Abstract

In search of technical innovations which could make development projects in mature fields more attractive, MultiLateral Well Drilling was identified as the most promising emerging technology. This year PETRONAS Carigali will drill its first trial well to assess the applicability of the technology in Malaysia.

The target reservoirs for the Multi-Lateral Horizontal Well consist of a stacked laterally continuous sand-shale sequence, containing medium heavy crude(19.5 API and 10 cP). The sands have good reservoir properties with high isotropy and a permeability over 1 Darcy.

The well is designed to provide three branches of horizontal drainage holes in different reservoirs. These are planned to be produced selectively through a dual completion.

Special attention was given to the design of the well trajectory. Due to the relative position of the platform and the main Bokor Field boundary fault, the well trajectory had to be curved to allow confident approach of the desired reservoir targets using MWD/LWD.

Since the upper two laterals branch from the main well bore in a prolificwaterbearing sand-shale sequence, it is essential for the success of the well, that isolation from the formation is achieved at these branch points.

The unconsolidated nature of the sands makes sand control a necessity. Standalone all metal screens are selected as the best sand control technique for the conditions in the Bokor Field.

Introduction

PETRONAS Carigali operates mature fields in the Baram Delta. Many of these fields consist of large sequences of stacked reservoirs. Development of reservoirs in these fields with horizontal wells was successfully implemented for the larger reservoirs in the Baronia Field, but in the other fields deviated wells completed on multiple zones are often more attractive.

A survey of developing technologies, with the potential to improve attractiveness of field development opportunities, was carried out. The technology survey identified Multi-Lateral Horizontal Wells as a newly emerging technology with potential for application in these multi-zone reservoirs. A feasibility study was carried out and a pilot project initiated.

PETRONAS Carigali will drill the first Triple-Lateral Horizontal Well in South-East Asia in September 1996, in the Bokor Field.

The Bokor Field is located some 15 miles offshore Sarawak in the Baram Delta(Fig. 1). The 55 stacked oil bearing reservoirs contain a STOIIP of some 750MMstb. Some 25 % of this is located in the most shallow oil bearing reservoir sequence: the A-reservoirs. These reservoirs are particularly suited for development with Multi-Lateral Horizontal Wells for the following reasons (Ref.1):

  • well understood simple geological structural model

  • excellent lateral continuity

  • three thick clean sands with good reservoir properties and significant reserves

  • well established fluid contacts

  • offtake from the existing conventionally completed deviated wells is constrained by the reservoir deliverability resulting from a limited PI and low reservoir pressure

  • edge water drive with the water undermining the oil forming Dietz tongues

The main sands in the A-reservoir sequence are the A3, A4 andA6-reservoir.

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