Abstract

Multi-lateral completion technology is evolving rapidly and continuing to mature in order to provide new methods for reservoir management and increase production potential.

ZADCO (Zakum Development Company) in conjunction with ADNOC (Abu Dhabi National Oil Company) / JODCO (Japan Oil Development Company) / JNOC-TRC (Japan National Oil Coraporation -Technology Research Center) / ADMA-OPCO (Abu Dhabi Marine Operating Company) and SSDS (Sperry-Sun Drilling Services) has successfully completed MLTBS Phase-1 (Multi- Lateral Tie Back System) utilizing an existing well, a level 5 TAML (Technology Assessment Multi-Laterals) completion and level 4 TAML hydraulic isolation.

MLT(Multi-Lateral Technology) application for the existing well was the first achievement in the world. In addition, several new technologies such as running and full cementing 7" liner in 8–1/2" lateral, recording cement evaluation logs over the cased lateral using TLCS (Tough Logging Condition System), and perforating the cased lateral with one run using TCP (Tubing Conveyed Perforator) were firstly implemented in UAE.

Three years of R&D, integrated planning, and testing were required by MLTBS project team before attempting the extremely aggressive trial.

The ultimate success of the Phase-1 trial on Well-A will encourage introducing MLTBS into Upper Zakum field to -:

  • Re-establish dry oil production by locating the horizontal section in an optimum layer of upper reservoir.

  • Allow access to upper cased lateral and lower barefoot lateral on demand through the newly designed dual completion.

  • Achieve effective stimulation increasing production capacity of both upper cased lateral and lower barefoot lateral.

  • Leave future options for reservoir monitoring and extending the well life by drilling a secondary lateral or applying selective water shut-off in the upper cased lateral.

MLTBS will provide planning flexibility to exploit reservoirs to their maximum potential, allowing ZADCO to create new development strategies.

Introduction

The upper and lower reservoirs have been developed simultaneously adopting a five spot water injection pattern in Upper Zakum field since 1984.

First water breakthrough was confirmed in the upper reservoir in the middle of 1991. Since then, the number of water cut strings gradually increased to reach about 40% of the total production strings. Well production capacity has declined rapidly once water breakthrough occurred. A high permeable layer at the bottom of the upper reservoir caused the unexpected early water breakthrough (Fig. 1).

Horizontal drilling technology has been widely applied since 1989. Dual or Multi-lateral drilling technology combined with dual completion with no access function to the lateral(s) in the upper reservoir has been applied for developing both reservoirs since 1994.

It was believed that an optimum placement of the lateral as well as introducing a new completion system with access function might offer an effective mean to improve productivity, monitor the breakthrough and reduce (or delay) the water production from the upper reservoir.

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