bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating Hole Cleaning Efficiency in Real-Time by Combining Along String Measurements and Hydraulic Modelling
Authors: Tamaddon S. , Gjerstad K. 
Published: February 2025

Abstract
Drilling operations require the continuous removal of drill cuttings to the surface through the drilling mud. Any accumulation of cuttings—such as beds in horizontal sections, avalanches in inclined sections, or sagging in vertical sections—must be promptly addressed to prevent severe complications. Without real-time insight into hole-cleaning conditions, these issues can escalate, causing delays, increasing costs, or even necessitating the abandonment and costly restart of the well. An Along String Measurement (ASM) system, combined with wired drill pipe technology, provides high-frequency measurements of multiple physical properties at various depths. This capability far exceeds the transmission rates of traditional mud pulse telemetry, offering new opportunities to gain real-time insights into hole-cleaning conditions.
This research focuses on identifying the real-time presence of drill cuttings in the mud by leveraging ASM readings, primarily downhole pressure, with optional inclusion of temperature data. A new cuttings estimation module has been developed and integrated into an existing system for drilling optimization and control. Currently, this module is being tested using historical drilling data from real wells.
The process starts by identifying periods when the well contains clean drilling fluid (i.e., free of cuttings) prior to drilling a new section. By analysing pressure differentials between adjacent sensors and leveraging known densities of clean mud and cuttings, the system calculates the cuttings fraction across different wellbore zones. This approach was validated by comparing its results to those of a physics-based model that has been extensively tested and proven reliable through years of operation as a real-time digital twin during drilling activities. The findings confirm the system’s ability to determine the proportion of drill cuttings in each zone by acceptable accuracy.
The paper presents the underlying concept of this methodology, offering a detailed overview of wellbore hydraulics and how these principles are applied to cuttings transport estimation. A sensitivity analysis highlights the robustness of the approach, demonstrating its resilience to typical uncertainties in parameters such as temperature, mud composition, and measurement data. Notably, the system is highly flexible, capable of functioning either as a standalone solution for estimating cuttings transport or as a complementary tool to existing physics-based models. By leveraging the strengths of both approaches, it delivers enhanced accuracy and optimal predictions for drilling operations.
Case Study - Efficient Drilling of High-Angle Wells: Overcoming Strength Anisotropy and Enhancing Hole Cleaning via Remote Real-Time Borehole Management
Authors: Gosavi S. V. , Adla A. , Sripada S. , Furey K. , Evans A. M. , Degroot A. K. 
Published: February 2025

Abstract
Drilling high-angle wells in oil fields can optimize reservoir exposure, boost production, and reduce the number of wells required for development. However, challenges like wellbore instability, hole cleaning, elevated Equivalent Circulating Density (ECD), and increased drilling loads arise. Rock strength anisotropy in shale causes significant instability in high-angle wells. Misconceptions about instability mechanisms and reluctance to use higher mud weight (MW) often lead to wellbore instability and Non-Productive Time (NPT). Despite many wells being drilled through unstable shale, significant NPT events can occur at higher inclinations. A low-angle well inclination limit is often proposed for successful drilling through anisotropic shale, citing instability due to strength anisotropy, drilling fluid invasion, and longer exposure times. Utilizing proper understanding of the failure mechanism, characterizing the shale strength anisotropy and using strength-anisotropy incorporated models it was deemed feasible to drill high angle wells through a challenging shale formation. To prove the concept, a pilot well was drilled at an intermediate angle which validated drilling feasibility beyond experience-based limits and gathered formation data for a wellbore stability model.
Following the pilot well’s success, a high-angle well was drilled using optimized parameters and higher MW, achieving NPT-free drilling. Remote real-time borehole advisory management system (BAMS) surveillance prevented unexpected events and NPT while drilling. Understanding failure mechanisms, a wellbore stability model for anisotropic shale, and an Integrated Hole Quality and Quantitative Risk Assessment (IHQ/QRA) approach were key to success. Careful planning and real-time surveillance, including transient hydraulics and hole cleaning (THHC) modeling, cavings characterization, and fluids surveillance, led to successful high-angle well drilling. This, and such work, has the potential to positively impact field development economics and may influence other offshore basin developments.
Efficiencies Are Driving U.S. Shale Drilling Costs Lower - How High-Frequency Embedded Drilling Dynamics Data is Improving Drilling Performance, Consistency and Reliability
Authors: Ference Zachary , Sugiura Junichi , Jones Steve 
Published: February 2025

Abstract
The U.S. shale industry is doing more with fewer drilling rigs, and the laterals are becoming deeper and longer. Well drilling/completion cycle times and costs have been reduced due to several changes. Batch drilling, smaller hole sizes and off-line cementing are some of these changes. But drilling efficiencies have also improved by drilling faster with fewer trips and making the process repeatable and consistent (often with rig automation).
High-frequency embedded drilling dynamics data recorders are proving to be an essential component in learning drill bit and mud motor/power section performance, reliability and durability. This paper details recent learnings from high-frequency embedded dynamics measurements, and how they are implemented to deliver performance and consistency to the drilling process.
Deploying high-frequency embedded drilling dynamics sensors in the mud motor bit box and top sub provides information that is not gathered from typical measurement-while-drilling (MWD) shock and vibration measurements because of the sensor placements in the bottom-hole assembly (BHA). Gyro (rotation speed), 3-axis shock (accelerations) and temperature measurements at the bit and above the motor power section provide a detailed understanding of drilling dynamics while certain rig operations are being performed.
Pulling off-bottom, distance off-bottom, transitional operations (slide to rotate), auto-driller set-points, drilling-advisory-system’s boundary conditions, clean-up cycles and rig automation settings can all be adjusted/tuned for optimal performance using the embedded drilling dynamics sensor data.
The results clearly demonstrate that embedded drilling dynamics data (acquired at the drill bit and above the mud motor power section) delivered critical information to optimize rig parameters and operational techniques to make the drilling process safer, faster and repeatable.
Initial analysis of the embedded senor data provided the results to commence strategic adjustments of the rig parameters and operational techniques. Embedded measurements were deployed again to validate the changes, and if further changes were required, the sensors continued to be deployed.
It was concluded that analysis of embedded sensor data, merged with rig electronic-drilling-recorder (EDR) data provided details of certain operations that were often being overlooked. This allowed the operator to set more stringent standard operating procedures to improve the overall drilling efficiency and repeatability.
Robust Model to Fingerprint and Distinguish Well Loss, Well Kick and Wellbore Ballooning Using Realtime Data
Authors: Zhang Shang , Samuel Robello 
Published: February 2025

Abstract
Wellbore ballooning is a significant challenge in drilling operations, often misinterpreted as a wellbore influx or kick, leading to unnecessary well control procedures. This study develops a robust real-time model to distinguish between lost circulation, well kick, and wellbore ballooning using real-time drilling and flowback data. The model analyzes flow behaviors and type-curve characteristics to accurately identify wellbore ballooning scenarios and kick/loss events. Validation with real-world data demonstrates its effectiveness in reducing non-productive time (NPT), enhancing real-time decision-making, and improving operational efficiency during drilling operations.
LLM-In-The-Loop: A Framework for Enhancing Drilling Data Analytics
Authors: Al Amin S. T. , Wu K. , Mathur A. , Koritala C. 
Published: February 2025

Abstract
Analyzing and visualizing drilling data is critical for optimizing operations and informed decision-making. As the drilling data are mostly structured data coming from downhole sensors and drilling equipments, traditional methods to analyze these data often require programming skills, causing delays and repetitive tasks for experts. On the other hand, advancement in large language models (LLMs) has enabled to chat with our internal data. Human-like or natural language can be used to extract meaningful and important information from large amount of data. With these motivations in mind, we propose a novel approach leveraging large language models (LLMs) to enhance drilling data analytics. By enabling natural language queries for complex data analysis, broader oil and gas users without traditional data analysis expertise can take advantage of it. Stakeholders and relevant personnels can easily perform data analysis and visualization without the need for specialized programming knowledge.
We introduce a framework to analyze drilling data with the help of LLM models. Our method retrieves relevant information and similarity pairs which are integrated into the prompt along with the user query. The enhanced prompt is subsequently fed to an LLM, generating source code which is executed by an agent through plans, actions and feedback. The processed answer is returned to the user. Our approach enables real-time, efficient, and accurate analysis of drilling data, making it accessible to all users. Experimental results indicate that LLM models exhibit superior accuracy when prompts are enriched with similarity pairs and contextual information, compared to processing raw user queries directly. We show that our framework can handle a variety of query types, including basic statistics, summarization, aggregation, comparison, filtering, correlation, and time-series analysis. We demonstrate high accuracy of our framework in these tasks using both zero-shot and few-shot learning approaches. Furthermore, the framework supports data visualization, enabling users to uncover hidden patterns and insights within the data. Our framework offers a significant advancement in real-time data-driven decision-making within the industry.
A Comparative Study of Fishbone Wells and Multi-Fractured Horizontal Wells for a Tight Carbonate Reservoir Case Study of the Sadi Formation in Iraq
Authors: Al-Saedi Asaad , Stephen Karl Dunbar 
Published: February 2025

Abstract
Development of a tight reservoir characterized by low permeability poses significant challenges to the oil and gas industry due to the low productivity and the excessive costs. This study explores the potential of utilizing "Fishbone Wells" compared to multi-fractured horizontal wells to maximize the net present value (NPV). The development approach is assessed for implementation in a tight carbonate reservoir in southern Iraq.
Numerical reservoir simulation models were utilized to predict oil production rates and optimize key parameters such as the number of branches for the fishbone well. Analytical models were used to calculate behaviour for both types of wells then, the outcomes were compared.
Our findings indicate that both multi-fractured horizontal wells and fishbone wells can achieve a positive Net Present Value (NPV) in the Sadi reservoir. However, the fishbone well consistently delivers higher NPV under specific conditions. Fishbone wells utilize smaller lateral branches, known as 'subs,' each containing 3 or 4 needles (or ribs) with a diameter of half an inch and 40 ft length. These needles usually have a 70% success rate in reservoir penetration. The well design limits each stage to12 subs because of the 40-foot spacing between subs and the 480-foot distance between hydraulic fracturing stages. Although 12 subs yield the highest production, our analysis found that a configuration with six subs optimizes NPV compared to one stage of hydraulic fracturing. It is important to note that the fishbone technology is most effective in reservoirs with permeability of 0.5 millidarcy or higher. In formations with lower permeability, hydraulic fracturing, which can be implemented below 0.5 millidarcy, may be the more reliable approach. While fishbone wells offer significant profitability potential, they also come with marginal risks and require favourable reservoir conditions to ensure success. As such, careful reservoir assessment is critical before selecting this technology for development.
This is the first study that compares the economic feasibility of fishbone stimulation technology to the multi-fractured horizontal wells implemented in a real case for tight reservoir formation.
CO2 Well Control Scenario Prediction Using Experimentally Verified Models
Authors: Skogestad J. O. , Lund B. , Feneuil B. , N'Gouamba E. , Aasen A. , Linga H. , Vold L. , Bruton Z. , Helgeland S. , Ødegård S. I. 
Published: February 2025

Abstract
Objectives/Scope: With the expected upscaling of the Carbon Capture and Storage (CCS) activity in coming years, the need for drilling infill wells for CO2 sequestration, i.e. wells that penetrate formations that already contain stored CO2, will inevitably arise. Hence, the risk of a CO2 well control event must be considered. This paper describes an approach to well control evaluation using software based on experimentally verified models, demonstrated through simulations of realistic case scenarios.
Methods, Procedures, Process: In order to achieve a software tool for evaluating potential well control scenarios for CO2 infill wells, it is crucial to obtain a good understanding of the behaviour of drilling fluids when exposed to CO2. This involves several aspects, such as density, phase state, rheology, robustness, particle sedimentation and risk of hydrate formation. Extensive laboratory studies have been performed to fill knowledge gaps in these areas and to obtain data for calibrating mathematical models describing the CO2-drilling fluid interaction. These models are then integrated into an existing hydraulic flow model framework, which is used in a well control evaluation software.
Results, Observations, Conclusions: Results from simulations using a well control software upgraded with capabilities for handling CO2 influx are presented and discussed. The input data for the simulations represent a case scenario supplied by an operator. In particular, the impact of CO2 influx on volume expansion and kick severity as the influx volume of CO2 is transported up the wellbore is discussed. Furthermore, the simulation software includes integrated models as resulting from laboratory studies of drilling fluid exposed to CO2. In a well control context, the thermophysical properties of CO2 may in many ways be more challenging than those of methane, e.g. with the presence of the critical point inside the typical operational envelope. It is also observed from the laboratory experiments that the impact of CO2 on drilling fluids is different than of methane. How these aspects contribute to different requirements for the models is discussed.
Novel/Additive Information: This study contributes to improved understanding of how a CO2 influx and its impact on drilling fluid properties affect the severity of well control incidents. For supporting the understanding, differences and similarities with respect to natural gas influx are presented.
A Downhole Closed-Loop Method for Wellbore Trajectory Control Based on Azimuthal Logging While Drilling Data
Authors: Wang Han , Chen Dong , Ye Zhihui , Mao Kaifeng 
Published: February 2025

Abstract
As the drilling operations face increasingly complex geological conditions, the geosteering technology is commonly used for drilling horizontal wells. The real time drilling data is usually transmitted to surface via mud-pulse telemetry to be reconstructed, while it is often obstructed by unpredictable signal impairments, resulting in time lag or error for decision making. Therefore, this study proposes a downhole closed-loop trajectory control method based on azimuth LWD data, aimed at addressing the challenges of horizontal drilling in complex geological conditions and enhancing the automation of geosteering technology. This algorithm identifies the formation near the drill bit using azimuth LWD data (e.g., gamma), by comparing the upper and lower logging data to control the wellbore trajectory. When the trajectory deviates from the target reservoir, the system automatically control the drill bit orientation and uses Dobbins curve to optimize the well path, ensuring it remains within the reservoir and achieving closed-loop control at each measurement point. Based on the logging data of a typical heavy oil reservoir from Girasol oilfield, the present method has been applied to provide an optimized wellbore trajectory, the results show that: 1. The optimized wellbore trajectory can be generated automatically by the algorithm, based on a 32s sampling rate; 2. The trajectory length calculated from present model is 11.9ft shorter than that of actual drilled trajectory; 3. Greater maximum build rate is more easier to drive the trajectory out from the target zone, the favorable value is about 6°/100ft for this example. In general, the present research provides an intelligent downhole closed-loop algorithm for wellbore trajectory control based on azimuth LWD data. It is expected that more drilling tool parameters are considered to achieve an auto-pilot mode for underground drilling operations.
Evaluating the Mechanical Durability of Well Cement and Geopolymer for Long-Term Integrity in CCS Wells
Authors: Hussain A. , Thiyagarajan S. R. , Emadi H. , Fernandez D. , Ispas I. , Watson M. , Henderson S. 
Published: February 2025

Abstract
Ensuring wellbore integrity is crucial for the long-term success of carbon capture and storage (CCS) projects. Cement durability under various environmental conditions plays a pivotal role in maintaining the integrity of wells and acts as the main barrier to leakage. This study investigates the mechanical behaviour of different formulations of well cement, focusing on the effects of supercritical CO2 exposure on the cement's porosity, permeability and mechanical properties.
The formulations tested in this study are neat Class H cement, neat Class C cement, a high porosity lightweight field blend, and a Class F Fly Ash Geopolymer. Cylindrical cement samples (7.5 cm x 3.81 cm) were cured at 60°C for 28 days and then exposed to supercritical CO2 for 28 days under 10.34 MPa and 60°C. Before and after treatment, porosity, permeability, and triaxial compression tests were conducted to assess mechanical properties at a confining pressure of 10.34 MPa. The study sought to determine changes in strength, elastic moduli, and overall integrity under these conditions.
Post-treatment analysis revealed minimal changes in the porosity of cement samples. The permeability and mechanical properties of all the samples demonstrated significant changes. The highly porous cement showed reduced strength and elastic moduli compared to the low-porosity formulations, yet exposure to supercritical CO2 did not significantly alter these properties. The Geopolymers exhibited different results when compared to the other cement types. These findings suggest that, under the conditions tested, the structural integrity of well cement is maintained, which is critical for ensuring long-term wellbore stability in CCS applications.
This study illustrates the robustness of several oilwell cements to supercritical CO2 exposure, highlighting their practical significance and appropriateness for long-term wellbore integrity in CCS projects.
Development of the AI Drilling Agent: AI-Physics Hybrid Model for Accurate, Adaptive and Autonomous Decision-making
Authors: Cao Jie , Muhammad Ressi Bonti , Gocmen Emre , Nabavi Josef , Oedegaard Sven Inge 
Published: February 2025

Abstract
This study investigates the development of the AI Drilling Agent through a hybrid methodology that integrates physics-based modeling and simulation with advanced agentic AI. The current focus is on training the AI Drilling Agent within a dynamic drilling simulation environment to optimize operations, predict potential issues, and enable autonomous decision-making. The AI Drilling Agent is trained using a comprehensive downhole drilling simulator that replicates real-world conditions, incorporating coupled hydraulics, temperature, and torque/drag models, as well as dynamic factors such as inertia, acceleration, and the effects of temperature and pressure changes on downhole fluid dynamics. Reinforcement learning algorithms enable the agent to iteratively improve its decision-making capabilities.
Initial results highlight the effectiveness of this hybrid approach, where the AI Drilling Agent interacts with the physics-based simulation environment to iteratively learn and propose optimized strategies aligned with predefined objectives. The physics-driven models provide a realistic and rigorous training environment, while AI methods ensure adaptability and optimization. Future work will expand this integration to include real-time data and digital twins, further enhancing the agent's situational awareness and operational efficacy. These findings demonstrate the transformative potential of combining physics-based simulation with AI-driven solutions to improve drilling operations, reduce risks, and enable consistent decision-making. This paper presents ongoing research progress, offering insights into the evolving role of hybrid methodologies in revolutionizing drilling practices through the seamless integration of agentic and generative AI with advanced modeling techniques.
Made in Brazil
Authors: Ferreira Ana Paula 
Published: February 2025

The present essay analyzes the emergence in Brazil at the turn of the 1960s of a postcolonial idea of a transnational “community” of Portuguese speakers. That idea is connected with a series of heterogenous and unequal groups linked by different degrees of activism against Portuguese colonialism. Examples include Brazil’s diplomatic turn to Africa and Asia under the Quadros-Goulart regimes; solidarities between African independence fighters and Brazilian Black activists (and supporters); the wide anti-Salazar and anticolonial activism promoted by the exiled Portuguese democratic opposition; and the cultural common sense, echoed by Maria Archer, that Brazil could safeguard the future of the Portuguese language owing to the ever-present history of slavery.