Abstract

Atlantic Richfield Indonesia Incorporated has started the implementation of a Supervisory Control and data Acquisition (SCADA) System for all of its offshore oil/gas production platforms in its Offshore North West Java contract area in Indonesia. This paper will outline the technical and operational requirements for the SCADA system and highlight some of the anticipated benefits for production monitoring, well testing, and management reporting.

Introduction

Atlantic Richfield Indonesia Incorporated (ARII) is a wholly owned subsidiary of Atlantic Richfield Company. ARII is a Production Sharing Contractor with Pertamina, the State owned oil company, for the development of the offshore North West Java contract area. The contract area was awarded in August 1966 and is located offshore in the North West Java Sea. It covers a surface area of 6.8 million acres, or approximately 27,700 square kilometers. Figure 1 is a field map of the contract area known as Ardjuna, Arimbi and Bima Fields. ARII's implementation of a SCADA system started in 1983 with the installation of one remote terminal unit (RTU) and one master station. This small SCADA system was expanded in 1984 into five remote terminal units as well as the addition of another master station and five remote terminal units for 1985 installation in a separate oil field. Figure 2 is a photograph of an offshore platform flow station where one of the SCADA master station's computer system is installed. Figure 3 is a photograph of a typical well platform with an RTU installed, along with solar panels, batteries, UHF radio, antenna, etc. In 1986 ARII will start installation of five additional SCADA systems which will consist of five master stations and 51 remote terminal units. Table 1 indicates the RTU distribution within the various oil/gas production areas.

Table 1: RTU Distribution per Production Area Existing Platforms New Platforms Field K P B E F L M Z A L

R T U 5 5 8 18 13 6 6 7 2 2

In parallel with SCADA system implementation new oil fields will be developed by the installation of new production platforms each of which will already be equipped with remote terminal units. In 1986 two new fields will be developed consisting of one master station on a central processing platform and 9 remote terminal units on production platforms. The two A platforms will be monitored and controlled from the Z field control platform. Currently producing oil fields will also be developed by the producing oil fields will also be developed by the addition of two production platforms. The two additional platforms to be installed in the L field will expand platforms to be installed in the L field will expand the number of production platforms controlled by the SCADA system to a total of 8 platforms. This represents a total of 72 production platforms that will be equipped with remote terminal units and 8 master stations which will be installed on central flow stations within each production field. New SCADA systems, remote terminal units and master stations, will be added as existing fields are expanded and new fields are developed. Production fields are spread over a large geographical area of the North West Java Sea, with some fields not even in line of sight with adjacent fields. Offshore platform SCADA systems provide production surveillance economics in the form of increased revenues due to increased production through continuous and better management of oil/gas production; and in the form of decreased costs due to decreased equipment inefficiencies, decreased loss of product and decreased maintenance.

PRODUCTION PLATFORMS PRODUCTION PLATFORMS ARII's primary objective of SCADA system implementation is to monitor wellhead pressures and alarm if well pressure deviation occurs. Figure 4 shows a simplified pressure deviation occurs. Figure 4 shows a simplified piping and instrument diagram of a production platform. piping and instrument diagram of a production platform. Each production platform contains a wellhead area where wellhead pressure transmitters are installed, see Figure 5, Production facilities include production separator, test separator and a gas lift separator where these are considered necessary. Oil, water and gas flow rates are metered and transmitted via the RTU to the master station computer, Gas flow rates are calculated, based on differential pressure (orifice plate), static pressure and temperature within RTU software. RTU gas flow calculations are based on American Gas Association Report No. 3. Supporting constants, orifice size, gravity, etc., can be hand entered into the master station data base and down loaded to the RTU gas flow calculation program. Various production platform valves are monitored for open and close status. Other alarm points monitored are intrusion detection, navigation aid failure detection, instrument air supply failure and battery low voltage. Fire and gas detection alarms, and a fire system malfunction alarm are transmitted to the master station where such facilities are installed on the production platforms, As shown in the simplified P + ID in Figure 4, platforms, As shown in the simplified P + ID in Figure 4, some platforms are equipped with submersible pumps which can be remotely stopped from the master station control console. Each pump's motor current is monitored as an indication of its production load and its on/off status is monitored from circuit breaker auxiliary contacts in the motor control center.

SCADA SYSTEMS

Each production field consists of an operationally independent SCADA system, consisting of a master station, located on the central flow station, and RTU's located on the remote well platforms, A typical SCADA system block-diagram is shown in Figure 6. Master station hardware consists of a microcomputer, a color CRT and keyboard, alarm printer, report printer, modem, UHF radio and omni-directional antenna. Each RTU consists of a micro-processor, analog to digital converters, pulse accumulators, status/alarm inputs, control, output relays, and communications interface consisting of modem, radio, and antenna. UHF Radio is utilized within each production field to provide data communications between the remote terminal provide data communications between the remote terminal units on production platforms and the master station on the flow station for that production field.

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