Extended Reach Drilling Limitations - A Shared Solution
Authors: Nixon J.U. , Nims D. , Rodman D.W. , Swietlik G. 
Published: October 2008

This paper describes the strategies and techniques employed to solve the problems associated with excessive torque during offshore drilling of the Miller Field template wells. A timely solution was required which would enable subsequent platform wells to be drilled economically. When available technology was judged inadequate to solve problems, a torque reduction subway designed, tested and made available for use in this series of critical, high angle, deep platform wells

In addition (o a description of the conceptual design of various solutions proposed, l)re paper details the concurrent engineering, testing and field application of the Drill String Torque Reduction (DSTR) sub. which was the preferred solution.

Introduction

It became apparent with the industry extending the range and Departure of directional drilled wells that the service limits of present drilling equipment would soon be reached if associated problems were not addressed

Higher torque inputs from the top drive, larger angular twist and on drill pipe. together with tool joint fatigue and casing wear, are manifest as a consequence of the frictional forces between the pipe and [he low side of the hole.

Earlier attempts al addressing the torque problems included modifications to Bottom Hole Assembly (BHA) components and the deployment of tools such as Roller Reamers and Non-Rotating Stubilisers/Roller Slabiliscrs. The results from these field trials were questionable and did not cater for the concerns over casing wear. They did not take into account the fact that in all eases the BHA lengths were considerably less than the total length of drill string and the summation of losses due to frictional effects was greater in the interval over the drill pipe length.

Earlier mathematical analysis of torque profile clearly Showed that the Section of hole from the Kick-Off Point (KOP) to the End Of Build (EOB) provided the greatest opportunity for reductions in torque to be achieved. With this understanding a new deviation plan was developed through the use of two build-up phases separated by an intermediate tangent section and also by lowering the KOP. These techniques were successful in easing the situation but they did not address the underlying mechanics] problem or that of casing wear. Other work on casing wear using different mud systems and aluminium tool joints also me[ with limitations.

Several obstacles therefore had to be over come in the design and development of the solution. The service industry responded with several potential solutions, however the so failed to provide (he minimum required objective of reducing off-bottom torque by combined with durability and reliability. to give a minimum of 20tJ rotating hours between service or Iaydown.

Given this situation and the impending requirement drill the ERD wells on the Miller development. a team waspulled together consisting of the operator. Service company and design consultant with the objective of con current engineering the solution during the drilling of the Miller development wells.