Using Rotary Closed-Loop Drilling to Increase Operational Efficiency and Reduce Operational Risk

Abstract

This paper reviews the operational experience gained of utilizing Rotary Closed – Loop Steerable (RCLS) drilling technology on development drilling projects in the UKCS for the period 1997 – 2000. Despite the general decline in drilling activity in this period, there was a significant increase in RCLS drilling activity. Sufficient operational experience has now been gained to a) fully evaluate the impact of the new technology on the drilling operation and to b) make a comparison of RCLS system performance against a conventional drilling operation. The paper focuses on the following three key performance measures of the RCLS operation:Reliability of the Technology: A review is made of the RCLS system performance, where problems occurred at the introduction of the technology and what solutions were implemented to improve system reliability.Operational Performance: An assessment of the factors which influence the operational efficiency of the RCLS operation is presented and a comparison is made with the operational efficiency of a conventional drilling operation.Safety – Environmental Performance: The introduction of RCLS technology facilitates a safer working environment for drilling operations at the rig site. The positive impact that the technology has made to the drilling operation is reviewed here. In reviewing past performance, the direct and indirect advantages of deploying RCLS are discussed in light of experience gained on a number of offshore UK North Sea assets including those projects managed by low cost operators or where field economics are marginal. Introduction Rotary Closed – Loop Steerable (RCLS) drilling technology was introduced to the UK sector of the North Sea in May 1997. This technology was originally developed in conjunction with ENIAgip in Italy for potential use on ERD type wells. Initially, the technology was limited to the 6 3/4" tool size to drill hole sizes in the range 8 3/8" to 9 1/2". Eighteen months later the 8 1/4" tool was introduced to drill hole sizes in the range 12 1/4" to 14 3/4". Since that time, the system has drilled 800,000ft which represents approximately 78% of the total rotary steerable footage drilled in North Sea UK sector. In view of the general downturn in drilling activity in the period 1999 – 2000, the growth trend in RCLS activity is significant. There were two main drivers which facilitated this growth in RCLS activity in the UK and North Sea, namely 1) the industry's need to reduce operating costs and 2) the technical limitations with conventional steerable drilling techniques. The degree to which RCLS technology could provide a satisfactory solution to these two areas would depend on the operational performance of the system (directional performance, dogleg capability, real – time data acquisition and system reliability). The next section provides a review of the RCLS operations in the UK sector of the North Sea. RCLS Operations Review Figure 1 shows the growth in RCLS activity relative to the overall drilling activity during the period 1997 – 2000, with expected activity to end of 2001. In the last three years the RCLS activity has shown 50% or better growth. Initially, the focus for utilising rotary steerable drilling technology was in situations where directional operations were considered inefficient with conventional steerable drilling methods, and therefore the emphasis was on cost reduction. Specifically, RCLS was deployed in situations where oriented or slide drilling proved difficult or frequent trips for bit and BHA changes were required.

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