bluuebunny/crossref_metadata_2025 huggingface dataset:
Innovative Fluid Migration Control Cement System Demonstrating Improved Results for Primary Cementing using Controlled Particle Size Distribution: A Novel Approach to Ascertain the Wellbore Integrity
Authors: Ali Wajid , Hashmi Ahmad Atef , Abdullah Al Turki Faisal , Bouaraki Mouloud , Aljardan Moaathe
Published: February 2025

Fluid migration after cementing is a well-known challenge in the oil and gas industry. Failure to prevent fluid migration is costly, extremely difficult to remediate, and more importantly, may lead to safety and environmental issues. This paper will review several case studies for deploying an engineered fluid migration control cement system as an important solution for primary cementing operations in case study wells with the risk of fluid migration.

Fluid migration has been of the utmost attention to oil and gas operating companies, as costly remedial cementing operations are needed to repair the deficiency in wellbore integrity caused by the formation fluid’s influx. After thoroughly reviewing the current practice of latex-based designs, the study identified a few limitations that persuaded the improvement of the cementing designs. Latex was replaced with three solid materials to provide lower permeability while maintaining the required compressive strength and fluid loss. This paper also illustrates the case studies where the innovative cement system was successfully applied to improve zonal isolation.

Cementing is a critical process that facilitates adequate zonal isolation for the lifetime of the well by placing cement slurry between the drilled formation and casing. The cement slurry system must be engineered to meet industry acceptance criteria, such as short transition time, low fluid loss, zero free water, and appropriate slurry density to prevent fluid migration. Latex-based slurry systems have been used to achieve these requirements. However, these systems are less effective at low downhole temperatures and generally exhibit delays in compressive strength development, which incurs additional costs to operating companies. To overcome these challenges, an engineered cement slurry system comprising a solid polymer, permeability reducer, and bonding enhancer was developed to offset shallow and deep hazards. As a result, the cement inside the shoe track was found to take more weight on the bit and had a slower penetration rate during drill-out, which confirmed early compressive strength development. Also, the sustained casing pressure occurrences were significantly reduced, even in areas historically prone to high severity of fluid migration through the cement slurry to the surface. This confirmed the effectiveness of this innovative solution.

This paper presents a detailed overview of the design of the novel fluid migration control slurry system to confirm its reliability and cost-effectiveness compared to a conventional latex-based slurry system. In addition, this paper demonstrates the case studies where this engineered solution was successfully deployed for the primary cement jobs to eliminate or mitigate the occurrences of sustained casing pressure with observed improvement in field deployment results.
AI Solution Provides the Most Autonomous Framework of Directional Well Sections in High-DLS Well Plans
Authors: Samba BA , Sahli Hussein , Oumba Roland Loubassou , Nkounkou Teddy , Olanubi Olakunle , Kim Jinsoo , Roh Si Jine , Ali Riyami Aktham
Published: February 2025

Well construction is currently being challenged to become more sustainable while reducing the skill sets needed to have efficient and consistent directional drilling operations. This paper presents an autonomous directional drilling artificial intelligence (AI) framework. This framework was used to drill the most autonomous section to-date on an offshore well in 2023. In 2024, the next level of performing autonomous directional drilling in a high-dogleg severity (DLS) environment was attempted.

Challenges related to directional drilling include encountering constantly changing formations, steering responses, planned trajectories difficult to follow perfectly, drilling data having huge uncertainties, especially the continuous measurements being affected by shock and vibrations, ever changing conditions between one well to another. These challenges often require significant human skillsets to become an efficient directional driller; and skillful directional drillers, who make best directional decisions, are difficult to deliver for service companies and operators.

This paper presents the latest AI system developed to perform autonomous directional drilling. The AI system derives drilling parameters and steering recommendations to automatically send downlink commands when enabled. In addition to complex sensor fusion for the best state estimation, an optimization engine outputs the best candidate trajectory at each decision point. Several enhancements were necessary to move from advisory to control. The system has been made much more resilient to unexpected measurement-while-drilling (MWD) telemetry or downlink issues. The system’s surface deviation controller actively monitors continuous data and takes the appropriate course of actions to rectify unplanned situations without overreacting.

With respect to downlinking automation, the system is designed to use plug-ins as drivers for different equipment. This design allows for accommodating a wide array of actuators, extending from drilling rig automation systems and flow bypass downlinker at the rig, even to cloud interfaces offered by some rig contractors.

Recently, the proposed AI system was tasked to perform drilling parameters control and steering control simultaneously while entirely taking the command of the rig control system. The deployment was performed in a field with high-DLS requirements often exceeding 6 °/100 ft. A comparison was made with wells drilled by the manual mode, those drilled in an advisory mode and finally those drilled in a fully autonomous mode.
Optimized Nitrified High-Solids System: A Customized Solution for the Balder Field (Norwegian Continental Shelf)
Authors: Knowles John S. , Barriero Jose , Jensen Stian , Johnson Carl R. , Bourada Nacera , Sakharov Sergey
Published: February 2025

In 2021, Vår Energi ASA faced the challenge of cementing conductor casings on the Norwegian continental shelf (NCS) with a high risk of destabilizing the subsea templates in the Balder field. The successful cement placement outside the conductors (with top of cement to seabed) was crucial for subsequent well construction operations. To address this challenge, the only viable solution to prevent the historic losses seen during the cementing of the tophole sections on the field was to utilize an extremely low-density cement slurry (requiring as low as 1.15 sg).

To meet these job objectives without compromising safety, an innovative and unique approach was introduced. This involved using an engineered high-performance, low-density cement slurry (1.45 sg) by replacing a portion of the cement content with lower-density particles of larger size, maintaining the solid volume fraction at a higher packing volume. This blend was then foamed using nitrogen (N2) to achieve the required downhole slurry density. This system exhibited superior set-cement characteristics, enabling the required set mechanical properties to be achieved at lower densities.

The first job was successfully executed on the West Phoenix semi-submersible drilling rig using the automated foamed cement process-control system. This system automatically synchronizes the amount of N2 and foaming agent according to the base slurry pumping rate from the cement unit. A total of 57 m³ of 1.45 sg high-performance, low-density slurry, foamed to the desired density of 1.15 sg, was placed in the annulus with full returns observed at seabed throughout execution, negating the need for any remedial or top-up operations. The slurry developed 3 bar compressive strength after only 9 hours, and no backflow was observed during verification of the float equipment.

Subsequently, multiple cement jobs using this technique have been flawlessly executed, meeting the job objectives for each operation. Three templates were completed successfully, resulting in significant time savings for the operator, including a considerable reduction in the operational carbon footprint (or CO2 equivalent [CO2e]) estimated to be around 25% versus an equivalent volume of neat class G slurry.

This case study demonstrates a successful foam cementing solution in a challenging subsea environment in extremely weak formations. This paper will describe lessons learned and best practices that Vår Energi ASA has subsequently incorporated into future operations, which other operators in the NCS with similar circumstances will also find useful.
Evaluation of Cemented Casing Test Cells with an Ultrasonic Phased Array Transducer for Cement Bond and Corrosion Logging
Authors: Guedes Orland , Van Os Roel , Titton Izabela , Li Zheng , Hori Hiroshi , Ishberdina Gulnara , Singh Kamaljeet , Gardner David , Simensen Per
Published: February 2025

Pulse-echo ultrasonic measurement techniques are used in the oil and gas industry for imaging casings and tubings for cement bond and corrosion evaluation. Conventional downhole ultrasonic measurement tools typically consist of one or multiple ultrasonic transducers, that probes inner surface and are rotated to provide full azimuthal coverage. This paper proposes a method of achieving this using phased array transducers.

Phased array pulse-echo methods are widely used in non-destructive testing and medical applications. In a typical operation, multiple elements are activated in collaborative fashion to transmit and receive the ultrasonic waves. By introducing de-phasing among the elements, the ultrasonic beam can be shaped and directed onto regions of interest to target. The main advantage of this technique for cased hole imaging is the versatility thanks to a high number of emitting and receiving elements that are placed around the circumference of the tool; electronic scanning can replace the mechanical rotation that requires complex mechanical systems.

SLB has developed such a phased array ultrasonic transducer integrated into an experimental prototype tool and conducted logging in test cells at the NORCE Norwegian Research Centre facility. The test cells are made of a variety of pipes with designed cementing defects. In this paper, we will introduce an overview of downhole phased array measurements and present test cell logs in comparison to the reference logs from commercial tools. The results show a good agreement between images obtained from the legacy and new phased array sensors in the tested conditions.

This paper reports one of the first well integrity measurements performed with an ultrasonic phased array for azimuthal cement bond and pipe thickness imaging. On the other hand, the simplification of the tool architecture allows a reduction of the outer diameter and unlocks the possibility to deploy such a tool on monocable in diameters starting from 3.5 in. casing/tubing, which was not available before.
Gas Tight Cementing Valves and Casing Annular Packer Prove Successful in Achieving Multiple Isolation Objectives Across a 10,200ft Interval in a Single Trip
Authors: Hrabovsky B. W. , Bermudez F. Z. , Bamber J.
Published: February 2025

Working in an offshore field, recognized as one of the world’s largest natural gas reserves, with a unique geological composition presents multiple challenges for oil and gas operations. The formations within the field are characterized by high porosity and varying permeability, which contribute to their potential for instability during cementing operations. The integrity of cement barriers is paramount, as failures can lead to gas migration, loss of hydrocarbon resources, and environmental hazards.

The geological landscape of the field includes a variety of formations, each with distinct characteristics that influence cementing operations. These formations often exhibit high-pressure zones interspersed with permeable intervals, making them particularly susceptible to breakdown during conventional cementing processes. The variability in formation properties complicates the cementing process. Traditional methods often struggle to maintain cement integrity in these environments, leading to issues such as loss of circulation, inadequate zonal isolation, and the risk of sustained casing pressure. Each of these challenges necessitates a tailored approach to cementing that considers the unique conditions encountered in this field.

Cementing is a critical process in well construction, as it establishes a secure barrier between the wellbore and surrounding formations. The ability to achieve zonal isolation and maintain pressure integrity is essential, especially in the presence of high-risk formations. This paper aims to explore the innovative cementing strategies employed in this operation, focusing on the integration of advanced technologies that enhance annular seal integrity, reduce operational complexities, and optimize well design.
Assessment of High-Magnesium Brine Resistance in Various Well Barrier Systems
Authors: Binns Matthew , Johnson Carl R. , Ficetti Silvina
Published: February 2025

Identifying effective well barrier materials for new energy applications such as carbon capture and sequestration (CCS), critical mineral mining and geothermal wells has become increasingly important in the energy industry. Laboratory testing was conducted to compare the brine resistance of various cement systems to a specific high-magnesium content brine under low and high-temperature/pressure conditions. This study was initiated due to the increased availability of pozzolanic blend components and the lack of recent studies using these new blend components.

Testing was conducted at low and high temperatures and pressures (60°C/121°C and 14.7 psi/5000 psi, respectively). Each sample was prepared from cured material and subsequently cored. Low and high-temperature testing involved curing cores for a minimum of seven days, with several cores at each temperature and pressure being tested prebrine exposure to provide reference data. Additionally, computerized tomography (CT) analysis was conducted on a single core in each system. For brine-exposure cores at low temperatures, each core was placed in an individual sample bottle containing a specific synthetic brine for 30 days. For brine-exposed cores at high temperatures, cores were submerged in the same brine inside a high-pressure high-temperature (HP/HT) curing chamber for 42 days.

The post-curing properties of the brine-exposed core samples revealed multiple effects relative to the type of barrier material being evaluated. Depending on the system, visual effects (cracking, precipitation, crumbling, flaking) and internal effects (reaction front, strength loss, mass changes) were quite distinguishable in some cases. All systems tested experienced brine attack to some degree, with several systems showing significant attack and integrity degradation. In one case, a thick gel precipitate formed, which, after X-ray diffraction analysis, was found to be a mixture of bischofite (hydrous magnesium chloride), tachyhydrite (hydrous chloride of calcium and magnesium), and levyne-Ca (hydrated calcium silicate mineral). The same sample had expanded, cracked, and was crumbling. CT analysis revealed there was an impact on the development of the reaction front depending on the slurry additives and fillers used, some beneficial and some detrimental, i.e., change in compressive strength. Test results and the varying degrees of resistance to the brine for all the systems are discussed.

New data are presented on barrier materials that use non-API (American petroleum institute) cements in the presence of certain pozzolanic materials. These materials enhance the set properties of the barrier material in an aggressive magnesium brine environment. Additionally, the impact of specific commercially available additives is discussed with recommendations. Overall, this work aims to support improvements in well integrity in wells such as geothermal producers, where aggressive brines can be common.
Novel Spacer Technology Improves Well Integrity in Complex Cementing Scenarios in the North Sea
Authors: Kaastad A. , Nascimento F. , Yasser H. , Lo R. , Bermudez F.
Published: February 2025

North Sea lithologies are often complex, creating challenging environments during cementing operations. Ensuring wellbore stability and zonal isolation are pivotal throughout a well's lifecycle and to achieve an optimal top of cement, therefore preventing lost circulation is imperative during the primary cementing operation. The deployment of this novel spacer technology has enabled superior cementing jobs, which not only helps operators in minimizing downtime but also enhances their environmental stewardship by avoiding remedial work, and reducing additional cement use.

In modern upstream activities, economics are key to any drilling and completion operations. Lost circulation is a costly problem for drillers, causing non-productive time, wasted material, additional trips, unplanned casing strings, and can even cause additional problems later in the life of the well if proper zonal isolation is not achieved. The cementing operation, while a small portion of an operator's overall drilling budget, is a key component of ensuring a well is constructed with the necessary annular barriers. This paper discusses a novel lost circulation spacer, showcasing its performance, and results from case histories.
Drill Bit Performance Improvements in Challenging North America Land Drilling Applications Through Optimization of PDC Cutter Technologies
Authors: Robertson A. , Hanafy A. , Valbuena F. , Gomez L. , Moulton H. , Tilleman D. , Ameri T. , Duffy S. , Bomidi J.
Published: February 2025

The continuous push for faster and longer bit runs in heavily directional, motor-oriented drilling applications requires Polycrystalline Diamond Compacts (PDC) cutters to better resist impact damage and abrasive wear while providing improved drilling performance. Moreover, drilling longer sections with interbedded lithologies requires PDC cutters to possess both high abrasion resistance and durability to resist dulling from the varied lithologies and overcome drilling dysfunctions inherent to such sections. This work will present optimized PDC cutters that enabled improved drilling performance in a variety of challenging applications.

This work details the optimization of PDC cutter technology by balancing the Polycrystalline Diamond (PCD) properties, PDC composite design, and cutting geometry according to an application's demands. Three applications are identified to showcase PDC cutter improvements in abrasion, impact, and general-purpose performance categories. Each application's typical dull was forensically analyzed to assess the appropriate design direction for improved PDC performance. PDC cutters were lab screened with a standard test protocol for assessing abrasion resistance and impact resistance. Cutting geometries were modelled via Finite Element Analysis (FEA) and cutting performance was verified with a pressurized single cutter rock cutting test. Each PDC cutter type was tested in the field against suitable offsets to confirm improvements in drilling performance and dull characteristics.

The optimized PDC cutters showed significant performance gains in terms of footage, rate of penetration (ROP), and dull grade across the performance spectrum. In lateral sections of Canada's Falher abrasive lithology, an abrasion-oriented PDC cutter improved drilling footage by 48% and 30% while also increasing the average ROP by 4% compared to offset runs. The Southeast USA Haynesville intermediate is challenged by high interbedding of hard, abrasive lithologies and high lateral vibrations induced by drilling dysfunctions. Here, a general-purpose PDC cutter combining high abrasion resistance and durability, and a novel cutting geometry optimized for drilling efficiency and durability drilled 32% further with equivalent ROP and better dull condition. In West Texas USA, lateral sections in the Leonard B formation are challenged with stringers that cause severe impact damage. An optimized impact cutter demonstrated 20% increased footage compared to offsets.

Optimization of the many facets of PDC cutter technologies proves effective in delivering drill bit performance in a variety of challenging applications. With the newly introduced cutters a higher footage per bit can be realized. Detailed analysis of the dysfunctions, lithologies, and operating conditions of a given application can further enable better PDC cutter designs and fruitful operating conditions.
Engineered Drill Bit Cutting Structures for Interbedded Applications Suppressing Lateral and Torsional Excitation at High Performance and Durability
Authors: Hanafy A. , Kueck A. , Duffy S. , Benzaoui T. , Fankhauser E. , Evans K. , Doster M. , Bomidi John
Published: February 2025

Drilling dysfunctions are big challenges while drilling interbedded formations. Adding to the excessive loads on cutters during soft to hard transitions, the lateral and torsional dysfunctions can be detrimental for the bit and BHA. Recent research proved that the excitation of these vibrations happens at the cutter/rock/fluid level (Jain et. al. 2014, Kueck et. al. 2023). This work evaluates the excitation of dysfunction by current cutting structures of drill bits and showcases the capability of a novel cutting structure that promotes stability, performance, and durability.

This work integrates modeling and simulation data with a full-scale drilling simulator and in-bit sensing to deepen the understanding of lateral and torsional excitation and drilling interbedded formations. Moreover, it lays out a framework to iterate on cutting structures to enable drilling stability without jeopardizing bit performance and durability. This iterative design tool is implemented to deliver a cutting structure that suppresses the excitation extent and enables performance and durability gains. The final cutting structure is benchmarked against the application established structure in a high-pressure drilling simulator. The potential stability and performance gains are validated in the field.

The design framework shows the capability to predict the different cutting structures responses with simulation validated by their performance in the lab and field. The newly developed cutting structure shows a significantly different excitation of High-Frequency Torsional Oscillations (HFTO) in simulations and lab drilling. Furthermore, the cutting structure enhances ROP response to applied WOB and helps distributing the cutting loads on the cutters to avoid shear failures due to overloading. The lab scale drilling simulator shows vibration reduction nearing 25% without HFTO or lateral vibration and performance gains up to 25% in ROP. The application in the field showed positive results with better bit dull grade and fewer bit and BHA failures.

Finally, this approach targeting challenging applications has proven the capability to shorten the number of bit design iterations. The coupling of modeling and lab simulation generating a better understanding of the bit response enabled guided cutting structure conceptualization and an efficient iterative design approach. Providing stable bits enables faster drilling and fewer bit and BHA related failures.
Enhancing Wellbore Integrity: The Impact of Fine Particle Mudcake on Fracture Initiation Pressure
Authors: Hamidov E. , Baldino S. , Ozbayoglu E. , Zhang J. , Chellappah K. , Routh A.
Published: February 2025

Wellbore integrity is essential for preventing lost circulation and ensuring drilling operations remain productive and cost-effective. This study explores the role of fine particle mudcake in enhancing fracture initiation pressure, building upon previous research to provide a deeper understanding of how fine particles contribute to wellbore strengthening. Utilizing an advanced true triaxial testing setup, this investigation evaluates the impact of various drilling fluid formulations on mudcake formation and wellbore stability. The effects of mudcakes, as well as scenarios without mudcake were examined. In addition, a series of modified API filter tests have been utilized using different mud formulations such as MgO, Latex and Ultrafine Barite. Our results reveal that both mudcake and fine particles can contribute to wellbore strengthening through a combination of fracture plugging, stress redistribution, and fracture propagation resistance. The results demonstrate the potential for optimized drilling fluids incorporating mudcake and fine particles to improve wellbore stability and mitigate lost circulation events, offering a promising alternative to conventional wellbore strengthening methods. This research underscores the importance of considering both mudcake and fine particles in drilling fluid design and provides a foundation for further exploration of their combined role in enhancing wellbore integrity and lost circulation management.
Re-Defining the Limiter in LWD NMR - Unique Case of Designing the BHA for Specific Objectives
Authors: Ijasan O. , Story S. , Jing I. , Fazal A. I. , Ramadan Z. , Seitz J. , Shrivastava C.
Published: February 2025

An innovative logging-while-drilling (LWD) Nuclear Magnetic Resonance (NMR) acquisition program was designed, tested, validated, and deployed to accurately measure bound-fluid pore volumes in siliciclastic formations. Field development in deepwater operations required bound-fluid logging in horizontal wells to reliably interpret water saturation, properly characterize reservoir quality, and improve rock physics modeling. However, LWD NMR has always been considered a limiter in the drilling bottom-hole assembly (BHA) due to low drilling rates required to avoid spin over-polarization and acquire measurement with optimal vertical resolution of formations in the subsurface. This often results in slower rates of penetration (ROP) which hinders operational efficiency in high cost deepwater environments.

A recent NMR acquisition sequence, with a 10-second acquisition cycle at 200 ft/hr, focusing on bound-fluid has redefined this limiting factor with deployment in deepwater operations. This lead to acquisition of high-quality NMR data for specific fit-for-purpose applications while doubling the ROP. Forward modeling was performed to evaluate strengths and limitations of this 10-second acquisition configuration. Furthermore, this robust bound-fluid sequence was extensively verified and validated with tool architecture, electronics, and hardware while all withstanding heavy duty cycles. Additional modeling was performed using known formation properties and the new 10-second sequence provided better vertical resolution of 2.8 ft while responding to facies variations in the wells of study. This is compared to 8.3 ft at 200 ft/hr with a standard 30-second sequence. The sequence was implemented in successful field deployment, thereby redefining the limiting factor of slow ROP for LWD NMR acquisition. This advancement achieves logging objectives while enhancing the overall efficiency of deepwater drilling operations.
Fatigue Strength Evaluation of a Variety of Drill Pipes for Challenging Drilling in 7000 m Water Depths, IODP Expedition "JTRACK"
Authors: Inoue T. , Sakurai N. , Santus C. , Romanelli L. , Bhukya S.
Published: February 2025

The fatigue resistance of a drill pipe is a critical factor affecting the performance of deep drillings. This study focused on the determination of fatigue strength, through full scale tests, on a selection of actual drill pipes, and the evaluation of the entire drill string fatigue resistance after the analysis of these test results. The fatigue tests cover a variety of drill pipes such as 165, 150 and 140 ksi grades with Delta, GPDS or DSTJ connection, new and used pipes. A resonant fatigue test machine was used to perform rotating fatigue tests on full scale drill pipe sections (or specimens) with dual measurements combined with a control software to keep stress amplitude constant. After these tests, the numbers of cycles to failure were experimentally evaluated along with the observation of the crack initiation locations that resulted to be dependent on several factors as discussed in the paper. Using these test results, the fatigue evaluation of drill string, planned for International Ocean Discovery Program (IODP) expedition 405 JTRACK operations, was examined by calculating the cumulative damage ratio to find the possible endurance of the operation. It was found that a specific type of drill pipe has higher fatigue strength than others, so the use of that drill pipe will contribute significantly to the prevention of fatigue failure during the offshore drilling expedition.
Real-Time Downhole RPM Range Prediction for Improved Stick-Slip Detection Using Ensemble Machine Learning
Authors: Zhang M. , Kaya M. E. , Habib N. , Groh A. , Small A. , Xue Y. , Walthall J.
Published: February 2025

Understanding downhole dysfunction, such as stick-slip, is critical for preventing downhole tool damage and reducing non-productive time during drilling. Common methods for quantifying dysfunction intensity, such as a surface Stick-Slip Index (SSI), often fail to capture the complex relationships between surface measurements and downhole behavior. This can lead to improper evaluation of actual downhole conditions and driller response. This paper presents a machine learning model for real-time downhole rotations per minute (RPM) range prediction with surface data which is coupled with an ensemble framework for more robust stick-slip detection and quantification.

This method utilizes a combination of models to blend machine learning with subject matter expertise and physics-based features to improve real-time detection of downhole stick-slip and to quantify its severity. In contrast to surface SSI, which focuses exclusively on surface torque, this method combines additional traces into a downhole RPM prediction model using gradient-boosted trees. Downhole data from 84 runs were used to train and validate the downhole RPM prediction model with eight runs being used as hold-out test data. This prediction was evaluated in combination with wavelet transforms to quantify the severity of stick-slip. Next, the model was deployed across the fleet to enable collection of data in real-time. The output is then linked to bit dull grade data for damage analysis.

When evaluating the model's predictions for downhole RPM range, we achieved good performance on the validation set, with over 50% RMS (root-mean-squared) error reduction from both the naïve predictor (average RPM range), and a surface SSI-based regression tree model. Similar improved performance was observed when evaluating the hold-out bit runs from the same region. The model's ability to generalize to other regions is an area for future study, but we hypothesize that the training dataset may need to be expanded with representative wells to achieve similar performance in new regions. Finally, timeseries data for 1,270 additional runs from 496 wells have been processed utilizing the full ensemble model. The results are compared with their associated bit dull grade records to understand the correlations between stick-slip metrics and bit damage.

This study presents a better approach for determining downhole stick-slip risk in real-time, using a data-driven approach to minimize the requirement for detailed engineering input to run the model. Additionally, it highlights that surface SSI is poorly correlated with actual downhole RPM behavior, only marginally outperforming the naïve estimator. This implies that surface SSI alone is not enough for identifying damaging stick-slip. Interestingly, the surface SSI ranked highly in feature selection, suggesting that there is meaningful information stored within the metric itself but that it loses value without additional context.
Low Thermal Conductivity Coating Extends BHA Life and Improves Drillstring Performance in Challenging High-Temperature Environments
Authors: Fard Reza S.
Published: February 2025

In shale plays like the Haynesville in the US, elevated formation temperatures and abrasive, high-weight drilling muds shorten the working life of bottomhole assemblies (BHAs) and surface equipment. The result is more trips downhole, increased nonproductive time (NPT), and costly tool repairs. This paper reviews a field study conducted by a major operator to evaluate a novel, low thermal conductivity-coated drillpipe for long-lateral drilling operations in the Haynesville.

The paper reviews the development of the low thermal conductivity coating, built on established coating solutions that protect tubulars in aggressive oil and gas environments from corrosion, wear, and deposit buildup while improving hydraulic efficiencies. Several coating formulations were evaluated for their ability to reduce heat transfer through the tubing to keep drilling fluids and bottomhole assembly (BHA) tools cooler and running longer. The paper also reviews the operator's modeling work to simulate the temperature profile while drilling through the formation, which helped optimize the coating design and drilling plan before going to the field.

The iterative coating development and testing process resulted in a coating system with a thermal conductivity of k=0.1808 W/mK, nearly five times lower than the initial coating formulation and 250 times lower than steel pipe. The temperature profile showed excellent alignment with the model in the first well drilled with the new insulated, coated drillpipe. The coated pipe kept sensitive BHA components cooler and reduced the number of roundtrips for tool repairs and replacements.

Based on these results, the operator estimates that the low thermal conductivity coating saved an average of two BHAs per lateral across the entire drilling area, with some of the hottest areas of the Haynesville basin saving more than four BHAs per well relative to historical performance. This BHA savings translates to significant savings in drilling costs and nonproductive time. It also minimizes the number of trips to retrieve heat-damaged BHAs, a significant saving considering that each trip costs several hundred thousand dollars. Drilling operations in other high-temperature, harsh downhole drilling environments, including geothermal and deepwater HP/HT wells, will likely see similar cost, time, and carbon footprint reductions with this low thermal conductivity-coating.
Design and Qualification of a Purpose-Built 3,000,000 Lb Landing String System Enables 20k Exploration
Authors: Sanclemente L. , Broderick E , Primeaux A. , Plessis G. , Muradov A. , Marchman K. , Sommer M.
Published: February 2025

One of the first 20,000 psi Paleogene development projects is located in the Green Canyon area, approximately 140 miles (225 km) off the coast of Louisiana, in water depths of approximately 5,000 feet (1,524 m). The subject well will be drilled to approximately 30,000 feet and will require six drilling casings plus production liner and tieback. A purpose-built drilling landing string with 3-million-pounds capacity will be needed to land the 16" and 14" casing strings and the 10 1/4" by 11 1/4" production tieback string.

This paper documents an extensive development effort spanning over seven years. Initially, 6 5/8", 7" and 7 5/8" solutions were considered with landing capacities of up to 4-million-pounds. A 6 5/8" 3-million-pounds design was selected for qualification testing. The development of the landing string's design configuration and performance specifications are presented.

Qualification testing of the landing strings included: friction weld qualification, FEA to optimize the connection pressure sealing capability, FEA of elevator shoulder/upset region for cross-sectional and elevator shoulder yielding, shear testing of the pipe body and slip-proof sections, combined load testing of the landing string assembly, and slip-crush testing of the pipe body and slip-proof sections. Test procedures and results are presented.

This 6 5/8" landing string has the highest capacity at 3-million-pounds of any purpose-built landing string manufactured.
Bigger isn't Better: Fundamental Differences in Flow Regime Development from Rotating Pipe
Authors: Rathgber D. C. , Johnson E. L. , Anderson R. , Lucon P. , Todd B. J. , Downey J. , Richards L.
Published: February 2025

Operators often look to use drill pipe rotation to increase hole cleaning effectiveness in horizontal and high-angle sections of wellbores. However, the effect of drill pipe rotation on cuttings transport is dependent on a range of factors, from fluid rheology and density, rotation rate, hole diameter, and pipe diameter. To identify cause and effect of these parameters, several multiphase flow simulations were performed to identify possible changes in flow regimes that would affect cuttings transport efficiency.

Computational Fluid Dynamics (CFD) software was utilized to develop and simulate a range of single - phase and multiphase flow models replicating a range of typical high-angle tangent and production sections. Wellbore diameters ranged from 8 ¾" to 12 ¼", and drill pipe diameters ranged from 4 ½" to 6 5/8", with rotation rates ranging from 0 to 150 RPM at 30 RPM increments. In order to observe the effect of fluid rheology, 2 field-sampled muds were modeled - a low density water-based mud and a medium density oil-based mud. Cross-sectional data including velocity, effective viscosity, and turbulent kinetic energy, were analyzed from single-phase models for changes in flow patterns, and models that showed significant differences at adjacent RPM increments were selected for multiphase model runs to determine if changes had an observable effect on cuttings movement.

Data from simulation results indicate linear increases in velocity in connection to pipe rotation rates. However, marginal differences between different hole or pipe diameter sizes were recorded. Distinct differences between effective viscosity profiles were observed when comparing larger diameter wellbores with smaller wellbores, with sudden increases in bulk viscosity at high RPM in 12 ¼" hole. At high RPM (120+), large wellbores show a sudden decrease in both Reynolds and Taylor numbers, indication a sudden change in flow regime cause by high rotation rates. This trend differs from smaller wellbores in which both Reynolds and Taylor numbers continually increase with increasing pipe rotation. Data suggests that hole size plays a critical role in the impact drill pipe rotation has on cuttings transport through changes in fluid viscosity and fluid turbulence.

Having a better understanding of the effects of hole size, pipe size, fluid rheology and pipe rotation rate could play a significant role in delivering wells more efficiently, through the reduction of non-productive time from circulations. Additionally, the risk-reduction from reduced torque, drag, stuck tools would make expensive, extended reach drilling more appealing - reducing environmental impact through emissions, surface footprint, and economic cost.
Modeling and Simulation of Gas Migration Influx from Multiple Zones During Sampling in Drilling
Authors: Kang Yongfeng , Samuel Robello
Published: February 2025

During well operations, an influx of hydrocarbon may be released into the well from the reservoir. When an influx is majorly composed of gas, it migrates upward along the well. As the gas migrates, it expands and displaces the mud out of the well, leading to a decrease in well pressure. If the pressure decreases excessively, it can result in an underbalanced condition that can trigger further influx, potentially leading to a disastrous situation.

This study models the migrating velocity of gas bubbles, and their expansion in response to changes in temperature and pressure. By considering the effect of time, the location and volume of gas bubbles in the well are calculated. An iterative method allows to obtain a pressure profile along the well. The pressure history at any given depth of interest is also derived. Compared to the pore pressure, the time-to-be-underbalanced at which the well becomes underbalanced at that depth can be determined. This information can guide well sampling operations in drilling by indicating how long the operation can be safely operated and when to take action for preventing issues.

This study models and simulates gas migration during sampling operation, providing pressure and temperature histories at key depths, including the casing shoe and influx depths. It also presents the total influx volume history which could be interpolated as pit-gain at the surface. Generally, well pressure decreases as gas bubbles migrate upward, especially as they near the wellhead. Here, rapid expansion causes a swift increase in total influx volume and a corresponding drop in well pressure. This suggests that operators should intervene before bubbles approach the wellhead. The calculated time-to-be-underbalanced is a valuable indicator of whether and when the well will become underbalanced. If the well remains balanced even when all bubbles reach the wellhead, it suggests the well will not become underbalanced. The total influx volume is flat once a bubble front reaches surface and bubble end not yet reaches surface. The study also explores special scenarios where well pressure decreases firstly then "abnormally" increases.

This study provides insights into well pressure behavior during sampling with gas influx. It introduces a time-to-underbalanced indicator, informing engineers whether and when the well may become underbalanced. This knowledge empowers operators to conduct operations confidently, minimizing potential gas kicks, thereby safeguarding lives and other values.
Drilling Automation: Revisiting the Digital Drilling Program
Authors: Cayeux E. , Daireaux B. , Pelfrene G. , Mihai R.
Published: February 2025

In parallel with the increasing adoption of drilling automation at the rig site, there is a notable emphasis on the digitalization of the drilling program. These activities should not be viewed in isolation, as reinventing the drilling program may lead to significant breakthroughs in how automated processes are seamlessly integrated into drilling operations. Drilling operations are largely predictable, with parameters such as the number of sections and stands typically set in advance and rarely updated. However, significant uncertainty often exists regarding formation depths, and geomechanical limits may differ from those prognosed. Additionally, the state of the drilling system is never known with certainty and can be significantly impacted by factors such as cuttings transport or drill-string vibrations. Furthermore, unexpected drilling events occur frequently, forcing the drilling crew to adapt to unforeseen circumstances that were not defined in the original plan. Efficiently managing uncertainty requires more of a strategy than a plan, enabling adaptation to various situations while fulfilling the objectives of the drilling operation. A set of strategies can then be directly utilized by drilling automation functions during well construction. These strategies form the foundation of a new version of the digital drilling program. The implementation of the digital drilling program presented in this paper is based on a top-down analysis that refines well design choices by controlling the level of detail. These choices are guided by constraints and uncertainties established by a multidisciplinary well engineering team. To avoid a combinatorial explosion in the number of considered drilling scenarios, the algorithm balances exploration and exploitation constraints at each stage of the optimization process. A similarity metric is defined to group together connectively equivalent scenarios, which are passed to the next step of the iterative process, resulting in only a few hundred possible solutions to work with, rather than an overwhelming number. At any stage, each possible choice is evaluated from a multi-objective perspective, such as through directional, hydraulic, or mechanical simulations. However, the level of detail for this evaluation varies with the depth of investigation. This approach helps uncover, as early as possible, alternatives that are not viable, allowing them to be discarded. Using this framework, the engineering team is left with a manageable set of design choices that respect its own rules and constraints, widely and efficiently sample the parameter space, and can be filtered and sorted to retain the most robust and effective well construction solutions. Digitalization is not only about the seamless transfer of information. By envisioning a comprehensive digital workflow from well design, engineering, and planning to construction, it is possible to optimize drilling operations to an extent previously unattainable.
Early Warning System for Diesel Engine Failures in Drilling Operations using Long Short-Term Memory Network
Authors: McCarthy K. , Ziehm T. , Mitkus A. , Gee T. , Reynerson P. , Lee H. , Gupta P. , Willerth M.
Published: February 2025

Efficient maintenance of rig components is vital for uninterrupted and efficient drilling. Common practices rely on maintenance scheduled by hours of use, often leading to either unnecessary costs or critical failures due to overlooking the scope of service intensity during operations. Excessive maintenance can lead to unnecessary repairs and waste, while insufficient maintenance risks failures interrupting drilling operations with costly and time-consuming repairs.

Condition-based maintenance leverages continuous monitoring of a component's health to schedule service more efficiently but requires having an accurate model of system performance. Building these models is challenging due to system complexity and interactions among various input channels. This study proposes a workflow for a continuous health assessment of diesel engine generators that power rigs.

This study employs machine learning techniques specifically designed to capture complex, non-linear relationships within system performance data. By focusing on key indicators of component health, the model identifies patterns that inform proactive maintenance decisions.

For a given engine, a Long Short-Term Memory (LSTM) network is trained on historical healthy engine data to accurately predict exhaust temperature, a critical indicator of engine health. This training process creates a detailed model of expected engine behavior under normal conditions. Post-training, the model's predictions are compared with actual exhaust temperature measurements. Significant deviations between the predicted and observed values serve as early indicators of potential engine issues, guiding maintenance actions. To evaluate the effectiveness of this workflow for continuous engine health monitoring, it was tested on multiple sets of historical engine data, including cases of both normal operation and known failures.

After the training period, the models developed through this workflow show mean absolute errors (MAE) ranging from 7 to 15 °F when comparing predicted exhaust temperatures to measured ones. Engines that do not experience heat-related maintenance issues continue to exhibit low MAE values, whereas increasing MAE values are observed before heat-related failures. This pattern demonstrates the workflow's ability to provide early warnings before failures occur. By enabling timely interventions, this approach significantly improves maintenance efficiency, leading to reduced costs and downtime.

The application of data-driven machine learning for condition-based rig maintenance provides a step change from current common practice, with the potential for cost savings and decreased rig downtime. The strategy of using degrading model predictions as an indicator of physical system change is also a novel use of an LSTM model. These methods are not unique to engines and similar workflows could be followed for condition-based maintenance of additional rig components.