bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristic Analysis of Flow Field and Cuttings Removal of Straight-Swirling Integrated Jet During Tubing Cleaning
Authors: Xiao Yongjun , Zheng Jian , Wu Chunlin , Chen Zhi , Luo Xin , Liu Bingxiao , Ren Yingqiao , Huang Haochen 
Published: August 2024

ABSTRACT:
Shale gas is a significant alternative resource to conventional gas. During the development of shale gas in Changning, the energy attenuation of the extracted shale gas leads to insufficient water discharge from the stratum. This ultimately leads to the gradual accumulation of sand from the stratum, which then clogs up both the tubing and casing over time, resulting in reduced or even halted productivity of horizontal wells. To improve the productivity of aging shale gas wells in Changning, a straight-swirling integrated jet (SSIJ) tool is designed. Computational fluid dynamics (CFD) method is utilized to investigate the velocity field and cuttings removal characteristics of the SSIJ tool, with comparisons made against the convergent-divergent jet (CDJ) tool. The findings suggest that: 1) Compared to the CDJ tool, the SSIJ tool's jet exhibits higher axial and tangential velocity extremes, stronger cavitation initiation capacity and cavitation erosion effect. 2) The SSIJ tool shows a greater cuttings-carrying capacity. However, this ability decreases with larger cuttings sizes, and increasing the viscosity of the liquid can greatly enhance the tool's cuttings-carrying efficiency. This research offers valuable insights for the design and optimization of downhole tubing and casing cleaning tools.

1. INTRODUCTION
Shale gas production has experienced a significant increase in the last ten years, largely due to advancements in horizontal drilling and hydraulic fracturing technologies(Dong et al., 2024). Shale gas accounts for a substantial share of China's natural gas production, with an estimated annual production of 30×109 m3 by 2025. The Changning shale gas field, situated at the southwest edge of the southern Sichuan Basin, has proven reserves amounting to 440×109 m3. In 2020, it reached a production capacity of 5×109 m3/a for shale gas (Ailin et al., 2020; Ma, 2021; Zou et al., 2016). However, while extracting shale gas in Changning, sedimentation may occur at the bottom of the well (Liu, 2019). When fracturing bridge blockage are milled, this can result in the accumulation of cuttings at the bottom of the well, showed in Fig.1. This situation has the potential to cause tubing and casing blockage, leading to decreased production or even complete shutdown of the gas well. Therefore, it is important to promptly remove the sand buildup in the tubing and casing during production.
Inversion of Creep Rate of Salt Rock Using Finite Element Method Based on Engineering Data
Authors: Li Ji , Lu Yunhu , Wei Shiming , Huang Chenxing , Li Hongda , Zhan Qing 
Published: August 2024

ABSTRACT:
The Carboniferous salt layer is buried deeply in the Tarim Basin. Affected by high temperature and high stress, the creep rate of salt rock is fast, which leads to a series of stuck bit and casing failure accidents. It is difficult and costly to obtain salt rock core from underground, and the outcrop core is difficult to represent the properties of deep strata, so it is difficult to determine salt rock creep rate by conventional rock mechanics testing. In this paper, the microstructure characteristics of salt rock were clarified by SEM analysis. The information on the stuck bit has been collected, and the relationship between the well diameter and time of the salt layer is mastered. On this basis, the finite element analysis model considering the creep of the salt layer is established, and the creep parameters of the salt layer are inverted based on the relationship of borehole diameter with time. This study solves the problem that the creep rate of salt rock is challenging to be quantitatively analyzed under difficult core-taking conditions and can provide technical support for drilling and completion of the salt layer.

1. INTRODUCTION
Salt layers are often encountered in both onshore and offshore oil and gas drilling. In the process of salt layer drilling, the complicated mechanical properties of salt layers lead to drilling stuck, casing stuck, casing failure, and other accidents (Al-Saeedi et al., 2011, Liu et al., 2021, Chengxin et al., 2023). Casing failure occurred in the carboniferous salt layer in many wells in Tarim Basin, China, resulting in frequent side drilling, which severely restricted the safe and efficient exploitation of oil and gas resources and brought additional economic losses. It is of great significance to determine the creep rate of the salt layer.
A series of studies have been carried out to determine the creep rate of salt rock. The most common method to obtain creep rate is to process salt rock into a standard sample of a certain size, and load it under constant pressure under uniaxial (Berest et al., 2005 and 2014) or triaxial (Maia et al., 2005, Moosavi et al., 2009, Chengxin et al., 2023) conditions, and measure its average strain change over a certain period. With the deepening of research in this aspect, some scholars began to introduce image recognition technology (Blaber et al., 2015) into creep rate test, which can obtain the change of strain with time at any point on the sample surface during loading (Ju et al., 2022). Using the creep rate test results, the creep equation of salt rock can be fitted and the creep rate of salt rock can be determined under specific temperature and pressure conditions (Zhou et al., 2011, Wang et al., 2014, Zhang et al., 2021). At present, rock mechanics testing is still the main method to study the creep rate of salt rock, and the conventional methods to obtain the creep rate of salt rock cannot get rid of the constraints on the shape and size of salt rock samples.
Analysis of Casing Damage Mechanism of Carboniferous Salt Layer in Tarim Basin
Authors: Liang Hongjun , Huang Chenxing , Qin Hongde , Luo Renkun , Deng Qingshan , Lu Hui , Zhan Qing , Lu Yunhu , Wei Shiming 
Published: August 2024

ABSTRACT:
The Carboniferous strata in Tarim Basin, China developed salt beds. Casing damage occurred in the drilling process, which led to frequent sticking and even forced sidetracking, which seriously affected the development of oil and gas in this block and caused great economic losses. To solve the problem of casing damage in the Carboniferous salt layer, the mechanism of casing damage is analyzed in this paper. Based on the statistical analysis of geological and engineering data, the casing damage mechanism of bending and stretching deformation is deduced, and the above casing damage mechanism is confirmed by establishing the finite element model of casing strength checking. The effects of borehole enlargement rate, casing center degree and casing program on the bending and stretching yield of casing are also analyzed. On the whole, the casing damage risk is positively correlated with borehole enlargement rate and axial tension, and negatively correlated with arm of force and casing center degree. In the casing program design, the salt layer should be located at the bottom of a certain run, and the anhydrite should be destroyed by reaming multiple times in the salt layer to avoid the formation of "hard fulcrum" during cementing, which can effectively reduce the risk of casing damage.

1. INTRODUCTION
There are a lot of oil and gas buried in salt layers around the world, such as the United States Gulf of Mexico, offshore Brazil, West Africa, and the North Sea (Greenhalgh et al., 2012; Chitale et al., 2014). Casing damage in the salt layer is a problem that has been discovered for a long time (Cheatham et al., 1964). This problem is still happening today, resulting in oil and gas wells being forced to sidetrack or even be abandoned, which not only wastes much money but also seriously restricts oil and gas production.
Rock salt can creep and deform, and creep begins the moment it is drilled into the salt layer (Wang et al., 2016). Even after the cementing operation is carried out, the cementing quality is often difficult to guarantee, so the rock salt creep will still exert force on the casing (Willson et al., 2002). At present, the damage modes of casing in the salt layer are mainly extrusion deformation and bending deformation (Clegg et al., 1971; Taheri et al., 2020).
The Slipping Characteristics of Bedding Interface Under Shearing Stress in Unconventional Reservoirs
Authors: Chen Lei , Li Fengxia , Huang Zhiwen , Zhou Tong , Chen Shijing , Zhang Min , Zhang Guangqing 
Published: August 2024

ABSTRACT:
The bedding interfaces with different cohesions usually exist in unconventional reservoirs. During reservoir stimulation, the slips induced by hydraulic fractures are related to the fracturing effects. In this paper, the rock specimens with cemented and uncemented bedding interfaces were selected to conduct direct shearing experiments, and the slipping behaviors were analyzed using the digital image correlation (DIC) method and acoustic emission (AE) technique. The results show that the slip weakening mode exists in cemented bedding interface during slipping, and the corresponding variation of AE b-value is small. The entire uniform slippage will appear in the uncemented bedding interface during slipping, accompanied by the larger variation of AE b-value. The effects of the interlayer cohesion on the slip weakening zone length, AE magnitude, and the difference between static and kinetic friction were discussed. It is found that the opening feature is not significant during slip weakening, but obvious during cohesionless slipping. And a relationship model was established to describe the opening displacement affected by slipping. This study can help to understand the slip mechanisms during fracturing in unconventional reservoirs.

1. INTRODUCTION
Unconventional reservoirs, such as shale, have been the key areas in oil and gas production (Gao et al., 2022). Unlike conventional reservoir rocks, unconventional reservoirs are usually characterized by bedding development. Therefore, investigating the slip of bedding plane in unconventional reservoirs during fracturing is one of the focuses in rock fracture mechanics (Zhao & Gray, 2021).
Microseismic monitoring results of in-situ fracturing demonstrate that hydraulic fractures can induce interlayer slip (Rutledge et al., 2016; Tan & Engelder, 2016a). The enhancement of hydraulic conductivity by slip (Zhao et al., 2013; Ye & Ghassemi, 2018) is a crucial factor for promoting shale oil and gas production (Urbancic & Baig, 2016; Wang et al., 2019; Zoback et al., 2012). In field hydraulic fracturing, the slip fractures are usually monitored by microseismic moment tensor analysis (Tan & Engelder, 2016b) and micro-resistivity scanning imaging technology (Zoback & Lund, 2019). Laboratory experiments have also demonstrated that hydraulic fractures can induce interlayer slip at the bedding plane (Chen et al., 2023). Some researchers think that the shear slips of interlaminations during fracturing are part of complex fracture networks (Bunger et al., 2013; Huang et al., 2013; Min et al., 2010; Ye & Ghassemi, 2018).
Gas Production Prediction Model and Parametric Analyses for Fractured Horizontal Well in Deep Coalbed Methane Reservoirs
Authors: Jia Yanran , Shi Juntai , Ji Changjiang , Xiong Xianyue , Huang Hongxing , Chen Ming , Wang Wei 
Published: August 2024

ABSTRACT:
To ensure the long-term, efficient, and stable development of deep coalbed methane, it's urgent to conduct research on gas production prediction and influencing factors analyses. In this study, based on the three zones (stimulated zone with proppant filled, stimulated zone without proppant filled, and un-stimulated zone) distribution in deep coalbed methane reservoirs developed with fractured horizontal wells, composite pseudo-steady-state gas-water productivity equations are established. Subsequently, coupling this productivity equation with pressure propagation models considering well shut-in, dynamic permeability models, and the material balance equations, a composite gas production prediction model for fractured horizontal wells in deep coalbed methane reservoirs is proposed and solved. Finally, the validations using commercial numerical simulation software and history matching with field case are conducted, and the influencing factors on gas production in deep coalbed methane reservoirs are analyzed. Results show good agreements between the predicted and actual results are achieved for both synesthetic case and field case. The sensitive influencing factors on gas production are ranked as follows: number of fractures, free gas saturation, fracture half-length, permeability of Zone I, Zone I size, degree of coal fines blockage, permeability of Zone II, Zone II size, permeability of Zone III, and horizontal well spacing.

1. INTRODUCTION
As a type of unconventional resource, coalbed methane is a very clean natural gas resource. Its development and utilization not only increase the rare low-carbon clean energy, but also serve as a practical carbon neutral industrial path, which can significantly reduce methane emissions during coal mining and reduce the greenhouse gas effect of methane. The shallow coalbed methane resources in China are 30.1 trillion cubic meters, and the preliminary estimate of deep coalbed methane resources can reach 40 trillion cubic meters. Obviously, deep coalbed methane resources are richer than those in the middle and shallow areas. Regarding the depth limit of deep coalbed methane, American scholars defined it as coalbed methane with a burial depth greater than 1,524 meters in the coal reservoir; Based on the progress of coalbed methane in recent years, Xu has proposed that deep coalbed methane specifically refers to those with a burial depth greater than 1500 meters in coal reservoirs. The industry gradually agrees that coalbed methane with a burial depth greater than 1500 meters is called deep coalbed methane.
Geomechanical Effects of Cyclic Loading on Rocksalt
Authors: Houben M. E. , van der Linden A. J. , El Azouzi K. , Marcelis F. H. M. , Coorn A. H. , van Schalm R. 
Published: August 2024

ABSTRACT:
Hydrogen-based solutions are gaining importance as a renewable clean energy source. A geomechanical challenge when hydrogen storage in salt caverns is considered is the cyclic loading and unloading of the host rock (rocksalt). As hydrogen is stored and removed based on fluctuating demand throughout the year the cavern wall will be exposed to pressure cycles, where in times of high demands the hydrogen is supposed to be readily available and in times of low demand, the hydrogen will be stored in the cavern. Ideally these pressure cycles do not influence the integrity of the cavern as a storage site. To investigate the effect of cyclic loading on rocksalt, several cyclic loading experiments have been performed in the lab using two different very pure rocksalt samples from Germany (Asse Speizesalz and Z3 Leine Rocksalt (both &gt; 98% NaCl). Loading stresses, number of cyclic loading event and length of high versus low differential stress have been varied to investigate the effect of cyclic loading. Daily loading cycles versus weekly loading cycles showed very similar strains on the sample. When reaching stresses above the dilatancy boundary of the rocksalt though the samples kept deforming.

1. INTRODUCTION
Hydrogen storage is one of the key necessary steps in the energy transition, where hydrogen-based energy solutions are gaining importance as a renewable clean energy (e.g.: Abdalla et al., 2018; Gulcin Caglayan et al., 2020; Lankof et al., 2020; Tarkowski, 2019; Zhang et al., 2016; Zivar et al., 2020). With energy consumption varying daily as well as seasonally, and the hydrogen supply-demand chain persistently being out-of-phase, flexible hydrogen storage solutions are critical. Specifically, in times of low energy demand excess hydrogen must be temporarily stored (Zivar et al., 2020), while in times of high demand the hydrogen must be easily accessible and readily available. A well-known hydrogen storage option is geologic sequestration in salt caverns (e.g.: Tarkowski, 2019; Heinemann et al., 2021). Salt is known as a natural barrier with general low permeability, frequently acting as a seal for hydrocarbons and widely considered as possible host rock for the storage of radioactive waste (e.g.: Arson et al., 2012; Gulcin Caglayan et al., 2020). In the past 30 years, research has been performed on the mechanical behavior of rocksalt (A selection of references: Schutjens, 1991; Peach and Spiers, 1996; van den Bogert et al., 1998; Hunsche and Hampel, 1999; ter Heege et al., 2005; Alkan et al., 2007), but less work has been performed on the cyclic loading of rocksalt.
Fracturing Breakthrough and Comprehensive Evaluation of CP1 Well in Yingxiongling Shale Oil Reservoir, Qaidam Basin
Authors: Y. Liu, Y. , G. Xian, C. , Y. Liu, , X. Chen, , Y. Zhang, M. , Cao W. , Wan Y. Y. 
Published: August 2024

ABSTRACT:
The Yingxiongling shale oil reservoir in the Qaidam Basin poses unique challenges due to its high stress differentials, steep stress gradients, abundant limy dolomite content, strong heterogeneity, and underdeveloped natural fractures. This paper conducts a comprehensive geoscience-to-engineering analysis of the CP1 well to offer insights for reservoir stimulation and production optimization. Results indicate that the "single well proactive interference and control" fracturing plan effectively manages fracture propagation. Comparison of liquid production across lithofacies reveals laminated limy-dolomitic shale's strong liquid supply capacity and layered limy-dolomitic shale's high oil production capacity. The spatial relationship between these lithofacies creates a distinctive enrichment and seepage pattern, forming the geological basis for maximizing the oil production potential of the Yingxiongling continental shale oil reservoir. Additionally, this configuration regulates post-fracturing oil and water production dynamics, emphasizing the significance of the interbed combination of laminated limy-dolomitic shale and layered limy-dolomitic shale as favorable lithofacies.

1. INTRODUCTION
China possesses abundant continental shale oil resources, with recent years witnessing significant advancements in exploration and development, particularly in the Jungar, Ordos, Songliao, and Qaidam basins (Zhao et al., 2021; Jin et al., 2021; Fu et al., 2022; He et al., 2022). Volume fracturing technology is the key to achieving efficient development of unconventional oil and gas reservoirs. With the goal of maximizing the effective stimulated reservoir volume (SRV) and single-well control of EUR, guided by the idea of geoscience-to-engineering integration, we targeted the characteristics of high stress differentials, steep stress gradients, high limy dolomite content, strong heterogeneity, and underdeveloped natural fractures in the Yingxiongling continental shale oil reservoir (Jiang et al., 2023). Following a "technically prudent, parameter aggressive" approach, we employed a core volume fracturing technique that includes "dense cutting of multiple segments and clusters, extreme flow limiting perforation, high pumping rate, high intensity continuous sand addition with slickwater with variable viscosity". This approach resulted in the formation of a complex network of fractures, establishing an artificial seepage system to enhance single-well production.
The Thrust-Penetration Gradient: Decoding Geomechanical Dynamics and TBM Response
Authors: Schlicke M. , Nübel K. , Wannenmacher H. , Amann F. , Marcher T. 
Published: August 2024

ABSTRACT:
The Thrust-Penetration Gradient (TPG) is an essential tool in analyzing and predicting the performance of Tunnel Boring Machines (TBMs). It evaluates TBM efficiency, reflecting geomechanical dynamics during tunneling. The TPG effectively captures the complex relationship between thrust and penetration rates across various rock masses, drawing a parallel to the CSM model (Colorado School of Mines model) but with broader applicability. Originating from the TBM's start-up phase, the TPG offers real-time, continuous insights into machine-ground interactions, highlighting non-linear gradients. It involves isolating shield friction from total thrust, a process revealing frictional variations even in consistent geological settings. TPG also accounts for supplementary losses due to cutterhead curvature. By comparing torque and thrust per cutter, it accurately determines shield friction for each stroke, using quadratic and exponential models to correlate thrust per cutter with penetration rate. More comprehensive than the Specific Penetration metric, this approach avoids linear reduction constraints, offering a more precise platform for TBM performance evaluation. TPG's utility extends to grouping gradients based on geomechanical non-linearities through a novel matrix system, facilitating forward predictions of penetration rates irrespective of project or geomechanical conditions.

1 INTRODUCTION
A non-linear correlation between the acting thrust at the cutter head and the corresponding penetration of disccutters in a specific rock mass greatly influences the performance of a Tunnel Boring Machine. This correlation is known as the Thrust-Penetration Gradient (TPG), and it reflects the disc-cutter indentation process within a specific rock type. The TPG is a specific and sensitive metric to evaluate the TBM's performance. It is considered a ground truth parameter for performance characterization, based on the Colorado School Mines Penetration Prediction for intact rock in the laboratory. The TPG represents the required work for rock mass mining and predicts performance for various rock conditions. The TPG for rock mass resembles the Colorado School of Mines model, representing the upper limit of disc-cutter indentation on massive rock conditions. A matrix notation is introduced as best practice to align specific TPGs towards rock strength and fracturing.