Abstract

Wells drilled from the Dulang D platform are the deepest and have the highest step-out ratio of any wells drilled by Petronas Carigali Sdn Bhd (PCSB) in their peninsular Malaysia operations. Well inclinations reach 83 degrees making perforation by conventional wireline techniques impossible. Additionally, several wells in this part of the Dulang field are characterised by perforation intervals which are very close to the oil-water contact. This means that perforation guns need to be precisely correlated on depth.

The use of drillpipe conveyed TCP guns overcame the problem of well inclination, but a method was still required to place the guns accurately on depth. Through the use of innovative 'rolling systems' type wireline tools, wireline logging runs with gamma ray and CCL were made through the TCP deployment string to place the guns on depth. The wells were drilled with logging while drilling tools (no open hole wireline logs were run) which gave clear markers for downhole log correlation.

The paper describes the background to the Dulang field development, the drilling and characteristics of the Dulang D wells, and the completion design. The paper focuses on the perforating aspects of the well completion operations. The innovative wireline tools and techniques used in achieving the goals of the well perforation will be explained. Completion operations on the most highly deviated Dulang D well will be described to provide a detailed insight.

Background

The Dulang Field is located in block PM 6 offshore Terengganu (fig 1) in a water depth of 76 metres. Exploration drilling by PCSB in 1981 and Esso Production Malaysia Inc (EPMI) in 1981 led to it's discovery. The Dulang field is divided into 3 areas (Fig 2):

  1. The Unit Area which straddles PCSB's and EPMI's contract boundaries

  2. The Western Area which belongs entirely to PCSB

  3. The Eastern Area which belongs entirely to EPMI Following the discovery of the Dulang field, EPMI and PCSB signed a Unitisation Agreement in 1988 to jointly develop and produce from the Unit Area with PCSB as the operator.

Facilities at Dulang field consist of:

  • three unmanned drilling platforms (Dulang A, Dulang C and Dulang D)

  • a central integrated production platform Dulang B

  • a Floating Storage and Offloading system (FSO)

  • a subsea pipeline network (fig 3)

In Phase I development, Dulang A and B platforms, the associated pipelines and the FSO were built and installed with first production coming on stream in March 1991. In Phase II the installation of the Dulang C platform was completed in 1993. Installation of the Dulang D platform was completed in phase III in 1995. In 1994 the average oil production was 48,000 bpd and in 1996 production has peaked at 76,800 bpd with Dulang D coming on stream.

The Dulang D platform is situated in the Western Area of the field (fig 2). Scissors-like north west and south east faults separate the Western Area from the Unit Area. It is assessed to contain approx 240 MMSTB of oil initially in place.

Dulang Field Challenges

Wells drilled from the Dulang D platform are the deepest and have the highest step-out ratio of any wells drilled by PCSB in their peninsular Malaysia operations. Additionally, several wells in this part of the Dulang field are characterised by perforation intervals which are very close to the oil-water contact.

These characteristics lead to a number of concerns with regard to drilling and completion of the wells:

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