Abstract

The North Rankin 'A' Platform has been in operation since Hay 1984 following an eighteen month period of Hook-up and Commissioning. This paper period of Hook-up and Commissioning. This paper provides a summary of the organisation and provides a summary of the organisation and activities associated with Hook-up, Commissioning and Start-up of the Platform Facilities and provides a number of examples of lessons learned from the Start-up process. Furthermore, significant ongoing problems and where relevant, their solutions are problems and where relevant, their solutions are also highlighted.

Introduction

The North Rankin 'A' Platform is the first platform to be installed on the gas fields of the platform to be installed on the gas fields of the North West Shelf Project. Its function is to tap the natural gas and associated condensate reservoir. located 135kn offshore from the town of Karratha off the North West Coast of Western Australia. The platform, located in a water depth of 125 metres, is platform, located in a water depth of 125 metres, is a combined drilling and production platform with gas and condensate processing facilities capable of handling up to 34.0 × 106m3/d (1200 MMSCFD) production through three identical process trains. production through three identical process trains. To date, seven production wells have been drilled and are available to meet the majority of gas supply requirements of Western Australia through the supply contract with the State Energy Commission.

PROCESS DESCRIPTION PROCESS DESCRIPTION Wellfluid is choked at the wellhead to the process operating pressure of 11.3 MPa (1600 psi), cooled in the Production Cooler and separated into two phases in the Production Separator. Gas dehydration is accomplished by contacting the wet gas with triethylene glycol in a trayed absorption column. The glycol is regenerated to remove the absorbed water and then recirculated back to the contactor. Condensate and formation water from the Production Separator is further cooled and passed through an additional separator to remove water and particulate matter. The condensate product is further filtered and passed to a coalescer for removal of remaining water down to less than 0.01% (100 ppm) volume. The treated condensate is then reinjected into the dry gas stream for transmission to shore. Produced water is discharged overboard. Total water content of the combined gas and condensate stream leaving the platform is 0.19 g/m3 (12 lbs/MMSCF). Onshore, gas and condensate are separated and further treated prior to sale as pipeline gas and stabilised condensate products. A simplified process schematic is given in Figure 1.

START-UP ORGANISATION

The start-up of any processing facility is the pinnacle of all previous activities and for the pinnacle of all previous activities and for the North Rankin 'A' Platform the start-up required the integration of Hook-up, Commissioning and Operations activities into one plan. To this end, a start-up Team was set up to plan, monitor and execute start-up of the production facilities. The team, which began its work some six months before the actual start-up date consisted of a core of four senior engineers drawn from Platform Operations, Engineering and Projects groups. Specifically, the team leader was Senior Production Engineer - Operations assisted by the Production Engineer - Operations assisted by the Senior Facilities, Senior Instrument and Senior Commissioning Engineers from other groups (see Figure 2). This mix of personnel was essential to ensure that the sometimes conflicting demands of Construction and Operations, together with initial designer's intent, were all recognised in a forum that was solely aimed at ensuring an ordered and timely start-up. The start-up team approach worked well and will be repeated for future platforms.

HOOK-UP AND COMMISSION

The Hook-up and Commissioning phase of the project was entirely managed by the Operator, Woodside Offshore Petroleum. The group was formed in 1981 initially providing technical assistance at the module fabrication sites and planning for the offshore phase. Offshore mobilisation took place in December 1982 with two offshore teams of discipline engineers reporting to an Offshore Resident Engineer supervising the activities of the Hook-up Contractor who was engaged to supply labour, supervision and equipment. The group's responsibility was to take the platform from module lift to the point where first gas could be taken on board. Three distinct phases were planned and executed. 1. Life Support 2. Drilling Support 3. Production Support Advanced life support was completed in January 1983 with the commissioning of living quarters, water systems, power generation, temporary fire and gas systems and some communications. This allowed for 200 people to be accommodated on board. Drilling support and completion of all life support facilities was achieved in August 1983 with the first production well being spudded on 24 August. During this phase all equipment and systems necessary for drilling a well were completed. Production support was achieved in May 1984 with the start-up activity bringing first gas on board on 7 May. Commissioning of Production and Utility systems ran in parallel with Drilling Operations. Platform commissioning was the responsibility of the Platform Commissioning Engineer (PCE) who reported to the shore-based Senior Commissioning Engineer The commissioning responsibilities included technical coordination with the vendor's discipline engineers and user groups as required to commission equipment and systems in accordance with the program me. The discipline engineers were drawn into program me. The discipline engineers were drawn into the commissioning team as required, together with a number of personnel from Operations and Maintenance who were seconded into the team to gain hands-on experience. Typically, as an entire system or viable portions of a system were completed, the responsible discipline engineer advised the PCE that the system was ready for commissioning. The PCE would in turn check the equipment, review the precommissioning Engineering Test Records (ETR) and assign a team leader to commission the system in accordance with the commissioning manuals. Statistics for Platform Commissioning are given in Figure 3.

Leak Testing

Leak testing of the production systems utilised a nitrogen/helium mixture rather than the conventional soap solution "bubble test". During the testing period, which was performed over a two month period, period, which was performed over a two month period, 559 leaks were found and rectified.

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