Abstract

The oil industry has lately seen the introduction of more complex, purpose built multilateral wells of the TAML (Technology Advancement Multilateral) levels 4 and 5 categories. The debris management issues, junction integrity and the risk involved in the well construction are still perceived as operational challenges to operators. In reviewing the risk profile, operators and service companies alike have sought to look into techniques outside the realm of conventional well construction methods. Expandable tubular technology is one such area. The manufacturing concept is to form a junction with a 9–5/8" trunk casing branching into two separate 7" liner legs. This junction is then pressed and formed in order for it to be able to pass through the drift ID of 13–3/8" casing. The junction is then reformed downhole using an innovative downhole swaging process.

This paper describes the process of deploying the TAML level 6 multilateral junction in the Erb West Field (offshore Malaysia) during the EWDP-A Revisit 4 Campaign (well EW-117S1). The discussion follows the full cycle of well construction for a level 6 multilateral junction. It encompasses the well planning phase, the deployment and the installation phase, the lateral drilling phase, and finally the completion of the level 6 multilateral well. The result is a multilateral well construction technique which eliminates the debris management, reduces well construction risk and provides a hydraulically sealed junction, integral with the trunk casing.

Introduction

The Erb West Field is situated, 125km offshore Malaysia, in approximately 215ft of water. The first discovery well in the field was EW-1, drilled in 1971, and subsequent development brought on first oil in October 1981.

In the field appraisal campaign almost 2 decades ago, a total of 6 exploration/appraisal wells were drilled. In subsequent development plans two offshore platforms have been constructed namely, EWDP-A and EWDP-B.

The EWDP-A Revisit 4 Campaign involves the sidetracking of existing wells to develop and produce from undeveloped blocks South-East of the Erb West structure. A total of 7 horizontal targets have been identified, and 5 candidate wells have been earmarked for the workover. However, slot constraint is a challenge, and the azimuth of the existing candidate wells are not aligned in the South Easterly direction.

The revisit campaign poses a daunting challenge across all disciplines in the well construction team. Amongst the options identified, the concept of a dual lateral multilateral well with long reach laterals gave the best fit within the solution set. The team consensus was that the campaign economics favored the adoption of a multilateral approach to well construction.

Description of the Reservoir Characteristics

The Erb West structure is an elongated hydrocarbon bearing sand layer, and it lies in a North-Easterly by South Westerly direction. The main faults in the blocks are in the East - West direction, concentrated in the Southern half of the structure. It is the entrapped hydrocarbon within these southern blocks that are targeted for the revisit campaign.

The main oil bearing layers in the cross section are the "N" sands, serialized from N-2 to N-7, and these are stratified fluvic deposits. The gas oil contact from offset information is around 6803ft TVD and the water oil contact is around 6930ft TVD. Oil gravity averages around 31 API, and the gas constituent is 92% methane.

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