Matterhorn Development Drilling-Innovation and Planning Equals Deepwater Directional Success
Authors: Forestier J.F. , Ables G.L. , Bertin D. , Ardignac D. , Hall C.R. , Lucas M.A. 
Published: October 2008

Abstract
This paper presents the successful development drilling program for the Matterhorn TLP Project operated by Total E&P USA. The paper reviews concept, design, planning, and implementation of the project and provides insight into technical and operational aspects which must be considered such as kicking off in soft formations, hole stability and shallow water flows. This unique combination of available technology resulted in reduced operational time and lower costs than originally planned. The paper demonstrates the viability of such combinations of activities for similar deepwater development projects.

Introduction
The Matterhorn platform is located in Mississippi Canyon, Block 243, and is in approximately 2850' of water. The field objectives are Plio-Pleistocene age sands ranging in depth from 3,000' to 7,500' below mud line. Five principal pay sands were identified during the exploration phase. The initial development plan included drilling a total of 8 wells : 7 "dry tree" wells at a central location and a subsea water injection well approximately a mile from the central location. The wells would be drilled to TD using a semi submersible drilling rig and temporarily abandoned after running and cementing production casing/liner. After releasing the drilling rig, a tension leg platform (TLP) would be installed on the central well cluster, and the wells completed individually after running the production risers (Fig 1). This central well cluster would be located with the #1 exploration well within the pattern to allow re-entering the well, if feasible, for more economical field development. The design resulted in the well spacing being on only 25' centers at the mud line.
This paper will review the process which was used to successfully drill the required development wells. It will specifically review two processes, 1) batch drilling which significantly helped to reduce time and cost, and 2) kicking off in the upper hole which was required to reach the shallower upper intervals. Nonproductive/nonplanned time which impacted the project will also be presented. Finally, time and costs savings as a result of the improvements and combination of technical planning will be shown.
Despite the relatively simple geology and normal reservoir characteristics, several drilling challenges were foreseen for this project. Because of the number of wells to be drilled, several time saving measures could be implemented in order to reduce the overall cost of the project. Some of these measures posed added risk for a single well; however the techniques learned could potentially produce substantial savings on the subsequent wells. Many of the techniques employed posed no additional risk to the project.
Shallow water flows were experienced on two of the exploration wells, and although they were not severe, contingency plans had to be made to deal with a severe flow due to the unpredictability of these events.
Because of the planned wellbore architecture, all of the wells were deviated with some of the wells requiring significant horizontal departure. Because of this architecture, aggressive build rates in the upper (30") section of the wells would be required for several wells. In addition, due to the complex completions planned for each well, the wells needed to be within specified maximum hole angles at the top of the upper intervals for completions needs (Fig. 2).