Oil and Natural Gas Corporation clinches Asian Oil and Gas Awards

The company aimed to address the bottlenecks in back pressure, intermittent flaring, and liquid carryover.

Integrated energy company Oil and Natural Gas Corporation (ONGC) brought home the Offshore Initiative of the Year - India at the Asian Oil and Gas Awards for its debottlenecking of FPSO through a novel approach to optimising the surface facility of unmanned wellhead platform.

Previously, the FPSO was deployed to take the production from offshore fields, due to the expansion and development of offshore fields, the production has increased. The increased gas feed is creating problems of surges, intermittent flaring and carryover of liquid and causing a bottleneck to the FPSO. Debottlenecking of FPSO through a novel approach of optimising the surface facility of the Unmanned Well Head Platform was done.

The well fluid from the fields was routed to XYZ unmanned platform. Furthermore, the well fluid from the unmanned platform was routed to FPSO via two 12’’ well fluid line streams. The free gas from the ZZ unmanned platform was also routed to the XYZ platform via a 10” line and further routed to FPSO via one 10’’ free gas line. However, due to the development of new fields, the production increased and the FPSO faced a bottleneck in handling the feed of 1.1 MMSMD gas & 23000 bbl/d liquid against the design capacity of 0.9 MMSCMD gas & 30000 bbl/d liquid, respectively. Whilst the free gas system is processing 0.22 MMSCMD against the design capacity of 1.2 MMSCMD, the increased feed is creating problems of back pressure, surges, intermittent flaring and carryover of liquid.

In the current situation, a major shutdown of FPSO is not possible for changing the surface facility. In this study a novel optimisation strategy is presented, that consists of multiple steps, including investigation of the problem, finding of bottleneck, various technical solutions, and an option selection. The aim of the study is mainly focused on how to debottleneck the FPSO and optimise the surface facilities.

The total well fluid coming to FPSO is via XYZ and the study reveals bottlenecks for handling of associated gas in slug catcher, but there is sufficient spare capacity available for free gas handling systems. As such, by separating the gas from the well-fluid stream and diverting it to the free gas stream, it will reduce the load on the slug catcher at FPSO and this will mitigate the problem of intermittent flaring and carryover of liquid.

The main focus of this novel approach of optimising the surface facility of the unmanned wellhead platform to process the increased production by limiting the CAPEX, compact, low-weight solution, in view of space and weight constraints at the wellhead platform. All the possible scenarios were simulated in software and studied. In view of the above, the use of an inline pipe separator is envisaged to be the best solution for the removal of maximum associated gas from the well-fluid before sending it to FPSO. By using this approach the load at FPSO will be reduced and this will mitigate the problem of intermittent flaring, surges and carryover of liquid.

The simulation study was done to prove the effectiveness of the solution for the separation of the gas from the oil well-fluid stream. There is overall pressure reduction in the piping system, leading to reduced back pressure on wells by 1-2 ksc. This novel approach thus brings about an additional benefit of production gain of 287 to 577 BLPD apart from de-bottlenecking the process facilities.

The Asian Oil and Gas Awards recognises exceptional initiatives in the oil and gas industry in Asia.

The Asian Oil & Gas Awards is presented by Asian Power Magazine. To view the full list of winners, click here. If you want to join the 2024 awards programme and be acclaimed for your company's outstanding contributions and initiatives in the oil and gas sector in Asia, please contact Danica Avila at [email protected].