Intelligent-Completion Technology in a Triple-Zone Commingled Producer
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 101021, "Application of Intelligent-Completion Technology in a Triple-Zone Gravel- Packed Commingled Producer," by W.R. Brock, SPE, E.O. Oleh, SPE, J.P. Linscott, and S. Agara, SPE, Mobil Producing Nigeria, prepared for the 2006 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 24–27 September.

Many oil fields contain stacked reservoirs, each requiring multiple individual wells for proper and timely depletion. By commingling multiple reservoirs in a single well, the total number of wells required for field development can be reduced, resulting in significant cost savings over conventional development especially in offshore areas. Use of intelligent-completion technology can properly manage the recovery of reserves from each individual zone in a commingled completion.

Introduction

The Usari field is approximately 16 miles offshore Nigeria in 72 ft of water. The field development currently consists of 25 wells from two wellhead platforms that produce into a central production platform.

In total, 35 reservoirs have been discovered in the Usari field. These reservoirs have been subdivided into three main categories on the basis of fluid properties, pressure regimes, and geologic setting. These categories are referred to as the shallow (18 reservoirs), intermediate (15 reservoirs), and deep (two reservoirs). Currently four reservoirs in the shallow, 10 reservoirs in the intermediate, and the two reservoirs in the deep are being produced.

Graben Geology

Seven reservoirs in the graben area were discovered by a near-field wildcat in 2001. The seismic data over this area are masked by shallow gas that causes a significant reduction in seismic-data quality. Therefore, confidence is low in the structural configuration. Because of the potential size of the graben resource, and the distance from existing platforms, mitigating the geologic uncertainty was necessary before any commitment could be made for additional platforms that would be necessary for full development. Key uncertainties identified to be addressed by three early development wells are potential reservoir compartmentalization, reservoir areal extent, and reservoir deliverability.

Completion Strategy

To reduce graben structural risk, the target location for the first of three development wells was less than 650 ft from the penetration point of this reservoir by the near-field wildcat. Seismic data and dipmeter indicated that the reservoirs are dipping to the north-northeast from 6 to 10°. Because the wellbore path was oriented in a downdip direction, progressively deeper reservoir penetrations will be further removed from their structural crest. However, all reservoirs were expected to be penetrated well above their original water/oil contact.

The well was planned as an extended reach from one of the existing platforms, with a high sail angle (75°) dropping to 20 to 25° across the target interval. The well completion would be across three of the seven reservoirs: the 7-US1G (upper reservoir), 8-US1G (middle reservoir), and 9-US1G (lower reservoir). Completion of these three reservoirs will provide information to help mitigate the uncertainties about reservoir deliverability and producing characteristics.