bluuebunny/crossref_metadata_2025_split huggingface dataset:
CO2 Foam Enables CCUS with Low Carbon Oil Production in Asia
Authors: Graue Arne , Alcorn Zachary Paul 
Published: February 2025

Abstract
Climate change concerns have accelerated efforts to reduce CO2 emissions from fossil fuel production. The IEA estimates that in 2035, 70% of energy consumption will still be from fossil fuels. Therefore, new energy resources must be developed, and the carbon footprint of fossil fuel production must be reduced. CO2 sequestration in geologic formations is a promising method to store large volumes of CO2 and help meet the goals of the Paris agreement. To mitigate climate change, gigaton volumes of CO2 must be permanently stored and this volume of CO2 is so vast that industry must participate. To attract industry, the economics of CO2 storage must be improved. This may be obtained by developing disruptive new technologies for CO2 sequestration which provide industrial revenues.
Combined CO2 enhanced oil recovery (EOR) and CO2 storage is effective to reduce emissions and provide energy security as part of the carbon capture, utilization, and storage (CCUS) value chain. However, early CO2 breakthrough and poor sweep efficiency are serious challenges in conventional CO2 EOR which severely limits oil recoveries and CO2 storage volumes. Adding surfactants when injecting the CO2 can generate in-situ foam, which reduces CO2 mobility, increases sweep efficiency, and improves CO2 utilization. An integrated enhanced oil recovery (IEOR) technology utilizing CO2 foam for low carbon footprint oil production has recently been developed at University of Bergen as an enabler of CCUS. To demonstrate the technology at a larger scale, we recently completed a CO2 foam field pilot in the Permian Basin of west Texas, initiated after conventional CO2 flooding.
The CO2 foam pilot produced an additional 40% of cumulative oil, compared to the baseline predicted conventional CO2 EOR performance. Cost savings exhibited a 20% reduced cost for CO2 and 75% reduction in expected operational time, compared to conventional CO2 EOR. This technology may represent a gamechanger with respect to sustainable economics in CO2 EOR because the Rate of Return was at a factor of 20. The pilot results confirm the ability of low concentration foaming solutions to reduce CO2 mobility, increase sweep efficiency, improve CO2 displacement, oil recovery and CO2 storage mechanisms. CO2 foam EOR may produce more oil in a shorter time, and more CO2 may be sequestered, compared to conventional CO2 EOR. CO2 foam EOR provides synergy between the need for increased energy production and the reduction in emission of anthropogenic CO2. Southeast Asia is the area of highest growth in energy demand and has increased CO2 emissions; thus, this technology is particularly relevant to Asia.
Automatic Detection of Hydraulic Fracturing Events by Real-Time Data Mining
Authors: Zhang Shuai , Sheng Mao , Meng Leifeng , Bai Kankan , He Jian , Tian Shouceng 
Published: February 2025

Abstract
Accurate, quick, reliable event detection is essential to Intelligent hydraulic fracturing. The real-time detection of events mostly relies on the expert knowledge. Although the machine learning algorithms had been used for events detection, the accuracy is still not stable that depending on the data quality and amount. This paper proposed an alternatively threshold-based algorithms with special sliding windows by integrating feature mining with expert knowledge from time-series data. The 378 stages of historical fracturing data were collected. More than 5 experts were organized to divide and label the six types of fracturing events involving wellhead pressure testing, plug ball seating, pad stage, proppant laden stage, flushing, and fracture closure stage from second-point data. The correlation between fracturing events and data features was built by using 10-seconds sliding window and forward difference to extract the slope features of pumping curves and their corresponding threshold values of pumping pressure, rate, and proppant concentration. Furthermore, the wavelet analysis was used to identify the fracture closure time from wellhead pressure after the fracturing is completed. Finally, the threshold-based algorithms by integrating feature mining with expert knowledge from time-series data were proposed to handle the fast detection of fracturing events. The model was tested on 200 stages of data and performed a high accuracy in fracturing events detection. Particularly, the accuracy of fracturing events detection ranges from 92.7% to 99.6%. The accuracy of Fracture Closure Pressure were 93.8%.
Multi-Scale Refraction Tomography Constrained by Geostatistical Information Method and its Application in Bohai Bay
Authors: Duan X. , Zhang Z. , Ding H. , Han M. , Gu Z. 
Published: February 2025

As the largest offshore oilfield in China, Bohai Oilfield has made good exploration discoveries in various target strata in the past decade, especially in the exploration of deep buried hills. Because the shallow favorable targets have been nearly drilled out, the exploration focus of Bohai oilfield is gradually shifting to the middle and deep layers. The buried hill have become the most important research hots pot of Bohai oilfield, and several large gas reservoirs have been discovered in Archean strata. The main reservoir type of buried hill oilfield is fracture, which has complicated characteristics with low porosity, strong heterogeneity and complex fracture distribution. The average depth of buried hill is about 4500m, so it is difficult to accurately predict and describe good fractured reservoir in the exploration and development.
Because of the deep buried depth, the quality of seismic data is usually very poor. On the one hand, the effective signal of fractured reservoirs are very weak, and the low S/N seismic data is hard to recognize fractured reservoir. On the other hand, there are a lot of residual internal multiples, and their amplitude is even stronger than the reflected wave of fractures. Taking the normal processing procedure into consideration, most of the multiples like surface-related multiples have been well suppressed during the seismic data processing. In order to clearly identify the real reflection wave of fractured reservoir, it is necessary to suppress the internal multiples and enhance the effective signals.
Generally, the methods of suppressing multiple waves are divided into two categories: one is the filtering method based on signal analysis and processing, such as τ-p transform and f-k transform; the other is the prediction subtraction method based on wave equation, such as wave extrapolation method and inverse scattering series method. The first kind of methods have certain limitations: the dynamic correction speed of multiple waves and primary waves is similar, which weakens the effectiveness of τ-p transformation, multiple and primary waves have similar slopes, which weakens the effectiveness of f-k filtering. The second type of method mainly uses the generation mechanism of multiple waves to predict and suppress multiple waves. It comprehensively considers the kinematic and dynamic characteristics of multiple wave propagation and can adapt to complex underground structure. It uses its own data as a multiple wave prediction operator, requires less or no assumptions about underground structure, and attenuates multiple waves without damaging the primary reflected signal. For internal multiple waves, the current effective method is the inverse scattering series method based on the point scattering model. This method does not need a prior velocity structure model, and has a good adaptability to complex structures, but the calculation is very large.
Influence Analysis of Thermophysical Parameters of Hydrogen-Doped Natural Gas
Authors: Jiang Xinhui , Liao Kexi , He Guoxi 
Published: February 2025

Abstract
Hydrogen energy is critical to the achievement of a "dual carbon" approach and has a key role to play in the future development of new industries. Adding hydrogen to the natural gas pipeline can achieve large-scale, low-cost, and long-distance hydrogen transport. The objective of the study is to investigate the effect of varying hydrogen doping ratios (HDRs) on thermophysical parameters such as the compression factor of natural gas based on the Lee-Kesler-Plocker (LKP) equation of state. The developed procedure allows the calculation of thermophysical parameters under different HDRs. The investigation considers the effects of temperature, pressure, and HDR. The results show that pressure fluctuations significantly influence the compression factor, followed by the HDR and, to a lesser extent, the temperature. The order of sensitivity for each parameter to the HDR is as follows: Joule-Thomson coefficient (JT)&gt; molar heat capacity at constant pressure (Cp) &gt; molar heat capacity at constant volume (Cv) &gt; compression factor (Z). These results provide a theoretical basis for understanding the transport of HDNG.
World Longest 9.625-Inch × 12.25-Inch Non-Directional Casing While Drilling in a Production Hole Section Through Highly Interbedded and Unstable Formations in an Operator.
Authors: Bethancourt R. , Kodiah B. , Aljabery R. K. , Al Reyami M. , Alsaweafi K. , Alwahedi K. , Faghaly T. , Ameh U. , Kosset T. , Nazarov T. , Khan Faisal Gul , Jouzy N. , Syafitri D. , Roberie J. , Balen A. V , Halma J. 
Published: February 2025

Abstract
The complexity of drilling 12.25-inch production hole in an operator encountered multiple drilling challenges such as total losses, wellbore instability, and unplanned trip due to bit failure drilling through highly interbed formations. These challenges affected both the drilling productivity and the well integrity. The adoption of Casing While Drilling (CWD) was a significant paradigm shifted in resolving these issues by maintaining well integrity and improving well delivery performance. This paper will illustrate how the CWD technology enabled drilling the longest 12.25-inch by 9.625-inch section in one run through unstable aquifer formations by saving 1.2 days of rig time and attaining achieving cementing quality.
The Non-Directional CWD Technology was deployed in a vertical production borehole section. The CWD used a casing string with a drillable body PDC bit and solid body centralizers for cementing. The approach emphasized careful engineering planning and preparation stages, customized to the requirements to overcome the main challenges for the CWD deployment in the pilot stage for final evaluation:
Drilling the section in one run and ensuring well integrity across aquifer zones during the cementing job. Drilling dynamics, hydraulics, bit design, offset well and casing centralization analysis were the keys to assess the feasibility of the CWD application through interbedded and unstable formations. Drilling with casing through highly interbedded zones with different hardnesses and mechanical properties was considered as one of the main challenges.
The CWD operation was finished in a single run with Zero QHSE incidents and minimum exposure of personnel to manual handling of heavy tubulars enhancing rig crew safety. The successful CWD implementation resulted in time savings of 1.27 rig days, in the production interval drilled in a single run (5,175 feet) through interbedded formations at a competitive Rate Of Penetration (ROP) of 47 feet per hour, enabling this to become a world longest 9.625-inch × 12.25-inch Non-Directional Casing While Drilling. The verticality was maintained at an average inclination of 0.3 degrees and a maximum displacement of 42 feet. The encountered losses were effectively reduced from 350 barrels per hour to 200 barrels per hour, demonstrating the plastering and wellbore strengthening effect of CWD which resulted in the subsequently good cement bond log across the aquifer formations. Exceptional cement bonding was maintained around the 9.625-inch casing indicative of good hole quality despite the significant dynamic drilling fluid losses.
Elastic Anisotropic FWI for Multi-Well Walk-Away DAS-VSP Datasets in a CCUS Pilot Field Onshore Japan
Authors: Nakayama Shotaro , Mouri Takuji , Podgornova Olga , Armstrong Philip , Khaitan Manish Lal , Bettinelli Pierre , Calvez Joel Le , Liang Lin , Zeroug Smaine 
Published: February 2025

Abstract
The application of Elastic Anisotropic Full Waveform Inversion (eFWI) to Multi-well Walk-Away Vertical Seismic Profiling (VSP) datasets, acquired with the Distributed Acoustic Sensing (DAS) technology, led to remarkable benefits in a carbon capture, utilization, and storage (CCUS) pilot project onshore Japan. Its application aimed to quantitatively estimate detailed subsurface properties by effectively accounting for complex wavefields in heterogeneous media through eFWI tailored to DAS data.
This novel approach employed in this study treats the DAS data as average strain along the fiber cable, enabling direct forward modeling and gradient computation based on strain measurements without necessitating data conversion. The inversion algorithm, which simultaneously inverts for multiple two-dimensional medium properties and source wavelets, incorporates three-dimensional well trajectory deviations and jointly utilizes multi-well datasets for a single inversion scheme to enhance subsurface property estimation.
Results from this application demonstrated the robustness of the algorithm to handle high background noise and significant amplitude variations inherent in our DAS datasets with minimal preprocessing. The applied inversion scheme effectively revealed detailed structural and stratigraphic features, aligning inverted compressional and shear velocities closely with existing well logs. Residuals between the observed data and simulated data confirmed the convergence of eFWI, leading to high accuracy of the estimated subsurface properties.
DAS-VSP has drawn significant attention in the industry, especially in the context of reservoir monitoring. By leveraging the ability of full waveform inversion, particularly its extension to muti-parameter inversion, a comprehensive and quantitative understanding of time-lapse changes in subsurface properties becomes realizable. These outcomes subsequently yield detailed insights into dynamic behaviors due to production and/or injection activities.
Improving Post-Salt Reservoir Image Quality Through Least-Squares RTM With DR-TLFWI
Authors: Yue M. , Chen Y. , Deng P. , Crabtree N. , Penman J. , Lange C. , Harrison A. J. 
Published: February 2025

Abstract
The reservoir imaging in Block 30, offshore Mexico, is challenged by complex overburden structures and sub-optimal acquisition setups, particularly in areas where intricate salt bodies overlay the reservoir. This study addresses these challenges by integrating Dynamic Resolution Time-lag FWI (DR-TLFWI) with Least-Squares Reverse Time Migration (LSRTM). The proposed DR-TLFWI optimizes contributions from low- and high-wavenumber components, improving velocity model accuracy for depths beyond the reach of diving waves. With the improved model, LSRTM compensates for illumination loss and enhances amplitude fidelity in complex subsurface conditions. The results demonstrate improved event focusing and gather flatness in the target reservoir, highlighting the effectiveness of DR-TLFWI with LSRTM for imaging zones with high-contrast in velocity.
Cutting-Edge Technique Fixing Control Line Leak in Corrosive Gas Wells
Authors: Kumar Rahul , Alkarbi Majed Ahmed , Al Hammadi Maryam Mohamed , Alkatheeri Mariam Taleb , Alkaabi Saeed Ahmed Sultan , Khalid Syed Farhan Bin , Makarem Abdallah , Hassan Mohamed 
Published: February 2025

Well Integrity assessment is all related to barriers. Double barrier envelope policy is a well-known worldwide well integrity requirement. This can be validated through international standards: API RP90 (1 & 2), Norsok D10, ISO 16530 (1 & 2). Wells with positive pressure at surface must comply with double barrier policy. Failure of barrier envelope leads to sustained annulus pressure as well as loss of primary containment scenarios (LOPC). It is preferred and usually mandated to identify exact leak source for evaluating and implementing SAP curing methodologies (Rig or Rigless). Many a times, leak hunting is impacted by loss of downhole accessibility due to DHSV malfunction attributed to control line leak. In such a case conventional wisdom is to put the well on WO schedule and carry out costly Rig based repair.
There are very limited solutions available for normalizing highlighted situation in Gas well to restore DHSV barrier integrity, since such wells are inherently of higher well risk in nature and need durable fail safe well barriers for prolonged well life.
As an alternative to this proposed rigless advanced solution, pressure-activated sealants are available. However, such sealants have been observed to be of limited ability to build sufficient pressure through the leak, which is essential for polymerization. Success rate is dismal in cases of large leaks. It can potentially block the control line and may pop out under pressure. Also, it can be pushed back into the control line, if the Annulus A pressure is greater than control line pressure (in cases leak is exposed to annulus A pressure).
Case Study – Failure Analysis of Collapsed Production Casing in an Elevated Temperature Well
Authors: Zaifullah Z. , Nurdin A. I. , Widianto D. R. 
Published: February 2025

Abstract
During the production test of a newly completed geothermal well in East Java Province, Indonesia, steam leakage was observed from the annulus between the surface casing (20" 133 ppf) and production casing (13-3/8" 68 ppf). Identical pressure readings at the wellhead and annulus indicated leakage in the production casing. The highest recorded temperature during the production test was 145 °C, which was considered low compared to the anticipated maximum static temperature at downhole of around 320 °C. Inspection using a multi-finger caliper revealed that the minimum measured internal diameter (ID) of the 13-3/8" casing was 10.523", while the drift diameter for this casing was 12.259", indicating that the casing had collapsed. The collapse occurred close to the surface, specifically on the pipe body just below the casing collar at depths of 12.7 m and 14.6 m from the top of the annulus. The top 23.5 m of the annulus was not cemented, and water was observed in this annulus section prior to the production test.
This paper conducts a failure analysis of the casing, illustrating how an isolated, uncemented casing section with trapped water and heat acts as a pressure vessel, leading to high pressure buildup in the annulus. Additionally, it explores the relationship between water volume, temperature, and annulus pressure, contributing to the failure. The analysis demonstrates that the failure was caused by annulus pressure buildup due to the thermal expansion of water trapped in the annulus. The failure likely occurred at a temperature even lower than the maximum recorded temperature of 145 °C.
This paper will benefit drilling engineers, completion engineers, production engineers, and other parties working with elevated temperature wells, such as geothermal wells, wells in compacting reservoirs, steam-drive wells, or high-pressure high-temperature wells, in preventing similar casing failures.
Producer Acid Stimulation in Unconsolidated Sandstone Reservoirs: Continuous Evolution in Overcoming Challenges and Enhancing Well Performance in an Offshore Oil Field
Authors: Zheng Jv , Zhang Yanxu , Gou Xinjun , Cui Qingzhen , Wang Yuejie , Fu Yangyang , Yuan Xiaonan , Dai Xianghui , Li Wentao , Zhao Ning 
Published: February 2025

Abstract
The objective of this paper is to review the evolution of producer acid design and the well performance of different acid formulations in an offshore oilfield in China. The focus is on addressing the persistent near wellbore plugging challenges encountered after water breakthrough.
Over the past 15 years, acid stimulation in studied oil field has experienced five major modifications since 2007. Initially, acid design considered potential causes of plugging only. However, after evaluating well performance and identifying new challenges arising from acid stimulation, an optimized process was developed. This process includes plugging mechanism analysis, experimental acid formulation selection, acid deployment, and comprehensive performance evaluation. Evaluation parameters encompass changes in productivity index (PI), oil and liquid production, skin, flow efficiency, and the impact on production facilities. Simplifying the operational process to reduce operational cost (Opex) has been a consistent goal and a key consideration in acid design assessment.
Continuous optimization in acid stimulation has been achieved through years of experience and lessons learned. The acid system has progressed from hydrochloric acid (HCl) system to a slow-released hydrofluoric (HF) based acid system, and later to a moderate-strength HF based acid system, and later to a weaker chelant acid system. The novel chelant acid system has been introduced as an alternative to moderate-strength HF based acid system, offering low corrosion, low reaction rate, and high efficiency, making it particularly effective for stimulating plugged producers in waterflooded unconsolidated sandstone reservoirs. Initially, this acid system demonstrated moderate production incremental; however, through continuous acid formulation and process optimization, its current results are comparable to those of the moderate-strength HF based acid system. The operation process has become simpler, minimizing its impact on the production facility through ongoing optimization.
This paper also introduced the recent advancements in the emulsified acid system, which has improved acid distribution across intervals exceeding 500 feet in thickness. Implemented in 2021, this advancement has shown promising production outcomes.
This paper will primarily focus on the evolution of the chelant acid system and the latest application of the emulsified acid system. It will discuss the continuous optimization of acid systems and operational processes, and will also cover field well selection criteria, well performance, and the impact of these processes on production facilities.