Mature-Field Subsurface Integrity: Holistic Diagnostic Approach in Malaysia
Authors: Carpenter Chris 
Published: February 2015

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 165634, ’Mature-Field Subsurface Integrity: Formulation of a New Paradigm Through a Holistic Diagnostic Approach for D Field, Malaysia,’ by Wan Rokiah Ismail and Almag Fira Pradana, Petronas Carigali, prepared for the 2013 SPE Latin American and Caribbean Health, Safety, Social Responsibility, and Environment Conference, Lima, Peru, 26-27 June. The paper has not been peer reviewed.

As a field matures, there is a crucial need to focus on integrity-related issues such as hazard prevention and mitigation. During the initial field development of D field offshore Terengganu in Malaysia, the well design was fit for purpose to meet production needs. However, extension of production requirements contrary to earlier plans, a production-driven operational philosophy, and irregular well-integrity surveillance have compounded integrity issues. To rectify this trend, a field redevelopment was based on a number of concrete steps.

Field Overview

D field is an oil- and gas-producing field that saw its first hydrocarbon discovery in 1981. After a series of appraisal wells and the formulation of a field-development plan, the field’s first oil production was realized in March 1991. The field’s primary production is oil from multistack major reservoirs X1 and X2, with 30 to 70% CO2 concentration. D field has a total of four producing platforms, consisting of one main platform with three satellite platforms. The production streamlines from the satellites undergo separation processes at the main platform before collection at the floating storage and offloading facility.

Currently, the field is operating with a total of 218 completion strings. The main platform consists of a separation-process unit, a water-injection module, a gas-injection module, and a produced-water-treatment system. Dedicated gas and water pipelines run to each satellite platform, meeting the requirement of water and gas injection to the reservoir as part of the reservoir- management plan. In addition, enhanced-oil-recovery (EOR) implementation is being assessed as part of the effort to increase production.

Problem Statement

From 2010 to 2012, a 60% decline in daily production rate was observed, largely as a result of integrity issues. Operating under a wide range of CO2 concentrations in hydrocarbons poses a challenge in the initial material selection for well completion, which can in turn greatly affect well integrity and life span. Furthermore, the early-optimization philosophy for water and gas injection led to the use of one well slot with dual-utility well completion, which complicates well intervention and deteriorating well-integrity assurance because of the difference in operating temperatures between the two strings in a wellbore.

Extensive diagnostic surveys and well-integrity logging were conducted from 2010 to 2012 in order to determine the condition of subsurface well integrity and safeguard the production and reservoir-management-plan requirements for the EOR project. To ensure deliverables, the team has adopted a series of systematic guidelines to diagnose well integrity.