bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimalisasi Kualitas Pelayanan Front Office Department Di Masa New Normal Terhadap Kepuasan Tamu
Authors: Elizabet Sagala Afrilia
Published: August 2024

Optimizing the quality of service during the new normal for guest satisfaction at The Royal Surakarta Heritage MGallery by Sofitel ". The object of this research is the front office department, and the type of method used is the descriptive qualitative method. The data in this study were collected by data collection techniques such as observation, interviews, and documentation. The resource persons taken were front office officers, operational managers, and hotel guests. The technique of data validity uses triangulation technique, source, and time. There is a difference between before and after a pandemic. The service quality contains 5 dimensions including Tangibles (physical evidence), Reliability (reliability), Responsiveness (responsiveness), assurance (Assurance), and Empathy (empathy). The conclusion from this research is that the dimensions of tangibles, responsiveness, assurance, and empathy have met the expectations of guests so that guests can be said to be satisfied. However, the reliability of the front office cannot be said to be satisfactory because the accuracy in housekeeping provides rooms so that it occurs in the lobby which causes not keeping a distance.
ANALISIS MINAT KUNJUNGAN KEMBALI TAMU SANGKAN RESORT AQUA PARK PADA AKHIR PANDEMI COVID-19
Authors: Yulius Kevin Gustian , Ferdela Fernandez  , Yosep Dudedes Timba
Published: August 2024

This study aims to analyze the factors that influence revisit intention to Sangkan Resort Aqua Park at the end of the COVID-19 pandemic. This research is an explanatory research with quantitative data collected through questionnaires. Results of the validity and reliability tests show that the research instrument is valid and reliable. The results of data analysis show that only the fulfillment variable has a significant influence on the guest's revisit intention. Physical environment, social environment, and price variables do not have a significant effect partially, but simultaneously these four variables have a significant influence on the guest's revisit intention. The coefficient of determination shows that the independent variable can only explain about 24.4% of the variation in intention to return. These findings can provide insight for the hospitality industry at Sangkan Resort Aqua Park to improve service quality and competitiveness. Hotel managers can focus more on meeting guest needs to increase interest in return visits. In addition, this research also contributes to scientific knowledge in the hotel and tourism industry. The results of this research can be used as a reference for developing tourism policies at the regional and national levels and helping local economic growth after the pandemic ends.
Creative Economy Promotion Model As Culinary Tourism In Kranggan Lumpia Leather Center, Semarang City
Authors: Amelia Tri Nursifa  , Nina Mistriani  , Ayu Puspita Rini  , Flores Harliesyahputra Laia  , Haidar Hafiiz Azzam  , Herni Susanti Ndruru  , Melvannisa Ayu Dara Ninggar  , Yasmin Carolina Gea
Published: August 2024

Creative activities are related to the food and beverage business which is popular with the public and adds value to the creative products of culinary industry players. The aim of the research is to analyze and develop the creative economy of the culinary tourism sector in Kranggan Village, Semarang City. This research uses a qualitative descriptive approach with survey and interview methods. The promotional model developed integrates the following elements: Promoting local culinary delights, collaborating with culinary industry players, and using a word of mouth promotion model. The research results show that this promotional model has succeeded in increasing visits to local culinary destinations in encouraging culinary business growth. The promotion model has become a tradition and cultural identity for the culinary industry around Kranggan Village, Semarang City. So that the Lumpia Skin Center is known to the public and culinary businesses in Semarang City. This has an impact on the economy of the surrounding community, as well as the creation of jobs in the creative economy sector.
Proses Penyusunan Proposal Corporate Event oleh PT Aldena Ganthari Kreatif
Authors: Rizki Tamara Trima
Published: August 2024

This study aims to analyze the process of preparing a proposal for the event "Re-Grand Launching BMW Performance Motors Indonesia" by PT Aldena Ganthari Kreatf. The purpose of this study is to understand the steps in the preparation of the proposal as well as the challenges faced and solutions implemented during the process. The research methods used are observation, secondary data collection through documentation, and interviews and analysis methods carried out are qualitative descriptive. The results of the study show that 1) In the process of preparing the BMW PMI Re-Grand Launching proposal, there are several discrepancies with the pitching process theory in Aryanti & Rudatin (2022). 2) The challenges faced in the proposal preparation process are the short time in processing and changes in the client's wishes that have the potential to change the concept. In facing these challenges, Event Organizers (EOs) must create vendor-related databases and create effective schedules to achieve short time targets and always maintain communication with clients.
Potensi Implementasi Teknologi Augmented Reality Pada Industri Food & Baverage Dalam Meningkatkan Kepuasan Pelanggan
Authors: Averil Rorizanda  , Bambang Suharto
Published: August 2024

The dynamic and competitive Food and Beverage (F&B) industry requires continuous innovation to maintain its competitiveness. One innovation currently attracting attention is the use of Augmented Reality (AR) technology in the context of consumer experiences. With AR, customers can interact with menus, view 3D visuals of dishes, and access additional information. The implementation of AR in the food and beverage industry has the potential to significantly enhance customer satisfaction through improved customer experiences. This research aims to thoroughly explore the potential offered by Augmented Reality (AR) technology in enhancing customer satisfaction in the Food and Beverage (F&B) industry. By focusing on the integration of AR within the F&B environment, this study intends to understand how the implementation of AR can alter the way customers interact with products and services, as well as its impact on their perceptions and satisfaction, an area that currently lacks extensive research. The research methodology employed is a systematic literature review with a qualitative approach, enabling the identification, evaluation, and synthesis of findings from various related studies. The analysis of ten reviewed literature pieces indicates that the use of AR in restaurant menu applications holds significant potential for enhancing customer experiences and adding value to businesses in the F&B industry. Factors such as design, device availability, and consumer acceptance also play crucial roles in the successful implementation of AR in food and beverage businesses. Furthermore, companies need to pay attention to product quality, customer service, and competitive pricing to enhance customer satisfaction. Continuous monitoring of customer responses to the use of AR is also necessary for companies, as they should be prepared to make improvements or adjustments based on customer feedback.
Estimating Well Specific Sanding from Numerically Generated Sanding Database
Authors: Xiao Yuxing , Vaziri Hans
Published: August 2024

Sanding at scale is complex due to dynamic changes in downhole conditions. To provide needed results for making practical decisions, this paper describes the latest improvements in a numerical model and its application in estimating well specific sanding. Two essential components of sanding mechanisms, rock disaggregation and fluid drag forces, are considered. The former is done through gradual reductions in average size and frictional properties of rock aggregates. The latter includes pressure drag - a function of drawdown - and viscous drag - a function of rock aggregates size, fluid flux and PVT properties. Sanding is the outcome of fluid drags overcoming rock aggregates' frictional resistance. As part of numerical model validations, two sets of field observations in cased and perforated wells were examined that involve effects of changes in gas PVT properties with depletion and sanding at low gas and water flux in weak formations. A numerical strategy has been implemented to generate the fieldwide applicable sanding database that covers ranges of all underlying sanding factors. The database and well specific downhole conditions are used to estimate well's sanding, and the results form a critical input for optimizing sandface completion design, well intervention and hydrocarbon production.

1. INTRODUCTION

Well specific sanding responses over its life are complex and dictated by downhole conditions and their dynamic changes, including drawdown, depletion, sandface fluid flux distributions, downhole water activities, and rock strength and its disaggregation state. They are controlled in turn by reservoir formation characteristics, sandface completions and production conditions and strategies. In practice not all of them can be reliably predicted in advance, and thus a sanding-fundamentals-based data integration has been developed to get them identified upon their occurrence through readily available datasets (Xiao et al., 2023b).

Regardless of whether we know downhole conditions and their dynamic changes in advance or not, sanding severity associated with them is important in making practical decisions to take a right course of action. Upon sanding we do need to act to mitigate sanding risk and optimize hydrocarbon production. However, some of options that often come up may be overly conservative, including changing sandface completions, conducting intervention, choking back well flow rate excessively, putting the well at a curtailed flow rate too long, etc. On the other hand, it may be overly optimistic and in the worst scenario leads to loss of well. To help strike a right balance in managing sanding this paper describes the latest improvements in our finite element numerical sanding model, referred to as Enhans, and its application in estimating well specific sanding in a timely manner.
Reservoir Compaction Damage Evaluation in Hydraulically Fractured Oil Wells Incorporating Geomechanics
Authors: Fernandes F. B. , Braga A. M. B. , Duarte M. C. , Gildin E.
Published: August 2024

The interaction between reservoir Biot's effective stress and pore pressure change is significant in stress-sensitive reservoirs. Consequently, coupling geomechanics and fluid flow to analyze pressure transient problems for stress-sensitive reservoirs may be necessary. Effective permeability loss monitoring in fractured oil wells is essential in maintaining economic reservoir productivity. This paper proposes a new analytical solution for the nonlinear hydraulic diffusivity equation (NHDE) in Biot's effective stress-sensitive reservoir fully penetrated by a fractured oil well. The proposed modeling considers the hydraulic fracture infinite and crosses the whole reservoir net pay. A new permeability stress-sensitive pseudo-pressure m(σ′) is presented, and the solution of the NHDE is derived in terms of this function. NHDE is expanded in a first-order asymptotic series, and an integro-differential solution coupled to a Green's function (GF) is used to represent the source/sink term. A set of pressure and permeability data from geomechanical literature is used and transformed into effective stress through Biot's equation. The effects of overburden, source/sink term, deviation factor, and Biot's coefficient are investigated to prevent severe permeability losses. Model calibration is performed using a numerical oil flow simulator named IMEX®, widely used in formation evaluation literature. The accuracy, ease of implementation, and low computational costs constitute the main advantages of the model addressed in this paper. Hence, it may be a valuable and attractive mathematical tool to identify flow regimes, providing permeability loss control and supporting well-reservoir management.

1 INTRODUCTION

The production of petroleum reservoirs results in a decrease fluid pressure and an increase in effective overburden stress (Fernandes, 2022). As fluid production proceeds, the progressive increase in effective overburden load will, in turn, compact the reservoir rock and change its stress state (Soares and Ferreira, 2002; Soares et al., 2003).

For reservoir rocks that are mechanically stable with fluid-flow properties e.g. the ones that permeability are not influenced by effective stress changes or are solely dependent upon fluid pressure change under a constant overburden load, pressure transient problems can be properly analyzed by conventional methods.

Nonetheless, for stress-sensitive formations, coupling geomechanics with flow equations become the modeling more realistic. The economic production of either wells completed in low permeability reservoirs, e.g. shales or damaged wells has been possible because of hydraulic fracturing. In this scenario, estimating hydraulic fracture's geometric parameters and flow characteristics represents useful information for the calibration of fracture design methods and permits forecasting well flow behavior (Miskimins and Barree, 2003; Miskimins, 2019).
Log-Log Analysis for Compaction Damage Evaluation Caused by Pores Collapse in Depletion-Dependent Oil Reservoirs
Authors: Fernandes F. B. , Gildin E. , Braga A. M. B. , Duarte M. C.
Published: August 2024

The impact of the mechanical formation damage in the production curve caused by the transient permeability hysteresis in pressure-sensitive reservoirs has an important role in oilfield developments. Hence, the petroleum industry has continuously sought new analytical approaches to provide adequate, well-reservoir performance management and surveillance. This work proposes anew transient two-dimensional (2-D) analytical solution for modeling the oil flow in a permeability hysteretic pressure-dependent reservoir during alternating loading/unloading cycles. The nonlinear hydraulic diffusivity equation (NHDE) is perturbed through a first-order asymptotic series expansion technique. The reservoir engineering literature shows that this first-order expansion represents the magnitude of the nonlinear phenomena regarding pressure-sensitive rock and fluid properties. A new hysteretic deviation factor is presented for flow (drawdown) and buildup periods. This deviation factor represents the permeability deviation during the drawdown and its partial restoration in the buildup period. A set of pressure and permeability field data is used as input to the computational code. The model calibration is performed by a porous media numerical oil flow simulator named CMG IMEX®, broadly used in formation evaluation and reservoir engineering literature. The results presented high accuracy for the drawdown and buildup of hysteretic and non-hysteretic cases.

1 INTRODUCTION

The mathematical modeling of the production loss caused by the reservoir compaction damage is essential to prevent premature well abandonment and field disinvestment (Fernandes, 2022; Fernandes and Braga, 2023).

The Hydraulic Diffusivity Equation (HDE) models the isothermal, single, and multi-phase flow in porous media. It is derived from the coupling of Darcy's law, continuity equation, and porous media constitutive equations for rock and fluid properties (Matthews and Russell, 1967). Often in the petroleum engineering and dynamics of fluids in porous media scientific literature, the Linear Hydraulic Diffusivity Equation (LHDE) is solved through Laplace and Fourier transform or Boltzmann transformation, (Everdingen and Hurst, 1949; Matthews and Russell, 1967; Peres et al., 1989).

In order to achieve cost savings and accurate model demand, analytical solutions for the Nonlinear Hydraulic Diffusivity Equation (NHDE) have been studied for many years by geoscientists, well-testing, and reservoir engineers.
An Innovative Combination of Scratch Test and Weibull's Statistical Fracture Theory
Authors: Zhang Yazhou , Jin Yan , Sun Xiuxia , Zeng Ping
Published: August 2024

The scratch test is fast and reproducible, as confirmed by recent research. To evaluate the high consistency of these two methods, which is scratch and uniaxial compression, respectively, the comparison of strengths have been conducted. Scratch tests are performed on Gulong shale and sandstone, and the statistical analysis of the experimental results is carried out detailly, which further reveals the longitudinal heterogeneity of Uniaxial Compressive Strength (UCS) of the rock samples. Besides, the original tensile stress state of Weibull distribution is extended to a compressive stress state, and a UCS-based model of Weibull distribution is developed and validated. The results provide evidence that the UCS profiles of sandstone and shale, can be considered to follow the two-parameter Weibull distribution with a significance level of 0.05. In conclusion, the scratch test provides an effective approach to obtain the continuous high-resolution UCS profile of the rocks. Meanwhile, the combination of the scratch test and the Weibull's theory, can further contribute innovative ideas and methods to clarify the geomechanical characteristics of the reservoirs.

1. INTRODUCTION

As a natural heterogeneous mixed material, rock is of great interest to us, and the effective determination of its properties is indispensable in many fields. In particular, the accurate test of strength[1-3] is very important.

Traditionally, Uniaxial Compressive Strength (UCS), is usually performed on a rigid servo testing machine[4]. However, this test is destructive, relatively time and cost consuming. Recently, the development of Continuous Scratch Testing (CST) techniques[5-7] has provided us with a powerful and fast strength testing method. Based on the strong correlation between specific energy and UCS[8], CST can offer us a continuous high-resolution UCS profile, which can be understood as the point strength located in each microcell of the rock sample. In this way, a large number of specimen data can be obtained at low cost, which can support other studies easily.

This principle coincides with the content of the Weibull's statistical fracture theory. Weibull distribution data set only needs the critical stress of each microcell for rocks, even if it is based on the assumption of tensile stress initially. For the Weibull distribution, which is mainly used for reliability analysis and life estimation, it has been studied by large numbers of scholars, who developed the theory[9] and tried to combine it with rock mechanics tests[10,11]. And, many achievements have been made.
Effects of Epidote and Chlorite on the Frictional Stability of Granite Faults: Implications for Seismicity in Deep Geothermal Reservoirs
Authors: An Mengke , Zhang Fengshou , Huang Rui , Elsworth Derek
Published: August 2024

Epidote and chlorite are both low-grade metamorphic minerals that are widely distributed in deep granite geothermal reservoirs. Hot fluid circulation promotes the precipitation of epidote and chlorite coatings on natural faults and fractures and this can in turn exert control on fault/fracture frictional stability. We use simulated epidote/chlorite gouges and conduct fault shear experiments at conditions typifying the ∼4 km depth typical of deep geothermal reservoirs to explore the effect of epidote/chlorite content on frictional strength and stability. Results indicate that the frictional characteristics of epidote and chlorite gouges vastly differ. Epidote gouge is frictionally strong, with a coefficient of friction of ∼0.73, nearly double that of the chlorite gouge (∼0.35). In addition, the epidote gouge exhibits strong velocity-weakening and unstable frictional behavior under the test conditions, while the chlorite gouge is velocity-strengthening and stable. Fault frictional strength and velocity-weakening behavior are all enhanced for epidote-granite mixed gouges as epidote content increases. However, chlorite-granite mixed gouges show the opposite trend with increasing chlorite content. Our results have important implications in understanding the frictional stability of epidote/chlorite-filled granite faults and its influence on seismicity in deep geothermal reservoirs inhabiting the shallow crust.

1. INTRODUCTION

The moment magnitude (Mw) 5.5 Pohang earthquake that occurred in November 2017 has been demonstrated as one of the largest and most damaging earthquakes on the Korean peninsula since the last century (Grigoli et al., 2018; Kim et al., 2018). This event has attracted widespread attention not only for the significant resulting hazard and damage but also due to its connection with the Pohang Enhanced Geothermal System (EGS) project in South Korea. This earthquake (Lee et al., 2019a) directly injured >100 people and resulted in >US$300 million in economic loss, and it is also the largest known injection-induced earthquake at an EGS site. Currently, it has been confirmed that an unmapped pre-existing critically-stressed fault was reactivated at a depth of ∼4.0 km by the fluid injection during EGS stimulation and finally trigger the seismicity (Lee et al., 2019a).
Hydration Impact on Pore Structure and Methane Adsorption in the Lower Silurian Longmaxi Shale of the Sichuan Basin
Authors: Wang Duo , Yuan Hang , Wei Shuijian , Li Xiao
Published: August 2024

For shale gas reservoirs in the Sichuan Basin of China, renowned for low water saturation and complex pore structures rich in clay minerals, exhibit significant fluid imbibition post-hydraulic fracturing. This study delves into the Longmaxi Formation shale in the Sichuan Basin, China. Employing quantitative isothermal adsorption techniques, it elucidates pore structure alterations pre- and post-hydration. Quantification of the impact of fluid imbibition on different pore sizes was conducted. It was found that the influence on organic matter pores and macropores larger than 50 nm was minor, whereas the effect on clay inorganic matter pores in the range of 2-30 nm was most significant. Additionally, the influence of water saturation on methane adsorption capacity was quantified. With increasing water saturation, methane adsorption exhibited a nonlinear decreasing trend. An empirical formula was established to predict the adsorbed gas content evolution based on pore structures ranging from 0 to 20 nm under shale imbibition conditions. The reservoir methane adsorption capacity was calculated based on different soaking times, indicating that the reservoir's adsorbed gas content exhibited the highest desorption efficiency after 6 days of soaking.

1. INTRODUCTION

Shale oil and gas originate from organic-rich hydrocarbon source rocks characterized by low porosity, low permeability, integrated source-reservoir systems, and developed bedding structures (Jarvie et al., 2003). In the development of shale oil and gas, horizontal well multi-stage fracturing technology is commonly employed to enhance production artificially (Curtis, 2002; Zhao et al., 2018). Furthermore, due to hydrocarbon generation pressure and gasification-driven liquid carrying effects in shale reservoirs, they often exhibit extremely low water saturation characteristics (Bennion et al., 2000; Bennion & Thomas, 2005). Moreover, shale composition and pore systems are highly complex, consisting of micro-nano pores in organic matter and inorganic pores in clay minerals and brittle minerals (Han et al., 2020; Xie et al., 2022), leading to strong water absorption capabilities in shale (Minardi et al., 2018; Zeng et al., 2021).
A Cross-Scale Characterization of Porous Rocks Altered by Flow and Dissolution
Authors: Xu Z. , Li W. , Kolanti A. , Sprouster D.
Published: August 2024

Flow and dissolution induce wormholes in porous rocks, which lead to a substantial increase in both permeability and flow heterogeneity of the rock formation. Wormholes originate from the initial micron-scale pore networks, and gradually transition to more prominent millimeter-scale holes. Wormholes have a crucial impact on the flow and reactions in subsurface technologies, such as critical mineral leaching, CO2 storage and reservoir stimulation. Understanding how wormholes form from pore networks is crucial for the effectiveness of these subsurface technologies. However, current studies are limited to two separate scales of characterizations: millimeter-scale wormholes and micron-scale pore networks. The transitional region, which bridges these features at the two scales, remains largely unexplored and inadequately characterized. This knowledge gap obscures our understanding of the underpinning physics that governs wormhole formation in porous rocks. In this study, we aim to bridge these two scales of study with multiscale characterization. We create wormholes in porous gypsum specimens through core flood tests. The wormholes are then scanned with low-resolution (26.70 μm) and high-resolution (3.43 μm) X-ray computed tomography (CT). We quantitatively characterize the geometry of the wormholes leading to pore networks regarding their diameters, and quantities. This 3D cross-scale characterization allows for an accurate depiction of the interactions between wormholes and pore networks and provides physical insights into the initiation of wormholes.

1 INTRODUCTION

Wormholes are long and finger-like channels resulting from the heterogeneity in flow and dissolution within a porous medium (Szymczak and Ladd, 2009; Li et al., 2022). Wormhole formation is common in many natural and industrial processes, such as enhanced oil production and CO2 storage (Hoefner and Fogler, 1988; Gouze and Luquot, 2011; Smith et al., 2013; Menke et al., 2015; Wang et al., 2016). Wormholes significantly increase the permeability of the porous media and localize the flow and consequently heat and mass transfer between the fluid and porous media. Understanding how the wormholes emerge and quantifying their impact on the porous media during the subsurface resource exploitation are crucial in the engineering of the aforementioned subsurface systems.
Four-Dimensional Stress Evolution and Optimization of Child Well Fracturing Parameters in Multi Sub-Layers Shale Gas Reservoir
Authors: Yang Haixin , Tang Xuanhe , Zhu Haiyan , He Xiao , She Chaoyi , Zheng Majia , Wu Jianfa , Song Yi , Huang Haoyong , Li Junfeng , Wang Dajiang , Li Yuanzhao , Song Junbei
Published: August 2024

The research is aimed at the first infilled multi-well pad in deep shale gas reservoir of Sichuan Basin China. Since parent wells are not able to improve producing reserves of the pay zone, the deployment of infill wells is imperative. Therefore, the effect on infilled well fracturing caused by parent well's pressure depletion need to be investigated. This paper calculates the four-dimensional in-situ stress evolution by a comprehensive numerical model. And then several fracturing parameters of infilled well are optimized from two aspects: fracture geometry and stress disturbance range. The results show that: Stress disturbance range in horizontal is about 1.6 times of fracture length, in vertical is approximately equal to fracture height. For the infilled well, W-type well pattern and cluster spacing 15m are more suitable, the best fracturing time is about 24 months after the production of the parent well.

1. INTRODUCTION

Based on the practical experience in the development of medium-shallow shale gas, the well spacing less than 300m is generally adopted for deep shale gas in China to improve producing reserves. However, due to the limited comprehension of the geomechanical characteristics, the horizontal and vertical stress disturbance range of parent wells are not able to cover the inter-well pay zone. At the same time, the hydraulic fracture height failed to achieve the expectation and also failed to cover the entire pay zone in vertical direction. Based on this, infill wells must be deployed above the parent wells on the top of main pay zone to achieve the purpose of increasing the reserve control range of the well group in vertical and horizontal. As the production of shale gas wells decreases by more than 50% in the first three years, there is a pressure drop of up to 20MPa in the reservoir around the parent well. The depletion of pore pressure affects the in-situ stress, causing the in-situ stress of the reservoir to continuously change over time (i. e. four-dimensional in-situ stress), leading to interference with the parent well during fracturing of the filling well, and even causing fracturing hits. Resulting in a sudden decline in the production of the old well. This is a new problem restricting the sustainable and efficient development of shale gas in China.
Fluid Geochemical Genesis of the Rehai High Temperature Geothermal System in the Southeast Himalayas
Authors: Liao Dawei , Wang Yingchun , Hao Yinlei , Feng Jianyun , Zhang Ying
Published: August 2024

Western Yunnan is located in the southeast Himalayas, with well-developed faults and abundant high-temperature geothermal resources. In the western Yunnan geothermal fields, the hydrochemical and isotopic characteristics of geothermal fluids are studied and analyzed, elucidating the genetic model of magmatic high-temperature geothermal systems, and revealing the hydrochemical processes and genesis of geothermal water during the circulation process. The Rehai geothermal water type is mainly HCO3 Cl-Na. The high Cl content of geothermal water comes from the supply of magmatic water, while Na, K, and HCO3 mainly come from the leaching of feldspar minerals by mantle-derived CO2. Water hydrogen and oxygen isotopes indicate the source of atmospheric precipitation, while Rehai hot spring water shows an "18O shift". It is related to the mixing of magmatic water and the interaction between water and rock. According to the Na-K cation thermometer, among numerous geothermal fields of the western Yunnan region, the deep reservoir temperature of the Rehai geothermal field is the highest, reaching 260 °C. The Rehai geothermal water undergoes deep circulation and obtains deep heat after being recharged by atmospheric precipitation infiltration in the metamorphic rock area of the Gaoligongshan group located in the northeastern mountainous area. Rising along the fault, exposed as a hot spring at the surface.

1. Introduction

Under the combined action of the collision between the Indian and Eurasian plates and the westward subduction of the Pacific plate, a Cenozoic orogenic belt belonging to the Tethys tectonic domain has developed in the southwest region, while a Mesozoic Cenozoic fault basin group belonging to the Pacific Rim tectonic domain has formed in the eastern region. It belongs to the Mediterranean Himalayan and Pacific Rim geotropics, respectively, which have shaped the highest heat flow in Southwest China and Taiwan, with higher heat flow in the east and lower heat flow in the central region. It controlled the enrichment of deep geothermal resources in China. The Indian Plate drifted northward and collided with the Eurasian Plate (Chen et al., 2015; Tang et al., 2017; Zhou et al., 2017). It subducted towards its lower part, causing the lower edge of the Eurasian Plate to be heated and melted, and to invade along the weak structural zone of the upper plate, which provided a very favorable tectonic background and heat source conditions for the formation of diverse geothermal activities in the western Yunnan region on the southeastern edge of the Himalayas. From the perspective of geothermal flow, western Yunnan is one of the most favorable regions for geothermal formation in China The average heat flow value in the southwestern region of Yunnan Province is 75 mW/m2, while the heat flow value in Tengchong County is 93 mW/m2, which is the highest in Yunnan (Figure 1).
Caprock Stress Contrast Measurement, Mechanism Investigation and Development of Area In-Situ Stress Characterization, Northern Lights CCS, Offshore Norway
Authors: Thompson N. , Meneguolo R. , Rasmussen S. , Bautmans P. , Reitan H. , Stroisz A. , Cruz L.
Published: August 2024

This work, focused on the Northern Lights CCS project (offshore Norway) builds upon the recognition by Thompson et al. (2022) of stress contrasts within a CO2 storage caprock shale by introducing newly collected in situ data and laboratory testing. Specifically, carefully designed in situ testing (microfrac) was performed to validate the stress contrasts suggested from the exploration/appraisal well observations, as well as full log suites obtained to investigate stress profiles. Laboratory tests, focusing on the degree of relative creep between the identified shale intervals, was performed to better understand the mechanism behind the stress contrasts observed. A viscoelastic stress relaxation approach is then used to characterize in situ stress from experimentally obtained creep parameters. In total, the stress contrasts are again observed through all methods, with a high consistency from well to well. A connection to mineralogy is further validated, where increased creep higher clay content is observed to result in higher relative minimum formation stress. These collective observations bring confidence that higher minimum formation stress is present in the caprock, allowing the project to define CO2 safe storage potential more confidently in the structure.

1. INTRODUCTION

As a means of achieving IPCC targets of reducing net atmospheric carbon emissions, carbon capture and storage (CCS) is experiencing rapid growth; project development activity has increased significantly in recent years, towards a projected storage need of upwards of 10 Gt/yr by 2050 (IPCC [2018], IEA [2021] Global CCS Institute [2023]). The Longship (including CO2 capture) and Northern Lights projects (CO2 transport, temporary storage and subsea pipeline transport to permanent subsurface storage) are frontrunners in this industry, realizing the full CCS value chain through establishment if capture sites at various industries, transport ships, a temporary storage facility and subsea infrastructure off the coast of Norway (Northern Lights JV DA [2024], Gassnova [2024]). Phase 1 of the project (up to 1.5 Mt/yr storage, for 25 years) is ready to receive CO2 in 2024.
Improving Rock Excavation Efficiency Through Monitoring of Pick Cutter's Wear Condition
Authors: Morshedlou A. , Dagli I. , Rostami J. , Moradian O. , Belviranli M.
Published: August 2024

In underground soft rock mines, continuous miner and similar machines are operated by a operator at the cutting face looking for visual cues to control the operation, exposing them to potential dangers. One approach to improve operator safety is to relocate them away from the working face, allowing remote operation. This paper explores how automation can enhance mine health and safety by monitoring cutting forces on pick cutters to detect bit wear conditions. This approach not only boosts safety but also increases the efficiency of the excavation process. For this purpose, full-scale cutting tests were conducted using various types of conical pick cutters in different wear conditions (new, moderately worn out, and worn-out) in different rock types. The goal is to understand wear conditions based on cutting forces, enabling remote assessment of pick cutter wear conditions. Machine learning classification algorithms, including support vector machines (SVM), K-nearest neighbors (KNN), random forest, naïve Bayesian, extreme gradient boost (XGB), and neural networks, were employed. The SVM model demonstrated superior performance, achieving an accuracy and F1-score of 80.95%. Lastly, the trade-off between accuracy and execution time for real time identifications of rock type and calculation of wear status have been conducted and presented in this paper.

1. INTRODUCTION

The working conditions in underground mines including coal/rock dust, methane emission, roof collapse and rock falls can compromise miners' health and safety. According to data from the Mine Safety and Health Administration (MSHA) and the US Bureau of Labor Statistics, 2023 saw the highest number of fatalities in the mining industry in the past ten years, with a total of 40 fatal injuries, nine of which occurred in coal mines. Over the past decade, coal mining has accounted for an average of nearly 36% of all fatal injuries in the mining industry. Added to this is the harmful working conditions that can impact miners' health such as respiratory illnesses and hearing losses.
Thermal Damage in Crystalline Rocks: The Role of Heterogeneity in Mechanical Performance and Fracture Mechanisms
Authors: Dang Yike , Yang Zheng , Yang Shangtong , Shang Junlong
Published: August 2024

Investigating thermally treated rocks' mechanical properties and failure processes is crucial for advancing geothermal energy storage and extraction technologies. Naturally occurring rocks typically exhibit inherent flaws and fractures. Nevertheless, existing studies on the impact of thermal treatment on rock damage predominantly utilize intact rock specimens, either through numerical simulations or experimental approaches. This research introduces the Grain-Based model (GBM) to represent the complex shapes of mineral grains accurately and incorporates the heterogeneity of grain sizes. By employing the Weibull distribution, the model captures the variability in rock internal strength due to microcracks, porosity, mineral composition, and other factors. Furthermore, it integrates the temperature dependency of rocks' physical and mechanical properties when subjected to elevated temperatures, the numerical simulation reproduced the phenomenon that the compaction stage of the stress-strain curve caused by thermal damage extends as the temperature rises. Overall, this study provides a complete understanding of the thermal effects on rock integrity.

1. INTRODUCTION

Rocks in nature commonly contain defects such as joints, fissures, and structural planes, which have a decisive impact on the mechanical behavior and stability of the rocks. Particularly under conditions of high temperature, the mechanical properties and failure mechanisms of rocks with such defects can vary significantly from those observed at room temperatures, thus impacting the safety and reliability of rock engineering projects. In geological engineering, nuclear waste storage, and geothermal energy development, rocks are routinely subjected to high-temperature environments. Temperature variations can intensify the expansion of internal defects in rocks, modify their mechanical attributes, and trigger new failure modes.

As a quintessential crystalline rock, granite possesses a markedly heterogeneous internal structure. This heterogeneity leads to unique thermal stress responses and failure mechanisms under high temperature and stress conditions, which are significantly different from those observed in homogeneous materials. The non-uniform thermal expansion can result in substantial stress concentration within the rock, facilitating the initiation and propagation of cracks. This process, in turn, impacts engineering structures' long-term performance and reliability.
The Energy Budget in Fluid-Driven Fracturing: A Continuum Damage Approach
Authors: Mobasher Mostafa E. , Waisman Haim
Published: August 2024

We present a numerical approach for the quantification of the energy transfer, storage, and dissipation mechanisms in fluid-driven fracturing. The analysis approach is motivated and originated in the energy statement describing continuum damage, poroelasticity, and the non-local effects in both of damage and transport. The thermodynamically consistent derivation leads to the definition of the state laws, as well the as analytical expressions of energy storage and dissipation in the porous media. The derivation leads to the identification of three major energy loss mechanisms: 1) viscous fluid-flow, 2) solid-damage effect due to the growth of voids and cracks in the solid skeleton, and 3) fluid-damage effect due to the accompanying changes in compressibility and permeability. The analysis model is implemented following the framework of mixed non-linear finite element; and the energy dissipation functions are calculated numerically within this framework. Several benchmark fluid-driven fracturing problems are modeled, and the results agree with the available data from experimental models in the literature. The model is then used to perform several parametric investigations to provide an engineering value of the proposed approach; for example, the analysis of different fluid-injection rates shows most of the additional energy input in higher injection rates is dissipated in viscous fluid flow rather than the sought solid damage. Moreover, the model is used in the analysis of the interaction between fluid-driven fracturing and pre-existing weak zones featuring combinations of reduced stiffness and permeability to represent natural and man-made fractures.

1 INTRODUCTION

Hydraulic fracturing is a process in which a fracturing fluid is pumped at high rates in order to increase the permeability in a fracture zone, ultimately leading to more economical oil production. Energy used in the process is transferred into the porous domain in the form of: (a) elastic energy stored in a deformed domain; (b) energy used to generate new fracture surfaces, resulting in the dissipation of energy through solid skeleton decay (damage); and (c) energy used to transport the fluid through pores, resulting in dissipation via fluid viscosity. The goal of an optimized hydraulic fracturing approach would be to maximize the dissipation due to solid damage, as this would result in the stimulation of a larger reservoir volumeBunger and Lecampion (2017); Shlyapobersky (1985). This paper provides a quantitative evaluation of energy stored and dispersed throughout the process of hydraulic fracturing, based on an non-local damage and transport (NLDT) model modelMobasher et al. (2017); Mobasher (2017); Mobasher et al. (2018); Mobasher and Waisman (2021a,b).
Simulating Coupled THM Problem and Wellbore Integrity Analyses with Two-Phase Fluid Flow in Naturally Fractured Reservoirs
Authors: Wang Yarlong
Published: August 2024

Multi-phase fluid flow in naturally fractured reservoirs (NFR) is a complex and important process to be studied in energy and environmental industries. Either during CH4/H2/CO2 injection/sequestration or thermal EOR process, both fluid pressure and temperature changes may take place which will lead to significant thermal-hydraulic-mechanical (THM) responses that will impact both safety and efficiency of the project. Simulating THM responses in NFR, Formulation for an implicit pressure and explicit saturation (IMPES+T) finite element approach with an explicit thermal coupling is developed. Different shape functions, i.e. Petrov-Galerkin method, are applied to the saturation, displacement, fluid pressures, and temperature with convective energy transport calculation. In addition, a simplified coupled hydraulic-mechanical (HM) algorithm is proposed for displacement-pressures calculations, which is also coupled to an independently calculated convective-conductive thermal process. The induced pore pressure and critical stresses are highlighted in a dual-porosity medium, evaluating the wellbore integrity during injection and production in naturally fractured formations. A thermally induced tangential stress increase of 1 MPa on the wellbore wall is equivalent to a formation strength reduction of the same magnitude and yet more than 50% increase of the effective tangential stress, the key stress affecting wellbore integrity, at the wellbore wall in the fracture system may be achievable in the naturally fractured media (NFM).

1. INTRODUCTION

To simulate multiphase fluid flow, heat transport and skeleton deformation processes in NFR [Bai et al., 1993; Khalili, and Valliappan, 1996; Khalili, 2008], numerical method such finite element method has been applied to approximate solutions of the Thermal-Hydraulic-Mechanical (THM) responses. Isothermal multi-phase fluid flow and non-isothermal single-phase cases are extensively dealt with, respectively [Lewis and Ghafouri, 1997; Nair et al., 2005; Pao and Lewis, 2002; Gelet et al., 2012; Khoei et al., 2016; Arzanfudi and Al-Khoury, 2017]. Simulating CO2 injection, energy enhanced production and geothermal energy extraction processes in a NFR, a fully coupled THM model with multi-phase fluid flow is required and thus developed in this paper.
A Simplified Finite Element Algorithm and Coupled THM Problems in Stress-Sensitive Naturally Fractured Reservoirs During Injection/Production
Authors: Wang Yarlong
Published: August 2024

Stress concentration in vicinity of a wellbore may suppress fracture network and restrict the fluid flux in naturally fractured reservoirs (NFR). Primarily reducing the absolute permeability in the fracture network, such an impact may be reach a significant level when productivity may not increase after a drawdown increase. To cope with such a possible reversal incremental fluid flow, a critical drawdown is identified, for the case when the permeability reduction effect may surpass those inremental contributions of a drawdown increase to the flow flux. A different strategy by increasing the external fluid pressure and maintaining a constant bottom hole pressure (BHP) should be applied, so that the near-wellbore permeability may remain unchanged. Both simulation and field applications are performed and more than 30% production rate increase can be expected depending on the in-situ stresses level against permeability changes for each well. Finite element method is used for a coupled THM problem and simplified finite element algorithm is applied with a dual-porosity mode in NFR

1. INTRODUCTION

Then the permeability perpendicular to a confining stress (Principal stress direction or fluid flow directions) is conventionally defined as a function of the effective stress. Practically speaking the principal directions of fluid flow and stresses seldom coincide and in what follows, we propose to define changes of the principal permeability as a function of the normal stress to the principal flow direction, the former may be calculated by the principal stress tensor and the latter is characterized of the natural fractures and the geological bedding. Furthermore, if plasticity, sliding along a fracture or joint, and dilatancy occur, the shear component of the stress tensor should be also used. Thirdly we can determine if a production decline can be reversed by controlling the wellbore drawdown, i.e. if the drawdown and stress concentrations fall into the aforementioned sensitive range. Fourthly we may diagnose if a production decline in a specific field is caused by these stress sensitive permeability change. Finally we may find alternative ways to increase drawdown without bringing down the permeability at the wellbore at the same time. In other words, once we can correlate producing well drawdown to the induced stress changes, which are in the stress-permeability sensitive range, then we can adjust the producing drawdown to serve the purpose for production enhancement. Once these factors are identified, a dual-porosity model is built and finite element method is utilized for production calculations. It should be realized that without considering these factors, any attempt to increase production by lifting drawdown will be neutralized by the consequence of permeability reduction. Production declines in a carbonated reservoir northwestern China are observed and enhancing strategies are proposed.