Development Update of an MWD Directional Drilling Package for 2-3/4" Openhole: Tiny Tools

Abstract

Abstract This paper documents the development and first applications of ultra-slim diameter mud-pulse-telemetry directional drilling tools for applications through 3-1/2" production tubing. The highly successful Coiled Tubing Drilling (CTD) program at Prudhoe Bay has concentrated on equipment required to re-enter 4-1/2" and larger tubing' sizes. Typical CTD re-entry operations have sidetracked existing wells at a cost 25% to 75% of past conventional rotary operations. However, there are a significant number of wells at Prudhoc Bay, other North Slope fields, and worldwide that have been completed using 3-1/2" tubing. The development of smaller diameter directional tools allow through-tubing CTD re-entry techniques to be extended to a dramatically larger number of existing wells and also allows options for zonal isolation using small ID intermediate strings in larger tubing sizes. Purpose built equipment needed to allow directional drilling through typical 3-1/2" tubulars has now been developed and utilized to drill the world's first directionally steered 2.75" bore holes at Prudhoe Bay. This newly developed equipment was used with CT to directionally extend the horizontal section below existing- 3 1/2" tubing strings. Economics of the first 6 wells would indicate a level of performance and cost effectiveness consistent with the larger CTD equipment. This paper details the design criteria and covers the operational implementation of the 2-3/8" OD directional drilling assembly, referred to as "Tiny Tools" by those developing the technology. Window milling and bicenter bit performance and results will also be discussed. The problems and solutions of tool development, along with the execution of the first CTD jobs through 3" tubulars are also addressed. P. 79