Optimum Development in Mature Fields: Sanga-Sanga Assets, Indonesia

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 158716, ’Renewal Plan: Efficient Strategy for Optimum Development in Mature Fields - A Success Story From Sanga-Sanga Assets, Indonesia,’ Andre Wijanarko, Bambang Ismanto, and Robhy Permana, VICO Indonesia, and Italo Pizzolante, Eni, prepared for the 2012 SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, 22-24 October. The paper has not been peer reviewed. VICO Indonesia is the operator of the Sanga-Sanga production-sharing contract (PSC) in Indonesia. Against a backdrop of 46% annual base decline, VICO generated and implemented an integrated and aggressive work program called the Renewal Plan. This is an integrated approach between reservoir management and technology application. This plan proved to be an efficient example of better reservoir management for optimum development of mature assets. Introduction The Sanga-Sanga acreage is located onshore in the Mahakam delta, East Kalimantan, Indonesia. The acreage is located within the Kutai basin, which is characterized by the Samarinda anticlinorium, with a series of highly prolific anticlines. Hydrocarbon accumulations are most often located within a series of mid-Miocene upper-delta and delta-plain sandstone reservoirs, and are principally characterized by fourway dip closure or two-way structural/ stratigraphic traps. VICO Indonesia has been exploring and developing this PSC acreage actively since 1968. There are seven producing fields (Fig. 1): Badak, Nilam, Semberah, Mutiara, Beras, Pamaguan, and Lampake. These together produce 385 MMscf/D of gas and 14,500 B/D of liquids from 420 active wells, which have mixed wellbore completions (single, dual-selective, monobore, dual-monobore, and horizontal). The surface facilities supporting the production include four main production centers, 12 gathering stations, and more than 90 compressors. After 40 years of production, these fields have now reached a fairly mature stage; most of the penetrated reservoirs/ tanks have been depleted from original pressures. Coupled with the annual production decline, this condition has resulted in significant challenges to delivering a continuous economic and efficient field-development strategy while maximizing field production. Renewal Plan VICO carried out a reserves-reassessment study—an integrated approach involving reservoir management and technology applications conducted by a multidisciplinary team. The seven components of the Renewal Plan are described in the following subsections. Securing Base Production. Securing base production is one of the keys to achieving a production target. Well monitoring and surveillance are the primary methods by which base production is secured. Previously, VICO wells were monitored by frequent production tests, mostly depending on human surveillance. In the Renewal Plan, automated real- time monitoring well surveillance of wellhead-pressure and flow-rate data on each well was implemented. This real- time wellhead surveillance (RTWHS) transmits the data from the wellsite to the VICO server; then, it is stored in a database. Operators and production engineers could monitor the behavior of the well in real time. This system has proved to minimize well downtime, leading to aggressive well reactivation. This installation has also become standard for new wells. Currently, 90% of VICO’s active wells are equipped with RTWHS.