A new tool (or better a new tool system) is showing up to face the "advanced wells" challenge in the next years. Having spent the first part of an extensive period of field testing, the system called "Rotary Closed-Loop System" (ROLS) looks much closer to being run in any extended reach, deep horizontal or complex multilateral well, also in an HP-HT environment. The ROLS was designed to automatically control the well geometry during directional drilling, even while rotating the drill string. The well path is adjusted by hydraulically powered expandable ribs which generate a radial steering contact force to the borehole wall. The amount and direction of the steering force is controlled by the integral downhole electronics, which are capable of steering the well to the desired direction. All parts of the system except a short steering sleeve work continuously in rotation. The ROLS may be operated with or without a downhole motor. Several sub-systems of ROLS have been field tested during 1994 and 1995, e.g., the hydraulic components, most electronic modules, and the bottom-to-surface communication. The first field trial of the complete unit was conducted in late 1995 in a special test well at Montrose, Scotland. Here, for the first time, the full scale of ROLS features was verified, such as the automated steering into any direction as required, the two-way communication link, and the programming of the downhole tool from the surface while drilling. On the basis of findings from this early field application, some technical changes were then made. The field test program was further continued in early 1996 to check ROLS drilling and directional performance with further broadened operating parameters. During the time at Montrose a total of 3,500 ft (1,067 m) have been drilled. The inclination was built from 50 to 710, and the total drilling time has been 354 hrs. All major functions of the system have been fully verified. One major application of the Rotary Closed Loop System will be to steer wells in extended horizontal sections when steerable motors are difficult to operate. Additionally, because of the elimination of sliding operation together with the precise course correction capability, conventional directional wells will also highly benefit in many cases. Introduction Drilling deep, highly deviated wells often requires the application of versatile systems for directional control.
This pawr waa aelaoted for presentation by an lA~iSPE PrQram Committee following review of information containtiIn an abstract submitted by the author(a). &ntents of the paper, as presentd, have not hen review~by the International~soclation of Drilfin9 Contractors or the Society of Petroleum Engineem and are subject to correction by the author(s). The material, as preaentd, does not nWsaarilY feffect anY Wsitfon of the IAN or SPE, their officers, or members. Papera presentad at the lADCiSPE meetings are aubjest to publication review by Editorial Committaea of the IADO and SPE. Electronic reprtiuction, distribution, or storage of any part of this paper for commercial pur~ses without the written sonaenl of the Society of Petroleum Engineers Is prohibited. Permission to re~oduw In print ia restricted to an abatract of not more than~words; illustrations may not b wpiad. The abstract must mntaln conspicuous acknowlmment of where and by whom the pa~r was presented. Write Librarian, SPE, P.O.~x 833836, Ffichatiaon, TX 75083-W36, U.6.A., fax 01-972-952-8435. AbstractThe Rotary Closed Loop Drilling System (RCLS) was developed as a joint venture project between a major oil company and a leading service company. A long term research and development program within the service company was supported by the Italian oil company over the past five years. The resulting drilling system is capable of steering a wellpath while the drill string continues to rotate, so penetration rates are not sacrificed while slide drilling, as is necessary when using conventional steerable technology. Furthermore, this unique system has several integral downhole sensors, enabling two-way communication between the downhole system and surface, while also providing FEMWD data. In addition, several automated drilling finctions enable the system to steer independently. During this operation, surface personnel are able to intervene at any time through direct control using a downlink signal. This paper will provide a detailed insight into the project's engineering strategy during the development. The paper also presents a review of the first year of field application, mainly in the Adriatic Sea offshore Italy, which concluded the prototype period. The philosophy of the pilot field application program is briefly described and an overview is given of the ongoing engineering efforts, as well as the considerable fiture development potential.
The main subject of this paper will be to outline the field experience achieved with a new type of well profile and directional drilling system. Reducing the cost of well construction has been a driver for many new technologies. The lean casing profile introduced by Eni about a decade ago was a successful step towards lowering the drilling and completion cost in the vertical, top hole section. Automated vertical drilling tools have been the technical enabler of such concept. Recently Eni has moved further towards an even more radical "Extreme Lean Well Profile". This paper gives a brief insight into the well design concept and the enabling technology behind it. The drilling technology is based on the well-known automated vertical drilling system, which has been enhanced by the capability to drill an enlarged hole size below a casing, without compromising the verticality and hole quality. In the main part of the paper two field applications, in the Mediterannean Sea offshore Egypt, are described. The paper will also cover the lessons learned especially from the second of the first two field applications. The extreme lean well profile and automated vertical reaming technology can provide value to several drilling campaigns not only through the reduction of well construction cost. Another major benefit is the ability to run an intermediate casing string, if required because of difficult well conditions, and still arrive at the same diameter of casing in the reservoir. The completion concept as well the enabling tool technology is very unique and has not been available to the industry until recently. Introduction It is the ultimate purpose of any oil and gas well to help develop a reservoir as soon as possible and with the maximum rate and volume of hydrocarbon recovery. Reaching the reservoir horizon quickly and safely requires, in many cases, the application of some smart well construction techniques. This is true even in the upper sections of the hole. A straight and smooth borehole curvature reduces the inherient risks of running casing strings. In addition, such geometry provides the optimum conditions for being able to drill the horizontal section to the maximum reach. At the same time, when the trajectory is of a "gun-hole" shape and quality, less annular space has to be reserved for the casing string running operation. If this concept is realized through all or most of the hole sections, the well will be less cascaded than with the conventional approach. This type of "Lean Casing Profile" allows for faster well construction, fewer consumables and an increased operational efficiency. The "Lean Casing Profile" concept was first introduced to the oil field in the early 1990's. Based on the economic success achieved, the operating company has recently decided to drive this concept even further. The new "Extreme Lean Casing Profile" reduces the annular gap even further than with the previous method. In a way, the extreme lean shape is an importants step towards the visionary monobore hole, yet much more realistic to do as of today. As with the previous method, this new well construction scheme is based heavily on the application of an enabling downhole technology that guarantees the required straightness and precision. This can be accomplished by means of an automated rib-steering directional drilling device that is fully operated in the sliding mode. In a hole's vertical section, eliminating drillstring rotation improves borehole stability. In order to facilitate the extreme lean casing well construction, some new dowmhole directional drilling systems had to be created, such as an automated steering system with an integrated reamer and an automated rib steering device with a special diameter. The new well construction process and made-for-purpose tools has been field-tested in a series of wells in the Egyptian Sea where operating conditions were critical due to hole stability problems.
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