Flow Assurance Strategies in Indian Deepwaters: Issues and Means of Mitigation

Rathod, P.Ramulu (Oil and Natural Gas Corporation Ltd) | Sinha, N. (Oil and Natural Gas Corporation Ltd) | Ravishankar, B. (Oil and Natural Gas Corporation Ltd)

OnePetro 

Abstract

The relentless exploitation of hydrocarbon resources to meet ever increasing demand has compelled upstream companies to focus on deep and ultra-deepwater. Flow assurance is one of the most critical aspects in field development. The hydrocarbon product needs to be transported from a remote well to the process facility, without experiencing significant energy losses to the environment. Some of the oil discoveries in Indian deepwater are having high wax content; high Wax Appearance Temperature (WAT) and pour point flow assurance is a major challenge in low ambient temperatures.

A number of solutions like chemical injection (CI), mechanical insulation (Vacuum Insulated Tubing (VIT), Pipe-in-Pipe (PIP) etc.), Pigging, Piggy back line (PBL) and Electrical heating of flowline (EHFL) are the available means of mitigation to address these flow assurance challenges. In addition to high ‘steady state’ thermal insulation performance, the system has to provide good transient cool down behavior to prevent wax or hydrate formation during shut down and to minimize the time required for start-up. Through this paper an attempt has been made to generate a matrix for identifying the likely option for the means of mitigation individually or in combination, both for steady state and transient scenarios.

The various options have been studied for suitability for flowline under different flow scenarios like steady state, shutdown, restart, and turndown and for redundancy. Emerging options are further technically analyzed qualitatively, based on the extent of field use, robustness, tangible & intangible benefits etc. and evaluated to arrive at a suitable flow assurance strategy. For field X located in 600–700 meters of water depth, the combination of PIP and CI with EHFL as a fall back is emerging as the most suitable option. During initial start-up, the flowline can be preheated using electrical heating and the sample taken for identification of suitable inhibitors and for arriving at the required dosage. During shutdown and restart scenarios electrical heating of flowlines can be adopted to prevent the fluid from gelling.

The solution matrix presented in this paper will help in evaluating the available options and to arrive at the best suitable flow assurance strategy and means of mitigation, to any field during all operating scenarios.