bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Importance of Boundary Conditions for Real-Time Transient Drill-String Mechanical Estimations
Authors: Cayeux Eric 
Published: February 2018

Abstract
The extraction of mechanical friction, during drilling operations, is an important source of information to estimate whether the downhole conditions are sub-optimal, for instance because of poor cuttings transport or additional tortuosity induced by the directional work. Traditionally, the friction factors are extracted using steady state torque and drag models. But, there are contexts, like when drilling from a floater, where it is difficult to find any periods where stable conditions can be observed.
A possible solution to this problem consists in running, in real-time, a transient torque and drag model connected to a high refresh-rate feed of measurements taken by the drilling machines sensors, and to utilize continuous calibration methods to extract information about the unknown or ill-defined parameters that influence the drill-string mechanical system. For those parameters that should stay constant throughout a bottom hole assembly (BHA) run, the estimation method shall account for the totality of the observations and therefore utilizes calibration methods based on statistical global optimization principles, while time-dependent parameters are estimated using a filtering technique.
This approach is only valid when utilizing a trustworthy transient drill-string mechanical model. Comparisons between estimated values from transient torque and drag models and actual measurements have highlighted the importance of robust modelling at the boundaries of the mechanical system. For instance, when modelling precisely the top-drive and the hoisting system mechanical behavior with its associated heave compensation system, it is then possible to obtain a good match between estimated and observed top-drive torques and top-of-string forces, while the bit is off bottom. Furthermore, it requires a precise modelling of the bit/formation interaction to get a truthful dynamic response of the model when the bit is on bottom and only passive heave compensation is used. Associated with its continuously updated calibration of the ill-defined parameters of the system, such a transient torque and drag model enables the visualization, in real-time, of the internal displacements of the drill-string even in the most complex drilling conditions.
Until recently, drill-string dynamic modelling has mostly focused on the lower part of the drill-string, i.e. just above the BHA, and has been reserved to post-analysis evaluations, as existing solutions have been very computer intensive. This paper describes a solution that runs in real-time and that considers the whole drill-string, allowing for the extension of drilling automation functions to very dynamic conditions like those encountered on a floater.
Mud-Cement Displacement in Eccentric Annuli: Analytical Solution, Instability Analysis, and Computational Fluid Dynamics Simulations
Authors: Foroushan Hanieh K. , Ozbayoglu Evren , Gomes Paulo J. , Miska Stefan , Yu Mengjiao 
Published: February 2018

Abstract
A successful cement placement can provide zonal isolation and environmental safety. Effective design of cement placement and mud removal impact all the stages of the wellbore life from drilling ahead to production. Accurate predictions of fluid displacement in the wellbore are vital to design fluid properties and plan the cementing job. In this work, an analytical model is developed to simulate the displacement of fluids in eccentric annuli.
This paper presents a novel method for the solution of cement/mud displacement and evaluation of inter-fluid contamination during displacement for eccentric annuli. This new approach starts by addressing the problem of single fluid flow in eccentric annuli by solving analytically the governing transport equations for a flow inside an unwrapped annulus. The solution is, then, extended to a system of two fluids in a vertical annulus by adjusting the boundary conditions for displacement. The model is completed by adding the time-dependent calculation of interface between the two fluids, enabling the accurate determination of the amount of mixing and displacement efficiency.
The analytical method proposed is used to simulate single and multi-fluid flows and study the effect of fluid properties of cement, spacer, and drilling mud at different flow rates on displacement efficiency, for both concentric and eccentric, vertical annuli. 3-dimensional Computational Fluid Dynamics (CFD) simulations were also performed and the results were compared to the analytical solution. Moreover, instability of the interface in all the cases was studied and the analysis offers an understanding of the role of fluid properties and proposes applicable optimized design to enhance the displacements. The amount of mixing and contamination that occurs during the displacement was calculated for both methods. The analytical solution and CFD produce results within a 13% difference, which validates the analytical model. Evidence was gathered to support that the improper design of fluid properties and flow rate along with a highly eccentric annulus can lead to substantial cement contamination. This may lead to under-designing the amount of fluids to be pumped to provide a complete mud removal and an efficient cement placement. On the other hand, learnings and models developed allow optimizing fluid properties that may lead to best outcomes even for highly eccentric annulus.
The undeniable importance of a complete cement displacement is addressed by means of an analytical solution of the displacement, which provides a realistic prediction of the amount of inter-fluid mixing and cement contamination. This approach coupled with the interface instability analysis, which offers improvement techniques for the displacement, provide beneficial enhancements for practical industrial applications.
In-Situ Fluid Rheological Behavior Characterization Using Data Analytics Techniques
Authors: Ettehadi Reza , May Roland , Dahl Thomas , Clapper Dennis , Swartwout Rosa 
Published: February 2018

Abstract
The accurate characterization of drilling fluid rheological properties at the in-situ downhole temperature and pressure is essential for designing the hydraulic program as well as for managing potential challenges during the drilling operation. A rheometer capable of operating at high temperature and high pressure (HTHP) is the common experimental method used to measure drilling fluid rheological properties at in-situ conditions. This method is costly and time consuming and requires skilled fluids laboratory personnel to carry out the tests. At the rigsite these devices are usually not available.
This paper/study presents an analytics based method to estimate drilling fluid rheological properties at in-situ downhole temperature and pressure and provide the required inputs for hydraulic modeling during well planning, for real-time monitoring and automation. The performance of the developed method is evaluated by utilizing data obtained from both, Mud Check tests and HTHP Viscosity measurements of synthetic and oil based drilling fluid samples.
Drilling fluid samples were collected from the rigs in operations around the world. An algorithm is developed to retrieve data out of unstructured field service laboratory databases and to uncover hidden patterns by utilizing the text pattern matching, text analytics, table-based approach, data visualization and classification techniques. Several computational intelligence techniques and statistical methods are applied to interpret the data by correlation of variables measured in the Mud Check tests and HTHP rheometer data. Of the available data 70 percent have been randomly extracted to train the data driven-model to predict drilling fluids rheological behavior at the in-situ downhole temperature and pressure.
The model is further tested with the remaining 30 percent of the available data to confirm that the model can not only fit the data used for training but also characterize the drilling fluid rheology at the in-situ downhole temperature and pressure with the required accuracy. This study indicates that in addition to temperature and pressure, several parameters including density, salt concentration, low and high gravity solid volume percentage, oil-water ratio, and oil phase volume percentage should be considered to accurately predict the rheological properties of drilling fluids at downhole conditions. Since the method presented here depends on several variables measured in the Mud Check tests, it can effectively be employed independent of location or formation.
The developed method can be utilized at the rigsite by field personnel to estimate downhole rheological properties of drilling fluids with a small error margin, without using expensive test equipment and time consuming procedures.
Using Aluminum Drill Pipe with Axial Oscillation Tools to Significantly Improve Drilling Performance
Authors: Mills K.. , Menand S.. , Grissom R.. , Kaufmann P.. , Schulte C.. , Evans N.. 
Published: February 2018

Abstract
Aluminum drill pipe has already been proven as a viable alternative to steel drill pipe when drilling long horizontal wells thanks to its lighter weight that does not compromise resistance to yield and buckling. At the same time, the development of unconventional wells has seen the deployment of numerous technologies to further improve the performance and increase the lateral section to reduce costs. An operator has recently and successfully tested a new aluminum drill pipe with an axial oscillation tool to push further the limits of the drilling system.
This paper presents the key findings of the case study using a mixed aluminum-steel string combined with an axial oscillation tool. First, the innovative drill pipe design is presented, followed by lessons learned during rig operations regarding pipe handling practices, rig compatibility and pipe inspection. Then, results of the drilling simulations performed during the well planning phase are presented. This modeling led to an optimum drill string design associating the steerable mud motor assembly, aluminum drill pipe, axial oscillation tool and steel drill pipe. The number and placement of aluminum drill pipe along the string was key to reducing friction and improving weight transfer between the bit and the axial oscillation tool.
Through extensive modeling and field data interpretation, this paper presents the comparison of the overall drilling performance between steel only and aluminum-steel drill pipe strings, and provides metrics in terms of weight transfer and rate of penetration improvement. This innovative and promising drill string design opens the doors to set new limits in terms of horizontal departure.
Dynamic Kill Method Using Staged Fluid Densities can Improve the Killability of Relief Wells for Challenging Blowouts
Authors: Chantose Prasongsit , Oskarsen Ray , Emilsen Morten , Negrao Alvaro 
Published: February 2018

Abstract
In the event of a blowout, the kill method that usually has the highest probability of success is a relief-well intervention. After the relief well gains hydraulic communication with the blowing well, a dynamic kill is often used to bring the well under control. In some cases, the pumping operation may call for more than one fluid density, which is referred to as a staged kill. Although the staged-kill technique has been around for a long time and has been successfully used on many blowouts, little information is available on applications, benefits, technical challenges, and operational requirements. In this paper, two case studies demonstrate how a staged kill can successfully kill challenging blowouts under various conditions. One example, for a staged-kill application, is an actual gas-condensate blowout that could not be brought under control with a standard dynamic-kill operation. Staging a heavy kill mud ahead of a lighter mud that would not fracture the exposed formations successfully killed the well. The second example summarizes the results from a relief-well contingency study for a planned high-pressure, ultradeepwater well with a weak formation that would be fractured by the required kill mud. Dynamic simulations demonstrate that a lighter mud circulated ahead of the static kill fluid could bring the well under control without fracturing the weak zones.
How to Manage Geomagnetic Field Disturbances in the Northern Auroral Zone to Improve Accuracy of Magnetic MWD Directional Surveys
Authors: Edvardsen I. , Nyrnes E. , Johnsen M. G. , Hansen T. L. , Aarnes I. 
Published: February 2018

Abstract
The auroral zone is the region surrounding the geomagnetic north and south poles and is where the largest and most frequent disturbances in the Earth's magnetic field are experienced. Since the accuracy of magnetic MWD directional surveys are affected by geomagnetic disturbances, surveying wells in the auroral zone is challenging. Development of industry practices to enable accurate surveying and safe operations in these areas is therefore important.
The objective of this study is to investigate how the geomagnetic field parameters declination, dip angle and total magnetic field intensity are influenced by magnetic disturbances in the auroral zone. This is done by analysing the statistical properties of data from 20 land-based magnetic observatories and variometer stations in Alaska, Greenland, and Scandinavia, all located in the auroral zone. The results are used to estimate models for magnetic field disturbance variations as function of distance and direction. Additionally, methods and correction procedures to reduce azimuth uncertainty using data from distant monitoring stations are presented.
Uncritical use of data from monitoring stations can result in uncertain azimuth measurements. In cases where data from more than one nearby monitoring stations are available, the challenge is often related to identifying which stations that provide the most accurate corrections. As will be shown, important criteria for the selection of monitoring stations are not only limited to directions and distances, but also the position of the ionospheric current relative to the rig-location. Procedures and methods for how to predict the positions of ionospheric currents are presented.
The datasets analysed in this study contain measured deviations from the quiet mean for periods with low, moderate and high geomagnetic activity. Station-pairs with mutual distances ranging from 150km to 850km are considered. The general trends are that magnetic data from station-pairs located along the east-west direction are more correlated than data from stations located along north-south, and that differences in magnetic fluctuations between station-pairs are lower east-west than north-south. This accounts for all distances, directions, and disturbance levels.
Unlocking Reserves in a BP Operated High-Pressure Gas Field through Reliability Based Casing Design
Authors: Miller Richard A. , Ramtahal Rishi , Owoeye Oladele O. 
Published: February 2018

Abstract
The BP project team has considered increased reserves recovery by lowering the reservoir abandonment pressure below the initial design value. Through a multi-disciplinary approach, design assumptions and equipment ratings were systematically reviewed to determine which aspects factored into the decision to change reservoir management. Collapse loading of the 10 in. production liner was identified as a key variable.
The conventional design factor, a ratio of the design load to the API collapse rating, was deemed to be an insufficient way of characterizing design margin, primarily due to the perception of conservatism in the rating. While design factors are convenient for screening a casing string against an agreed-upon set of inputs and assumptions, there is little insight gained from comparing a 1.03 design factor to a 1.02 other than one value is higher than the other. The team embarked on a scope of work to characterize the probability of collapse as a function of reservoir abandonment pressure using reliability based design (RBD).
Physical testing was conducted to characterize the distribution of collapse resistance and the distribution of dimensional and strength parameters which govern collapse. The quality data sets are combined using the Klever-Tamano limit state equation to indirectly derive a distribution of collapse resistance. The destructive collapse tests provide both a direct measure of the distribution of collapse and a way to calibrate the limit state equation model uncertainty. Both the direct and indirect methods are useful in determining the probability of collapse for a design load.
Load uncertainty was characterized by considering variability of conditions across the wellstock, including depth, temperature and completion configuration. Casing wear was also considered in the assessment.
This paper outlines the RBD methodology used to support the decision to lower reservoir abandonment pressures. Details on how to construct the statistical collapse model are provided along with a discussion on interpretation and continuous improvement activities.
New Design Limits Plot for Overview of Load-Resistance Relationship in Wellbore Tubular Design
Authors: Liu Zhengchun , Samuel Robello , Gonzales Adolfo , Kang Yongfeng 
Published: February 2018

Abstract
In the tubular design of oil and gas wells, visualization of the loads and design limits (resistance over design factor) in a single 2D plot can help provide well designers a safety-factor overview of a particular string section. This plot is called a design limits plot (DLP). This paper illustrates the theoretical foundation and construction procedure of a new DLP, which is believed to more accurately represent safety factors.
The new DLP was built by plotting differential pressure, ΔP, vs. equivalent axial load Feq (= Fa + min(pi, po)×AS, where Fa is the axial force, AS is the cross-sectional area, and pi and po are the internal and external pressures, respectively), for both envelopes (design limits) and load points. Temperature-deration effects were applied to load points instead of envelopes so that the safety factor could be neatly represented by the relative load-point location with respect to the room-temperature envelopes. For comparison, the triaxial yield envelope was plotted together with API envelopes (axial, burst, and collapse).
A field example is presented that demonstrates the application of the new DLP for wellbore tubular design. It is shown that, for load cases in which counter-load pressures (which are defined as pi for collapse loads and po for burst loads) are high, the new DLP represents the safety factors more accurately and comprehensively.
Using the equivalent axial load instead of the axial force in the new DLP allows for better consistency with both the von Mises triaxial yield criterion and the API 5C3 2015 addendum. The new DLP not only represents a more accurate overview of safety factors, but also facilitates direct reading of pipe burst/collapse ratings.
Novel Drill Bit Technology Combined with System Matcher Increases Torque Efficiency and Reduces Stick-Slip and Vibrations
Authors: Rahmani Reza , Omidvar Navid , Hanley Chris 
Published: February 2018

Abstract
Major performance challenges for deepwater applications from a drill bit standpoint were identified as (1) High surface torque in salt is one of the major ROP limiters. (2) Inability to control depth of cut in soft rocks including shale and salt and when drilling in interbedded formations results in torsional oscillations and stick-slip. (3) Improper combination of bit and reamer induces drillstring vibrations. This paper presents the development of new drill bit technologies combined with a new system matching analysis package to address those problems.
Salt mechanical behavior was evaluated using triaxial testing under confining pressures up to 5,000 psi. Full scale pressurized testing was then conducted to evaluate salt drilling behavior versus rock characteristics. The following specific challenges were addressed: Non-planar PDC geometries were tested in salt, among other rocks, to identify a geometry which results in maximum increase in ROP at any given torque.New insert shapes were developed and tested for more effective and accurate depth of control.A full drillstring analysis model was developed with the ability to predict downhole and surface torque and WOB as well as drillstring dynamics, torque, and drag.
The new shaped cutter full scale pressurized test resulted in an increase in ROP/torque ratio throughout the different rock and a 28% increase in salt. The cutter also increased ROP/WOB ratio by 42%. Furthermore, the new insert shapes proved to be more effective in controlling depth of cut, resulting in an extra 35% reduction in torque/WOB ratio compared to standard insert shapes.
The project is now in field evaluation and the new drill string analysis tool has been applied to several field applications including some in the Middle East, North Sea, Gulf of Mexico, and the Caribbean for different purposes. Some of those purposes include buttonhole assempbly (BHA) selection for given bit and reamer, bit selection for a given BHA design and reamer, and drilling parameter optimization for a given BHA design, bit, and reamer. New insert shapes were run in multiple applications in North America, including in North Dakota and Oklahoma, with promising results proving that although the project was focused on deepwater drilling challenges, the novel solutions are applicable to a wide range of applications.