bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of Decalin and Metal Nanoparticles-Assisted Bitumen Upgrading During Catalytic Aquathermolysis
Authors: Hendraningrat Luky , Souraki Yaser , Torsœter Ole
Published: June 2014

Unconventional oil reservoirs such as heavy oil, extra heavy oil, oil shale and oil sand/bitumen are very interesting since these kinds of oil are currently proven to constitute a huge amount of total world oil reserves. However, it is difficult to handle these kinds of oil due to very high viscosity. Thermal application methods may have great possibilities for heavy oil and bitumen production. Prior to shipment to downstream markets, the bitumen needs to be upgraded to produce higher value of liquid hydrocarbon products. However, the issues in oil sands industry are environmental challenges such as green-house-gas (ghg) emission, huge amount of fuel and water consumption, liquid and solid wastes disposal. The objective of this study is to investigate an effective and efficient upgrading process by adding decalin as hydrogen donor, water and various type nanometal particles (40-500 nm) as catalysts into Athabasca bitumen.

Athabasca bitumen has been successfully upgraded by reducing its viscosity about 80% (measured at 60 °C) by applying catalytic aquathermolysis at 240 °C during 12 hours. As hydrogen donor, decalin is very interesting. Besides cheap, it could dramatically accelerate viscosity reduction with concentration of 5 wt.%. The degree of viscosity reduction will increase with increased decalin concentration. However degree of bitumen upgrading will decrease with presence of water. It seems that synergetic effects to the upgrading process did not work effectively. Hence water consumption during aquathermolysis process might be reduced to minimize the cost. Since earlier studies have shown that nanoparticles may reduce heavy oil viscosity, four types of nanometal particles have been studied and some of them accelerated viscosity reduction during catalytic aquathermolysis process at particular concentration. Improper nanometal particle type and concentration are reversed effect. Temperature and heating time have vital role in the upgrading process.
Seismic Frequency Versus Seismic Interval Velocity Based Pore Pressure Prediction Methodologies for a near Salt Field in Mississippi Canyon, Gulf of Mexico: Accuracy Analysis and Implications
Authors: Mannon T. , Salehi S. , Young R.
Published: June 2014

Oil and gas plays are continuing to move into increasingly hostile drilling environments, including near and/or sub-salt proximities. The ability to reduce the risk and uncertainly involved in drilling operations in unconventional geologic settings starts with improving the techniques for pore pressure modeling. Nearly all of the modern day pore pressure prediction methods utilize interval velocities from seismic surveys to detect abnormal pressure along a proposed wellbore trajectory. Seismic interval velocities have long been known as being sensitive to formation properties such as lithology and porosity which may give way to erroneous pore pressure values; additionally, salt intrusions have proven to be a significant hindrance when predicting pore pressure from seismic interval velocities. A relatively new approach, which predicts pore pressure by way of seismic frequencies, has addressed the pitfalls seen in seismic interval velocity applications. With the goal of offering a valid seismic-based alternative to pore pressure prediction, a study has been conducted in a near-salt field in deepwater Gulf of Mexico that will compare and analyze the accuracy of seismic frequency versus seismic interval velocity based methodologies for pore pressure prediction. For the first time in the literature, the outputs between the two seismic models will be quantitatively assessed for accuracy. Accuracy standards will be based on the agreement of the seismic outputs to pressure data obtained while drilling and petrophysically based pore pressure outputs for each well. The results will show significantly higher accuracy for the seismic frequency based approach in wells that were in near/sub-salt environments and higher overall accuracy for all of the wells in the study as a whole.
New Generation of Sour Service Drill Pipe Allows Addressing Highly Sour Field Challenges
Authors: Rodrigues Ricardo , Flores Vincent , Thomazic Aurelie , Thebault Florian
Published: June 2014

With the increasing demand of gas worldwide, some highly sour oil and gas reservoirs have been explored in Russia, Middle East, China and North America. The development of such fields, which contain a high percentage of sour gas, represents significant technical challenges regarding drill pipe integrity and operations safety. Sour service drill pipe have long been used with tool joints and tubes meeting separate criteria for sour service as defined by several industry standards. This solution is still acceptable today for most of the current fields. However, the new challenges associated with the particularly sour fields require new highly engineered drill string solutions in order to increase the safety margin related to Sulfide Stress Cracking (SSC) failure risks, especially in the welded zones.

Drill Pipe are commonly produced by assembling pipe and tool joins through friction welding. The weld, as a result of this process, presents, nevertheless, some challenges for preserving SSC resistance due to some metallurgical factors such as heterogeneous microstructure, different chemical compositions between the tool joint and the pipe body and high hardness values close to the welded line. Hence a new drill pipe configuration has been developed including modified chemical composition and modified manufacturing process. These modifications allow for the improvement of mechanical properties performance and SSC resistance in the welded zone.
Fracture Gradient from Leadoff Test: Pitfalls of Using LOT Data from Non-vertical Wells
Authors: Rai Udai Bhan , Ghodke Nikhil , Schutjens Peter , Shete Kaustubh
Published: June 2014

Leak off tests (LOTs) are a routine in the drilling industry, typically conducted after drilling a few feet below a new casing shoe. The leak off pressure (LOP) recorded during a LOT primarily establishes the upper mud weight (MW) limit for the next hole section. Additionally, it can help to determine the cement integrity and the minimum total principal stress, which is close to the minimum horizontal stress in normal or strike slip faulting regime. The maximum operating mud pressure is usually maintained slightly lower than the LOP to permit safe well-control operations.

Field-wide LOP data generally show some spread at a given depth. The lower bound trend of LOP data is often used as the base case for fracture pressure prediction and for planning of future wells. For the field under investigation, values of LOP obtained at the 9 5/8" casing shoe showed a scatter of 1200 psi (3 ppg mud weight equivalent). The average depth of the casing shoe is ∼7900 ft and the LOTs are spread over a depth interval of only 260 ft.

Taking the lower bound of a wide spread in LOT data for fracture gradient estimation may lead to an overly conservative well design, because the difference between the pore fluid pressure and the LOT-based fracture pressure is (too) small. This so-called "small drilling window" can constrain casing design and mud weight. For example, when exploring deeper HPHT prospects, an excessively low (so conservative) fracture pressure estimate may increase the number of casing strings needed to reach the target. This can significantly change the well and drilling economics, and put the exploration/drilling plan at risk.

The study investigated the scatter seen in the LOPs to understand the cause of scatter in terms of rock mechanics, well trajectory and in-situ stresses. The redistribution of stresses around the borehole is known to depend on the orientation of the borehole with respect to in-situ stresses. This affects the measured LOP. Using rock mechanics models and field data, the study confirmed that LOP measured in inclined wells may need an adjustment (numerical correction) prior to use for predicting fracture pressures for future wells with a different trajectory (inclination and/or azimuth). The study also provides an understanding of the cause of losses reported in some wells in the field.
Threat and Error Management: The Connection Between Process Safety and Practical Action at the Worksite
Authors: Thorogood JL , Crichton MT
Published: June 2014

High Reliability Organisations have five important characteristics: a preoccupation with failure, a reluctance to simplify, sensitivity to operations, resilience, and a respect for expertise. Experience from recent incidents suggests that these qualities may generally be lacking in organisations that manage drilling operations today. Research sponsored by OGP and others has suggested that creating a sense of ‘chronic unease’ in relation to barrier integrity and operation of safety-critical systems, combined with understanding of the psychological issues that create error-producing conditions, will strengthen defences against major accidents occurring. The question remains as to the best way to embed the necessary skills through teaching, coaching, and assessment and their integration into routine working practices.

Experience from aviation suggests that successful implementation of non-technical skills needs to be combined with a clearly defined operational framework. Such an operational framework, however, is not widely observed in the drilling community at present. A standardised approach that defines how drilling operations are to be executed, activities monitored, decisions made or changes managed in a time-constrained environment provides the context in which the necessary individual and organisational skills can be taught. Training needs to address the underlying psychological theory, in particular cognitive biases, of non-technical skills to counter threats and errors in the workplace.

The paper summarises the principles of high reliability organisations and their contribution to process safety in the context of drilling operations. Next, we describe Threat and Error Management, which evolved from aviation-based Crew Resource Management to produce the levels of safety that today we accept as normal. We introduce operational risk management in drilling as the analogous link with aviation. The paper concludes by illustrating how these concepts can be used in drilling operations to enhance routine risk management activities, and will describe the tools and techniques involved.

The advantage of this approach is that effective non-technical skills can be observed, coached and assessed on a routine basis in the workplace. Active use of these methods in every-day drilling operations promotes the essential characteristics of a high reliability organisation by instilling the sense of chronic unease and concern for barrier integrity, thereby reducing the chance of minor anomalies cascading into major accidental events.
High-Frequency Torsional Dynamics of Drilling Systems: An Analysis of the Bit-System Interaction
Authors: Jain Jayesh R. , Oueslati Hatem , Hohl Andreas , Reckmann Hanno , Ledgerwood L. W. , Tergeist Mathias , Ostermeyer G. P.
Published: June 2014

Recent advances in downhole vibration monitoring have enabled detection of high-frequency torsional oscillations (HFTO) of drilling systems in the field. The general understanding of torsional behavior of drilling systems derived from elaborate efforts in the literature does not explain the mechanism responsible for HFTO. Even for the well-known and extensively studied stick/slip vibrations, the mechanism perpetuating the vibrations is not agreed upon by researchers.

The paper discusses findings from experimental and analytical studies regarding the HFTO of bottomhole assemblies (BHAs). The phenomenon is investigated and reproduced in field tests, full-scale laboratory tests, and computer modeling. Drilling conditions are identified in which the drilling system is prone to exhibit the vibrations. Interaction of the bit and the drilling system, which can generate self-excited vibrations, is investigated using analytical methods. Cutter-rock interaction as a possible excitation source is studied using laboratory experiments to elucidate its interaction with the system.

The integrated analysis investigating rock, cutter, bit, and BHA interaction identifies HFTO as a bit-induced BHA torsional resonance that can occur at vibration modes higher than the fundamental mode of the BHA. It is demonstrated that modes most susceptible to exhibiting HFTO can be identified and the dominant mode predicted. The understanding gained can be employed to mitigate torsional resonance and enhance drilling performance.
Improving Safety Through Logic: Programmable Logic Controller for Conventional Casing Running Equipment
Authors: Naill N. , Madgwick S. , Bratten C. , George M.
Published: June 2014

Running casing with conventional equipment is a labor intensive process requiring multiple personnel on the rig floor. Due to the dynamic environment of running casing with this equipment, there is elevated potential for accidents. Two specific operational hazards associated with hydraulic power tong operations (the "mule kick" and "rattlesnake") have been addressed, and the authors are developing solutions to mitigate future related incidents. A new system, utilizing a programmable logic controller (PLC) and position sensors, as well as hydromechanical and electromechanical devices, has been devised to reduce the chance for injury and enhance safety for casing power tong operators. Risk mitigation through engineered safety controls is a primary objective for service companies, and the operators and contractors they work with.

Hydromechanical, electromechanical, and electronic control (PLC) devices for land-based, conventional casing equipment are under development and revision. These devices are being customized for incorporation into power tongs and hydraulic power units. In conventional operation of power tongs, the power unit modulates the amount of hydraulic power provided to the tong based on required flow rate and pressure. The PLC provides the ability for electronic communication between the power tong and power unit, virtually eliminating lag in response time. The logic control can also determine, based on the magnitude of tension in the backup line, if the tongs are actively in make-up or break-out mode. These devices under development will prevent the violent backlash and stored energy associated with the "mule kick" and "rattlesnake". In addition, due to the flexibility of the system, Human Machine Interface (HMI) screens can be provided to adapt the system to changing conditions.

The application of the logic controller and mechanical devices on land-based, conventional casing running equipment is a significant step in reducing operator and equipment error, and increasing the casing crew's safety threshold. This paper will discuss the evolution of this system, from conception to application.
A Method to Evaluate Lost Circulation Materials—Investigation of Effective Wellbore Strengthening Applications
Authors: Savari Sharath , Whitfill Donald L. , Jamison Dale E. , Kumar Arunesh
Published: June 2014

With increased drilling activity in deeper, harsher, and more complex environments, controlling non-productive time (NPT) during drilling is critical to lowering the cost of well construction. Lost circulation (LC), one of the main contributors to NPT, is a widely discussed topic drawing industry attention, as is evident from recent publications and forums/workshops on the topic. The literature on LC reveals several means of mitigation, ranging from the simple use of Lost Circulation Materials (LCMs) to the use of gunk/chemical sealants and methods for altering near-wellbore stresses (stress caging or wellbore strengthening). There is a subtle difference between lost circulation and wellbore strengthening, and any research should help facilitate a better understanding of the two.

Presented previously (Kumar et al. 2010; Savari et al. 2012) were novel insights into LCMs for wellbore strengthening applications. Continuing the research effort, this paper discusses another approach for designing LCMs to withstand higher wellbore pressures within a fracture. A property of Plug Breaking Pressure (PBP) was determined for different LCM combinations using a permeability plugging apparatus (PPA) with tapered slots. LCM combinations with differing mechanical properties behaved differently when compared using the PBP data. Particles, such as ground marble (GM), alone were not able to plug the tapered slot and hence the PBP was zero. Based on the previous work described by Savari et al. (2012), the addition of resilient graphitic carbon helped with plugging the tapered slot, with a PBP of approximately 900 psi. Adding fibers to the LCM combination was also evaluated. Plugging did not improve when fibers were added just to one other type of particulate LCM. But, the combination of ground marble, resilient graphitic carbon, and specific fibers was found to provide the most efficient plugging with the highest PBP of approximately 2,100 psi.

This work confirms that all LCMs are not equal and that the LCM type plays a role in terms of both plugging and "toughness" that better withstands displacement pressures. It also validates that, most of the time, combinations of LCM work more effectively compared to using just one type alone. The novel PBP data on different LCM combinations can provide a qualitative comparison of their ability to withstand displacement and/or failure pressures when designing LCM combinations in wellbore strengthening applications.
How can the Petroleum Industry Benefit from Human Reliability Analysis?
Authors: Li Yuandan , Cho Joseph J. , Ren Yali
Published: June 2014

In the petroleum industry, the study and impact of human reliability on safe and efficient operations is receiving heightened awareness. According to recent studies, human errors contributed to an estimated 60 to 90 percent of all accidents across many industries (petroleum, nuclear and aviation industries, etc.).

Human errors can result in two possible outcomes of concern: safety risks and the cost of failure. In operations where the consequences of accidents may be unbearable, the emphasis on safety drives the study and research of human reliability. This effort has led to a number of human reliability analysis (HRA) methods, and they provide useful references for managing human errors.

This paper examines how the petroleum industry could utilize and benefit from the available HRA methods by applying them to daily operations. Several HRA methods are reviewed in this paper from three aspects: human error identification, human error prediction of given tasks, and factors that contribute to human errors. A good data collection system can substantially support the HRA study qualitatively and quantitatively. This paper also introduces a practice for human error data collection that was implemented in the nuclear industry—human event repository analysis (HERA). Suggestions and remarks are provided about developing similar human error data collection systems tailored for the petroleum industry. The expected benefits of HRA include a better understanding of the causes and influencing factors of human errors in specific operation conditions, and insights into error-reduction measures for reducing accident risk and the cost of product failure.
Drill Cuttings Re-Injection Well Design and Completion: Best Practices and Lessons Learned
Authors: Gumarov S. M. , Shokanov T. A. , Simmons S. , Anokhin V. V. , Benelkadi S. , Ji L.
Published: June 2014

As part of the well drilling and completion process a significant amount of waste streams including drill cuttings, discarded mud, completion brine, oily drains, and residual pits volume are generated. These waste streams must be properly handled, treated and disposed of in a most environmentally friendly and compliant manner.

Drill cuttings sub-surface injection, or Cuttings Re-injection technology is one of the major widely used drilling waste management techniques in most global E&P areas and represents a process of degrading drill cuttings, mixing into slurry and injecting into the subsurface via pumping at pressure exceeding the formation's fracturing pressure gradient. As any subsurface operation the Cuttings Re-injection has its own inherited risks and complexities which must be proactively addressed via comprehensive front-end design to minimize those risks and potential eventualities. These risks and complexities are predominantly applicable to injection wells – a core asset in the injection system and key to the success of the entire drilling campaign.

Industry literature cites general guidelines for a safe cuttings injection well design and completion practices; however, this paper addresses and discusses different options, compares pros and cons and shares some best practices and lessons learned from large-scale injection projects. Topic included are: optimum tubing and casing design, solids settling and wellbore displacement efficiency in deviated wells, tubing erosion assessment and field observations, cement bond resistance to pressure-temperature cycles supported by surveillance results and perforation. This paper was developed based on challenging experiences in a broad practice as a cuttings re-injection international service provider and intends to complement previously published general guidelines with practical examples.
Advancing Deepwater Kick Detection
Authors: Johnson Austin , Leuchtenberg Christian , Petrie Scott , Cunningham David
Published: June 2014

Numerous developments in automation have made the modern mobile offshore drilling unit a marvel of engineering achievement and a model of efficiency. Yet, even with the surge in advancements, kick detection, which can be comparatively elementary for a fixed drilling unit, has proven significantly more difficult to master on a vessel which subject to wave motion and currents. A lack of consensus on universal standards and regulations have left kick detection largely ignored. But further, the lack of innovation has been coupled with drilling in greater water depths which are subject to the use of longer risers with greater volume and weight. Thus, in addition to the complications of dynamic environments are the material requirements to properly intervene during an influx event. Operators and shipyards have kept pace with these material issues by designing larger, smarter vessels with greater capacities and better controls systems to cope with the complexities of drilling in deepwater environments. Despite the best efforts and ballooning costs, influx events continue to occur because an operating envelope and a universal philosophy for deepwater kick detection have yet to be established.

With the primary driver for deepwater and ultra-deepwater drilling being to access the most productive formations possible, a recipe is formed such that a slight variation between formation pressure and fluid pressure has the potential to draw a significant hydrocarbon volume into the well bore. When well control procedures are initiated, a series of checks take place which, though proven and reliable for detecting kicks, consume valuable response time and potentially aggravate the initial problem. After an influx has been confirmed, remedial work often takes days and sometimes weeks to recondition the well for drilling. Whether in terms of personnel, equipment, facility, environment, or finance, the risk presented to the drilling operation by influx and loss events is substantial. Therefore, an advanced approach should be adopted which views kick/loss detection as a safety critical measurement and incorporates a modern, control system based design philosophy with established methods to overcome shortcomings.

This paper will describe experiences, challenges, and approaches to solving the problems related to creating an advanced early kick detection system suitable for floating mobile offshore drilling units. Necessary components, operational considerations, and design limitations will be discussed. Additionally, a discussion will offered on the current state of regulatory requirements related to kick detection and considerations for future standards.
The Need for High-Frequency Vibration Measurement Along with Dynamics Modeling to Understand the Genesis of PDC Bit Damage
Authors: Oueslati Hatem , Hohl Andreas , Makkar Navish , Schwefe Thorsten , Herbig Christian
Published: June 2014

Drilling vibration can be harmful to the bit and the bottomhole assembly (BHA), resulting in damage and tool failure and subsequent non-productive time (NPT). Bit damage while drilling offshore is costly, and any improvement in bit life can save multiple unplanned trips and lead to savings for operators. Consequently, dynamic dysfunctions have been the focus of industry research to understand and mitigate their effects.

In this paper, the authors present a field case study from an offshore application. A high-frequency, in-bit sensing device (1400-Hz sampling frequency) was installed into the bit shank in conjunction with a well-established measurement while drilling (MWD) tool in the BHA. The intent was to capture the dynamics behavior of the BHA and the dynamics directly at the bit. Multiple measurements along the BHA gave a better understanding of the behavior of the entire drilling system. The measurements were then used, along with dynamics modeling and simulation, to correlate bit and cutter damages with instances of backward whirl and stick/slip. The developed kinematic model of whirl corroborated well with measurements and showed how polycrystalline diamond compact (PDC) cutters can exhibit relative backward motion that potentially leads to severe cutter damage. The extended frequency range of the measurement module also enabled the capture of new dynamics phenomena at much higher frequencies than are usually reported in literature.

The insights gained in bit dynamics and cutter damage helped to improve bit design by building dynamically stable PDC bits with increased rate of penetration (ROP) and reduced NPT. The need for high-frequency measurements is also discussed and the benefits are presented, i.e., avoiding bit design iterations around misunderstood vibration issues. In today's challenging drilling applications, the measurements are important in characterizing the harsh drilling environment and understanding high-frequency dynamics phenomena that are rarely measured or discussed.
A Step Change in Deepwater Test Operations with Downhole Wireless Telemetry
Authors: Maizeret Pierre-David , Keidel Conrado , Nwagbogu Ifeanyi , Vannuffelen Stéphane
Published: June 2014

Drillstem tests provide crucial information about well deliverability and reservoir characteristics, but gathering such critical data may require many days of rig time, which can be prohibitively expensive in deepwater environments. As the information gathered during the test is generally available only when the string is pulled out of hole, well test engineers are usually conservative when designing the duration of the flow and shut-in periods to ensure sufficient data is acquired to meet test objectives. However, in some cases, the planned test durations were not sufficiently long to capture the necessary reservoir data for interpretation.

A relatively common practice of obtaining bottomhole data before the end of the test is running a conventional surface readout (SRO) system on electrical cable to establish communication with the bottomhole gauges, but this technique may pose a major risk to the operations. Recently developed wireless downhole reservoir testing systems can be the solution to this challenge. The system transmits information to and from the bottomhole tools in real time with no risk to the drilling operations.

This paper describes a field case where such a system was used on a deepwater well offshore Brazil. The wireless telemetry system took less time to rig up than wireline equipment and allowed the test sequence to be adjusted during the test. The data was available during flow and shut-in periods. It was used to monitor cleanup efficiency in real time as well as to obtain key reservoir information before ending the test. The reservoir engineers were able to

■ observe perforating guns' effect on pressure and confirm dynamic underbalance ■ compute productivity when the well was flowing ■ validate that sufficient data was acquired during the initial and main buildup periods ■ eliminate the need for a wireline run ■ establish reservoir pressure after the initial postperforating flow period.

The paper reviews the benefits and limitations of the current technology and makes recommendations on how to use the technology most effectively.
Modeling Method to Estimate the Casing Wear Caused by Vibrational Impacts of the Drillstring
Authors: Samuel Robello , Kumar Aniket
Published: June 2014

The increasing complexities of wellbore geometry imply an increasing potential of damage resulting from casing wear downhole. Much work has been performed to quantify and estimate wear in casing; however, the results of such predictions have been mixed. While the locations of critical wear areas along the casing string have been predicted fairly accurately, quantifying the actual amount of wear itself has been a challenge. The existing casing wear models were developed only for static wear conditions, where there is constant rotational contact between the tool joints and the inner wall of the casing. However, drilling activities and operating conditions have advanced rapidly, leading to several other downhole wear mechanisms contributing to casing wear.

The casing wear predicted using these static models cannot correctly estimate the actual volume of the wear, thus resulting in several different studies being conducted to improve the accuracy. This study is aimed at exploring and modeling one of the contributing factors to casing wear—wear caused by vibrational impacts of the drillstring on the inner wall of the casing. Impact wear in casing strings is observed at certain rotational speeds when the drillstring experiences resonating frequencies that lead to dynamic vibrations. These high-frequency vibrations generate an impact force acting on the inner casing wall as a result of the drillstring contact and thus influence the casing wear.

An analytical model to estimate and quantify the wear caused by drillstring impact is presented as a more comprehensive casing wear model. Various impact force models were considered in this study to better understand this phenomenon; namely, the parabolic model, the elliptical model, the cosine model, and the positively skewed force distribution model.

The different impact force distribution models were then applied to estimate downhole casing wear caused by impacts, and the estimates were compared to the linear static wear. As previously mentioned, static wear occurs because of continuous contact of the casing and the drillstring along a certain portion of the wellbore. Impact wear occurs over and above static wear, and the combined effect of both provides an improved prediction of the actual wear in casings downhole. This paper presents a field example to estimate the casing wear caused by impacts using a simulated case study. Estimation of the depth of the wear groove using the new casing wear model was alsoperformed using field drilling parameters and is presented as well.
Real-Time Operations Support for Geographically Dispersed Operations
Authors: Kucs Richard , Lehnert Wolfgang , Thorogood John , Spoerker Hermann , Whatson Neal
Published: June 2014

Presentations on real-time drilling support activities have been focused on large-scale operators or service companies that have full-time dedicated centers serving multiple rigs. These are staffed on a full-time basis with specialist monitoring teams and are supported by an extensive integrated communications infrastructure.

This paper addresses the problem faced by an operator working on a much smaller scale needing to provide a few geographically dispersed rigs with the benefits of real-time support technologies through high quality communications and a clearly defined workflow involving collaborative working between the rig, operations office and the head office in Europe. We describe how the real-time systems were implemented for a number of global drilling operations without installing a real time operation center. A case study of implementation in one area is presented.

This approach enabled the decision makers in the field to access the experience of and support from the rest of the organization. The global real time collaboration environment allowed the specialists to direct their attention, as required, to operations most in need of support at any particular time. By not installing a real-time operations center, the organization saved resources and encouraged the local teams to use the analysis tools themselves to manage their operational performance.

The head office organization provided technical and administrative support. It facilitated the design of the workflows and set common standards for the IT and communications architecture. The workflows were essential in order to create a structure for using the software tools within a local drilling team and to make sure that problems were detected as early as possible. The workflows aimed to strike a balance between not allowing early warning signals to be overlooked while giving the operations team the freedom to responsibly manage the operation on the rig. Through the way that the system and the workflows were used on a daily basis, the rig personnel gained confidence that the system was set up purely to support them and for their benefit. The design and the implementation of these workflows utilized industry-leading real time drilling data analysis and drilling support tools.

When difficult operational problems were encountered, by acting as a knowledge broker, the central organization drew from its world-wide skill pool to organize problem-specific multi-disciplinary support for problem-solving, peer review and functional sign-off for program changes. These "on-call" teams ensured that the knowledge of the organization was leveraged and experience shared. It enabled the head office organization to provide resources to assist in following up the analysis of positive and negative events will be done properly and result in lessons learnt and updated best practice.
Nanosilicas as Accelerators in Oilwell Cementing at Low Temperatures
Authors: Pang Xueyu , Boul Peter J. , Jimenez Walmy Cuello
Published: June 2014

Accelerators are important cementing additives in deepwater wells where low temperatures can lengthen the wait-on-cement (WOC) time, potentially increasing the cost of operations. The cement-set accelerators traditionally used for shortening WOC times are inorganic salts, such as calcium chloride (CaCl2). These accelerators are known to have the potentially negative side effect of increasing the set-cement permeability. Nanosilicas, on the other hand, can be advantageous compared with conventional cement-set accelerators because they reduce the permeability and increase the mechanical strength of cement-based materials. For this reason, nanosilicas are known to be particularly good candidates as replacement materials for traditional salt accelerators.

This study investigates the feasibility of the use of different sizes and aspect ratios of nanosilicas as cement hydration accelerators under low-temperature conditions of 59°F (15°C). The nanosilica activities are herein defined through their comparative advantages with respect to traditional accelerators, as well as through the advantages and disadvantages of the different nanosilicas resulting from their various sizes and shapes. Although hydration of oilwell cement is known to be accelerated by the addition of nanosilica, the effects of nanosilica particle shape on cement hydration kinetics has not been previously investigated. The isothermal calorimetry experiments conducted in this study reveal that just as smaller nanosilica particle sizes increase the cement-set acceleration, so do higher nanosilica aspect ratios.

The effects of slurry density on the relative merits of CaCl2 and nanosilicas are also investigated. In regular-weight slurries, the effectiveness of nanosilica acceleration appears to be weaker than that of CaCl2, especially during early ages (≤ 3 days). In lightweight slurries, the effectiveness of nanosilica acceleration can be much stronger than that of CaCl2, especially when mid- to long-term properties (≥ 2 days) are considered. Smaller particle sizes and higher aspect ratios enhance the acceleration effect of nanosilicas. The compressive-strength development of lightweight oilwell cements with and without accelerators was also investigated. Lightweight cements accelerated with nanosilica displayed 7-day compressive strengths up to 136% higher than those accelerated with CaCl2.
Case Study of Weak Signals and Confirmation Bias in Drilling Operations
Authors: Thorogood J. L. , Crichton M. T. , Bahamondes A.
Published: June 2014

The paper presents a case study of the circumstances leading up to a situation where a supposedly vertical well ended up at 14° before the deviation was detected and a correction could be made. This case study illustrates how a relatively routine activity could end up off the plan, and also highlights the impact of weak signals and confirmation bias on the situation.

Process safety has become a focus of attention, with much work done to ensure that organisations are educated and trained in the techniques necessary to avoid catastrophic incidents. Human error has come under the spotlight and "human factors", including non-technical skills, are being included into training programmes, such as well control. However, the language around human factors, and the psychological terms used, such as "cognitive bias", "chronic unease" and "weak signals" are abstract and unfamiliar to the drilling community.

Furthermore, limiting human factors training to well control suggests that non-technical skills are only required during abnormal events. Yet, as this case study will show, developing these skills in general brings benefits in avoiding what might be regarded as "normal" non-productive time incidents.

By describing a real and very recent wells incident, the paper shows how the same set of circumstances can be investigated from several different perspectives and how different conclusions about root cause can be drawn depending on the agenda of the investigator. There is no doubt that no single perspective fully explains what happened in this incident, and why, but traditionally there is little evidence of a human factors perspective being adopted during incident investigations beyond the use of the label of ‘human error’.

The paper will show how, without the benefit of hindsight, the rig team made a perfectly reasonable set of decisions under the circumstances with which they thought they were being confronted. There was evidence in some of the data to suggest that the well was deviating from the vertical, but there were competing pressures on the team for them to disregard the warnings.

While there are certain obvious procedural and technical lessons to be drawn from the event, deeper lessons relate to the difficulties associated with overcoming the tendency to see what is expected and the central role played by leaders to support and commit to the time and cost of precautionary actions.

It is hoped that the paper will encourage the drilling community to look beyond the apparent interpretations of an event to consider why it was that otherwise sensible people did what they did. There are many incidents of this type from which the community can learn at relatively low cost, particularly focusing on the human factors aspects. Yet, the learning from these incidents, and the training to avoid them will, ultimately, develop the skills that will be instrumental in helping teams identify and react to conditions that might otherwise develop into a catastrophe.
Application of In-House Prepared Nanoparticles as Filtration Control Additive to Reduce Formation Damage
Authors: Contreras Oscar , Hareland Geir , Husein Maen , Nygaard Runar , Alsaba Mortadha
Published: June 2014

Nanoparticles (NPs) are currently being studied as a drilling fluid additives especially for application in very low-permeability formations such as shales. Application for conventional permeable rocks is still a subject of discussion. In this work, successful application of in-house prepared iron-based nanoparticles (NP1) and calcium-based nanoparticles (NP2) to reduce filtration loss in conventional permeable media has been experimentally quantified for oil-based mud (OBM) utilizing the high-pressure high-temperature (HPHT) filter press at 500 psi and 250°F. Ceramic discs were used as the filtration medium in this application to test the performance of the NPs and glide graphite as a conventional lost circulation material (LCM) for porous media. These experiments were carried out in the presence of graphite at low and high concentrations. Filtration reduction trends were observed and a reduction up to 76% was achieved. API filter press was also used to investigate the behavior of NPs and graphite under low pressure and temperature conditions (LPLT). NP1 and NP2 at the two graphite concentrations showed a reduction up to 100%.

NP1 gave higher reduction especially at low concentrations under HPHT conditions, while NP2 yielded significant reduction at high concentration under HPHT. These trends were reversed under LPLT, giving a new insight on NPs performance under different pressure and temperature conditions. At HPHT and LPLT, the effect of graphite as a filtrate reduction agent is less significant as the NPs concentration increases. High graphite level had a positive effect on filtration reduction in combination with NP1 at HPHT and LPLT. This was not the case for the blends containing NP2 at HPHT. The effect of NPs and graphite was tested individually showing a different performance compared to the combination of them. Impact of NPs and graphite on rheology was also quantified allowing identification of the more sensitive parameters in the blends. It is concluded from this study that blends containing NPs and graphite can be successfully implemented in OBM to minimize formation damage in porous media.
Using Water to Control Water in Underbalanced Drilling With Nitrogen
Authors: Guo Boyun , Zhang Hui , Feng Yin
Published: June 2014

Underbalanced drilling (UBD) has been recognized as an effective technique for reducing formation damage and finding new discoveries of oil and gas reserves in Southwestern China. However, the excess production of formation water in UBD has hindered the application of this technology in several other regions. The rate of formation water production increases with the gas injection rate that decreases bottom hole pressure. Adding water to the injected nitrogen stream can moderate bottom hole pressure and thus mitigate the water production problem. Optimizing nitrogen and water injection rates to depress formation water production requires accurate prediction of water influx from the formations under various drilling conditions. Currently there is no rigorous method that can be used to perform such a task with adequate accuracy. This paper helps fills the gap.

The NODAL analysis technique traditionaly employed in oil and gas production forecast was introduced to UBD in this work to predict water influx rate and optimize nitrogen gas and liquid injection rates. This paper presents analytical models and solution procedure that are necessary for performing NODAL analysis in nitrogen-UBD design. Inflow performance relationship (IPR) is established on the basis of horizontal well productivity models. The outflow performance relationship (OPR) is constructed using a close-form analytical solution for gas-water-solid 3-phase flow in annular space. It was found that the NODAL analysis technique was able to predict water influx rate with drilling time and thus cumulative water production under the nitrogen-UBD conditions in Sichuan, China. This paper provides drilling engineers a practical method for controlling formation water production in UBD operstions.
External Filter Cake Buildup in Dynamic Filtration: Mechanisms and Key Factors
Authors: Kalantariasl Azim , Zeinijahromi Abbas , Bedrikovetsky Pavel
Published: June 2014

The external filter cake build-up with its final stabilization has been widely reported for waterflooding in oilfields, drilling, produced water re-injection and disposal of produced water in aquifers. The brief overview of the models for cake formation and stabilization is presented. We derive the mechanical equilibrium equation for stabilized cake accounting for electrostatic force and for varying permeate force factor. The main empirical parameter of the model, highly affecting the stabilized cake prediction is the lever arm ratio for the particle on the cake surface. The lever arm ratio was calculated from laboratory cross-flow filtration experiments and from well injectivity data. It was also determined from Hertz's theory for the elastic particle deformation on the solid cake surface. Good agreement between the results validates the developed mechanical equilibrium model with the lever arm ratio determined from the elastic particle deformation theory.
Experimental Determination of the Effect of Pressure on Fluid Loss for Several Fracturing Fluids
Authors: Sanchez Reyes J. , Hutchins R. D. , Parris M. D.
Published: June 2014

Recent studies have offered evidence of unique shear viscosity loss of borate crosslinked fracturing fluids when exposed to hydrostatic pressures, such as those encountered during deep water hydraulic fracturing. This phenomenon can have important implications for proppant transport and for the resulting fracture geometry that needs to be accounted for in fracture design. Another important aspect for fracture design is the fluid loss. Since crosslinked fluids have superior fluid loss characteristics compared to linear polymers, the question arises as to whether fluid loss of borate-crosslinked formulations is also affected by pressure. Fluid loss is a fundamental property in hydraulic fracturing treatments and may dictate the attainable fracture geometry and the retained conductivity. Prior knowledge of fluid loss is also important for designing special additives to overcome the effect of excessive fluid loss.

This experimental study was designed to determine the pressure effect on linear guar and both borate and zirconium-crosslinked polymers. The concept of melt point utilized for the viscosity dependence was incorporated to select fluids. A unique high pressure, high temperature fluid loss apparatus was developed for the experimental testing. Test parameters varied from 160 to 260°F, 1000 to 9000 psi and 0.1 to 10 mD sandstone cores. Spurt and fluid loss coefficients were determined and compared to determine the pressure effect.

The results indicate that fluid loss behavior of fluids comprising borate-crosslinked guar is susceptible to moderate pressure effects. In particular, spurt losses increased with pressure, whereas fluid loss coefficients were independent of pressure. The increase in spurt loss with pressure was more pronounced as the permeability of the core sample increased. Conversely, the fluid loss behavior for linear guar or derivatized guar crosslinked with zirconium was not influenced by pressure. The implications of these findings for hydraulic fracturing applications are also discussed.