This paper will present the results to date of a project to develop an electric drillstring, together with some ideas and visions of how this technology could make a step-change in well construction. The electric drillstring should enable electric power to be transmitted through the drill pipe, while simultaneously multiplexing data back to surface from the downhole drilling system. This could allow a range of improvements to the drilling process, that we shall call "smart drilling", which should result in reduced drilling costs and optimized well placement for maximum productivity. The project has followed the normal phases in any technology development, but only the initial two phases of feasibility and benefit assessment have been completed. The initial phase was to learn what had been done in the past to transmit electrical power and telemetry in a drillstring, identify the key problems and try to come up with some novel solutions incorporating technical improvements from both within and outside the drilling industry. The key benefits of the new system were identified, together with a range of potential applications that could be available in both the short and longer term. The heart of the system is a reliable electrical connector integral with a premium drill pipe thread that will behave like a normal tool joint during operation. This is combined with mid-body conductors, in this case sandwiched between a metal inner layer and the drill pipe body. The development of the first two prototypes, which are on the route map to the initial field test, will be discussed. Smart drilling via an electric drillstring can offer a wide range of possible advantages over conventional drilling operations, which could include:Reduced drilling costs from the optimization of the drilling process by control of weight on bit using downhole traction or thrusters, and maintaining bit speed independent of flow rate.Reduced wellbore stability problems due to both reduced ECD via reverse circulation and knowledge of the pressure conditions from sensors distributed over the length of the well.Reduced costs by replacing wireline logging with real-time LWD systems.Reduced stuck-pipe in ERD-type wells from traction tools distributed along the drillstring.Improved well productivity from improved geosteering via immediate data feedback from the high quality telemetry path.The development of Seismic-while-drilling (SWD) utilizing downhole sources and recievers.The possible development of new sensors that take advantage of the excess power available downhole. These concepts will be briefly discussed in the paper together with the results of an initial benefit assessment. Introduction The drilling industry has accomplished some quite extraordinary achievements with very limited telemetry from downhole tools powered either by batteries or turbines. This is especially so when compared with the large increases in data telemetry rates that have occurred in other industries in the last few years. It is our contention that, with a higher data telemetry rate and the ability to power and control a range of downhole drilling tools, this so-called "smart drilling" will enable a step-change in the way wells are drilled and how the drilling process is controlled.

No abstract

This paper describes a joint industry project to develop an electrically powered bottom hole assembly for use in coiled tubing drilling (CTD) applications. Phase I of the project, recently completed in Aberdeen, produced a highly successful prototype assembly that recorded over 190 hours of drilling time without failure. Whilst the prototype was made almost entirely from existing technology, the success of the test has generated confidence to develop a more fit for purpose' motor. A system overview explains the concept behind, and the advantages of, electric coiled tubing drilling (ECTD). The bottom hole assembly is described in detail, along with various surface components and the electrical power transmission system. The testing program and operational procedures are outlined, together with some of the key results. The development plan for the technology is reviewed to highlight the ultimate goal of producing a smart' drilling system. It is envisaged that, based upon feedback from near-bit sensors, such a system would be able to automatically adjust certain parameters to optimize drilling performance. The paper concludes that electric coiled tubing is a feasible and practical alternative to conventional CTD, although there are certain technological barriers that must be overcome. P. 61

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper considers the ongoing development of an electrically powered bottom hole assembly that has been designed for use in closed-loop, coiled tubing drilling (CTD) applications.The electric BHA has been conceived and designed through a European Drilling Engineers Association [DEA(E) 1 ] joint industry project. This paper introduces the project and reviews its progress to date.Electric coiled tubing drilling, or E-CTD, was delineated as a three phase project to stage progress and reduce technical risk. Phase I of the project, completed in late 1997 was designed to prove the feasibility and concept using standard motor technology.Phase II, currently in a bench testing programme, intends to deliver a fit-for-purpose electric downhole motor (EDM) suitable for drilling a 3.75" hole. The motor is being incorporated into an electric bottom hole assembly (BHA) which incorporates pressure, temperature and vibration sensors. This is shortly to be field tested in Aberdeen.Phase III of the project, scheduled to start mid-1999, integrates geo-steering and variable-bend directional technology to provide what has been termed the 'all electric' BHA. The ultimate goal of the project is to integrate the electric motor into a closed-loop drilling system. It is envisaged that, based upon feedback from near-bit sensors, such a system would be able to automatically adjust drilling parameters to optimise drilling performance.Upon successful completion of basic closed loop functions, the intention is to incorporate the controlability of the BHA into what they describe as an 'intelligent' drilling system. This paper outlines a definition of this 'intelligence' and the authors also provide an insight into how far they believe that this technology may be taken, in terms of the autonomous decision making ability of a surface computer.

Whilst previous papers have considered the background to, and details of, the development of a coiled tubing deployed ESP system, this paper considers field experience from the system to date. The system has been used to deploy ESPs in two locations; the first onshore, United Kingdom and the second offshore in the Middle East. The second case is of particular interest as the four well minimum facility development was completed using a coiled tubing unit on a derrick-less platform. Several intervention operations have since been performed, also using a coiled tubing unit. Since the industry has been reluctant to use ESPs in remote locations such as subsea wells or minimum facility developments, due to questions of completion reliability, this represents an ideal test scenario; the system was originally conceived to enable rigless ESP completions. Whilst the system has been generally acclaimed as successful, various technique aspects of the system are discussed with particular emphasis on design improvements that will enhance future performance.