bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydro-Mechanical Behavior of a Granite-Based Geopolymer Sealant Exposed to MgCl2-Brine: Implications for CO2 Geosequestration
Authors: Hajiabadi Seyed Hasan , Khalifeh Mahmoud , van Noort Reinier
Published: February 2025

The stability of geopolymers (GPs) as alternatives to Portland cement for CO2 geosequestration is critically dependent on their performance under brine exposure typical of downhole conditions. This study investigates the hydro-mechanical behavior of a granite-based GP system subjected to brines of different MgCl2 concentrations (0-15 wt.%). The use of MgCl2 brines as opposed to the more commonly studied NaCl solutions addresses the often-overlooked impact of Mg2+ ions. Employing an imposed flow technique, GP samples were subjected to MgCl2 brines at 90°C and a confining pressure of 13.8 MPa. Subsequent analyses included mechanical property testing and microstructural evaluations. The results demonstrated a salinity-dependent reduction in GP permeability, ranging from 28% to 79% as MgCl2 concentration increased. Mechanical tests revealed that higher salinity enhanced compressive strength and Young’s modulus, while reducing Poisson’s ratio. These alterations suggest enhanced material rigidity, but also indicate a heightened risk of mechanical failure under strain. Additionally, although the ratio of compressive strength to Young’s modulus (CS/E) decreased relative to the reference sample, it remained consistent across varying MgCl2 concentrations. Microstructural analysis identified robust calcium-aluminosilicate-hydrate (C-A-S-H) gels and zeolites formed in the presence of brine, contributing to the GP’s resistance to deformation and potential cracking. Furthermore, Mg2+ ions facilitated the formation of hydrotalcite, improving the GP’s Cl- ion adsorption capacity and potentially reducing the risk of chloride-induced corrosion in steel. These findings offer new insights into the performance of granite-based GPs for CO2 geosequestration and underscore the significance of material composition and environmental conditions in optimizing the durability of sealants.
Long-Term Evaluation of the Thermal Conductivity of Class H and G Cement Under Various Additives, Temperatures, and Curing Conditions
Authors: Abid Khizar , Velásquez Andrés Felipe Baena , Teodoriu Catalin
Published: February 2025

The thermal conductivity (TC) of the cement is one of the important parameters used in different simulations and numerical models to find or predict the integrity of the well cement, especially if the old oil and gas wells have to be retrofitted for geothermal or Carbon Capture and Sequestration (CCS) projects. Hence, it is important to use the true value of cement thermal conductivity, which can only be achieved after long-term testing.

The control samples used in this study consisted of Class G and H cement, as it is the most common cement used in the petroleum industry. The additives incorporated in the neat sample consisted of 5% Gilsonite and Bentonite. The samples were cured for 486 days and were placed in two different conditions, i.e., dry and wet. Moreover, the effect of temperature on the TC value was performed on the Class G cement, with one set of samples exposed to a 75°C (60°C for 1.5 months) water bath and the other placed in ambient conditions for almost 1 year. The testing of TC was measured throughout the curing period with the help of Thermtest Portable Measurement Platform −2.

Our findings suggest that the addition of the additive to the control samples significantly influences the TC of the samples. The value of TC for dry or wet cured samples continues to evolve with the curing period and becomes consistent after certain curing periods. However, wet-cured Class G and H incorporating 5% Gilsonite kept on fluctuating till 300 days of curing and became relatively constant after that. Whereas, the TC value of neat samples became consistent after 28 days of curing. Samples that were exposed to 75°C showed lower thermal conductivity as compared to the sample exposed to the ambient condition. Moreover, an increase in the TC value was noticed when the samples were switched from 75°C to 60°C for 1.5 months and then decreased again when brought back to 75°C. This trend emphasizes the effect of temperature differential on the thermal conductivity of the cement samples. It was also noted that irrespective of the curing condition, the highest values of TC at 486 days of curing were from Class G and H. Whereas the lowest in the wet and dry cured samples were from Class H+5% GS, and Class H+5% Bentonite, respectively.

This paper presents, for the first time, the long-term thermal conductivity of a sample cured under different temperatures, additives, and curing conditions for more than 450 days. Hence, the information from this study can be crucial in determining the optimal curing period for different cement types in various conditions from which the consistent value of thermal conductivity can be obtained.
Next Level Instrumentation in PDC Bits: Measuring Temperature at Every Cutter While Drilling
Authors: Panayirci H. M. , Robinson A.
Published: February 2025

This paper presents a unique experimental study, where every cutter on a modular PDC bit is instrumented to measure the temperatures while drilling. This level of instrumentation is enabled thanks to the recent miniaturization in electronics and advancements in additive manufacturing techniques. A modular bit concept is introduced to utilize these capabilities, where instrumented blades are designed to house all the electronics and sensors necessary to instrument the cutters. Cutter temperatures are measured while drilling and the recorded data are presented. It is shown that the cutter temperatures react to the drilling parameters and therefore can be used to assess the drilling performance. Furthermore, the data acquired in the experiment presents a unique opportunity to calibrate and further improve existing numerical models.
Sealing and Durability Evaluation of Microannulus Treatment with a Resin-Based Material: Permeability and Tracer Measurements in a Full-Scale Test Section
Authors: Jimenez K. Beltran , Kragset S. , Skadsem H. J. , Lima V. N. , Stormont J. C. , Taha M. Reda
Published: February 2025

Annular cement can be compromised due to suboptimal placement or operational and environmental loads during the lifetime of the well. This can result in sustained casing pressure, and several sealing materials are offered as solutions to repair the faulty cement. This paper presents a review of current treatment solutions and a novel experimental methodology for testing the effectiveness of materials injected into a full-scale diameter test section with a debonded inner casing. A test cell was constructed consisting of two concentric sections of 9 5/8-in and 7-in casings, respectively, with conventional class G well cement in the annular space. Controlled pressure manipulation was utilized to debond the inner casing from the annulus cement sheath and form a leakage path with gap-width less than 100 micrometer. The initial condition of the annulus before treatment was determined by gas and water permeability measurements along with tracer measurements. Subsequently, treatment material was injected into the annulus and cured for two days. Finally, gas and water permeability were measured to evaluate the treatment's effectiveness. The measurements were periodically repeated while pressure cycling to assess the material's durability. The methodology shows the potential to test different chemical treatment materials and compare the outcomes. The first test conducted and presented in this paper showed the results of injecting a nano-modified polymer sealant. Findings indicated that after the first injection, a drastic reduction in leakage rate for both water and gas of 97% was achieved. Tracer measurements revealed that the arrival of tracer at the outlet of the cell was substantially delayed by the treatment, in qualitative agreement with the reduction in leakage rate. To evaluate the durability of the treatment, the cell was submitted to cyclic loading of casing pressure with periodic permeability measurements. The leakage rate did not substantially increase after 80 cycles of radial casing expansion, but radial fractures in the cement may have been induced. This work presents a new experimental methodology that allows quantitative performance evaluation of new treatment technologies in full-scale test sections following the recommendation given by the UK Guidelines for material qualification (issue 2).
Assessing the Absolute and Relative Accuracy of Magnetic Variometers Compared to Observatory Data for IFR2
Authors: Beggan C. D. , Clarke E. , Knight P. , Lawrence E. , Marr T. , Martyn T. , Turbitt C. , Wang G. , Williamson J.
Published: February 2025

The Earth's magnetic field changes constantly on short timescales (minutes to days) due to the Sun's influence on the magnetosphere and ionosphere and on longer timescales (months to decades) due to processes in the outer core. Accurately estimating the static and changing fields at a drilling location, along with associated uncertainty, can be achieved with IFR2 using real time data from an absolute magnetic observatory.

In 2022, British Geological Survey installed three new magnetic variometer sites in the UK: in western Northern Ireland (FLO), central England (LEI) and on the south coast (HTX) to monitor space weather activity across Britain. These consist of a vector fluxgate magnetometer buried in the ground on a levelled plinth attached to a digitizer/logger and modem to transmit real time data. The systems are powered by a solar panel with batteries. The sites have been running for several years and offer a long-term experiment to determine the relative and absolute quality of the data when compared to the UK INTERMAGNET-standard observatories (LER, HAD and ESK). Using the IFR2 technique, we estimated the magnetic field values expected at each variometer site and compared it to the measured data.

We show results from the three variometers, outline the issues arising and compute uncertainties for each site. We find that, in general, while the variometer systems capture the short-period magnetic field variation well (which they are designed to do), action is needed to remove erroneous data such as spikes and man-made interference. However, we also find that even with great care taken to align the systems initially, the absolute accuracy is not well constrained due to temperature, instrument drift, subsidence and/or man-made disturbances. This pushes the uncertainties well beyond the ISCWSA-recommended limits of 0.1° in Dec, 0.05° in Magnetic Dip and 50 nT in Total Field.
Geopolymer-Based Hardening Spacer Fluid to Enhance Well Integrity
Authors: Khalili P. , Khalifeh M. , Delabroy L.
Published: February 2025

This study explores a specialized spacer fluid based on geopolymerization, designed to set and develop mechanical strength while maintaining a low slurry density. This innovative spacer can act as a supplementary barrier to cement, reducing the risk of sustained casing pressure and preventing fluid leakage. This work examines the spacer's mechanical properties at elevated temperatures to evaluate its potential for enhancing well-cementing operations and improving well integrity. Key properties, including rheology, density, and thickening time, are measured at 50°C bottomhole circulating temperature (BHCT) to assess the fluid-state properties of the spacer. Furthermore, its compatibility with Class G cement is assessed, focusing on the effects on rheological and mechanical characteristics. The effect of two different dosages of Na2CO3 in the spacer design as strength booster on mentioned properties is also examined. The results show that the spacer has a low slurry density (1.3–1.5 s.g.), enabling safe placement in weak formations. Its density can be increased by incorporating barite or granite to create a greater contrast with the drilling fluid. The spacer's thickening time offers a pumpability window of at least 7 hours at 50°C BHCT, aligning with typical cementing schedules. The compatibility results indicate that the hardening spacer is rheologically compatible, as evidenced by the measured R-index. When the cement was contaminated with 10% spacer, its compressive strength showed a 29% reduction after one day at 70°C BHST. While additional testing and refinement are necessary for the spacer to function as an independent barrier material, it shows potential as a complementary component to primary barriers like cement in its current stage of development.
Shaping the Future with PDC Cutter Technology, Progress, and Next Steps
Authors: Centala P. K. , Roberts T. S.
Published: February 2025

Recent improvements in Polycrystalline Diamond Compact (PDC) cutter technology manufacturing capability have led to denser, stronger diamond structures with much greater durability. The step change has made it possible to implement complex geometry PDC cutters on a much wider scale. This paper demonstrates the development of application-specific shape PDC cutters over the past decade, which provide greater drilling efficiency in various rock formations without sacrificing durability, benefiting the drilling industry. Over a 10-year period, a range of new complex geometry cutters that are more efficient and durable were developed and designed for greater drilling performance. Detailed research focused on improved rock failure mechanics. Analytical and experimental methods were used to optimize for greater impact strength to withstand breakage under high loading conditions. Pressurized single-cutter tests simulating downhole conditions were performed, measuring both axial and shearing forces on multiple new geometries with various rock types. Finally, these were complemented with full-scale drill bit tests prior to field testing in challenging applications globally. Single-cutter laboratory test results demonstrated that optimizing the diamond table geometry can improve performance with different rock formations. In many cases, lower forces and torque were measured while drilling, indicating greater drilling efficiency. In other examples, specifically enhanced geometry provided increased robustness. Under high loading conditions, the engineered geometry absorbed higher impacts without loss of structural integrity. The evaluation of five specific cutter geometries based on their drilling efficiency and durability illustrated that each provided individual benefits in certain rock types. Some were better suited for clastic carbonate-type formations, while others provided greater durability in harder interbedded limestones and conglomerates. A review of each of the five geometries will be presented, demonstrating their advantages. Standard round PDC cutters have dominated for almost 50 years, with thousands of bit iterations providing incremental advancements for the drilling industry. This research and development clearly show the benefits of novel PDC geometries and how they provide far greater drilling performance. The intricate process outlined is beneficial to the industry.
Optimized Surveys Enhance Trajectory Planning, Operation Efficiency and Minimize Shut-Ins
Authors: Zachman N. , Ledroz A. , Lowdon R. , ElGizawy M. , Rakhmangulov Rustam , Huitron F.
Published: February 2025

The advantages of combining survey data from different tools, such as MWD and gyros, have been quantified and demonstrated in previous publications, Chia et. al., Ledroz, et. al. However, the focus has been limited to individual wells. In this paper, we extend the scope of the analysis to a multi-well offshore platform to show the value of combining surveys to field development.

When envisioning the survey program for an offshore platform, much of the time and energy goes into the top-hole sections and how to safely kick off the wells in areas of magnetic interference and close proximity to multiple wells and casings. Once the kickoffs have been addressed, the survey and drilling plans for the deeper sections typically only involve an MWD tool and, depending on the cost and complexity, advanced survey corrections. The combination of surveys reduces the positional uncertainty by up to 30%, which allows more flexibility in the planned trajectories, larger allowable deviation from plan (ADP), and overall risk reduction.

A platform designed, with a nominal separation of 8 feet, was used for the analysis. The minimum kickoff depth was established at 1000 feet, with deeper kickoffs for wells drilled later in sequence. The results show that the reduction in wellbore positioning uncertainty allows for planning wells with lower torque and drag values and larger safety factors related to collision avoidance. The ability to combine surveys in real-time while drilling provides immediately actionable information to reduce deviation from plan and enhance risk management by ensuring the survey program is achievable. Additionally, due to the reduced risks, the number of shut-ins is minimized. Finally, if further wells are considered for the installation, including conductor sharing or open hole sidetracks, the new trajectories can be safely planned due to the increased space given by reduced positional uncertainty.

The use of combined surveys for uncertainty reduction has been limited to extended reach wells and specific challenging scenarios. The comprehensive use in every well of a platform is examined here, with all the implications for risk reduction and field development optimization.
Mechanical Specific Energy: Derivation, Understanding and Relationship to Formation Strength
Authors: Macpherson John D.
Published: February 2025

The Mechanical Specific Energy (MSE) model is used widely in the drilling industry. However, its use has been questioned in a two-part series in the SPE-IADC Drilling Conference, "Mechanical Specific Energy (MSE): Claims and Implications – Facts, Fallacies, and Pitfalls" (Samuel and Mensa-Wilmot, 2023 SPE 212508, 2024 SPE 217727). This paper will independently develop the theory of the MSE, leading to an improved understanding and an appraisal of the conclusions in the two papers.

This paper develops the theory underlying the MSE from fundamentals and explains its applications and constraints. The theoretical development uses the concept of instantaneous mechanical power, which it transitions to drilling energy and then to drilling energy per a specific volume of rock, the MSE. The development pays particular attention to physical units. Of special interest is the relationship of the MSE to rock parameters, and its use in defining mechanical efficiency, and limits, of the drill bit. The paper further examines the validity of the Samuel and Mensa-Wilmot claims.

The MSE is a valid method for describing the amount of energy delivered by the drilling system to the drill bit to destroy rock. It is calculated as specific to a certain volume of rock, which in physics relates to the strain energy density (SED) of the formation. That is, the concentration of mechanical energy required to catastrophically fail (destroy) a volume of rock.

Comparison between the MSE and the SED of the formation describes the mechanical efficiency of the drill bit in converting input mechanical energy to output energy. Hydraulic energy applied at the drilling workface can both improve (e.g., clean, kerf) or impede (e.g., increase pressure overbalance) energy transfer at the workface. It is, therefore, considered separately.

Current oilfield measurement capabilities, and theoretical misunderstandings, introduce simplifications and errors in the MSE. It is important to understand this when using the MSE. Several of Samuel's and Mensa-Wilmot's deprecating claims about the MSE are questionable. The paper examines these claims and describes why they are incorrect. However, they do advocate a holistic approach to drilling process management—essentially an operational approach—which has merit. Understanding of the MSE is important in that approach.

This paper details the theoretical development of the MSE from a concept of instantaneous drilling power. This places the MSE on a firm theoretical basis and leads to an understanding of its limitations, and valid application. The relationship of the MSE to the energy density of the formation shows that the MSE should not be compared to the compressive strength of the formation, which leads to an improved understanding of drill bit mechanical efficiency.
Model of Rotary Drilling Dynamics for Rig Automation
Authors: Whitlow Z. W. , Paikoff B. , Auld S. , Kern S.
Published: February 2025

Drilling automation is critical for improving efficiency and consistency in drilling operations. Using a combination of models and data helps build an understanding of system dynamics and uncertainties used to develop effective automation systems. Autodrillers serve a critical role in drilling automation by regulating surface weight on bit (SWOB), top drive torque, or standpipe pressure. The model of rotary drilling dynamics presented here provides a simple tool that describes the dynamic relationships between surface inputs block velocity, top drive velocity, and flow rate; and outputs such as weight on bit (WOB), torque, and differential pressure.

Model development is based on simple mechanical relationships coupled with a simplified hydraulics model. Dominant rotary dynamics relevant to autodriller control are captured while neglecting complex high frequency dynamics which are beyond the autodriller control bandwidth. The simplicity and frequency range covered makes the model appropriate for autodriller control design and analysis.

Model parameters were estimated and the model was compared to data for several wells to demonstrate fidelity. Linearization and frequency domain analysis shows the difference in dynamics from block velocity input to WOB and pressure outputs and demonstrates the challenges of pressure regulation compared to SWOB regulation. The model shows that dynamics from block velocity input to WOB output behaves as dominant first-order. However, dynamics from block velocity input to differential pressure output is dominant second-order with a significant phase lag between WOB output and differential pressure output. This explains the delay in pressure signal relative to SWOB commonly observed while drilling and shows that the delay is frequency dependent. Sensitivity analysis shows a wide range in dynamics with respect to drillability and motor volume.
Comparison of Supervised and Unsupervised Machine Learning for Well-Log Depth Alignment
Authors: Acharya S. , Fabian K. , Westeng K.
Published: February 2025

Well logs, crucial for drilling and post-drilling analysis, provide continuous measurements of subsurface formations as a function of depth. Logging while drilling (LWD) and electrical wireline logs (EWL) are commonly used techniques for well-log acquisition. Both methods are prone to depth measurement errors due to various factors, which need to be aligned to a common depth-scale for subsequent analysis. This study compares two automated machine learning approaches for aligning repeated measurements of the same parameters from LWD and EWL logs of the same well. The first approach is based on supervised learning and the second on unsupervised learning. The supervised approach trains a 1D convolutional neural network (1D CNN) classification model on actual well-log data from the Norwegian North Sea, using LWD-EWL pairs of log slices. A specific depth discrepancy is introduced for each pair, and the logs are divided into various classes based on the depth error between them. The unsupervised method combines autoencoders and K-means clustering to identify potential lithological boundaries in EWL and LWD multiparameter log data. These predicted boundaries are validated by requesting a maximal Pearson correlation. The performance of the classification model is evaluated using metrics such as accuracy, precision, and recall. The optimal number of clusters for K-means clustering is identified using silhouette scores and the elbow method. Depth alignment is verified through visual inspection, correlation analysis, and Euclidean distances between logs. Supervised and unsupervised approaches significantly improve the alignment of various logs, such as bulk density, deep resistivity, sonic compressional, and neutron porosity. Both methods outperform maximization of cross-correlation for specific logs, such as deep resistivity and neutron porosity. These results highlight the potential of machine learning for efficient and accurate depth alignment of well logs, with promising implications for enhancing drilling and post-drilling analysis in the oil and gas industry.
Kvitebjørn Evolution: Driving Excellence in HPHT Project Management
Authors: Beeh Hany , Paulus Steven L. , Færo Erlend , Caycedo Alberto , Moldekleiv Rune , Mohanova Yelena , Egar Caroline E. , Zahoor Syed , Svenningsen Sondre , Naley Helge M. , Azher Mohammed , Reese Lasse
Published: February 2025

Kvitebjørn is a gas and condensate field in the Norwegian sector of the North Sea which was discovered in 1994. Kvitebjørn produces from Middle Jurassic sandstone in the Brent Group with secondary reservoirs on the Lower Jurassic Cook formation and Upper Triassic Statfjord group. The reservoirs lie at a depth of 4000 mTVD-RKB (meter True Vertical Depth – Rotary Kelly Bushing) with initial HPHT (High Pressure High Temperature) conditions. The field started production in 2004 and have experienced several drilling campaigns to access different areas of the field and maintain production.

In the recent campaign, the targets were further away from the platform. This resulted in well design and construction that is outside the originally established drilling scope at the time of designing the drilling module on the platform. Moreover, the improvement of subsurface understanding resulted in uncertainties regarding overburden flow units and barrier requirements for well integrity aspects. These pose challenges in the project which resulted in cost overruns and high Non-Productive Time (NPT) at the start of the campaign.

The Kvitebjørn One Team implemented structured improvement plans to overcome the various challenges in the current drilling campaign. The improvement plans covered one run strategy in all sections, using drill-bit and cutters technology for specific section challenges, thorough fluids strategy during execution, use of stage cementing equipment to replace long cement job, use of spacer with particles to mitigate risk of gas entering wellbore during wait-on-cement, enhancing the BHA (bottom hole assembly) with fit-for-purpose FPWD (Formation Pressure While Drilling) logging tool, continuous evaluation of wellbore strengthening materials to manage depletion, and several others. This publication covers the main improvements and the One Team organizational perspectives.

The Kvitebjørn project were able to turn around the NPT trend and deliver the longest well (A-16 B) successfully. Resulting in +/- 36 days ahead of budget (20% budget time reduction) and significant NPT reduction (from 46% to 16%) while managing an increasingly more complex well design and operations. The improved performance significantly increased well delivery efficiency by 50-80% compared to project's historical average and it was achieved with zero HSE (Health, Safety and Environment) and well control incidents.

The paper serves as an experience sharing of a successful organizational learning process and well construction deliveries in a mature HPHT field with complex challenges. The recent success provided opportunities in the field to access previously unfeasible targets. The key improvements that are presented with context of the background challenges could serve as a suggestion towards the industry for implementation in other projects.
Analysis of the Efficiency of a Vibration Mitigation Tool Using Modeling and Downhole Measurements
Authors: Nguyen K. L. , Mahjoub M. , Dao N. H. , Menand S. , Bonstaff W. , Servaes L.
Published: February 2025

When drilling complex wells, excessive vibrations can lead to damages of the bottom-hole assembly (BHA) and increase non-productive time. Employing a vibration reduction downhole tool to the BHA can help overcome this issue. We focus in this paper on a particular vibration reduction tool (VRT) composed of multiple parts designed to absorb and dissipate lateral shocks and vibrations. The upper and lower bodies of this tool are interconnected in such a way which allows relative deflection. The connection between these two parts is protected by a bladed sleeve for stabilization and is equipped with anti-vibration rings for damping.

The behavior of the vibration reduction tool is simplified for modeling purposes by a reduced stiffness combined with a distributed damping coefficient. This model is implemented for numerical simulation using the finite element method (FEM) both in frequency and time domains. The modeling results are validated against downhole data where the tool was equipped with two sensors in its upper and lower bodies. Lateral and axial accelerations as well as bending velocities acquired at a high frequency rate are used for the comparisons.

The numerical simulation predictions show an agreement with the downhole data. Based on that, new simulations are conducted where the VRT is replaced by a standard stabilizer with the same dimensions and where all the other parameters are kept the same. The comparison with the baseline simulations shows the level of vibration reduction gained by the VRT and allows us to better understand its vibration mitigation mechanisms. Moreover, a parametric study is conducted by varying the position of the VRT's within the BHA to investigate the optimal placement and operating conditions of the tool for a given BHA without completely changing its directional tendencies.

The novelty of this work lies in demonstrating a reliable model of a vibration reduction tool to predict its effectiveness in mitigating BHA vibrations, which could subsequently be employed to optimize the VRT position along the BHA and determine optimal drilling parameters.
Controlled Mud Level (CML) Modeling: Dual MPD with Combined CML and Surface Backpressure (SBP)
Authors: Callerio S. , Yoon D. , Ashok P. , van Oort E. , Hariharan P. , Tuckwell N. , Van Noort R.
Published: February 2025

Controlled Mud Level (CML) offers enabling managed pressure drilling (MPD) technology for drilling deepwater wells with narrow pressure windows. CML technology is now being extended with the addition of Surface Back Pressure (SBP) technology, creating a "dual MPD" technology. However, modeling CML operations in combination with SBP functionality and control has been difficult due to the lack of robust hydraulic models. This study presents a CML multi-phase drift-flux model with added SBP functionality, incorporating such features as the subsea pump module (SPM) operation, mud return line (MRL), SBP choke, and an active control device (ACD) placed in the marine riser.

The developed hydraulic model significantly extends an existing model for SBP Managed Pressure Drilling (MPD) operations to include CML operations. In this model, the riser is subdivided into a lower riser section below the ACD, an upper riser section located above the ACD, and the section associated with the mud return line (MRL). The SPM, which features automatic speed control, acts as a sink upon the lower riser, adjusting the riser level to regulate the target bottom hole pressure PBHP. The built-in ACD can be used to restrict flow between riser sections and can be used to regulate pressure from the lower riser section for SBP application and influx management. A surface choke connected to the MRL outlet allows the system to adjust PBHP by adding SBP. Future work will extend the model to kick management.

The use of SPM and MRL sub models in the hydraulic model have resulted in accurate replication of CML and CML+SBP drilling operations under both dynamic and static conditions. Simulations furthermore show that switching to CML with SBP application during static periods optimizes connection procedures, thus reducing connection time and enhancing overall operational efficiency. These results showcase the model's potential to significantly enhance the planning and execution of deepwater dual MPD operations, expanding opportunities for drilling deeper, lower-margin wells.

This work represents the first integrated multi-phase hydraulic model that seamlessly integrates CML and CML+SBP modes, with the capability to transition seamlessly between them. Furthermore, it is the first to fully integrate and reflect the performance of a CML+SBP MPD system, with the integration of the SPM, the MRL, the surface choke, and an ACD.
Dynamic Pressure Management for Well Integrity in Subsea Wells: Defining Safe Operating Limits Through the Annulus Operating Envelope
Authors: Kalil I. A. , Fischer R. , Foote C. , Trevisan R. , Howard J. A.
Published: February 2025

Ensuring well integrity in subsea wells is vital to preventing the escape of wellbore fluids into the environment, necessitating the presence of two effective pressure barriers. The evaluation of key components, including the production tubing string, production casing, and downhole production packer, is critical to avoiding issues such as casing burst, tubing collapse, and ensuring the reliable operation of the downhole packer.

This methodology defines the maximum and minimum allowable pressures for both the tubing annulus ("A" annulus) and tubing head, considering the highest pressures expected during the well’s life cycle—such as those encountered during production, shut-in of hydrocarbons, fluid injection, or kill operations—and the lowest pressures, such as zero pressure or a depleted production state. The approach accounts for the dynamic nature of the well’s life cycle, with early life characterized by higher pressures and late life marked by high water cut and potentially higher temperatures. The maximum allowable wellhead operating pressure (MAWOP), as defined by the American Petroleum Institute (API) in API RP 90-1, is referenced to ensure safe operation, while the minimum "A" annulus pressure is determined to prevent failures in the well barrier elements. These pressure limits, combined and compared against the operating limits of the production packer, potentially restrict the "A" annulus pressure below the calculated MAWOP in specific scenarios. The resulting annulus operating envelope (AOE) is graphically represented with tubing head pressure on the x-axis and "A" annulus pressure on the y-axis, providing a clear visualization of the safe operating window. The final envelope, typically rectangular, may become trapezoidal in cases where the packer’s operating constraints alter the shape of the AOE.

This dynamic approach, which adapts to the well’s life cycle and varying pressure conditions, serves as a practical tool for operations teams to visualize and manage safe operating limits in subsea wells.
Robust Mitigation of Axial-Torsional Drilling Vibrations Through Distributed Downhole WOB-RPM Control
Authors: Zhang Yifan , Ashok Pradeepkumar , Chen Dongmei , Oort Eric van
Published: February 2025

Coupled tri-axial drillstring vibrations are widely recognized as major causes of compromised drilling efficiency and safety. Excessive and self-sustaining drillstring oscillations, occurring at different frequencies, can result in premature drilling system failures, bit wear/damage, compromised hole quality, reduced rate-of-penetration (ROP), and non-productive time (NPT). In this study, a novel distributed in-bottom-hole-assembly (in-BHA) drilling vibration control system is proposed to robustly and efficiently suppress coupled drilling vibrations once they are detected. Multi-input-multi-output (MIMO) in-BHA controllers with local state-/output-feedback were designed following robust and optimal control theories. Lower drillstring dynamics and downhole drilling parameters are utilized to simultaneously control the at-bit weight-on-bit (WOB) and rotation speed (RPM). Ideally, the proposed control system requires no communication with surface once deployed, which significantly accelerates system control response action and expands the control bandwidth. Comprehensive simulations are performed to illustrate that the proposed controllers outperform existing drilling vibration mitigation technologies in terms of robustness, stabilization time, energy consumption, and actuation requirements.
The Benefits of Real-Time Drilling Dynamics Measurements from a Mud Motor Designed for U.S. Shale Drilling
Authors: Jones Steve , Sugiura Junichi , Ference Zachary
Published: February 2025

Embedded high-frequency drilling dynamics data recorders have become commonplace in U.S. shale drilling applications. The benefits of these data recorders are that they are small enough to place at the drill bit and mud motor top sub. These recorded measurements provide drilling dynamics information that cannot be seen from measurement-while-drilling (MWD) shock and vibration measurements; hence they provide post-run information that can be used throughout the pad to optimize the drilling process.

A new mud motor has been developed that can transmit real-time drilling dynamics data. The real-time mud motor data is just like embedded drilling dynamics data placed in the mud motor. The advantage is that the drilling dynamics data from the motor can be used in real-time to optimize drilling parameters and rig operations. This allows for fine-turning of parameters on-the-fly to optimize drill bit life and power-section performance/life.

Transplanting drilling dynamics measurements into the rotor catch of the drilling motor, along with a short-hop transmitter to be received at the MWD, enabled measurements to flow in real-time to surface. The measurement placements were critical to provide similar drilling dynamics readings as would be seen from the drill bit.

The advantage of placing the measurements in the rotor catch is that the devices do not interfere with the general construction and strength of the drilling motor. Field tests have successfully proven that the real-time mud motor measurements deliver results very similar to what can be seen from embedded dynamics data recorders post-run. Using the real-time data allows for monitoring of dynamics results as soon as changes are made, providing instant feedback to the operator while drilling.

This paper will compare the mud motor rotor catch measurements and MWD short-hop receiver measurements with the embedded high-frequency data recorder measurements at the bit and motor top sub. The data will clearly demonstrate how the measurements compare to each other, and how the real-time measurements can be used to optimize drilling parameters for longer and more repeatable runs.

Conclusions will be drawn to show the operational advantages of real-time mud motor dynamics versus standard MWD shock and vibration measurements.
Implementation of EVXT at Equinor’s Fram SØR Project
Authors: Wernø T. G , Pettersen B. , Sandstad H. , Arnøy S. A.
Published: February 2025

The Fram Sør subsea development project will be the first Equinor project to utilize electrically controlled subsea X-mas trees (eVXT), marking a milestone in the subsea industry. The development will consist of up to 4 templates and 12 eVXT’s, marking a significant milestone in the subsea industry. The use of electrically controlled subsea X-mas trees is claimed to improve efficiency and safety in subsea operations. This paper will highlight the all-electric technology and its potential to shape the future of subsea developments.

Further, this paper will present Equinor's overall approach for the development and implementation of the eVXT technology through participation in a JIP with a structured approach to design, testing, and qualification of the eVXT system. The decision to implement eVXT as part of the Fram Sør development is an important part of Equinor’s phased approach to new technology as it includes installation, commissioning, and operation of the eVXT system. The importance of collaboration with suppliers and industry partners to ensure that the eVXT system is optimized and meets the industry standards will be highlighted.

This paper focuses on Equinor's decision to start implementation of the eVXT technology, which is a vital part of the All-Electric Subsea (AES) system goal for subsea development. Here are some key points from the paper: AES systems provide improved reliability, reduced maintenance costs, and increased operational flexibility.The eVXT technology is presented as part of Equinor's overall approach to subsea development, involving a systematic process of design, testing, and implementation, as well as collaboration with suppliers and industry partners.Observations from the development and qualification of eVXT technology shows improved valve control, functional visibility, and enhanced condition monitoring,The contribution to the ongoing digitalization initiatives as well as paving the way for remote control of unmanned intervention operations.Continued development and collaboration is expected to further optimize AES systems and ensure their long-term success.Present the development and implementation of eVXT technology as part of an overall environmental initiative within operators to reduce the environmental footprint in offshore operations.

In summary, the paper aims to highlight the innovative nature of the technology that will be implemented on the Fram Sør project and its potential to shape the future of subsea development. Details on Equinor's overall approach to the development and implementation of eVXT technology is presented, including participation in a JIP with a structured approach to design, testing, and qualification. Benefits of AES systems, and the importance of collaboration with suppliers and industry partners will be discussed. Observations from the testing of the eVXT technology is presented, including improved valve control and enhanced condition monitoring.
Revolutionizing Drilling Efficiency: A Case Study of Integrated Closed-Loop Automation Across Multiple Basins
Authors: Singh K. , Welch T. , Ait Larbi K. , Ibrahima F. , Braga D. , Yalamarty S. S. , Cheatham C. , Fox W. , Pereda E.
Published: February 2025

This paper provides an update on the implementation and results of a closed-loop drilling automation system (SPE-217693-MS) after drilling 100 wells in the Bakken, Delaware, and Eagle Ford basins. This technology, developed through an integrated collaboration between a rig contractor and a Software as a Service (SaaS) provider, primarily aims to minimize the cost per foot drilled by utilizing Machine Learning (ML) models to optimize autodriller setpoints remotely.

The ML based ROP optimizer processes real-time WITSML data and static inputs, such as Bottom Hole Assembly (BHA), mud data, and survey information, to generate setpoints for Differential Pressure (DPRESS), Weight on Bit (WOB), Rate of Penetration (ROP), and Rotations Per Minute (RPM). These setpoints are then transmitted to the rig contractor’s cloud and subsequently forwarded to the hardware autodriller on the rig, enabling automated rotary drilling with minimal human intervention. The technology has been utilized on over 100 wells in multiple basins in different formations in collaboration with several major Oil and Gas operators.

Achieving optimal Rate of Penetration (ROP) improvements in the 1-22% range in the lateral and 0-58% improvement in the intermediate compared to non-ML drilled offsets was observed when the utilization of the ML ROP Optimizer in closed-loop mode reached or exceeded 70%. Higher ROP was consistently correlated with fewer manual limit changes by both onsite and remote operators. Additionally, successful implementation of this technology was strongly associated with comprehensive rig onboarding, clear communication between the rig crew, onsite and remote support teams from both rig contractor and SaaS companies. Continuous fine-tuning of the ML algorithms was necessary, particularly with specific logic adjustments to ramp setpoints such as Weight on Bit (WOB), Rotations Per Minute (RPM), and ROP. These adjustments were critical in accommodating the diverse control system configurations of different rigs, ultimately leading to more stable and efficient drilling operations.

This abstract presents a case study of successfully scaling integrated closed-loop technology across 100+ wells, involving a collaboration between a rig contractor and a SaaS provider. The paper highlights key observations and success factors for the widespread adoption of automated drilling technology across various basins and major operators
New Filling Sub/Coring System Solution and Core Cryopreservation Technique Applied to _reserve Microbial Populations for Hydrogen Gas Storage Field Conversion Feasibility
Authors: Delmar Ludovic , Febo Giuseppe Di , Pozzovivo Vincenzo , Mantegazzi Andrea , Zanchi Augusto , Stogit Marco Severgnini , Menin Barbara , Bassani Ilaria
Published: February 2025

The application and integration of new technology and recent developments using a coring system are discussed, presenting the successful methodology used during various well phases with the aim to preserve the microbial population for hydrogen gas storage field conversion feasibility. This includes the coring phase, onsite measurement, preservation, and full evaluation of core samples. A field case is presented discussing methods for obtaining accurate microbiological, geomechanical, petrophysical, mineralogical, and granulometric characterization of cap rock and the reservoir.

A project team was created to optimize coring system and freezing preservation coring methods, and to help minimize uncertainties with respect to these new operations. The coring system was initially designed to be used in an 8.5-in. section. The project team developed a new system specific to the 6-in. hole phase. This new size was used for the first time globally during this project.

The effectiveness of this technique for preserving core samples from drilling mud infiltration was confirmed by the results of microbiological analyses alongside the success of the core freezing preservation (cryopreservation) procedures applied to preserve the microbial populations from external agents and oxygen exposure.

Molecular analyses performed on the core samples preserved using the coring system technology allowed characterization of the native microbial population of the reservoirs, with a clear distinction from the microbial profile characterizing the controls collected during coring operations (i.e., coring system fluid and drilling mud from various steps during the coring operation), confirming the effectiveness of the coring system technology at preventing mud infiltration. Realistic petrophysical parameters and a microbial profile characterization of the reservoir were obtained from noninvaded, native-state core samples.

The experience and results obtained during coring operations on four wells (nine core runs) in Italy are examined. This experience concerns coring processes and the quality of geological and microbiological evaluation obtained.