Joachim Oppelt

Advanced Tools for Advanced Wells: Rotary Closed Loop Drilling System - Results of Prototype Field Testing

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 (RCLS) looks much closer to being run in any extended reach, deep horizontal or complex multilateral well, also in an HP-HT environment. The RCLS 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 RCLS may be operated with or without a downhole motor. Several sub-systems of RCLS 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 RCLS 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 RCLS 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 5° to 71°, 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.

A simplified framework and performance analysis for while-drilling telemetry systems in underbalanced drilling operations

As it stands, underbalanced drilling (UBD) operation has been beneficial in the exploration of hydrocarbons and production, with advantages like faster drilling control of lost circulation, stuck pipe situations, minimal or less formation damages and an enhanced ability to expedite development of brown fields. In spite of its edge over conventional drilling, the techniques can be more complex as well. Thus, a telemetry system is required to link downhole and surface while-drilling components transmitting and providing useful information under the real-time condition to the driller during drilling operations for more precise wellbore placement to ensure maximum reservoir exposure, ultimate production increment and monitoring conditions. A novel and systematic decision support system model based on distance-based approach has been developed for performance evaluation and optimal selection of while-drilling telemetry systems for the potential development of a depleted reservoir field. The proposed methodology attests to the need for the relative importance of criteria for a given application, without which inter-criterion comparison could not be accomplished. It requires a set of model selection criteria, along with available telemetry techniques and their level of criteria for optimal selection; and it successfully presents the results in terms of a merit value which is used to rank the while-drilling telemetry systems. This aims at delivering reliable drilling performance resulting to deliverable of real-time downhole data collection and most importantly places the matured well with minimal non-productive time during UBD operations. The scientific value of this study is the development of a simplified user-friendly decision support system for telemetry systems performance evaluation and selection optimization. The proposed framework was being validated and applied to a matured reservoir for an optimum selection of telemetry techniques in the UBD operation. The result of computations displayed similar results obtained by expert judgment demonstrating the significance effect and need for telemetry systems.