABSTRACT:
Particles produced by the hydro-mechanical processes during sanding in hydrocarbon wells is a highly complex physical process. Sanding onset is influenced by a number of factors which include mechanical failure and hydrodynamic erosion. Over the years a number of mathematical and numerical models have been developed to describe the sand production process, involving sanding criteria or constitutive laws of mechanical or hydro-dynamical nature. In this work we propose a new simplified model working along the lines of the hydro-dynamical constitutive law of previous research works. The model amounts to a set of two ordinary differential equations coupling the mechanical process of plastic yielding with hydro-dynamic erosion, including degradation of the material. The model is constructed for hollow cylinder tests which allows cylindrical symmetry which is particularly useful for determining the sand production coefficient λ from such tests. The sand production coefficient as a function of the externally applied stress is estimated from previously published experimental data via a single parameter best fit. It is shown that the sand production coefficient is nearly constant for the range of values of the external stress considered. Additionally, the mathematical sand production curves capture fairly well the experimental data.

1. INTRODUCTION
The production of sand particles from oil and gas wells is a phenomenon by which detached rock solids, due to erosion, migrate from the exposed surface of the well along with reservoir fluids during production. Predicting sand production is highly important in hydrocarbons recovery because they can cause a number of operational problems like: local formation failure, blocking of perforation channels, inability of sand control measures, which may lead eventually to local well collapse or in extreme cases cause catastrophic failures (Wilson et al., 2002; Rahmati et al., 2013; Volonté et al., 2013; Wang and Sharma, 2016; Li et al., 2018; Eshiet et al., 2019). The majority of rocks that are prone to sand production are sandstones, mainly poorly consolidated or even consolidated, but also hydrocarbons provinces. For these reasons, petroleum companies are seeking collaborations with academia in search for solutions via advance modelling to help in the understanding of the physics and the mechanics of this phenomenon because it costs to the entire industry 2 billion per annum (Gravanis et al., 2015; Gravanis et al., 2016; Sarris et al., 2021).
A Comprehensive Constitutive Model Solver
Authors: Chieslar J. D. 
Published: October 2022

ABSTRACT:
The object-oriented software concept is applied to material mechanics calculations. The result is a comprehensive predictor-corrector which has been employed to solve virtually all of the constitutive exercises in a mature, general-purpose, finite element program. In addition to updating internal variables consistent with global inputs (corrector), the software also produces consistent material tangents (predictor), without resort to formulae. Coupled mechanical-thermal-porous flow problems are addressed as well as compound mechanical responses: creep-plasticity, creep-damage, etc. Material and spatial coordinate transformations are incorporated as well as transformation to and from local material axes. Internal calculations may be undertaken in either spatial or material coordinates, depending upon the native definition. Even viscoelasticity and hyper-viscoelasticity, via Prony series, are efficiently handled by the sparse solver. A tool to exercise any material model, simulating global inputs, is incorporated. Historical plots may be produced and inputs may be cyclical or otherwise simulate complex histories. This is accomplished by using PostScript operators.

1 INTRODUCTION
It is perhaps most common in commercial modeling software that each constitutive model is self-contained, that is, each solves the responses and forms the material tangents (algorithm-oriented software design). There is much advantage to be gained by employing a uniform solution/tangent formation strategy for all material models. Indeed, this is the subject of this communication. At first examination, this may seem incongruous considering the different solution strategies employed for different models. For example visco-elasticity, via a prony series, is most often solved by a recursive solution scheme, whereas plasticity would be solved via a Newton-Raphson scheme. Of course, for simplified versions of these models, a forward difference integration scheme is employed, Flac3d, for example. If the constitutive model is algorithmically nonlinear, it is tacitly assumed that any path dependence is captured by taking small time/load steps. The highly nonlinear nature of strain-hardening models, however, generally requires iteration at the constitutive level. This is generally not supported in forward difference programs so the material models in these codes tend to be relatively simple.
Understanding Salt Mine Ground Behavior Through Geotechnical Monitoring and Data Analysis
Authors: Gregory S. A. 
Published: October 2022

ABSTRACT:
The Waste Isolation Pilot Plant (WIPP) was constructed for the permanent disposal of defense-generated transuranic waste from DOE sites around the United States. WIPP functions as a category 4 mine and category 2 nuclear facility. The waste is to be deposited 660 m (2150 ft) beneath the Earth’s surface inside of the Delaware Basin salt bed for permanent disposal. The first waste shipment arrived at WIPP in 1999 and is currently anticipated to operate beyond 2050. Due to the creeping nature of salt and the hazards involved in handling nuclear waste, it is paramount to monitor the changing conditions of the mine. Throughout the WIPP’s project life, geotechnical and mining engineers have developed and improved upon the data collection methods, instrumentation, and analysis that is required to monitor the ground movement in this unique salt mine. Using forecasting methods, WIPP’s geotechnical engineering team has predicted several ground falls and provides support to the site’s mining endeavors. A review of the historical ground movement data collection methods and analysis is given, as well as examples of ground falls and geotechnical abnormalities. In addition, ongoing application of operations research and engineering statistics will be discussed.

1. DISCLMAIMER
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Analysis of Pillar Strength and Design in a Karst-Affected Underground Stone Mine
Authors: Soni A. , Monsalve J. , Ripepi N. 
Published: October 2022

ABSTRACT:
Underground stone mines are often prone to karst formations created by the gradual erosion of carbonate rocks due to groundwater flow. The prevalent fracture network in these stone deposits offers favorable conditions for acidic dissolution, which leads to the formation of large karst cavities. The interaction of these cavities with the extensive presence of discontinuities is the major cause of ground control problems encountered during stone mining operations. This paper presents a case study for analyzing the effect of the karst cavity on the strength of a pillar in an underground room-and-pillar stone mine. Numerical analyses show that the presence of these voids in a pillar contributes to a considerable decrease in load-bearing capacity. Any development through excavation or blasting into the affected areas may pose a safety hazard to the miners. Apart from that, this may also disrupt production and burden the pre-planned mine operations. The study for estimating pillar strength using numerical modeling could provide a pragmatic approach to designing future pillars affected by karsts. The shape and volume of the karst cavities inside the concerned pillar were approximated using ground-penetrating radar (GPR) surveys. LiDAR scans were performed to map the discontinuity network around the pillars, and Discrete Fracture Network (DFN) technique was implemented to simulate the joint network in the pillar’s rock mass. The behavior of the pillar with the increase in axial compressive stress was observed with the help of Distinct-element modeling (DEM) using 3DEC software. The pillar’s rock mass is simulated using Elastic and Mohr-Coulomb constitutive models. Two scenarios are presented to assess the pillar strength with and without the presence of karst. Pillar strength is compared to the estimated current stress levels to understand the potential for improvement in the pillar design. The research emphasizes the importance of pillar design while maximizing safety and production in underground stone mines with karst cavities to prevent pillar instability or local roof failures.
Vermiculite as an Anti-Sag Additive for Water-Based Drilling Fluids
Authors: Basfar Salem , Ahmed Ashraf , Elkatatny Salaheldin , Bageri Badr 
Published: October 2022

ABSTRACT:
Barite is widely used as a weighing material since it has several advantages such as high specific gravity, readily accessible, and environmentally benign. Even though, several difficulties with barite particle settling particularly at high-pressure high-temperature drilling operations and removal efficiency necessitate further investigation. The utilization of magnesium-aluminum-iron silicate (vermiculite) with its ecofriendly effect was studied in this work as an additive for improving the drilling fluid characteristics. Variable concentration of vermiculite was added to the water-based mud (WBM) to address the static and dynamic sag tendencies at 250 and 120 °F, respectively. Furthermore, the influence of vermiculite on rheological characteristics and filtration performance was studied under HPHT circumstances. The sagging experiments showed that adding 4 lb/bbl vermiculite improved the WBM stability properties by increasing the suspension capacity of barite particles. Also, this amount of vermiculite significantly enhanced the rheological characteristics as the plastic viscosity to yield point ratio (YP/PV) was increased from 1.6 to 2.5. The HPHT filtration showed that 4 lb/bbl decreased the filter cake thickness by 37.5% and reduced the filtrated volume by 39%.

1. INTRODUCTION
The solids sagging, thermal breakdown of polymeric compounds, and flocculation are commonly encountered when drilling deep wells with elevated temperature and high-pressure formations (DeAngelis et al., 2011; Kruszewski and Wittig, 2018; Reinsch et al., 2015; Saasen et al., 1995). Therefore, an optimization of the common water-based mud (WBM) with qualified additives becomes necessary to fulfill the challenges in such harsh conditions (Ahmed et al., 2021; Fink, 2015). At WBM, the sagging phenomenon of solids, such as barite, usually exhibits when the temperature reaches 250 °F (Ahmed et al., 2020; Tehrani et al., 2014), resulting in density variation and inconsistent drilling fluid properties which exhibits severe technical, operational, and well control issues; since the mud weight at the upper sections will not maintain the sufficient pressure control, while at the bottom, the precipitation of the solid elevates the equivalent circulation density and raises the potential pipe sticking and loss of circulation (Amighi and Shahbazi, 2010; Bern et al., 1996; Murray et al., 2013; Scott et al., 2004; Wilson, 2014).
Testing and Analysis of Potential Damage Factors in Carbonate Reservoir
Authors: Xia X. , Mou J. Y. , Zhang Y. C. , Li X. M. , Li Y. L. 
Published: October 2022

ABSTRACT:
The pollution damage of injected water, fracturing fluid and drilling fluid in carbonate reservoir are mainly studied, however, the potential product precipitation damage have been seldom studied. Majiagou Formation in Daniudi gas field mainly has two kinds of rock samples, one with dolomite as the main component and the other with gypsum as the main component. On the one hand, through mineral composition analysis, the main composition of dolomite sample is CaCl2 and MgCl2. Then the ion concentration of acid rock reaction product solution was tested, the results show that the highest Ca2+ content and the highest Mg2+ content in the four groups are lower than the lowest solubility of Ca2+ and Mg2+, so the products will not reach supersaturated state and precipitate in the solution. On the other hand, for the rock sample dominated by gypsum, the mass of rock plate changes little after water immersion and acid solution corrosion. Then the gypsum samples were subjected to acid displacement, and the surface morphology changes of the samples were observed and the mass changes were measured. The test results showed that the dissolution amount of the samples was small. Therefore, it shows that water and acid will not react with gypsum and will not produce potential precipitation.

1. INTRODUCTION
Carbonate reservoir is a part of unconventional oil and gas resources. The key technology of developing carbonate reservoir is acid fracturing. (Arthur B et al., 2010). However, the acid fracturing construction process will also bring negative effects, mainly manifested in the damage to the reservoir.
At present, carbonate reservoir damage mainly studies the pollution damage of injected water, fracturing fluid and drilling fluid (Tiner R. L et al., 1974, Moore W. R et al., 1996, and Shi F et al, 2018). Under the action of high differential pressure, some fracturing fluid will leak out and enter the reservoir matrix (Reinicke A et al, 2010, and Fang W et al., 2016). Usually, this part of fracturing fluid is difficult to completely break the gel, which is easy to cause mechanical blockage of matrix pore throat and reduce reservoir permeability. In the process of fracturing fluid invasion, flowback and production, due to the carrying effect of fluid on reservoir particles, when the particles migrate to the hole roar with small radius, they will be blocked, resulting in a certain degree of damage to reservoir permeability (Gray D. H et al, 1996, Wilson M. J ,2014, Q. Zhang et al, 2014, and AlMubarak T. A, 2015).
Prediction Method of Cutting Settling Velocity in Gas-Liquid Two-Phase Flow Based on Multi-Gene Genetic Programming
Authors: Zhu Zhaopeng , Song Xianzhi , Han Liang , Zhang Rui , Liu Wei , Fu Jiasheng , Hu Xiaoli , Li Dayu , Qin Furong , Yang Donghan 
Published: October 2022

ABSTRACT:
The cuttings settling process becomes erratic in the complex gas-liquid mixture under gas kick, it is very difficult to accurately describe the migration process of cuttings. Meanwhile, the traditional empirical formula based on fitting experimental data is difficult to accurately predict the complex cuttings settlement. Neural network and other intelligent models with high prediction accuracy are difficult to be popularized and applied due to their black box properties. Multi-gene genetic programming can accurately describe complex nonlinear problems and automatically optimize the structure and parameters of the mathematical model, so as to effectively reduce the complexity of the model. Based on the multi-gene genetic programming algorithm, this study used a variety of input parameters to predict the settling velocity, explored the relationship between the input variables and the result, and established an explicit mathematical model of settling velocity with RMSE of 0.0896 in test set and R2 of 0.9292, which breaks the accuracy limits of traditional empirical model and the inexplicability of neural network model. This new method for predicting cuttings settling velocity in gas-liquid mixture can provide theoretical guidance for efficient cuttings migration in wellbore during gas kick.

1. INTRODUCTION
The migration of bottom-hole cuttings during oil and gas well drilling and the migration of solid proppant in cracks during fracturing are examples of particle settling in the field of petroleum engineering (Xu et al, 2017). When the particles settle freely in the fluid, they will be affected by their own gravity, buoyancy and resistance (Nouri et al, 2014). When these three forces reach an equilibrium state, the particles will reach a stable settling velocity, which is called the particle terminal settling velocity (McCabe et al, 2004). Understanding the settling law and properties of solid particles in their fluid environment, such as rock cuttings and fracturing proppant, is critical for enhancing drill cleaning efficiency and fracturing design. Until now, Many industry specialists and academics have devoted a significant amount of time and effort to the study of particle settling velocity.
Influencing Factors of Acid Etching Fracture Conductivity of Tuff Reservoir in Northeastern Sichuan Block
Authors: Xie Jinyang , Zuo Luo , Hou Bing , Dai Yifan , Li Jiaxin , Zhuang Li , Elsworth Derek 
Published: October 2022

ABSTRACT:
With the continuous depth breakthrough of two ultra-deep exploration wells in northeastern Sichuan block, tuff reservoir was finally discovered at the depth of 6700-7300 m. It belongs to ultra-deep tight gas reservoir with low brittle mineral content and high clay content. Hydraulic fracturing is hard to be reformed this special reservoir, easy to appear hydration expansion and other problems. However, the research and development of such tight tuff reservoir with high temperature and high pressure are relatively low in the domestic and overseas until now. Therefore, it is of great significance to carry out experimental research on relevant reservoir reconstruction methods of such rocks and explore the factors of fracture conductivity here. In this study, the influence of acid type, sanding concentrations, proppant size was research by a new experimental installation. The factors of fracture conductivity are analyzed by experimental data and the reconstitution of fracture surface. The results show that before the abnormal point, the acid etching effect of crosslinked acid on tuff is better than that of gelling acid. At the condition of closure pressure is lower 30 MPa, the higher sanding concentrations, the higher fracture conductivity, then narrowed the gap among them. Meanwhile, the larger proppant size, the higher fracture conductivity in low closure pressure. With increasing closure pressure, fracture conductivity of smaller size proppant decreased slowly. In conclusion, it is also convenient for the field operation to choose the best acid and proppant parameters.

1. INTRODUCTION
As an important new field of exploration and development of oil and gas resources in the world, igneous reservoir have gradually received extensive attention from geological and petroleum researchers all over the world. The exploration and research on the igneous reservoir has a history of more than 130 years. Now, some igneous reservoir have been exploited in the United States, Indonesia, Japan, Brazil, Australia and other countries (Tang, et al. 2020). Its oil and gas mainly come from athrogenic rock reservoir. Athrogenic rock is a transitional type between magmatic rocks and sedimentary rocks, and it is also one of the important reservoir rock types. It has the advantages of thick pay information and large reserves (Li, et al. 2015). The tuff reservoir is very complex and special and has both lithologic characteristics in terms of petrophysics and diagenesis (ZHANG, et al. 2012). The low degree of development of original porosity and poor connectivity of pore throats indicate that such reservoir is tight reservoir (Zeng, et al. 2021). At present, the well known athrogenic rock reservoir in the world including East Anatolia Basin in Turkey (Gecer-Buyukutku, et al. 2005), Bohai Bay in China (Zhao, et al. 1996), Erlian (Guo, et al. 2013) and Hailar (Yu, et al. 2013) basins.