Summary This article presents a new model for describing well-position uncertainties. An analysis for surveying position uncertainties. An analysis for surveying errors is given that demonstrates that they are mainlysystematic rather than random. The error model, based on systematic errors, compares well withpractical experience. A graph is presented that shows practical experience. A graph is presented that shows typical lateral position uncertainties of deviated wellsfor various kinds of surveys. Introduction During the past 10 years, the uncertainties involvedin determining the true course of a borehole havebecome a cause for concern. The more deviated anddeeper the holes were drilled, the more often were theoperators faced with inexplicable differences betweenvarious surveys made in the same well. As early as 1971, Truex mentioned that possible lateral positionerrors of highly inclined wells could be up to 30 m ata depth of only 2000 m. Two years before that, Walstrom et al. introduced the ellipse-of-uncertainty concept to describe the positionuncertainty, which can be expected with various surveymethods. Experience, however, has shown that theellipse calculated by this random error model isunrealistically small, which is thought to be duemainly to the nature of the statistical error modelused.The essential differences between the existingrandom error model and the model proposed in thisarticle are illustrated by the following simplifiedexample. Consider the straight and inclined part of awell with these directional characteristics: total depthalong hole (AHD or DAH) 2500 m, surveyed at100 stations at 25-m intervals, and all having aninclination of I Delta I = 30 0.5 and an azimuthof A Delta A 90 1.The bottomhole position of this well in north, east, and vertical coordinates easily is found as N = D AH sin I cos A = 0, E = D AH sin I sin A = 1250 m, andV = D AH cos I = 2165 m. The position uncertainty of the bottom of thiswell, according to the error model presented in thisarticle, follows straightforwardly from theassumption that the measuring errors at all 100 stations havethe same magnitude (they are correlated fully).Hence, by simple trigonometry, as sketched in Fig. 1, and In the random error model, however, it is assumedthat the measuring errors vary randomly from onestation to another, which gives them a tendency tocompensate one another. This randomness of themeasuring errors causes the position uncertainty tobe smaller than the former values - in our example, by a factor equal to the square root of the number ofmeasuring stations, which is 100 = 10. JPT P. 2339
In the automotive industry, Henry Ford and Alfred Sloan moved manufacturing from craft production (highly skilled workers using simple but flexible tools to make what the customer asked for – one at a time) to mass production (narrowly skilled professionals who design products made by unskilled or semi skilled workers tending expensive, single purpose machines). Later Eiji Toyoda and Taiichi Ohno pioneered the concept of lean production which combines the advantages of craft production and mass production whilst avoiding the high cost of the former and the rigidity of the latter. The application of lean production created the most developed form of customer – supplier relationships (being developed elsewhere under the guise of alliances and partnerships) and achieved the highest productivity and quality in the industry. Studies have shown that productivity exceeds mass production by as much as fifty percent and the associated high level of quality is free. This outstanding result was not achieved through automation but through development and adoption of new organizational concepts. The drilling industry today resembles most closely the automotive craft production of the past; mass production has not been adopted due mainly to the non repetitive nature of drilling activities. Studies have concluded that lean manufacturing can replace both mass production and craft production in all areas of industrial activity. Lean manufacturing consequently has the potential to be applied to drilling or, more appropriately, well construction. This paper describes the key elements of lean manufacturing and presents an analogy with the well construction industry which provides the necessary insight for the well construction industry to adopt them. The results achieved in the automotive industry show that major cost savings and improvements in quality can be achieved in the well construction industry through this application.
When depletion strategies for BP Amoco's Valhall field on Norway's continental shelf required the drilling of extended reach drilling (ERD) wells, problems appeared which threatened the project economics. Average trouble costs approached 35% and occasionally exceeded 50%, while some wells failed to reachtheir objectives and the projects were not completed. Sound principles foraligning the operator/supplier team were applied to a very challenging ERD well following successful applications on exploration wells in Norway and development wells in other areas. Starting with a slot recovery that historically took 29 days being completed in 18, the well concluded 31 days(30%) ahead of past performance. It is clear that re-organization of a select group of operating and service company candidates into an aligned team made the difference. This paper will describe the challenge, the transformation and the result. Introduction - Valhall Field Performance BP Amoco's Valhall field in Norway can be best summarized as a field with many drilling challenges. In the over burden they include:–extensive faulting - both active and sealing,–shallow gas,–over pressured shale formations,–lost circulation zones,–pockets of waste domain from annular injection,–a high density of wellbores (producing and abandoned),weak rock in the Miocene,–an Eocene with hard stringers and–subsequently a very tight equivalent circulating density (ECD) envelope. These challenges were increased by distorted and blurred seismic data over the crestal area of the field due to a gas cloud caused by migration from deeper horizons. Many bottom hole assemblies have been sacrificed while drilling highly deviated / extended reach (ERD) wells, with sail angles approaching those of the bedding planes, in an effort to access undepleted parts of the reservoir on the flanks of the field. When circulation is lost, sometimes the rock will "cave" as a consequence of fluid invasion thus necessitating sustained circulation time, often resultingin a stuck BHA or lost hole. In terms of pore pressure and rock strength, the stable drilling corridor is very narrow. In the reservoir, horizontal-drilling technology is being applied to achieve sections in excess of 1000 m length. Successfully drilling these sections is dependent on entering the reservoir at a point where the pressure is sufficiently high such that differential pressures from the heel to the toe can managed. Drilling is also burdened with course corrections in the reservoir section due to faulting and thinning as re-drills are frequent to continually stay within the most productive reservoir sections.
This paper highlights key knowledge that was shared at the SPE Collision Avoidance and Well Interceptions Applied Technology Workshop held in Inverness, September 2012. It has been written to raise awareness of critical issues concerning well bore collisions and interceptions.Planning to ensure well collisions do not occur during drilling is a complex and demanding task which is often not given the high priority it requires in drilling programs. Assumptions are made of the validity and accuracy of historical data which is unfounded. Conversely, planning well interceptions when required in operations such as relief wells / drainage intercept wells requires a sound working knowledge of wellbore positioning technologies and techniques.Well bore interceptions and proximity placement are becoming critical applications for development of some reservoirs, specifically tar sands and coal bed methane. Well bore collision avoidance is entering the everyday skills requirement of drilling engineers as they plan more infill wells and more cluster (pad) drilling. Ultimately, demonstrating knowledge of the bore hole position during the whole drilling process is becoming more of a regulatory requirement that demands greater understanding by the drilling engineering community and drilling / asset managers. Are drilling engineers trained, competent and adhering to procedures designed to manage the intricacies of well bore surveying requirements as applied to collision avoidance and well interceptions?The workshop covered the topic under the following headings:The outcome of the workshop was to emphasize that wellbore collisions must be treated as high risk events with serious consequences that must be managed through systematic survey management procedures. Borehole position errors are a critical input to subsurface modeling and can have a major impact on field economics. Several members of the workshop committee are also members of the SPE Wellbore Positioning Technical Section that has published two SPE papers providing the industry with the ellipse of uncertainty error models commonly referred to as the Industry Steering Committee on Wellbore Survey Accuracy (ISCWSA) models. Summary of the SPE ATW WorkshopAttendees at this workshop shared and learnt about current good practice related to the management of the complete cycle of well positioning activities. Planning, policies, data management, practical application and technology were all addressed. This was accomplished during sessions of presentations, discussions and breakout groups with industry experts. The workshop produced some in-depth presentations and insightful results, including • Good Practice in designing a survey program.
This paper presents results and knowledge shared from the SPE Applied Technology Workshop held in Vail, Colorado USA in July 2012 titled Well Construction Automation -Preparing for the Big Jump Forward.Automation in drilling and completion operations is coming quickly, and its rapid adoption will leave many industry players behind if they are not aware of the future it will bring. Advances in control and automation of the whole drilling and completion process will increase improvements in safety, performance, quality, reliability, consistency and interoperability. This progressive application of automation will also create shifts in skills and competencies, and transform the role of the driller, rig crew, and service specialists along the way. Advances in automation are being made on multiple fronts, and many lessons are available from its adoption in other industries and the transformation industrial automation afforded in the 1990s.This workshop included important lessons learned from other industries and provided an update on the latest advances in automation developments. It explored the applications of such technologies as robotics, machine learning, and autonomous task performance without continuous human guidance, along with the speed with which these technologies can be applied.This was the first workshop that has actively brought people involved in automation from other industries into the discussion on drilling systems automation. The workshop involved key speakers and participants from leading edge applications including academia and the Defense Advanced Research Projects Agency (DARPA). These organizations are automating things that the drilling industry has not yet heard about. The workshop participants developed plans for adopting these technologies into drilling systems and created a vision of rapid automation adoption into drilling operations. Workshop SummaryThe workshop was attended by 120 participants that included a broad cross section of experts connected to automation inside and outside oil and gas (Fig 1).The business case for automation, highlighted by drilling industry practitioners, was the improvements in safety, drilling performance, and consistent / predictable drilling operations. It is anticipated that automation can solve the current situation whereby the driller is overloaded with inputs and tasks. Successful automation projects will require a multi-skilled team that includes well engineering, process automation control / optimization and information technology.It is anticipated that systems integration will enable interoperability (a.k.a. plug and play) between downhole and surface tools and machinery from different Original Equipment Manufacturers (OEM's) and that operators will begin to specify automation and adherence to specific communication and interoperability protocols in their contracting documents, but there is a significant division around the need to implement standards for interoperability. Essentially, standards were the The workshop participants collectively agreed...
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