bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Bullheading Study in an Instrumented Well
Authors: Samdani Ganesh Arunkumar , Rao Sai Sashankh , Moganaradjou Yashwant , Almeida Mauricio A. , Kunju Mahendra K. , Santos Otto , Gupta Vishwas Paul 
Published: March 2023

Abstract
Bullheading involves pumping produced fluids back into the formation using a kill-fluid. A key operational parameter is the required bullheading rate which depends on surface pressure, available horsepower, and erosion limits. There is wide variation in current guidelines for bullheading rates, especially for large-diameter wellbores. Therefore, a well-scale bullheading test program was conducted using a 5200-ft-deep vertical well with 9-5/8"x2-7/8" casing/tubing annulus located at LSU test well facility. The tubing was instrumented with 4 downhole pressure gauges and fiber optic DTS/DAS to obtain data on the downhole flow dynamics and determine bullheading efficiencies. In a typical test, a large nitrogen cap placed at the top of the annulus was bullheaded by pumping fluid in annulus with continuous returns taken from the tubing side. Tests were conducted with varying fluid rates (50 to 500 gpm), initial gas-cap size (30-60 bbl), gas pressurization method and kill fluids (water and synthetic base mud). It was observed that the bullheading process involves simultaneous gas compression, gas bubble breakage, gas dispersion, and gas displacement, unlike the typical assumption of bullheading a large gas slug. The breakage of the initial gas slug depended on the surface pressure and the extent of gas-liquid mixing. The minimum water flowrate required for gas bullheading matched to water velocity just above small bubble velocity in water. Increase in water flowrate increased the bullheading efficiency, e.g., bullheading with 350 gpm required &lt;50% water volume compared to 150 gpm water flowrate. Experiments with a highly pressurized initial gas cap and a larger initial gas cap volume resulted in relatively more efficient bullheading due to lower slip velocity resulting from higher average gas-holdup in the gas-swarm. In one test, the gas was bullheaded for some time and then allowed to migrate upward in a shut-in well. It was observed that the gas migration velocity (0.71 ft/sec) was higher than the gas slip velocity during bullheading (0.3-0.6 ft/sec). Contrary to the popular belief, the gas also did not carry its pressure while migrating in a shut in well. The experimental observation of bubbly flow instead of slug flow during bullheading under sufficiently higher surface pressure helped understand the multiphase flow dynamics of bullheading and it can help provide realistic bullheading guidelines based on well conditions.
Drill-Off Tests for Drilling Optimization: Pitfalls and How to Avoid Them
Authors: Chhantyal Khim , Kyllingstad Åge , Hetland Anders T. , Thor Birgisson Kjartan 
Published: March 2023

Abstract
A drill-off test is a special drilling test where the drawworks is locked and the string elasticity causes the bit to penetrate the formation at a decreasing weight on bit (WOB). It is often used as a tool for finding how the rate of penetration (ROP) varies as a function of WOB and for finding optimal drilling parameters. This paper sheds a critical light on the use of drill-off test by discussing various errors and pitfalls usually ignored today. The paper starts by presenting a simple but widely used method for converting surface hookload data into an ROP vs. WOB curve, commonly known as a drilling performance curve. Next, it discusses and tries to quantify various error sources, such as hookload sensor errors, residual wellbore drag, and formation inhomogeneities. The paper uses real field data and a comprehensive simulation model to illustrate the magnitude of the various errors and how they affect the drilling performance curve. Finally, the paper suggests ways to check the accuracy and validity of the drill-off tests. The analysis shows that the variable wellbore friction is an error source that depends on many parameters, such as string length, wellbore inclination, rotational string speed, and ROP. It also shows that it is possible to model the errors and apply correction formulas to improve the quality and accuracy of WOB and ROP. Although friction-related errors can be reduced by applying proper corrections to the estimated WOB and ROP, there is still a need to check the validity of the drill-off test results with other types of drilling tests. The paper presents several proposals for alternative and complementary drilling tests, such as drill-on test (here defined as a test where WOB is continuously increased), steady state (constant WOB) drilling test, combo test, and sinusoidal perturbations test.
Time-Lapse Evaluation from Ultrasonic Pulse-Echo and Pitch-Catch Configuration and Sonic Logging Data for Potential Formation Creep and General Annulus Solids Segregation
Authors: Obando Palacio Guillermo Andres , Govil Amit , Agrawal Gaurav , Gupta Shilpi , Delabroy Laurent , Kristiansen Tron Golder 
Published: March 2023

Abstract
Verification of annular well barrier elements is an essential process during the well construction and plug and abandonment phases. This topic has been the subject of many publications and is governed by regulations in different countries around the world. In this paper we focus on the evaluation of shale creep barriers. We describe how sonic and ultrasonic pulse-echo and pitch-catch configuration data are used to monitor the evolution of formations creep around the casing to eventually form annular barriers.
Multiple annulus logging evaluations were performed across wells from the Valhall, Ula, Alvheim, and Jette fields on the Norwegian Continental Shelf (NCS). This was done using ultrasonic pulse-echo and pitch-catch configuration data as well as traditional sonic logs. The logging data were collected, reprocessed, and compared as part of a collaborative effort between the operator and a service company. In this study we examine the progression of annular solids through time from formation creep.
Our intention was to study the ability of shales creep to form barriers, and to simplify the well design and achieve isolation around the production casing without the need for conventional cementing operations.
The log data provide information of annulus material with a detailed map of the axial and azimuthal variations of the annulus contents. Crossplotting state-of-the-art measurements also helps to identify the material accumulating in the annulus as published in many other industry papers. This approach has garnered interest over the years as a novel solution during well abandonment operations. The results provide solid evidence of shale creep-forming barriers and has been used by the operator to further refine their zonal isolation strategy.
Comparing ultrasonic data with a particular interest on the progression of formation creep, has become a popular subject within the NCS. Innovative use of historical logging data holds a great potential to help make decisions that result in reduced cost and environmental impact. Because of this novel usage and analysis of ultrasonic logging data, the operator was able to make informed decisions faster, saving rig time and cost while reducing the carbon footprint.
Drilling Parameter Optimization in Real-Time
Authors: Mal Anwesha , Oedegaard Sven Inge , Helgeland Stig , Navabi Josef , Skogestad Jan Ole , Bjoekevoll Knut Steinar , Lien Morten , Weltzin Tore , Rudshaug Bjørn 
Published: March 2023

Abstract
There is an increased demand for contactless and/or low touch activities as well as a requirement for most product delivery and services to be such. This paper aims to demonstrate how drilling parameter optimisation in real-time provides a drilling team with an Edge based solution that can continuously improve performance and avoid problems without the need of subject matter experts. Results from testing the Edge-System on multiple wells from several operators are presented related to auto-calibration of real-time prediction models and for optimization of drilling parameters. This system based on cloud technology with Model based reasoning in Artificial Intelligence (AI) is able to give real-time and forward advice for operational parameters, ref SPE-204074-MS
The key enabler for such system is "automatic" auto-calibration of models which is used for multiple forward-looking and what-if calculations to find optimal drilling parameters within the well envelope ahead.
A simplified configuration has been made so that the rig-team can operate and maintain the system without the need for subject matter experts. "Automatic" Auto-calibration at stable conditions and/or during ramping conditions removes the need for subject matter experts. Such a system helps reduce operational costs as the rig-team can operate the system without the need of back-office support. Comparison will be made to document operational improvements.
Field Deployment of a LSTM Neural Network Tool for the Rock Formation Consolidation Inference of Brazilian Sandstone Reservoirs
Authors: Rodrigues Gonçalves da Silva Fabio , Ribeiro Carriço Victor Hugo , Zacarias Ignácio Pereira Alexandre , Leibsohn Martins André 
Published: March 2023

Abstract
The objective of this work is to present a methodology based on the analysis of drilling parameters to infer if a reservoir formation is well consolidated or not, as a support to the selection of sand control strategies.
This work proposes a statistical classification model and the usage of a memory based neural network, known as LSTM (long short-term memory) network. This model explores time series characteristics of the problem and it is validated using a cross strategy. Training performance is evaluated using F1-score, which is a metric that balances precision (percentage of true positives compared to false positives) and recall (percentage of true positives compared to false negatives), chosen because the dataset is unbalanced, there are more samples of one class than the other. The dataset consists of pre-tagged wells, each of them with at least nine hours of drilling data.
Considering 48 cases from different drilled wells, the model was trained to learn how to tag between both patterns. The model analyzes 23 different drilling variables to reach a conclusion.
After training the model, tests were performed and the results showed a high identification efficiency: around 90% of accuracy. That way, mechanical data analysis from the drilling process plays a very important role, supplementing that information and allowing a better understanding of formation behavior by employing what can be considered full-size and a real-time scratch test. Match the collected data with those from wells in which there is logging information, provides geomechanics calibration, and allows consistent rock profiling. It helps to define not only if there is a need for sand control but also the kind of technique to be applied to the analyzed formation accordingly to its consolidation state. The impact of that information is expressive to the completion process.
This feature will be very useful in Brazilian post-salt wells that present sandstone as its reservoir rock formation. Also, as this tool was designed to run in a drilling digital twin, it can be automatically run as soon as the total depth is reached in the drilling phase, providing a fast insight to anticipate completion design.
It is the first time in literature that this approach is used for this specific objective: define if a gravel pack or even any kind of sand control is indeed necessary to be installed based on information gathered while drilling the well. Its great results led this tool to the deployment phase. This work also aims to illustrate the first outcomes of that application in real-time decision-making.
Real-Time Prediction and Detection of Drilling Bit Issues Based on Along-String Measurements (ASM) Along Wired Pipes - A Case Study
Authors: Gomar Mostafa , Elahifar Behzad 
Published: March 2023

Abstract
When it comes to optimizing drilling, the focus is on running the bit into the well and performing the drilling efficiently. Included in this are methods for optimizing rate of penetration (ROP), determining the right time to change drilling bits, and managing bit run to reduce other drilling costs, such as tripping, hole conditioning, material consumption, and detecting drilling problems at the right time. The present study employs a new approach to drilling bit modeling that utilizes along-string measurement (ASM) data to continuously monitor the status of the drilling bit.
A two-pronged approach is employed in the monitoring of drilling bit condition in addition to estimating rock drillability to keep track of change in lithology. First step involves developing a model for polycrystalline compact drilling (PDC) bits. It examines micro forces at the bit cutters and then upscales these forces to parameters applied to the drilling bits, such as weight and torque. Upscaling involves geometric remodeling of bits as equivalent cutters and equivalent blades. In the second part, a data-analytic approach is used to combine continuous measurement of downhole data with the developed experimental-based model. The real-time data is measured by using an along-string measurement system on the wired pipe.
The results of this approach can be grouped into three categories. First, the drilling bit condition is estimated in real time in each equivalent cutter. A quantitative assessment could be undertaken based on model output, or a qualitative assessment could be carried out by analyzing specific energy. Having knowledge of the status of bit, the second conclusion is to monitor rock drillability according to variations in specific energy at the bit and publishing numerical value of rock drillability. In addition, the last corollary is to generate knowledge regarding drill string dynamics and the way to differentiate between vibration at the bit and at the drill string. In this paper, however, the first two outcomes are addressed. This approach is tested on a set of ASM data captured during drilling operations on the Norwegian continental shelf. The results are consistent with those reported from the field.
Currently, the selection and evaluation of drilling bits requires knowledge of nearby well records. A drilling penetration rate model that requires calibration for a specific field may also be used to estimate bit condition in some cases. This research presents a new bit status simulator that overcomes the limitations of existing techniques by applying a delicate and intelligent application of ASM data to predict drilling events and mitigate them in real-time.
Experimental Investigation of Geopolymers for Application in High-Temperature and Geothermal Well Cementing
Authors: Denduluri Veerabhadra S , Ulerio II George , Genedy Moneeb , Juenger Maria , van Oort Eric 
Published: March 2023

Abstract
With recurrent calls for a reduction in carbon emissions, geothermal energy has received increasing attention in recent years as a prominent source of clean energy. With current drilling technology, geothermal wells are being constructed in extremely challenging temperature environments, which could reach up to 600°F/315°C in-situ temperature and beyond. However, geothermal well-cementing technology has not changed much over the past few decades, with Ordinary Portland Cement (OPC) still being the primary choice of cementing material. OPC has several drawbacks such as brittle behavior, shrinkage upon setting, poor bond strength to formation and casing, susceptibility to acid gas attack, temperature-induced strength retrogression, low tolerance towards drilling fluid contamination, etc. These factors could lead to a poor cementing job, thus compromising well integrity and not ensuring proper zonal isolation for the life of the geothermal well. Thus, there is a need to develop an alternative material that is compatible with the geothermal environment and able to provide long-term zonal isolation. With a low carbon footprint, self-healing ability, and low shrinkage sensitivity, geopolymers or alkali-activated materials could be a suitable option to augment or even replace OPC. Some of the previous studies on geopolymers have shown that they could be a potential candidate for oil and gas well cementing and civil engineering applications, with some being stable at very high temperatures (up to 1470°F/800°C). Geopolymers are formed by mixing an aluminosilicate source such as fly ash with an alkali-activating solution, such as sodium or potassium hydroxide or silicate.
The aim of the study reported here is to demonstrate the applicability of geopolymers for geothermal well cementing. An experimental investigation was carried out to understand the behavior of geopolymer formulations made from fly ash, metakaolin, and blast furnace slag in a high-temperature environment. The material properties such as porosity, viscosity, thickening/pump time, compressive strength, tensile strength, and bond strength were tested in the laboratory. It was found that geopolymer formulations can be formulated to have the desired rheological properties with adequate pump time and resistance to drilling fluid contamination. In addition, the formulations can exceed the required compressive and tensile strength for geothermal cementing operations, while obtaining excellent bond strength values. These findings indicate that geopolymers are cementing materials that are well-suited to provide long-term zonal isolation in high-temperature geothermal wells.
Definitive Survey Methodology – Update to an Old Concept for Higher Reliability
Authors: Naschenveng André , Isaac Lucas , Laroca Fernando , Franceschi Cláudio , Neves Alex , Canté Fábio , Ledroz Adrián , Carrasquilla Abel 
Published: March 2023

Abstract
Data quality assurance applied to well positioning optimizes contingency plans to reduce the time to drill a relief well and provides greater reliability in autonomous and remote drilling operations. In addition, it provides the highest degree of agreement with the well design, making it possible to reach the best productive zones of the reservoir and avoid geological risks. This data quality assurance procedure supports the construction of high-productivity wells in the offshore pre-salt fields in Brazil. The objective of this work is to present the results of the Definitive Survey Methodology in pre-salt wells, to improve the survey quality assurance and the reduction of uncertainty ellipses - during operation and in real-time - using two survey tools with different physical principles.
The Definitive Survey Methodology promotes the verification of error models of the survey tools and reduces the Ellipses of Uncertainty (EOU), well to well, creating an external directional data quality assurance, which goes beyond specific internal quality controls used by service companies. The methodology consists of the use of three tests that compare independent surveys. The first and second tests are statistical, Relative Instrument Performance (RIP), and Chi-square, in which the reliability of the used error models is verified. The RIP test is a comparison that produces results with quantitative values about the agreement of overlapping surveys. The Chi-square test is a quality fit test that compares two surveys and their compliances with their error models. The third test is a qualitative geometric test that compares the uncertainty ellipses of different survey tools at the same depth, allowing a quick interpretation of graphic representations and can be applied during or after drilling.
The methodology was applied in four pre-salt wells named in this paper as Well_A, Well_B, Well_C, and Well_D. The final measured depths of the wells range from 5078m to 6801m. The tools used were: gyro while drilling (GWD) for all inclinations in real-time (inrun), GWD outrun memory mode (OMM), drop gyros, and measurement while drilling (MWD). The methodology resulted in a reduction of 74.55% (Well_A), 50.93% (Well_B), 33.69% (Well_C), and 60.05% (Well_D) of the ellipse of uncertainty at the top of the reservoir.
The use of the Definitive Survey Methodology enhances the quality of the directional data, verifying the error models used well to well. The reduction of uncertainties provided by the gyroscopic tool ensures the reliability of the contingency plan and the entry into the top of the reservoir. Consequently, by optimizing the positioning of the wells, it is expected to make the most of the natural resources in the long term, while also building safer contingency plans, and making the extraction activity of this natural resource more sustainable.
Expandable Geopolymers for Improved Zonal Isolation and Plugging
Authors: Gomado Foster Dodzi , Khalifeh Mahmoud , Aasen Jan Aage 
Published: March 2023

Abstract
Generally, the expansion of cementitious materials has been regarded as a promising avenue for better sealability. The sealability performance of an expanding geopolymer is compared to an expansive commercial cement in terms of the shear bond strength and the hydraulic bond strength at curing conditions of 25°C and 34.5 bar. A Neat Class G and a neat geopolymer were characterized alongside its corresponding expansive versions. The impact of these expansive agents on cement and geopolymers is evaluated in terms of linear expansion using the annular ring test. In terms of its performance for P & A operation, the push-out test was used to characterize the shear bond strength between the casing-cement interfaces, whereas the hydraulic bond strength is measured with a custom-made setup which eliminates any pressure and thermal shocks. These materials were characterized in terms of its shear bond strength, hydraulic bond strength and linear expansion. The shear bond strength of Neat G and expansive cement were estimated to be 22.37 bar and 22.76 bar respectively. Whereas that of the neat geopolymer and expansive geopolymer were recorded at 7.47 bar and 10.14 bar respectively. On the basis of the hydraulic bond strength, expansive cement had the highest followed by expansive geopolymer. Both the neat recipes were observed to have the same values in terms of the hydraulic bond strength. This study reveals that geopolymers can be deployed as an alternative to Portland cement upon optimization.