Abstract

The introduction of roller cone bits incorporating a unique gauge cutting mechanism, in combination with other gauge and hydraulic modifications, dramatically increased drilling efficiency and lowered the costs of two major development projects offshore Sarawak, Malaysia. The aforementioned technical modifications and other continuous improvement practices, which resulted from close interaction between operator, contractor and bit company, saw drilling costs reduced nearly US$378,000 on the Baram and Baronia development programs.

This paper describes the evolution of operator-driven tool development and operational practices that led to increased footage and penetration rate per bit in the interbedded shale, sandstone and limestone intervals intrinsic of the directional wells drilled offshore Sarawak. The authors will review the two fields (Baram and Baronia), detailing the tool and operational modifications that significantly improved the economics of the development drilling campaign.

Introduction

In early 1994, Baram Delta Operations (BDO) launched an aggressive development drilling program on its Baram and Baronia fields, two of nine structures discovered offshore Lutong, Sarawak, Malaysia. Fig. 1 shows the location of the two fields on the SK15 concession at the mouth of the Baram River.

A total of 61 wells have been drilled in the development program, including 33 on the Baram field - discovered in 1963 with exploration well Baram-1 - and 28 on the Baronia field, which was discovered in 1967.

The two fields are located in the structurally complex Baram Delta Province, where nearly 730 hydrocarbon-bearing reservoirs have been identified. The region features abrasive intervals and extremely depleted reservoirs that possibly overlay severely overpressured formations. Generally, the structures are complexly faulted, comprising interbedded sand and shale with limestone and dolomite intervals. The sands, which are fine and angular, tend to be sharp and highly abrasive. Fig. 2 is a cross-section of the Baram field, highlighting its structural complexity.

The often unpredictable geology of the Baram Delta Province has caused numerous development drilling problems, particularly in the deeper wells. Chief among the drilling problems are stuck pipe, lost circulation and abrasion-induced drillstring washouts.

Owing to its complexity and highly troublesome characteristics, the Baram field was selected as the testing ground for most of the experiments directed at improving efficiencies in the development drilling program. The knowledge gained in the Baram experiments was subsequently implemented in the younger Baronia field.

BDO Drilling Efficiency Program

A typical well in the recently concluded Baram Delta Operations campaign was drilled directionally from either a cantilevered jack-up or from a tender-assisted rig on the "F" platform. On the average, a BDO well was drilled to a total measured depth of 8,000 ft.

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