Successful Implementation of Field Start-Up Strategy for Deep Water Unconsolidated Oil Fields with Flow Assurance Challenges - A Case Study in KG Offshore, India
Authors: Kyatham Ashwith , Kumar Anand , Marandi Pratik , Kumar Ratnesh , Gubbala Santoosh 
Published: November 2024

KG-DWN-98/2 is India's Deep water Eastern Offshore Block with water depth ranging from 400 to 2890 m. A part of the block comprising three fields namely BC-1, BC-2 and BC-3 is being developed in which 5 oil producers and 2 water injectors had to be connected to Floating Production Storage and Offloading (FPSO) system using subsea production system. The objective of the paper is to formulate a start-up strategy to successfully flowing the first oil to FPSO in tandem with reservoir deliverability and flow assurance constraint.

The main challenge in development of these fields was subsea environment having seabed temperature around 5°C with unconsolidated reservoirs limiting quick production ramp up operation which was required to attain temperature above pour point in subsea loop. Constraints from reservoir till topsides were analysed providing an overall picture and depicted clear ranking to develop the start-up strategy. The well opening sequence and bean up strategy was used to device different scenario, so as to achieve turndown rates required to maintain temperature in subsea jumpers, flow lines, manifolds and riser with optimum drawdown in initial start-up of wells.

The fields are present at water depth of 400 to 600 m having Pliocene reservoir with unconsolidated nature sandstone and waxy crude oil with bulk wax appearance temperature (WAT) 40°C and Pour point around 39°C. Fields had major flow assurance challenges of hydrate formation, wax and scale deposition and slug flow. Pre-opening strategies involving hot diesel circulation and xylene flushing followed by pour point depressant (PPD) and methyl alcohol (MeOH) injection in the well prior to well opening were the key decisions that equipped this start-up overcome flow assurance challenges followed by sequential well-opening. The FPSO came streamline on 7th Jan 2024, at 04:00 hrs the first well X-2 was started and flare was ignited at 09:00 hrs. Followed by, the remaining wells were successfully opened as per the start-up strategy. Combined ramp-up of all the wells was carried out up to the planned bean size and cumulative production of 12,000 BPD was achieved with manifold temperature above the pour point. Optimal drawdown and continuous pressure/ temperature monitoring played key role in achieving the first flare at FPSO.

This paper will present how the bean up strategy and methodologies along with flow assurance studies help in field execution plan and implementation. With the use of real-time data, online monitoring, and accurate production information an effective strategy can be implemented. This strategy integrates subsea data with pressure/temperature profiles to provide engineering and operations a real-time snapshot of conditions from down hole to topsides. Based on this data, further adjustments to flow assurance chemical dose rates can be optimized to maximize production while minimizing operating expenditures.