bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydraulic Design of Shale Drill Bit Using an Integrated Numerical and Experimental Approach
Authors: Moslemi Ali A. , Rahmani Reza , Graham Ryan , Ivie Brad 
Published: March 2015

Abstract
Hydraulic design of drill bits for shales is challenging due to the sticky nature of the drilled formation which may cause balling. An integrated numerical and experimental approach was used to tackle this challenge. Computational Fluid Dynamics (CFD) along with a new particle tracking method was used to hydraulically design a fixed cutter drill bit for shales. Following CFD simulations, experimental tests in Pressurized Drilling Lab (PDL) were performed to validate the CFD results.
Spherical particles with diameters ranging from 0.1 mm to 10 mm were injected from cutters surface and their average velocities were calculated when leaving the drill bit using discrete particle modeling (DPM) technique. The ratio of average particle velocity to average annulus fluid velocity at a plane with one bit diameter from bottomhole, referred to as the bit Cuttings Transport Ratio (Ct), was then evaluated to study the hydraulic performance of drill bits under different conditions. Effect of nozzle orientation on drill bit hydraulic was modeled in CFD and then validated in the lab using special adjustable oriented nozzles. Furthermore, effects of nozzle count and blade height as well as flow guide on drill bit hydraulics performance were studied both numerically and experimentally.
Baseline bits with different nozzle orientations were tested in PDL. Rate of Penetration (ROP) increased up to 17% compared to the baseline bit using improved nozzle orientations. Also, it was found that higher nozzle count is helpful for drill bit cleaning improving the drill bit performance. Drill bits with different blade heights were built and tested in PDL and it was found that there is an optimum blade height which can improve the bit drilling performance. Also, the effect of flow guide on drill bit hydraulics was modeled using CFD and particle tracking method and then it was tested in PDL. Both CFD and PDL results indicated drill bit hydraulics improvement when flow guide was added to drill bit. ROP for the bit with flow guide increased 10% and 20% in high and low hydraulic conditions, respectively.
The final shale bit was designed using improved nozzle orientations, proper blade height as well as flow guide. While the final bit balling tendency decreased, the ROP increased about 35% compared to baseline bit in PDL tests indicating the significance of drill bit hydraulics in its drilling performance.
Anti-Collision Considerations for Arctic and Other High Latitude Locations
Authors: Chatar Crispin , Beck Nathan , Simeone Davide , Buchanan Andrew , Borri Luca , Occhionero Lara 
Published: March 2015

Abstract
A significant contribution that some oilfield services companies provide for drilling operators today is directional well planning. A major task in the process is to identify and analyze the risk of wellbore collisions. If there is a risk of collision beyond acceptable limits, risk management must be applied. The first part of this process is to collect data. The second step is to analyze the potential risk. The risk not only involves a financial aspect but also HSE (Health Safety and Environmental), so it is imperative that we make the right decision using the most effective tools. Failure to take the right precautions may result in potentially catastrophic human and environmental implications.
Generally this is already a complicated task. It gets particularly complicated when this is done at high latitudes and in certain wellbore orientations. Much of the industry today still believes that wellbores are represented accurately by surveys. While in the majority of cases this is somewhat true, the uncertainty and probabilistic nature of the measurement is often overlooked or misunderstood. Few people in the industry today actually understand how this translates to anti-collision also known as collision avoidance. Even fewer understand how much effect your latitude can have on this type of calculation.
This paper will address these complications. After a short overview on wellbore placement, the paper will first discuss some theory on what makes high latitude wellbore placement challenging and when is it a relevant consideration. How it relates to collision avoidance will be explained. The current gaps in the industry today will be revealed and options to close those gaps are discussed. Upcoming technologies for reducing risk are reviewed. The second part of the paper will focus on risk management; namely mitigation and prevention. Case studies will be reviewed. Common misconceptions will be eliminated. The paper will attempt to set a foundation of understanding of the fundamental important considerations for anyone involved in collision avoidance in high latitude locations such as the Arctic.
Time Dependent Borehole Stability: Effect of Static vs. Dynamic Mud Weight
Authors: Nes Olav-Magnar , Stenebråten Jørn , Fjær Erling 
Published: March 2015

Abstract
From field experience, even if a borehole is stable while drilling through a shale, it may turn unstable with time when the well is left static for a sufficiently long period of time. This may in some cases be explained by the collapse limit being located somewhere in-between the equivalent circulating density (ECD) and the corresponding static density (ESD) of the mud. In such cases, the combination of formation conditions and properties, and well conditions will determine the timing for possible onset of instability in the vicinity of the borehole wall.
We present a set of highly specialized hollow cylinder (HC) laboratory tests on a field shale core. While subject to a confining stress and an applied pore pressure, the borehole pressure has been systematically varied according to scaled-down field conditions to simulate the effect of ECD vs. ESD at connection on borehole stability. The laboratory results suggest that the mud weight (MW) may be kept below the classic static collapse limit for shorter periods of time, like those occurring at connections, without inducing borehole collapse due to low permeability, plastic nature, and time dependent strength of the shale. The borehole diameter may however gradually decrease due to irreversible plastic deformation induced during each low pressure cycle. When at total depth (TD) and the when well is left static, the ESD may have to be increased to maintain stability, compensating for the loss of ECD.
We illustrate the dynamic stability effect with a North Sea field case where the near horizontal well was stable while drilling, but turned unstable when left static for a period of time after reaching TD. The observations are compared to corresponding modelling of the time dependent stability.
This shows the importance of accounting for the potential time dependence of borehole stability while drilling through shale. The combined effect of ESD, ECD, and timing may determine whether the borehole will be sufficiently stable from an operational point of view, allowing the well to be drilled and completed without excessive problems.
Investigating the Benefits of Induced Vibrations in Unconventional Horizontals via Nonlinear Drill String Dynamics Modeling
Authors: Wilson J.K. , Heisig G. 
Published: March 2015

Abstract
Inducing vibrations while drilling is a relatively new concept that shows promise in directional applications. Instigating motion of the drill string, particularly in the sections lying on the low-side of the wellbore, can lead to substantial improvements in managing the two limiting factors of the long horizontal wells that are typically associated with today's unconventional shale plays: removal of formation cuttings from the borehole, and frictional drag between non-rotating drill strings and the wellbore wall. Minimizing these effects, by introducing controlled vibrations, increases the overall drilling efficiency and reduces the cost associated with the well. The difficulty in implementing such actions, however, is consistency. Because the behavior of drilling assemblies is inherently nonlinear, it has been difficult in the past to reliably predict their response to dynamic events. This, in turn, creates a challenge when trying to optimize the performance of arbitrary Vibration Inducing Devices (VIDs).
This paper presents a detailed analysis of the fully coupled, three-dimensional, nonlinear behavior of drill strings under the action of induced vibrations. Specific focus is given to the dynamic characteristics of a drill string, during horizontal drilling operations, in long unconventional wells and how this behavior affects the success of the well. The response of the drill string, due to induced axial and lateral oscillatory motions, is examined through linearized dynamic analysis and nonlinear timedomain simulations.
Solutions obtained from the study provide a clearer understanding of the dynamics experienced down-hole and lead to suggestions for improved practices when drilling with lateral VIDs, particularly with regards to hole-cleaning. Further insights into the sliding and rotational behavior of the drill string, while using these types of tools, are drawn from animated modeling results. Finally, the future applications of this technology are discussed.
An Experimental Study of the Swelling Properties of Unconventional Shale-Oil Rock Samples Using both Water-Based and Oil-Based Muds and Effects of Invasion on Rock Mechanical Properties
Authors: Emadi H. , Soliman M. , Heinze L. , Moghaddam R. , Samuel R. 
Published: March 2015

Abstract
Knowledge of swelling properties of shale-oil formations as well as the effects of various drilling fluids, including both water-based and oil-based muds (OBMs), which are of critical importance to wellbore-stability problems, requires a better understanding of shale-oil properties. Drilling through shale-oil formations is highly problematic and imposes substantial costs to the operators owing to wellbore-stability problems. These problems include, but are not limited to, tight holes, stuck pipe, fishing, sidetracking, and well abandonment. To more efficiently and effectively drill through these formations, we should better understand their properties.
Only few experiments have been conducted on shale-oil samples to better understand their properties. Most experiments performed thus far were run on common shale core samples, which are significantly different from shale-oil samples in the matter of mineralogy and mechanical properties. Subsequently, the results of those experiments cannot be equally applied to shale-oil and shale-gas formations.
In this study, we first determined the mineralogy of shale-oil core samples from the Eagle Ford field and then investigated the swelling properties and cation exchange capacity (CEC) of the core samples in the laboratory. Experiments have been conducted with the samples partially submerged in distilled water, potassium-chloride (7% KCl) brine, and OBM. Several experiments have been performed using strain gages to measure lateral, axial, and diagonal swelling in both submerged and non-submerged areas. We also performed unconfined compressive strength (UCS) tests to investigate the effect of the invasion of various drilling fluids on the compressive strength of the core samples. The experimental setup was modified to accommodate five linearly variable displacement transducers (LVDTs) to measure Young's Modulus (E) and Poisson's ratio (v). Various experiments were run to quantify the effect of temperature on the rock compressive strength, E, and v. Experiments have shown a distinct change in the mechanical properties of the rock. The results demonstrate that the swelling properties and CEC of the shale-oil core samples are different from the common shale core samples. This study proposes the quantification of the shale/fluid properties, the interaction, and the effects of different fluids on rock properties in unconventional reservoirs. This paper presents and documents the differences in the swelling properties between conventional and unconventional shale. The results of the study will help us to more precisely understand unconventional shale-oil rock properties and can be used to design a more effective drilling fluid for field applications, as well as more accurately predict the mechanisms of formation failure.
SMART Kick Detection; First Step on the Well Control Automation Journey
Authors: Brakel J. D. , Tarr B. A. , Cox W. , Jørgensen F. , Straume H. V. 
Published: March 2015

Abstract
In 2010, based on the safety performance results achieved through the automation revolution in its oil & gas downstream business, an operator set out to initiate the same revolution in its upstream business. Automating the initial well control response to an influx was identified as the initial focus area with the goal of assisting rig personnel to identify and stop any influx without delay. This led to a well control automation collaboration project being initiated between an operator, a rig contractor and a rig equipment supplier. The first phase of the project was to develop a system that could detect an influx across a broad spectrum of well construction related rig operations. This paper describes the development, deployment, and field testing of the first upgraded kick detection system from this collaboration.
To understand where to focus the kick detection system upgrade efforts, a fault tree style sensitivity analysis of kick detection and well shut-in procedures was undertaken. The results pointed to the high value of improved sensor data (both accuracy and reliability) and of improved detection software for alarming (both in terms of coverage and how the driller is alerted to respond to a confirmed kick condition). Based on this sensitivity analysis, a kick detection system upgrade functional specification was created and used to develop a trial upgrade plan for a deepwater rig.
Initial implementation operational performance results are presented to demonstrate that most of the kick detection system upgrade objectives were achieved.
Operational feedback from using the upgraded kick detection system is included which highlights the new, “SMART”, features that were designed to provide easily understood alerts to the driller; including unique pop-up kick alarm windows for drilling or circulating, making a connection, and tripping in or out.
Defining Fragile - The Challenge of Engineering Drilling Fluids for Narrow ECD Windows
Authors: Knox David , Bulgachev Roman , Cameron Iain 
Published: March 2015

Abstract
Over the last decade, the challenge of drilling narrow Equivalent Circulating Density (ECD) window wells has put increasing pressure on the performance of the drilling fluid. As a result of this, so-called ‘Fragile Gel’, or ‘Flat Rheology’ fluids have been developed by the industry and have become widely utilised across the globe. Although the design of these fluids is primarily aimed at optimising performance in deepwater environments, the lower pressure fluctuations imposed on the formation (as compared to more conventional invert emulsion fluids) that is attributed to these fluids has contributed to their increased use in other, non-deepwater areas, where ECD management is still viewed as critical.
Although the perceived benefits are now widely understood and accepted, the industry has not yet developed a comprehensive and universally-accepted benchmark for the properties that satisfactorily define these fluids. The authors of this paper believe this to be due to a number of factors, including the different approaches taken within the service industry in developing chemistries that either significantly reduce, or even completely replace, the requirement for conventional organophilic clay-based viscosifiers.
BP have developed an internal set of guidelines based on operational experience in regions where these fluids have been successfully implemented; however, these have limitations when universally applied, particularly as new fluids featuring novel chemistries are introduced.
This paper discusses the key engineering parameters used to define the engineering guidelines for what BP refers to as ‘Flat Rheology Fluids’. A description of these parameters and how data collected from recent field trials in Norway is being used to help refine and validate these parameters is also described.
Application of Modern Technology to a Multi-position Down Hole Drilling Electronic Circulating Valve and Integral Disconnect Mechanism
Authors: Hunter Gordon , Ollerenshaw Andy 
Published: March 2015

Abstract
There are several areas where modern technologies can be applied to improve hole conditions reducing the chances of tight hole and stuck pipe. Hole cleaning has always been a key issue in inclined and horizontal wells where cuttings bed form and can lead to time consuming, difficult hole conditions and sometimes stuck pipe when attempting to trip out the hole. Annular velocity is one of the critical parameters that can improve cuttings bed removal but power hungry BHA's and bit hydraulics can sometimes compromise the ability to provide sufficient flow rate to clean the hole. A circulating sub is often installed above the BHA that can be opened to bypass the BHA and provide maximum flow rate to clean the hole. It can also be used to dump high concentrations of LCM in a lost circulation situation that would otherwise block the BHA and bit nozzles. Almost all circulating subs are of a drop ball/dart type that has a limited number of cycles, usually 6 to 9. Balls have to be dropped to open and separate balls dropped to close. These subs have limitations when it comes to hole angle, as the balls require gravity to reach their seats. They are unreliable in inclinations above 65 deg, require surface intervention and are usually only two positions i.e. open or closed. In a packed off situation where the annulus is sealed around the BHA and circulation is prevented, the balls or dart sometimes do not reach their seat and the sub cannot be opened to try and relieve the pack off.
This paper discusses the development of a multi-position electronic circulating valve that can be set to multiple positions by surface down linking. The circulating valve can be configured as a standalone tool or combined with a unique motorized disconnect clutch mechanism that is activated by sensing its environment, working through internal logic modes before being in a position to receive a surface signal to disconnect. This has application in a stuck pipe situation where the tool can be commanded to disconnect and the drillstring recovered avoiding the need for surface intervention and any form of wireline and explosives. This tool has application in any well but particularly high angle wells where the circulating valve can be down linked to the first position for partial BHA bypass increasing annular flow and the final, maximum bypass, position can be used for dumping LCM or fast wellbore clean up at section TD or at any point in the well. Deepwater operations with spread rates in excess of $1M per day can benefit from the time savings in wellbore clean up, response to lost circulation and flexibility and control in a stuck pipe situation without waiting for wireline crews or explosives to perform a disconnect.
Casing Collapse Strength Enhancement Due to Cement and Pipe Support via Modelling and Testing
Authors: Jammer Peggy , Hariharan Hari , Klever Frans J. 
Published: March 2015

Abstract
The API 5C3 collapse strength formulas are widely used in the industry for casing design. While these formulas provide estimates of the collapse resistance of pipe alone, they do not consider the supporting effect of cement sheath, outer steel pipes, or formation. Given the increasing complexity of the industry's wells, as well as the importance of safety, the ability to accurately assess a well's risk is becoming more and more important. This study aims to facilitate such a reliability-based design approach by investigating the collapse strength of a pipe-cement-pipe system.
A finite-element analysis (FEA) model was developed and used to analyze collapse behavior for various configurations and loading scenarios: casing only, or casing cemented into casing; possibly incomplete cementing scenarios; loading by annular pressure and/or external pressure; collapsing the inner pipe, outer pipe or the composite. The FEA results were benchmarked against a full-scale experimental program.
The study focused on an 11 ¾ in. 65 lb/ft P-110 HC casing cemented into a 13 ⅝ in. 88.2 lb/ft Q-125 casing, and the results clearly and consistently indicated the supporting effect of the cement sheath in providing improved collapse resistance of the casing (even with varying degrees of void in the cement). Experimental results showed an increase over the pipe-only collapse strength of about 60% (pipe-cement-pipe, annular pressure collapsing the inner pipe) or about 260% (pipe-cement-pipe, external pressure collapsing the composite pipe), for a perfectly cemented condition. The FEA results tracked the experimental values of pressures with a satisfactory degree of accuracy, while evaluating loss of collapse strength enhancement as the cement void angle increased.
The procedures and results presented in this paper may be used to assess the true risk of collapse of casings deeper in the well under worst case discharge (WCD) conditions.
Drilling Depleted Sands: Challenges Associated With Wellbore Strengthening Fluids
Authors: Chellappah Kuhan , Kumar Arunesh , Aston Mark 
Published: March 2015

Abstract
One way of overcoming the challenge of drilling depleted sands is to use so-called “wellbore strengthening” (WBS) techniques, whereby engineered particles are added to drilling fluids to increase the fracture initiation or propagation resistance. Although the mechanisms are not comprehensively understood, most explanations suggest that an increasing proportion of large particles is required to achieve a greater extent of ‘strengthening’. These large particles can create practical challenges while drilling; such as particle attrition, settling, and erosion of equipment. Field examples are presented which highlight these issues. Experimental work to identify solutions to the practical challenges is presented. A laboratory attrition test developed in-house confirms walnut shell as a promising material to resist grind-down when large particles need to be retained in the system. Formulations prepared using controlled size distributions of this material are shown to give a good fracture sealing performance in the laboratory. The accurate maintenance of particle size will require regular solids monitoring at the rigsite to keep the fluid within design specifications. Some data from real-time particle sizing techniques are presented. Overall, the findings presented in this paper should lead the industry towards wellbore strengthening systems which are effective, more efficient and practical operationally.