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.

Hydrates and waxes are the main flow assurance threats in the development of deepwater fields. Prevention of wax deposition is a key component of preferred subsea deepwater system design. This paper discusses the challenges associated during the design of a deepwater field in the Indian offshore and the means of mitigation during the entire operating envelop. The deepwater discoveries for development lie in 400 – 800 mts of water depth, spread over 25 km with a recoverable volume of around 30 MMt of O+OE of gas and are envisaged to be tied back to a centrally located FPSO for handling and further evacuation. The fluid properties are very severe with high WAT and pour point. Limited case histories exist for deepwater fields developed with similar fluid properties. Low ambient temperature and poor fluid properties aggravate the likelihood of wax deposition and hydrate formtation. Based on the fluid characterization data for the development, issues due to wax deposition are expected. The present means of preventing flow assurance issues is through use of passive insulation, active heating or by chemically altering the thermodynamic behaviour. Various means were analysed either alone or in combination to arrive at an effective wax management strategy to surmount the deepwater barrier and to convert resources into production. The use of dual pipe-in-pipe system with high performing insulating material, combined with cluster based development aid in fluids arriving at temperatures above WAT over major part of the profile period. During the transient conditions wax management is envisaged through flooding of the well jumpers with chemicals and displacement of flowline contents, after the no touch time. Since the fields are to be developed on a fast track basis, limited data poses challenges in design. This paper highlights the flow assurance challenges that were studied to develop suitable wax and hydrate management during operational phase while maintaining the flexibility to accommodate modifications after actual fluid property data is available. The wax and hydrate management strategy proposed in this paper would facilitate in addressing a unique challenge of handling high WAT and pour point crudes with limited fluid data specifically in deepwater environment.

Subsea flow lines in deep water are typically exposed to high pressure and low temperature conditions which can create problems due to formation of gas hydrate. The gas hydrate formed can plug the flow lines causing not only loss of production, but may also create severe safety and environmental hazard. Moreover, dissociation of these plugs may take weeks or even months. Assessment of the hydrate formation potential during both steady is therefore an essential part of field development studies. The paper presents a case study of a gas field located in KG basin of India which was brought on production in 2018. The objective of the study was to assist the on-site team on issues related to hydrate inhibition during ongoing initial start-up operation and assess the arrival time of rich MEG in the onshore plant in view of turn down flow conditions during commissioning. The study also demonstrates how the transient simulations helped to monitor progress, identify and respond quickly to address the challenges during initial start-up operation of the deepwater gas field in Indian east coast. It emphasizes the need for accurate estimation of rich MEG arrival time and the minimum required gas flow rate from the subsea wells to ensure timely return of rich MEG to the onshore plant in order to avoid disruption in hydrate inhibition in the subsea system.