bluuebunny/crossref_metadata_2025_split huggingface dataset:
Well Control Simulator: Enhancing Models with Compositional PVT Models and Kinetics
Authors: Bjørkevoll Knut S. , Skogestad Jan Ole , Frøyen Johnny , Linga Harald 
Published: February 2018

Abstract
Details of the interaction between natural gas and oil in drilling fluids currently not taken into account, will in extreme cases be significant for the safety of drilling and well control operations. The paper describes such effects, in particular time dependence (kinetics) and compositional PVT with dense phase included. The importance of validation and tuning of PVT calculations, even when using state-of-art tools, is demonstrated by integrating new methods in a well control simulator.
We consider sub-models for kinetics (time dependence of gas dissolution and boiling) and compositional PVT for the drilling fluid-natural gas mixture, and study different effects and assumptions numerically by integration in a well control simulator. Available laboratory data are used for model development and tuning of existing software. The dense phase may be important to consider in HPHT wells, where the conditions allow for the drilling fluid-gas mixture to exceed the critical point. This influences the gas absorption capability of the drilling fluid, as well as the density.
The paper illustrates the impact of kinetics and improved PVT calculations through a sensitivity analysis using realistic well and fluid data. Two specific base-oils, a refined mineral oil and a linear paraffin, are used in combination with methane gas. The simulations show how kinetic effects can be important in some cases, both for early interpretation of a kick and for the response seen at surface as gas approaches and enters topside equipment. Furthermore, it demonstrates that dense phase effects can be significant, and that even state-of-art PVT software requires tuning when used with new combinations of oil-base fluids and hydrocarbon gases. Although the effects discussed are small compared to safety margins for many wells, ignorance may cause drilling teams to run into severe risks without knowing in advance for other wells.
Combining advanced PVT models capable of representing dense phase behavior and a kinetics model with hydraulic flow modelling represents a leap forward in simulation of well control events. In addition, the importance of tuning adds valuable knowledge. These elements enable earlier detection and safer handling, thus increasing the safety on the rig.
Reducing Stick-Slip by Avoiding Auto-Driller Control Dysfunction
Authors: Adam Derek 
Published: February 2018

Abstract
Analysis of historical drilling data in the Delaware Basin revealed stick-slip was being initiated by the rig control system. It was determined that a weight-on-bit (WOB) road map with calibrated range values delivered near-maximum rate of penetration (ROP) and reduced stick-slip. This was achieved by simplifying the auto-driller's parameter limits and avoiding differential pressure control. Details of the statistical analysis process and results from field trials is presented and compared to historical performance.
The road map was developed using data from top performing offset wells. The standard deviation of the auto-driller's active control limiters was cross-plotted against the standard deviation of the ROP. Intervals in which the differential pressure was the primary control or the ROP range was excessive displayed a high standard deviation, indicating unstable control behavior. Data from the non-dysfunctional areas determined the WOB and ROP ranges to be targeted through an interval. Use of these range limits steadied the application of WOB and reduced the need to control the auto-driller via differential pressure.
Wells using the parameter road map were compared to high-performing offsets. The comparative analysis focused on ROP, mechanical specific energy (MSE), downhole accelerations, and bit damage. Performance in formations known to cause dysfunction are highlighted. Benefits have been observed in the rotary steerable control collar RPM data. Depth-of-cut (DOC) through the Brushy Canyon was improved by use of the road map. Traditional auto-driller limiters (torque and differential pressure) were avoided due to the limits of the drilling system embedded within the road map's setpoints. Data are presented showing that differential pressure control can result in stick-slip. This dysfunction is avoidable with the use of a road map employing accurate range values for WOB and ROP to control the auto-driller.
Improved auto-driller range management addressed a specific source of dysfunction and positively impacted performance at the bit. The visual road map conveyed WOB and ROP guidance directly to the driller, which accelerated the rig's learning curve. When combined, the product of these data-driven concepts increased bit life and ROP.
Probability of Wellbore Intercept Made Easy
Authors: Codling Jeremy 
Published: February 2018

Abstract
Wellbore intercept probability calculations are important not only for avoiding collisions but also for relief-well planning and planning for wellbore reentry in abandonment projects. This study reviews the current methods for calculating probability and their sensitivity to the input variables. A probability of intercept calculation is presented that is proven, robust, and can be implemented in a spreadsheet as input-wellbore positions and survey-error dimensions.
Given the lack of availability of empirical wellbore collision-frequency data, it was necessary to model the wellbore-intercept scenario using a Monte Carlo simulator constructed by breaking the two wellbores into short segments. The validity of the simulator is highly sensitive to the probability distribution of the input-survey errors. The input-probability distribution of well separations in the high side and lateral directions is determined from survey-comparison studies for both systematic and random-error sources. The simulator is used to compare the accuracy and reliability of different probability integration types and sensitivity to the input data and distribution of errors.
It is observed from survey comparisons that the distribution of survey inclination and azimuth errors behave as "heavy tailed" probability distributions such as Laplace or Student's t. This increases the probability of intercept at higher sigma levels than the previously assumed normal distribution.
The results of this study exhibit the sensitivity of the probability result to the degree of sophistication of the probability calculation from simple one-dimensional (1D) projection to three-dimensional (3D) integration of probability density. There is a law of diminishing returns with the sensitivity of complex models being lost in the reliability of the input-error values and assumptions on probability distributions.
One observation is that there is no "pedal curve" effect for high-angle well crossings. The simple point-to-point collision calculations using this vector method do not include the confidence in the relative direction of the two wellbores. Therefore, probability calculations and separation-factor calculations that engage the pedal-curve distances are overly conservative.
A reliable prediction of wellbore-intercept probability is achieved using a relatively simple method. This study shows the importance of the angle of intercept to enhance interception probability for relief wells and abandonment re-entry operations.
Attenuating Heave-Induced Pressure Oscillations using Automated Down-hole Choking
Authors: Kvernland M. , Christensen M. Ø. , Borgen H. , Godhavn J.-M. , Aamo O. M. , Sangesland S. 
Published: February 2018

Abstract
In this paper, a new tool to be placed in the bottomhole assembly (BHA) is introduced for the purpose of counteracting heave-induced down-hole pressure oscillations in offshore drilling. The tool contains a control choke, sensors and computing capability, and will operate autonomously with minimal implications for standard drilling procedures. A small-scale prototype is developed and successfully tested in laboratory experiments showing significant reduction in down-hole pressure oscillations. Realistic, full-scale cases investigated using computer simulations also show good performance. The paper gives a description of the small-scale lab as well as the mathematical model used for the computer simulations. A full-size autonomous choke prototype is currently being constructed for further testing under more realistic conditions. Design aspects of the prototype are presented in the paper.
Case Study: Reactive Torque Failure Prevention
Authors: Pettit G. 
Published: February 2018

Abstract
Reactive torque failures occur when an underreamer or hole opener stalls suddenly. The right-handed momentum in the components underneath the stalled tool applies a left-handed torque to the connections. If this left-handed torque is high enough, the connection can back off.
In fact, an operator had a reactive torque failure in just this manner. We study that failure as an example in this paper, outlining the way to prevent it in the future. In short, the makeup torque applied to the connection must remain higher than the left-handed torque that the tool might see. While simple enough, the complication comes when trying to calculate the magnitude of left-handed torque under a stalled underreamer.
The simplest method is to apply an energy approach when calculating the left-handed torque. This is straightforward mathematically, and in most cases it is conservative due to the lossless assumptions that are used.
Unfortunately it is becoming common that something more sophisticated is necessary. This is due to the fact that vibrations are typically ignored in a simple energy model. Since in many holes friction will quickly damp out any vibrations caused, this often does not cause problems. However, if reaming a very big hole—as was the case in our study, and is often true of the larger hole sizes in deepwater operations—the friction may be low enough that torsional vibrations will play a significant role.
In order to calculate the reactive torque that might be applied in these latter instances, a numerical approach must be employed that considers the torsional shock wave applied to the components underneath the stalled hole opener.
This paper considers these different mathematical approaches, particularly as they were applied to both the reactive torque failure and the resulting preventative design processes.
A Novel Practical Approach to Borehole Breathing Investigation in Naturally Fractured Formations
Authors: Baldino S. , Miska S. Z. , Ozbayoglu E. 
Published: February 2018

Abstract
Occurrence of reversible mud losses and gains while drilling in naturally fractured formations is of primary concern. Borehole breathing can greatly complicate the already difficult practice of fingerprinting the changes in the return flow profile, hence undermining the reliability of kick detection. Issues can also derive from misdiagnosing a kick and attempting to kill a breathing well. The objective of this work is to correctly address the phenomenon and increase insights of its physical characterization. The fluid progressively flows in and out of fractures as a consequence of three mechanisms: (1) bulk volume deformation, (2) fluid compressibility, and (3) fracture aperture variation. To represent this complex scenario, a model involving a continuously distributed fracture network is developed. A time-dependent, one-dimensional dual-poroelastic approach is coupled with a variable fracture aperture and a passive porous phase. Finite fracture length is considered and no limitation on the number of fractures is posed. The latter permits us to analyze long open-hole sections intersecting several fissures, which is a more realistic approach than the available single fracture models. The proposed model is able to quantify pressure distribution in fractures and pores, together with the flow rate entering or exiting the fractures. When the fissured space is reduced to zero and incompressible bulk volume is considered, the solution reduces to that of classical reservoir engineering. A sensitivity analysis is performed on the physical properties of the formation and the drilling fluid. The latter provides a deeper insight on the factors that significantly influence breathing phenomena (i.e. drilling fluid weight, rheology and formation mechanical properties). Furthermore, a very useful application of the model is proposed by suggesting its application as a breathing discriminator during kick diagnosis. The shut-in drill pipe pressure, recorded from a real kick, has been compared to one caused by a simulated breathing case. Although the two SIDPPs show great similarities, the correct modelling of breathing can significantly help the identification of the major differences between a kick and breathing. Altogether, a comprehensive in-depth characterization of borehole breathing can help with kick diagnosis and can be used to effectively design unconventional drilling techniques such as Managed Pressure Drilling.
Optimizing Remote Operations Support Using an Effective Real-Time Model for Improved Drilling Performance
Authors: Robert Seth , Fiffick William , Davis Drew , Guillory Robert , Myers Joshua , Mandava Chakra 
Published: February 2018

Abstract
The wider use of robotics, remote controls, real-time remote monitoring systems, artificial intelligence, and other techniques are setting new standards of performance. The exciting culmination of these engineering and technological efforts have given us "The Rig of the Future".
However, how should we develop and manage the support systems to leverage this modern drilling technology? Do we have the people, processes, tools, and infrastructure needed to successfully apply these technologies?
The following case study reviews key elements necessary to support modern drilling, including: Real-Time Operations Centers, competent field service technicians, custom software applications, new processes and drilling performance technology. Properly applying these systems enhances drilling operations, ultimately leading to better drilling performance with decreasing non-productive time (NPT). The synergies between remote support, field operations, drilling technology, and other critical components are discussed in detail. This case study describes how the Real-Time Operations Center concept was conceived and developed. These support systems optimize field service performance by leveraging remote equipment condition monitoring, automating alerts, providing real-time rig data, and remotely interfacing key systems to improve the overall reliability of drilling operations.
As a result, many issues can be corrected remotely, decreasing average resolution times, resulting in better customer satisfaction ratings.
We discuss the necessary support processes, roles, and responsibilities. By leveraging the "Internet of Things", we achieve greater efficiencies. Augmenting the conventional roles for Field Service Technicians and other supporting functions adds additional value and efficiency. Working together, these distinct disciplines coordinate and mesh key responsibilities resulting in an "ecosystem" to support drilling operations.
While some struggle to provide systematic, comprehensive service and support models, a template of best practices has been developed and validated. This details remote operations centers, enhanced equipment technology, enhanced software applications, as well as enhanced employee development practices (for the necessary team of competent field service technicians). This model drives best-in-class drilling performance and is what "drilling rig of the future" looks like today.
Application of a New Dynamic Tubular Stress Model With Friction
Authors: Zwarich N. R. , McSpadden A. R. , Goodman M. A. , Trevisan R. , Mitchell R. F. 
Published: February 2018

Abstract
A new dynamic model for casing and tubing design with friction has been developed. This paper applies the model to a field case study, an actual installation of a single trip, multizone completion in an offshore highly deviated ERD well. This is the first application of a comprehensive model with complete friction history to both installation and in-service loads.
The field case demonstrates the results of a novel dynamic model for tubular stress and displacement with changing friction loads. Recorded hookload data during completion running and calibration of effective wellbore friction coefficients provided validation of the model. Accumulation of localized stresses at critical well locations is considered. The sensitivity of worst case downhole forces to the order of operational life cycle loads including stimulation, production and gas-lift was assessed. Stresses and displacements associated with each step of the setting process for multiple isolation packers were simulated. Theory and detailed description of the dynamic model are presented in an associated paper.
A dynamic model of tubing forces is necessary to predict local pipe velocity which in turn determines the magnitude and direction of the local friction vectors. Distribution and orientation of wellbore friction contact is determined by the pipe running events but then is subject to change as cement and packers are set and as downhole operating conditions change. Order of life cycle conditions such as stimulation followed by production versus production followed by workover has significant impact on the magnitude of forces at worst-case locations. The investigation included the change in tubing wellbore frictional contact when completion brine is displaced with dry injection gas in conversion to gas-lift. The model demonstrated the significance of a different order of linked operations and showed that the standard available analysis tools may overlook or fail to identify worst case loads. Potential for acute load localization due to successive stimulation and production events was quantified. Impact of migration of friction loads during cyclical load events was also evaluated. The predicted initial axial load profiles were verified with recorded hook loads and corroborated with standard torque and drag model results. Comparisons are made against a previously published analytical technique.
For the first time, a dynamic friction model enables seamless integration of running loads into a fully sequential analysis of subsequent well life cycle loads for landed strings. Current industry models tend to separate installation loads from the in-service life envelope. Ability to predict the changing friction orientation on installed tubulars is significant. Modelling life cycle loads in true sequence provides more accurate results for tubular design and enables a true analysis on the real-world order of well events.
Digitized Uncertainty Handling of Pore Pressure and Mud-Weight Window Ahead of Bit; Example North Sea
Authors: Lothe A. E. , Cerasi P.. , Bjørkevoll K. S. , Haavardstein S.. 
Published: February 2018

Abstract
A digitized workflow from pre-drill pore pressure modelling with Monte-Carlo approach, till update of pressure prognosis while drilling from e.g. sonic and/or resistivity data is described. The innovative approach will reduce the uncertainty in the mud-weight window ahead of the bit.
For the 3D pressure modelling, a basin modelling software method is used, where the pressure compartments in the study area are defined by faults interpreted from seismic. Key input parameters like minimum horizontal stress, vertical stress and frictional coefficients for failure criteria are varied. The output is pressure profiles along the planned well path, with uncertainties.
The work presented in this paper was carried out on a North Sea dataset. The results show that the uncertainty in the pore pressures will highly influence the uncertainty span in both the fracture gradient and the collapse gradient. Representing the mud-window in terms of a most likely collapse and fracturing curve, with on each side of both, limits the minimum and maximum pore pressure derived limits, makes for a more realistic prediction, stating the uncertainty in the result.
While drilling, log-data will be automatically used to update the pressure and mud-weight prognosis ahead of bit. The digital updated prognosis can help the drilling crew in the decision-making during drilling campaigns.
Improved Methods to Understand and Mitigate Stick-Slip Torsional Vibrations
Authors: Bailey J. R. , Payette G. S. , Wang L. 
Published: February 2018

Abstract
In this paper, it will be shown how stick-slip vibration distributions can be used to evaluate drill string and parameter redesign options to mitigate stick-slip on the next well. It will also be shown how stick-slip vibration data can be used to estimate the time interval during which the bit is stuck when operating at or beyond full stick-slip.
The torsional vibration example to be discussed in this paper is based on the distribution of stick-slip vibration data when downhole data is available, or alternatively using surface torque swing data. The operator's frequency-domain dynamic model relates torque swing at the surface to the variation in bit rotary speed, as a function of the drill string design and surface RPM. Linear relationships between this distribution function and several variables are investigated, including the critical torque swing at full stick-slip, rotary speed (RPM), and downhole torque.
The operator drilled several wells in a vibrations-prone formation, and one well had extreme stick-slip vibrations whereas another well experienced minimal stick-slip as a result of limiter redesign. An understanding of the differences in the factors that led to the vibration reduction has been generalized into a procedure that can be applied to future wells. Although prediction of stick-slip in advance of drilling is difficult, with the benefit of data from one well it is possible to determine new parameters for a second well that will have significantly less stick-slip tendency.
In a well in a different field, high frequency torsional measurements at the bit provided data illustrating the rotary speed swing of the bit stick-slip cycle, highlighting the duration of time that the bit was in the stuck condition. Results from the dynamic drill string torsional model have been compared with downhole data, and application of the dynamic model and some new relationships enable stuck time to be related to the drilling parameters. The variation in stored potential energy on each stick-slip cycle can also be calculated.
These new understandings improve efforts to redesign relevant drilling parameters to mitigate stick-slip vibrations. Historically, prediction of stick-slip vibrations in advance of drilling has been fraught with challenges. Although we know what factors influence stick-slip, and what directional changes are required to mitigate this dysfunction, there is a need for a simple methodology to quantitatively determine the degree of dysfunction and the effects of one or more redesign parameters.