New Opportunities for Time-Sensitive Gulf of Mexico Completions
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 18857, "New Opportunities for Time-Sensitive Gulf of Mexico Completions," by Allen W. Womble, SPE, Ed Van Sickle, SPE, and Mike Mckown, SPE, Baker Oil Tools, prepared for the 2007 Offshore Technology Conference, Houston, 30 April-3 May.

Adaptation of single-trip multizone sand-control completion systems in the Gulf of Mexico (GOM) for frac packing has created new opportunities for time-sensitive completions. Frac packing involves relatively large amounts of complex fluids and deployment of capital-intensive equipment. Time becomes a significant variable in project economics. In 1990, after completing several hundred wells successfully in California, single-trip multi-zone technology was introduced to the GOM. Two key drivers provided the initial opportunity for GOM applications: minimizing rig time and reducing formation damage by reducing formation exposure time to completion fluids.

Introduction

Single-trip multizone gravel-pack systems are not new to the GOM, but the adaptation to frac packing has created new opportunities for this technology. Single-trip multizone gravel-pack completions were proved first in the early 1980s in the Beta field offshore California. The productive interval there was composed of as many as nine separate zones with a gross interval thickness of 1,200 ft. The system provided zone isolation in the form of packers without the normal packer slips; hence, the first zone-isolation packers were created. The gravel-pack-liner assembly consisted of a series of screen/isolation-packer/gravel-pack port combinations, one combination per zone. Sealbores were positioned above each isolation packer and below the gravel-pack port, to be used for positioning of a gravel-pack-seal assembly during gravel packing. All producing zones were first perforated simultaneously by use of tubing-conveyed-perforating guns. The appropriate number of gravel-pack assemblies was assembled as a single unit, and a conventional gravel-pack packer, with slips, was positioned at the top gravel-pack assembly. The entire single-trip multizone system then was run to bottom on drillpipe. Once the system is positioned across the producing interval, the upper gravel-pack packer is set, the setting is released, and the gravel-pack-seal assembly is used to set all zone-isolation packers hydraulically. A smaller pipe string was run concentrically through the drillpipe to bottom and stung into the gravel-pack-seal assembly. The lowermost zone then was gravel packed, with slurry transported down the inner work string and clean return flow moving up the miniannulus between the two strings. Repositioning the tool to pack all upper zones required pulling both the drillpipe and concentric pipe up the incremental distance between zones. This original system, given the name "Beta" system in reference to the field where the system was used, was used successfully in more than 250 wells involving more than 2,000 zones from 1981 to 1991, resulting in significant completion time savings.