Ram/Powell Tension-Leg Platform: Horizontal Well-Design And Operational Experience
Authors: Lester G. Scott , Lanier Gary H. , Javanmardi Kaz , Bernardi Tony , Halal Afif S. 
Published: October 2008

A key focus of the Ram/Powell project is to utilize high rate (&gt;20,000 BOPD), high volume wells (i.e., reserves several fold greater than that of shelf wells) to enhance project profitability. Completions with large 5-1/2" production tubing and horizontal open hole gravel packs exceeding 2000 feet in length have been successfully implemented. The horizontal open hole gravel packed design, the first implemented in the deepwater Gulf of Mexico, was selected as a means to improve well reliability over prior horizontal completion designs and sustain high production rates without plugging. A high rate of sand control failure and plugging have plagued prior Gulf horizontal non-gravel packed completions. Achieving high quality completions is a major project emphasis. Drilling, completion design, and operational experience of the wells drilled and completed to date are discussed.

Production from the Ram/Powell tension leg platform (TLP) development, Shell's 3rd TLP, began in September 1997. The TLP is located at Viosca Knoll block 956 in 3214 feet of water. Four wells were predrilled prior to TLP installation. To date 6 wells are completed, and a 7th is currently drilling. Five of the 6 completed wells are horizontal, open hole gravel packs, and one well is a cased and perforated, selective gravel packed completion. Additional wells are planned.

Introduction

Ram/Powell is a joint venture project consisting of three companies: Shell, Amoco and Exxon. Shell is the operator. The field is a unit consisting of 8 leases in the Viosca Knoll area (Fig. 1). A tension-leg platform (TLP) is set in a water depth of 3214 feet in the 956 block. The platform is very similar to Shell's Mars TLP. The platform consists of five modules: production process and utilities, power generation, personnel quarters, drilling, and wellbay modules. The structure can accommodate up to 20 wells plus two well slots designated for top-tension oil and gas export risers. A removable platform drilling rig, capable of drilling in excess of 20,000 feet, currently is installed. Waterflood facilities are installed for a possible future injection program, and provisions are in place to accommodate potential subsea satellites. The initial name plate capacity of 60,000 BOPD and 200 MMSCFD has since been increased from a debottlenecking operation to 70,000 BOPD and 260 MMSCFD.

Much of the project design and fabrication tasks involved participation by technical and managerial staff from all three companies based in a single office. Additionally, joint company committees were formed in the beginning to address key project issues such as selecting the development system.

In 1994 the project and subsurface teams revised the development plans to provide for some horizontal wells with larger tubing. This included increasing the dual casing production riser size from 9-5/8" to a larger 10-3/4" riser so that larger 4-1/2" production tubing with a full bore surface controlled subsurface safety valve (SCSSV) could be used. Subsequently, a maximum tubing size of 5-1/2" was incorporated to provide for even higher production rates. To date 6 wells are completed, and a 7th is currently drilling. Five of the 6 completed wells are horizontal open hole gravel packs, and one well is a cased and perforated, selective gravel packed completion. Additional wells are planned.