Abstract

Subsea well completion design and implementation in TotalFinaElf's Aconcagua Field and Marathon Oil Company's Camden Hills Field posed unprecedented challenges. Water depths in the area of planned development (up to 7209 ft) were greater than for any well previously completed in the world. Limited gas reserves in this high-cost, deepwater environment precluded future economic intervention, so the completion design had to balance the potential complexity of multiplezone production with high life-of-well reliability. Conducting the completions from a dynamically positioned (DP) drilling vessel, which had not yet been done at the time completion planning was underway, presented additional challenges. The extensive pre-planning, preparation for contingencies (for both the installation and production phases), and application of lessons learned for continuous improvement throughout the six-well installation program are presented in this paper. Because of limited space, only the most essential lessons can be discussed here.

Introduction

The Aconcagua Field (Mississippi Canyon Block 305) is located in the Gulf of Mexico about 140 miles southeast of New Orleans (Figure 1). The Camden Hills Field is located in an adjacent block (Mississippi Canyon 348). These fields, along with the BP-operated King's Peak Field, produce into the Canyon Express gathering and processing system.1 Produced gas from subsea wells in all three fields is conveyed approximately 55 miles via dual pipelines to the host processing platform operated by Williams Energy Services, located in Main Pass Block 261 and known as Canyon Station. The well completion budget comprised about 50-percent of the total project cost.

The producing reservoirs are a series of high permeability, unconsolidated sands, underlain in several cases by waterbearing sands. Well, rock, and fluid data are summarized in Table 1. Experience has shown that wells completed in reservoirs of this nature will water-out very quickly once water production begins. The ability to drain the multiple gas sands and shut-off water production without intervention was a key driver of the completion design.

The design of the high-rate deepwater gas producers eventually came to include stacked frac-pack sand control, pressure-operated fluid-loss/well control devices, and intelligent well completion equipment, with cleanup flow to temporary facilities on the rig. Completion work was conducted over a 9-month installation campaign from a dualderrick DP drillship. Significant challenges were met and overcome, and numerous "firsts" for both the operators andthe industry were established.

Development of Aconcagua and Camden Hills consisted of batch completion of six predrilled gas wells. Completion work was conducted from the Transocean Discoverer Spirit drillship between January and September 2002. Production startup occurred just after the sixth completion, and all wells are capable of producing at or above design rates (50 MMcf/D per well). Of equal importance to the well performance is the factthat all rig operations were conducted with a flawless safety and environmental record. No lost-time or OSHA-recordable incidents, environmental incidents, or Minerals Management Service incidents of noncompliance were incurred.

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