Coiled Tubing Drilling: Real Time MWD With Dedicated Powers to the BHA

Abstract This paper describes and analyzes the development and ongoing field trials of a Real Time MWD Coiled Tubing Drilling System. The new system holds great promise for advancingthe state of coiled tubing drilling for certain applications. The system is designed for through-tubing, short radius re-entry and drilling highly deviated wells as horizontal laterals to a geologic target with minimum wellbore tortuosity. Currently, 4- 1/2' production tubing is the smallest re-entry candidate. Real time MWD and Bottom Hole Assembly (BHA) control is achieved by the use of a combination hydraulic and electric umbilical internal to the coiled tubing (CT), allowing continuous data collection and selective surface control of the BHA components, This communication line allows orientation in 10' increments (or less) while drilling, applies weight-on-bit and operates a reusable circulating valve. In addition, the umbilical provides real-time monitoring of weight-on-bit, circulating pressures of the drilling fluid internal and external to the BHA, dedicated hydraulic system bottom hole pressure, downhole temperature and survey data from logging equipment. Introduction In. June of 1992, Cameo Products & Services formed a coiled tubing drilling team that consisted of engineering representives from Reed Tool Company, Hycalog. Cameo Coiled Tubing Services and Cameo Products & Services. The team's objective was to investigate the technical and economic viability of drilling with CT. Invitations were extended to experts and consultants with experience in slim-hole and CT drilling to address the team on existing and potential problems. The major technical difficulties identified were:CT bucklingpipe fatiguelack of real-time dataweigh t-on-bitreactive torquedependable emergency release from the BHAability to drill under balanced Key to solving these technical difficulties is the ability to provide hydraulic and electric power to the BHA via an umbilical installed in the CT, The umbilical allowed the development of hydraulically and electronically powered down hole tools and instrumentation that comprise the BHA. Purpose built surface equipment designed specifically for the BHA was developed to provide surface power and selective controls. After conceptual drawings of the BHA were completed, Cameo and BP Exploration (Alaska) began a development project for specific application at Prudhoe Bay, where CT drillingtechnology is considered to be a very valuable tool. Many of the existing wells at Prudhoe Bay could potentially benefit if replaced with horizontal completions. CT drilling offers the potential of achieving horizontal sidetracks without pulling the existing tubing. This offers a significant cost advantage over conventional sidetracks.