bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diagnostic tests: Purposes and two case studies
Authors: Rylands Leanne , Shearman Don 
Published: March 2023

It is not uncommon to use what are called diagnostic, placement, readiness or competency tests once students arrive at university to gauge their basic skills in mathematics or literacy. This paper begins by discussing diagnostic mathematics tests and identifying the key reasons for which these are run. Two such tests with repercussions for students are discussed. These two tests are for different student cohorts and are run for different reasons. We identify the purposes for which the tests were developed, and actions which eventuated. We identify any additional purposes the tests served beyond those intended. The tests had a positive impact on student learning. It is not uncommon to use what are called diagnostic, placement, readiness or competency tests once students arrive at university to gauge their basic skills in mathematics or literacy. This paper begins by discussing diagnostic mathematics tests and identifying the key reasons for which these are run. Two such tests with repercussions for students are discussed. These two tests are for different student cohorts and are run for different reasons. We identify the purposes for which the tests were developed, and actions which eventuated. We identify any additional purposes the tests served beyond those intended. The tests had a positive impact on student learning.It is not uncommon to use what are called diagnostic, placement, readiness or competency tests once students arrive at university to gauge their basic skills in mathematics or literacy. This paper begins by discussing diagnostic mathematics tests and identifying the key reasons for which these are run. Two such tests with repercussions for students are discussed. These two tests are for different student cohorts and are run for different reasons. We identify the purposes for which the tests were developed, and actions which eventuated. We identify any additional purposes the tests served beyond those intended. The tests had a positive impact on student learning.It is not uncommon to use what are called diagnostic, placement, readiness or competency tests once students arrive at university to gauge their basic skills in mathematics or literacy. This paper begins by discussing diagnostic mathematics tests and identifying the key reasons for which these are run. Two such tests with repercussions for students are discussed. These two tests are for different student cohorts and are run for different reasons. We identify the purposes for which the tests were developed, and actions which eventuated. We identify any additional purposes the tests served beyond those intended. The tests had a positive impact on student learning.
Real-Time Digital Log Generation from Drilling Parameters of Offset Wells Using Physics Informed Machine Learning
Authors: Sheth Prasham , Sistla Sai Shravani , Roychoudhury Indranil , Gao Mengdi , Chatar Crispin , Celaya Jose , Mishra Priya 
Published: March 2023

Abstract
By 2026, USD 5.05 billion will be spent per year on logging while drilling (LWD) according to the market report from Fortune Business Insights (2020). Logging tools and wireline tools are costly services for operators to pay for, and the companies providing the services also have a high cost of service delivery. They are, however, an essential service for drilling wells efficiently. The ability to computationally generate logs in real time using known relationships between the rock formations and drilling parameters provides an alternative method to generate formation evaluation information. This paper describes an approach to creating a digital formation evaluation log generator using a novel physics-informed machine learning (PIML) approach that combines physics-based approaches with machine learning (ML) algorithms.
The designed PIML approach learns the relationships between drilling parameters and the gamma ray (GR) logs using the data from the offset wells. The decomposition of the model into multiple stages enables the model to learn the relationship between drilling parameters data and formation evaluation data. It makes it easier for the model to generate GR measurements consistent with the rock formations of the subject well being drilled. Since the computationally generated GR by the model is not just dependent on the relationships between drilling parameters and GR logs, this model is also generalizable and capable of being deployed into the application with only retraining on the offset wells and no change in the model structure or complexity. For this paper, the drilling of the horizontal section will not be discussed as this was done as a separate body of work.
Historically collected data from the US Land Permian Basin wells is the primary dataset for this work. Results from the experiments based on the data collected from five different wells have been presented. Leave-one-out validation for each of the wells was performed. In the leave-one-out validation process, four of the wells represent the set of offset wells and the remaining one becomes the subject well. The same process is repeated for each of the wells as they are in turn defined as a subject well. Results show that the framework can infer and generate logs such as GR logs in real time.
Rock Mechanics Analysis of Observed Borehole Instabilities in an Ekofisk Field Extended-Reach Well
Authors: Diaz Lopez Jairo Alexander , Omdal Edvard , Rutherford James S. , Skadsem Hans Joakim 
Published: March 2023

Abstract
The drilling of extended-reach wells is an increasingly common practice for improving the recovery from mature fields, and for producing distant oil and gas resources using existing infrastructure. From a geomechanical point of view, the drilling and completion of extended-reach wells may become technically very challenging, as these wells often have long sections drilled at high inclinations that can be prone to borehole instability problems such as pack-offs or collapse of the wellbore wall.
The case of an extended-reach well drilled in the Ekofisk field in the North Sea where borehole stability issues were observed and eventually resulted in the loss of the well is presented. A wellbore stability assessment is performed with well-specific stress and formation strength data that explores the possible failures that may have resulted in the loss of the well. In particular, a plane of weakness model is used to model possible shear failure along the bedding of the overburden shale formations. The uncertainty in the rock matrix strength is accounted for, as well as the cohesion, friction factor and orientation of the bedding plane, on the mud window using a Monte Carlo approach. This paper focuses in particular on how the properties of the bedding plane affect the minimum required mud weight, and compare to the actual mud weight used in operation.
The generated mud window acknowledging failure along the weakness planes suggests that this type of failure was a relevant failure mechanism over the 13 1/2-in section of the well, as the mud weight employed was not high enough to avoid it. Accounting for uncertainty and the failure along the weakness planes in extended-reach wells to be drilled in the Ekofisk area may generate safer mud windows that in turn may reduce the occurrence of wellbore instability in the field.
Introducing Automated Advisory and Control Applications to a North Sea Jack-Up, Technology, Human-Centric Challenges and Resulting Performance Improvements at Scale
Authors: Forshaw Matthew , Hovda Sigve , Macpherson John 
Published: March 2023

Abstract
As we begin a new decade, drilling systems automation has left its primary residence of PowerPoint slides and is now seeing wider adoption. In areas, the industry sees positive return-on-investment for automation technology development; both financially, from reduction in well construction cost, and in helping meet increasingly prominent ESG targets through emissions reduction.
This paper describes a long-term case study covering the introduction of multiple automated monitoring, advisory and control systems into an already highly optimized jack-up in the North Sea. These resulted in adding incremental value, delivering a multitude of operations significantly below AFE, as well creating a trend of increasing performance spanning a full field development campaign.
In addition to quantifying resulting operational cost-out, the paper addresses several points related to challenges of adoption: –Necessity for un-biased operational needs to drive technology development. The industry is often drawn to high-end solutions to complex problems when in fact there are low-hanging fruits, such as simple business-process-automation for reporting, which are highly desired by end-users.–The notion that while there is a lot of rigor in technology development processes, there is not enough focus on the critical human element of adoption. Linked to this is the common misconception that automated systems require less training, when in-fact the opposite is true.–End-user resistance on initial introduction of a black-box system for automated directional drilling. Retroactive software development moves to more grey- or white-box systems, with an associated positive response in user acceptance.–Critically of interoperability between operator, OFS and OEM systems. How this will become more important as both closed-loop control systems, and linkages to enterprise level systems, proliferate.
This long-term case study definitively demonstrates that automated systems add value. However, due to the human-component, management-of-change must be carefully considered as we scale adoption.
Continuous or Stacked Cement Bond Logs – Does It Matter?
Authors: Lohne Hans Petter , Arild Øystein 
Published: March 2023

Abstract
As part of the permanent plug & abandonment of a well, the annulus casing cement sheath may be considered a barrier element provided that its integrity can be verified. Operators use a combination of data to evaluate the integrity of the casing cement sheath; cement job parameters and displacement calculations, results from FITs and LOTs, bonding logs and sustained casing pressure being the most common ones. The cement length is a key quantity for qualifying annulus cement as a well barrier element. If using the standard NORSOK D-010 rev 5 as the decision basis and provided a correct positioning, a length of 30 m MD is required when using bonding logs as the means of verification. Since the annulus cement sheath usually is considerably longer that 30 m, 30 meters of good cement can be achieved either by presenting a bond log showing 30 m of continuous good cement or by presenting a bond log that in total has 30 m of good cement.
Operators have different requirements and views when it comes to stacked versus continuous. To better understand the implications in terms of sealing ability of a continuous annulus cements sheath versus a stacked annulus cement sheath we have conducted studies of both quantitative and qualitative nature. For a quantitative comparison we have used Darcy’s law and capillary pressure, for a qualitative comparison we have looked at cracks, shear failure and the effect of zones with a poor bond log.
Full-Scale Solids Control Testing of a Light Density Hollow Glass Beads Drilling Fluid
Authors: Kostov Nikolay , Penny Glenn , White James , Shoykhet Nissan , Zeilinger Sabine , Gupta V. Paul 
Published: March 2023

Abstract
Light density drilling fluids with hollow glass beads (HGB) are growing in applications for drilling depleted formations with minimal losses and increasing rate of penetration. However, there is a lack of studies on how best to utilize typical solids control equipment, as current practices and procedures based on barite weighted muds are inefficient. We report a systematic full-scale test program to study and optimize solids control efficiency with shale shaker, hydrocyclone and centrifuge with such fluids.
A non-aqueous-based hollow glass bead drilling fluid was formulated in the lab and a large batch (&gt;40bbl) was prepared and tested using field scale solids control equipment. The inlet and effluent streams were monitored for density, particle size distribution, retort, rheology, and rheological properties and evaluated to determine the optimal equipment conditions to maximize solids control efficiency while minimizing loss of beads in the discharge stream. Variables included shaker screen sizes, flow rates and deck angles, hydrocyclone flowrates and operating pressures, centrifuge flowrates, differential speeds and other parameters. The amount of glass beads in the fluid was also varied.
The drilling fluid was contaminated with a variety of sized solids which mimic drill solids. Based on the data gathered, effective procedures were developed for monitoring hollow glass beads and drill solids in each stream. Through the systematic test program, conditions could be identified to achieve high solids control efficiency from the shale shaker, the hydrocyclone, and the centrifuge. This was achieved at hollow glass beads concentrations of around 11% and 22% by volume. While some previous field experiences had indicated severe challenges with centrifuge usage with these fluids, effective centrifuge operation could be demonstrated once the proper settings were identified. Overall, the testing results showed that most of the drill solids can be removed using conventional solids control equipment and fluid properties (e.g. rheology, fluid loss, etc.) can be maintained at desired levels without the loss of any significant amount of beads with the discharged solids.
Since the beads are lighter than base oil, their behavior in the solids control equipment is quite different from conventional solids. As such, equipment procedures and conventional settings had to be updated or changed. It was demonstrated that high solids control efficiency can be achieved even at high bead concentrations. This work addresses a barrier in the field application of these fluids and points towards practices that allow optimizing the application by minimizing drilling fluid dilution.
2nd Mode Shape Torsional Vibration - Observation, Identification, Mitigation
Authors: Keshiyev Sahet , Naterstad Tarje , Murray Ross 
Published: March 2023

Abstract
This paper investigates the drill pipe twist-offs that occurred while drilling an S-shaped well in the 12 ¼" section. The presence of the 2nd mode shape of torsional vibration was observed and linked to the failure. Conditions that lead to a 2nd mode shape being triggered and sustained are discussed in addition to recommendations to prevent fatigue failures.
2nd mode shape torsional vibration is a standing wave with two nodes created along the drill string, with the first one being the top drive and 2nd located along the drill string. The drill pipe experiences the highest torque fluctuations in the rotational nodes during torsional vibration.
A high-resolution drilling dynamics recorder was utilized to record a spectrum of torsional vibration frequencies, confirming the presence of the 2nd mode shape of torsional vibration. The multiple degrees of freedom spring-mass model was used to identify the node location, which was later compared to the locations of the actual twist-offs.
The presence of the 2nd mode torsional vibration, its transition from the fundamental mode to the 2nd mode, and the conditions for the transition to happen were observed.
Recommendations were developed on how to recognize the 2nd mode shape with the surface instrumentation, on the drill string design, and preventive inspection.
Knowing the location of the node gives a possibility of selective inspection of the drill pipes once the 2nd mode shape was observed while drilling, minimizing the risk of fatigue failures. Also, the drill string design could be revised by increasing drill pipe strength within the nodes.
The twist-off locations were found to match the calculated location of the node caused by the 2nd mode shape with a high degree of accuracy.
Low Friction Drilling Fluid Additive Technology
Authors: Akaighe Nelson , Zeilinger Sabine , Cutler Joshua , Bhandari Dhaval , Bunquin Jeffrey , Bharadwaj Nidheesh 
Published: March 2023

Abstract
The use of lubricants is commonplace when drilling with water-based drilling fluids. They are less frequently applied when drilling with non-aqueous fluids, as the oil-based drilling fluid is thought to impart a high lubricity.
With increased reach of the wells, lubricants are also applied in non-aqueous fluids (NAF) to reduce torque and drag at high angle, for extended reach and horizontal wells to improve drilling efficiency. However, the performance of these lubricants in NAF at extended periods of elevated temperature at downhole conditions is often inconsistent, thought to be hampered by ineffective metal binding and hydrolytic instability of the lubricant molecule. This requires frequent re-dosing and therefore higher cost to maintain performance.
In order to identify a better-performing lubricant, it was necessary to better understand the fundamentals of lubrication in a drilling fluid. For example, what portion of the well contributes most to torque and drag? What is the frictional regime that dominates the lubricity between a drill pipe and its contact points?
Looking at theoretical analysis and modeling, it was found that the horizontal portion is dominated by the boundary and mixed layer friction regime, which is a combination of surface forces and fluid viscosity. Additionally, understanding of tribology from other industrial applications was employed to better design a molecule that can deliver optimum lubricity in a NAF.
This new understanding led to identifying an optimized lubricant for NAF. A lubricant derived from a plant-based raw material was specifically designed to be chemically and thermally stable, binding strongly to metal surfaces, and providing a tenacious film that reduces metal-to-metal friction factors during drilling, casing run and other completion operations.
The identified lubricant was tested for compatibility with NAF, including effects on rheology, elastomers, and formation damage potential. Coefficients of friction and fluid rheology comparisons and research-related field trials are presented. The results show significant (20%) reduction in the coefficient of friction after treatment, especially after hot-rolling, indicating thermal and oxidative stability of the product.
Problems to Solve to Achieve Cost Efficient CO2 Injection Wells
Authors: Manum Henrik , Borgerud Line Kristin , Stokke Ragnar 
Published: March 2023

Abstract
This paper reviews particular challenges for offshore CO2 injector wells, and how these can be mitigated by improving tools, methods, and best practices. Further, challenges with assessment of leakage risk through existing wellbores is reviewed. Finally, a possible cost reduction path for offshore CO2 injection by simplifications in well design is given.
4D Radar Imaging of Wellbore Geometry While Drilling
Authors: Øy Lars , Bye Inge , Lauritzen Magne , Herbert Mike , Grunwald Kamil , Grunwald Kamil , Rød Anne Mette , Kane Danny 
Published: March 2023

Abstract
Despite advances in Measurement-While-Drilling / Logging-While-Drilling (MWD/LWD) technologies, the oil & gas industry has until recently lacked viable technologies and tools to measure wellbore geometry in large hole sizes (&gt;12-1/4″) while drilling and subsequently the ability to visualize and describe the borehole shape and size in an intuitive way.
A direct mechanical measurement solution such as used on wireline, e.g., multi-finger tools, is not feasible to implement on MWD/LWD tools due to the nature of the drilling operation. Conventional technologies and methods, including acoustic- and density-based measurement methods have been used with reasonable results in smaller hole sizes (≤12-1/4″) when combined with low mud weights. However, many commercially available tools within the industry have low vertical and azimuthal resolution due to sparse sampling or sparse storing in its internal downhole memory of such caliper measurements, resulting in limited use of such data for borehole shape and size purposes. Such conventional technologies and methods have not been, or very seldom used in large hole sizes, primarily due to lack of available technologies and tools, resulting from challenges related to the sensor to wellbore interface standoff distance.
A novel Logging-While-Drilling Caliper tool based on impulse radar technology has been developed to overcome the challenges related to mud weight, sensor to wellbore standoff in oil-based muds and at the same time addressing challenges related to sparse datasets. This tool enables the oil and gas industry to accurately image borehole shape and size with both high vertical and azimuthal resolution, including within large hole sizes where there has not been any viable solution whilst drilling. The high sampling rate together with a large downhole memory (128 GB) allows the industry to evaluate the borehole shape and size as a function of time (timelapse).
An Impulse Radar Caliper tool has been pilot tested in several wells on the Norwegian Continental Shelf (NCS), in borehole sections ranging from 12-1/4″ to 17-1/2″. During the pilot testing, the Impulse Radar Caliper tool acquired wellbore shape and size measurements while drilling, and some intervals while pulling out of hole. Several wellbore features, not previously imaged in such large hole sizes, have been identified and their time-dependent development studied in detail. The results from this pilot campaign are discussed in this paper together with the 3D/4D tunnel-view visualization used to assess the processed caliper measurements.