Improving Hole Quality and Casing-Running Performance in Riserless Topholes—Deepwater Angola

Summary The operator and coventurers are developing several Angola Block 15 fields in water depths of up to 1400 m. To date, 83 development wells and 33 exploration/appraisal wells have been drilled in the block. Most have experienced hole quality issues in the riserless interval that are manifested as tight hole while tripping the bottomhole assembly (BHA) and as abnormal/excessive drag while running casing. In a few cases, casing could not be run to total depth (TD), and in one unfortunate case, the casing buckled in open water. There has been uncertainty as to the root cause of the hole-quality issues that have been attributable to various factors since drilling was initiated. A review of available literature revealed very little published information on riserless drilling and casing-running practices. The operator undertook a study of its riserless drilling and casing-running practices to look for trends that may suggest certain sources as the root cause and to allow a re-examination of long-accepted practices. The study, combined with some new perspectives on directional-drilling mechanics, identified micro-tortuosity as the root cause of casing-running difficulties. Micro-tortuosity has been known to exist in deeper, more consolidated sediments. The study revealed that microtortuosity can also exist in large diameter holes drilled in soft sediments. Changes to drilling practices have resulted in improved riserless hole quality and smoother casing-running operations.

10 - Single-shot titanium/carbon fiber reinforced composites/aluminum stacks holes drilling

Hydraulic fracturing experiences were gathered over the years, from a tight sandstone reservoir of Late Carboniferous to Early Permian origin to find the root causes for the persisting challenges of high formation breakdown pressures and low fluid injectivity. It was soon realized that a single root cause could not account for these challenges. Instead, a multitude of reasons acting at the same time during the injecting sequence of that particular fracturing stage could easily be responsible, and no single re-occurring pattern would explicitly repeat in the consequent stages under similar conditions. It was found that the known complex nature of the depositional environment of the targeted formation played an important role, but the overall hydraulic fracturing mechanics played an equally critical part in the success of the fracturing attempt. Having realized this complexity in deciphering hydraulic fracturing performances it became imminent that not only the fracturing execution had to be refined, but all the preceding activities from drilling operations, to well placement, to wellbore preparation, to the choice of completion equipment and its deployment. These operations critically influenced the near wellbore region. The drilling fluid properties, wellbore hydraulics, well trajectory, the wellbore clean-out procedures, and hole quality were important contributors in the geo-mechanics domain coupled with the impact of the geological setting. Thus, a workflow was developed to analyze and rationalize the root causes for the injectivity challenges with the goal of optimizing every well construction step that would enhance hydraulic fracturing and ultimately deliver optimum well productivity.

Lightweight materials are finding plentiful applications in various engineering sectors due to their high strength-to-weight ratios. Hole-making is an inevitable requirement for their structural applications, which is often marred by thermal damages of the drill causing unacceptable shortening of tool life. Efficient cooling of the tool is a prime requirement for enhancing the process viability. The current work presents a novel technique of cooling only the twist drill between drilling of holes with no effect of the applied cryogenic coolant transferred to the work material. The technique is applied in the drilling of two commonly used high-strength lightweight materials: carbon fibers reinforced polymer (CFRP) and an alloy of titanium (Ti-6Al-4V). The efficacy of the cooling approach is compared with those of conventionally applied continuous cryogenic cooling and no-cooling. The effectiveness is quantified in terms of tool wear, thrust force, hole quality, specific cutting energy, productivity, and consumption of the cryogenic fluid. The experimental work leads to a finding that between-the-holes cryogenic cooling possesses a rich potential in curbing tool wear, reducing thrust force and specific energy consumption, and improving hole quality in drilling of CFRP. Regarding the titanium alloy, it yields a much better surface finish and lesser consumption of specific cutting energy.

World's energy demand is on upsurge and Oil & Gas industry has been directed towards the exploitation of deepwater oil and gas resources. To make this operation successful petroleum industry is continuously demanding new innovative drilling technology that can be easily implemented. One of the constraints that hinders the deepwater exploration is its continuously shrinking narrow window between pore pressure and fracture pressure that further limits the reliability of old conventional riser drilling technique.Dual gradient drilling (DGD) is a managed pressure drilling that involves use of two different annular fluids for drilling a prospect providing a favorable annular pressure profile and simpler, safer & economical well design.In any of the rotary drilling operation, drilling hydraulics is the most complicated and least understood drilling variable as it involves complex relationship between drilling fluid, drill bit and formation. Riserless drilling, one of the type of DGD, eliminates the use of marine riser (u-tube is imbalance) and involves use of an additional subsea mud pump at seabed which, supplements to the complication for hydraulics computation as compared to conventional drilling.In drilling HPHT deepwater wells, drilling fluid is constantly exposed to its own column pressure and formations geothermal gradient which subsequently affects the mud rheology and density. These altered rheological parameters leads to inadequate hole cleaning and lowers the drilling efficiency. High temperature in the wellbore cause's fluid expansion and high pressure causes fluid compression and these changes get extremely severe as water depth and drilling depth increases. Hence it becomes necessary to consider the HPHT effects on Equivalent Circulating Density (ECD) and to correct & optimize the hydraulic program to ensure the best utilization of the hydraulic energy for effective hole cleaning.This paper presents a detailed study of Well hydraulics for riserless drilling considering the HPHT effect on Equivalent Circulating Density and its optimization so as to ensure riserless drilling operation is conducted in safe and effective manner. Also the paper is concluded with some recommendations on operational and design strategies.

Improving hole quality is a major factor for accurate formation evaluation and reduced well construction costs in deepwater. Further optimization of the borehole quality using new generation drilling assemblies is now possible. Not only to improve formation evaluation, increase penetration rates, and reduce the risk of drill string failure, but also to reduce the load points of salt formations on completions. Concurrent drilling and reaming techniques have been successfully used to mitigate the effect of non-uniform, transverse loading of salt formations on completions as well as improve hole quality for higher wireline log success rates. During the execution of deepwater wells in offshore Brazil, multiple bottomhole assembly configurations were deployed to drill the various hole sections and the use of logging-while-drilling (LWD) imaging and wireline calipers provided a direct comparison of hole quality performance of each drilling system. A culmination of various drilling systems were evaluated, during a drill-off test, in a single well while performing enlarging-while-drilling (EWD) of a 12 ¼" to 14 ¾" hole. Salt formations were drilled to fully compare each system in a common drilling environment without variations due to formation types.

The paper describes the improvement in drilling efficiency obtained in five mature North Sea fields, by using a systems approach. The drilling program was managed by a drilling efficiency group consisting of a service company, drilling contractor and operator engineers drawn from several disciplines. All of the well sections were geometrically complex. Data was gathered using downhole pressure and vibration sensors, and acoustic caliper sensors. MWD annular pressure measurements had shown that conventional steerable motor/bit combinations required extensive circulation and occasional back reaming to ensure adequate hole cleaning. MWD vibration measurements and BHA modeling had proved that particularly high levels of vibration were caused by both circulating and back reaming. This was directly associated with MWD, motor and other downhole tool failures. It was concluded that the basic problem was hole quality and attention was directed to eliminating hole spiraling deduced from MWD logs and calipers. A new combination of compatible steerable PDM and long gauge bit was designed with input from the operator. This was designed to achieve improved hole quality from long gauge bits without losing the rapid deviation response of conventional motor/bit combinations. The aim was to improve overall drilling system efficiency, particularly poor hole cleaning, excessive torque and drag, and slow ROP when sliding. The paper discusses the initial data gathering and diagnosis and how measurement and modeling of downhole conditions led to the optimal solution. Comparison between 8 conventionally drilled hole sections and 8 hole sections drilled utilising the new drilling system showed more than 50% reduction in overall drilling time. Significant time savings have been made when drilling in the orientated mode. Other benefits are reduced drilling WOB from 30,000 lb to 3,000 lb, reduced drilling torque and drag, and an overall improvement in hole quality reflected by improved hole cleaning.

Optical trepanning provides a drilling mechanism by using an annular beam. This paper investigates the temperature distribution in the workpiece due to pulsed annular laser beams. The annular beams allow numerous irradiance profiles to supply laser energy to the workpiece and thus provide more flexibility in affecting the hole quality than a solid laser beam. Such profiles include half Gaussian with maximum intensities at the inner and outer radii of the annulus, respectively, and full Gaussian with maximum intensity within the annulus. In addition to this spatial beam shaping, the temporal profile of the laser pulse can be shaped to improve the hole quality. The Hankel and Laplace transforms have been used to obtain an analytic solution for the temperature distribution in a semi-infinite workpiece. The effects of the temperature distribution on laser drilling are analyzed to design an efficient drilling process.Optical trepanning provides a drilling mechanism by using an annular beam. This paper investigates the temperature distribution in the workpiece due to pulsed annular laser beams. The annular beams allow numerous irradiance profiles to supply laser energy to the workpiece and thus provide more flexibility in affecting the hole quality than a solid laser beam. Such profiles include half Gaussian with maximum intensities at the inner and outer radii of the annulus, respectively, and full Gaussian with maximum intensity within the annulus. In addition to this spatial beam shaping, the temporal profile of the laser pulse can be shaped to improve the hole quality. The Hankel and Laplace transforms have been used to obtain an analytic solution for the temperature distribution in a semi-infinite workpiece. The effects of the temperature distribution on laser drilling are analyzed to design an efficient drilling process.

The practical application of new technologies, including rotary steerable drilling systems are overcoming previous limitations in directional drilling to make designer, multilateral and extended reach wells easier to drill. In this paper, the authors will discuss the tremendous value that can be achieved through application of winning technology and teamwork that has been proven as an effective tool in maximizing business opportunity in Asia Pacific. Multilateral wells offer tremendous advantages including reducing the size of platforms, surface locations, subsea completions and total wells required to fully exploit a hydrocarbon reservoir. However, such complex 3 dimensional well applications can be severely limited by a number of factors including: Prohibitive well costsRig sizing considerationsLess than optimal directional controlTorque and dragUnreliable WOB transfer and poor hole cleaningEnvironmental considerations. One technology having a significant impact on such designer well applications are rotary closed loop drilling systems. These systems provide enhanced drilling-while-steering efficiency and improved hole quality. It comprises a non-rotating steering unit, a downhole guidance system, formation evaluation (with optional LWD) and downhole pressure monitoring. These tools can automatically guide the bit to a preprogrammed target and two-way surface communication allows rigsite engineers to adjust the well trajectory to meet drilling objectives and redirect the wellpath based on real-time formation logs. This eliminates the "wait and see" aspect of drilling which often results in less than optimal well placement, unnecessarily complicating the forward directional plan for the well or missing the target all together. In 1998 Petronas Carigali Sdn. Bhd. commenced the Sotong field development in offshore Peninsular Malaysia. The objective was to efficiently drain marginal reserves using multilateral Level 4 technology. The wellpaths are precisely placed in an optimal position using rotary steerable technology in order to ensure maximum production life of well. Modern communications systems has allowed this technology to transfer real-time wellsite data from rigsite to shore. The critical well path decisions can be made in real time by the team in the office and relayed to the wellsite instantaneously and changes can therefore be made immediately.

The author is the Community Services Coordinator at FMQAI: The Florida ESRD Network. She is also a member of D&T’s Editorial Advisory Board. G uest Edtorial The number of patients involun­ tarily discharged from facilities is a concern throughout the coun­ try. Many of these individuals become displaced, with no facility willing to accept them. These patients are forced to go to hospital emergency rooms for treatment, thus contributing to an already over-burdened system, and receive little or no continuity or coordination of care. Any end-stage renal disease (ESRD) patient without access to regular chronic dialysis and the necessary support services is at increased risk for morbidity and mortality. The new ESRD Conditions for Coverage mandate that facilities inform patients of their right to file a grievance without reprisal or denial of services. Further, patients must be informed of the facility’s policies for transfer, routine or involuntary discharge, and discontinua­ tion of services. Patients must receive a 30-day written notice of an involuntary dis­ charge, and the facility must follow specifi c involuntary discharge procedures. A patient being involuntarily discharged must have an order for discharge signed by the facility’s medical director and the patient’s attend­ ing physician. An abbreviated discharge procedure is allowed only in the case of immediate severe threats to the health and safety of others. The medical director has specific responsibilities and accountability to the governing body for patient care and outcomes and is responsible for ensuring that the interdisciplinary team adheres to discharge and transfer policies. With these new regulations in place, the challenge for providers is to fi nd creative solutions to work more effectively with diffi cult and special needs patients.

With the current market's high prices for drilling units and sophisticated directional and formation assessment services, low systems reliability or poor directional performance in the execution of complex wells (ERD, HPHT, Deep Water applications) can spell costly Non Productive Time (NPT) for operators. Over the past two decades, many Bottom Hole Assembly (BHA) models have been developed to address the directional performance issue, but their application in an operational environment has generally failed for lack of strong associated BHA analysis methodologies. This paper presents a unique automated methodology for Post Analysis of BHA directional behaviour. It is based on modern 3D analytical models, combining BHA, BIT and formation effects with highly flexible data management. Implemented in user-friendly BHA management software, it can be used to define a BHA run segmentation and to determine the influence of the BHA settings in particular geological formation blocks. The Post Analysis clearly displays the final results of the BHA (objectives and performances versus prediction window), highlighting any problematic intervals drilled. Already, the methodology has solved challenging directional performances issues, generating significant savings and optimising the learning curve process. The field applications referred to in the paper have demonstrated that, without a proper methodology, a model offers little added value. The examples discussed here from Total E&P affiliates deal respectively with Rotary, Rotary Steerable System (RSS) and Steerable Motor (SM) directional BHAs. Case studies have led to BHA and bit design modifications. The results were well beyond expectations, ensuring good well positioning through the reservoir by improving BHA stability and manoeuvrability. Efficient drilling (reduced sliding, improved hole quality) was also achieved with a single SM BHA in 17 1/2" applications during kick-off, and successive build-up and slant drilling intervals. The methodology and its associated BHA Management® software have proved an undeniably valuable tool for the drilling community. The model is also run at the well Pre Engineering stage to check BHA design proposals by making multiple sensitivity analyses and by fine-tuning solutions to the operational context. Finally, in an industry with high personnel turnover, the software's global data management system ensures good capitalization of know-how and ongoing learning curve benefits.

The identification of defect causes plays a key role in smart manufacturing as it can reduce production risks, minimize the effects of unexpected downtimes, and optimize the production process. This paper implements a literature review protocol and reports the latest advances in Root Cause Analysis (RCA) toward Zero-Defect Manufacturing (ZDM). The most recent works are reported to demonstrate the use of machine learning methodologies for root cause analysis in the manufacturing domain. The popularity of these technologies is then summarized and presented in the form of visualizing graphs. This enables us to identify the most popular and prominent methods used in modern industry. Although artificial intelligence gains more and more attraction in smart manufacturing, machine learning methods for root cause analysis seem to be under-explored. The literature survey revealed that only limited reviews are available in the field of RCA towards zero-defect manufacturing using AI and machine learning; thus, it attempts to fill this gap. This work also presents a set of open challenges to determine future developments.

A review of alarm root cause analysis in process industries: Common methods, recent research status and challenges

ObjectivesUnintended events (UEs) are prevalent in healthcare facilities, and learning from them is key to improve patient safety. The Prevention and Recovery Information System for Monitoring and Analysis (PRISMA)-method is a root cause analysis method used in healthcare facilities. The aims of this systematic review are to map the use of the PRISMA-method in healthcare facilities worldwide, to assess the insights that the PRISMA-method offers, and to propose recommendations to increase its usability in healthcare facilities.MethodsPubMed, EMBASE.com, CINAHL, and The Cochrane Library were systematically searched from inception to February 26, 2020. Studies were included if the PRISMA-method for analyzing UEs was applied in healthcare facilities. A quality appraisal was performed, and relevant data based on an appraisal checklist were extracted.ResultsThe search provided 2773 references, of which 25 articles reporting 10,816 UEs met our inclusion criteria. The most frequently identified root causes were human-related, followed by organizational factors. Most studies took place in the Netherlands (n = 20), and the sample size ranged from 1 to 2028 UEs. The study setting and collected data used for PRISMA varied widely. The PRISMA-method performed by multiple persons resulted in more root causes per event.ConclusionsTo better understand UEs in healthcare facilities and formulate optimal countermeasures, our recommendations to further improve the PRISMA-method mainly focus on combining information from patient files and reports with interviews, including multiple PRISMA-trained researchers in an analysis, and modify the Eindhoven Classification Model if needed.

Root-cause identification for quality-related problems is a key issue in quality and productivity improvement for a manufacturing process. Unfortunately, root-cause identification is also a very challenging engineering problem, particularly for a multistage manufacturing process. In this paper, root-cause identification is formulated as a problem of estimation and hypothesis testing of a general linear mixed model. First, a linear mixed fault-quality model is built to describe the cause-effect relationship between the process faults and product quality. Then, the estimation algorithms developed for a general linear mixed model are adapted to estimate the process mean and variance. Finally, a hypothesis testing method is developed to determine if process faults exist in terms of statistical significance. A detailed experimental study illustrated the effectiveness of the proposed methodology.<br><br>Note to Practitioners-Economic globalization brings intense competition among manufacturing enterprises. The key to succeed in this competitive climate is to rapidly respond to fast-changing market demands with high-quality and competitively priced products. To achieve this, we need to quickly identify root causes of quality-related problems in a complicated manufacturing system. However, the current widely adopted quality-control techniques focus more on monitoring than on root-cause identification. These techniques can efficiently detect the changes in the process but the root cause identification is often left to the plant engineers or operators. In this paper, a systematic estimation and testing method is proposed to identify the variational root causes in multistage manufacturing processes. First, a linear model is built based on the design information to describe the cause-effect relationship between the process faults and product quality. Then, an algorithm is developed to estimate the mean and variance of the process faults from the quality measurements of products. Finally, a statistical testing method is developed to determine if process faults (i.e. root causes) exist in terms of statistical significance. A detailed experimental study illustrates the effectiveness of this method. The method presented in this paper is a new quality-control technique and can be used for quality improvement of multistage manufacturing processes.