Flow Assurance continues to remain a major challenge in offshore production operations. Current methods for avoiding gas hydrate problems are generally based on one or a combination of the following three techniques:injection of thermodynamic inhibitors (e.g. methanol, ethylene glycol) to prevent hydrate formation,use of kinetic hydrate inhibitors (KHIs) to sufficiently delay hydrate nucleation/growth, andmaintaining pipeline operating conditions outside the hydrate stability zone by insulation and/or active heating and/or by controlling pressure.1 However, for many production operations, particularly deepwater fields, those requiring long tiebacks, and mature reservoirs (where water cuts can be very high), the above techniques may not be economical and/or logistically practical. Thus the industry needs novel and improved techniques to tackle flow assurance problems for such challenging conditions. The new approach presented in this paper -HYDRAFLOW- aims to meet this need. HYDRAFLOW is a novel 'cold flow' concept, which breaks from the tradition of straightforward hydrate prevention. Instead, gas hydrate formation in pipelines is intentionally induced and managed, eliminating the need for expensive thermal/chemical inhibition while improving the economics and practicalities of multiphase fluid transport. Experimental analyses of low and high GOR systems for various different production scenarios with and without AA (Anti-agglomerant) have been undertaken as part of HYDRAFLOW concept development. The effect of simulated shut-in on fluid transportability has also been tested. A new experimental set-up for measuring the viscosity of the fluid system under high-pressure conditions has been designed and commissioned in order to evaluate the rheology of the systems under investigation. Results prove that the concept is viable (at least under laboratory conditions), and strongly suggest that HYDRAFLOW technology could offer significant benefits over existing flow assurance strategies, providing a novel low CAPEX/OPEX solution for challenging (e.g. deepwater, long tie-backs, mature fields) operations. Introduction Generally, most of the existing gas hydrate flow assurance techniques are based on avoiding solid hydrate formation. This is normally achieved by either reducing water content, reducing heat loss to the environment (e.g. by insulation and/or active heating) or the injection of thermodynamic and/or kinetic hydrate inhibitors. However, all of these approaches have limitations, particularly in the case of deepwater operations, high water cuts (e.g. mature fields) and/or long tieback systems. As forecasted by ITI Energy, global oil and gas production is increasingly being dominated by exploitation of mature fields, meaning existing techniques - which are more geared to new developments (lower water cuts) - are becoming less practical/economic.2 Thus the requirement for alternative strategies is expected to continue to increase in the future. HYDRAFLOW is a new, patented flow assurance technology, which aims to meet this need. The concept of HYDRAFLOW is to be able to transport oil/gas without any thermal (i.e. insulation or active heating) or high dosage chemical treatment, thus greatly reducing the costs of multiphase hydrocarbon pipeline transport. The absence of thermal and/or major chemical treatment means HYDRAFLOW falls under the umbrella of 'cold flow' technologies.

Summary Flow assurance is a major challenge in offshore and deepwater operations. Conventional approaches for preventing gas-hydrate formation involve using thermodynamic inhibitors (e.g., methanol, glycol) or kinetic hydrate inhibitors or operating outside the hydrate- stability zone by insulating the pipeline and/or active heating. These techniques are not always economical and in some cases are not practical for deepwater operations, long tiebacks, or aging reservoirs with high water cuts. The industry needs new and novel flow-assurance techniques to address these challenging conditions. The approach presented in this paper is a wet cold-flow-based method in which gas-hydrate management rather than prevention is the goal. The HYDRAFLOW concept is to allow/encourage gas-hydrate formation, but prevent agglomeration in the pipeline and thus avoid blockage. The idea is to convert most of the gas phase into hydrates and transfer it in the form of hydrate-slurry in the pipeline. Where produced water is insufficient for maximum hydrate formation, excess water can be added from other sources such as seawater (hence wet cold flow, because the presence of a free aqueous phase is desired). It is also possible to adjust the hydrate-slurry viscosity by adjusting the amount of water. Antiagglomerants (AAs) and other additives may be necessary to control the hydrate-crystal size and prevent solid blockage in these systems. Where possible, it is proposed to use a closed-loop concept that allows partial recirculation of the liquid phase and its associated additives. The recycled fluid acts as carrier fluid, transferring produced hydrocarbons to their destination (e.g., platform). In this case, part of the additives, including AAs, can be recycled, reducing the operational costs and potential environmental impact. This paper presents the latest developments of the HYDRA- FLOW technology, including studies on hydrate-growth rates, viscosity/transportability of slurries for different low- and high- gas/oil-ratio (GOR) systems, and the effect of salts from reservoir brines and/or seawater.

Flow Assurance is a major challenge in offshore and deepwater operations. The current approach is based on preventing/delaying gas hydrate formation by using thermodynamic inhibitors (methanol, etc) and/or kinetic hydrate inhibitors and/or operating outside the hydrate stability zone by pipeline insulation and/or active heating. The above techniques are not economical and in some cases practical for deepwater operations, long tiebacks, and ageing reservoirs (i.e., high water cut). The industry needs new and novel techniques to tackle Flow Assurance in these challenging conditions. The approach presented in this communication, i.e., Hydraflow, is based on gas hydrates management, instead of prevention. HYDRAFLOW concept is based on allowing gas hydrate formation but preventing their agglomeration and pipeline blockage. The idea is to convert most or all of the gas phase into hydrates and transfer them in the form of hydrate slurry in the pipeline. Where produced water is limiting factor for hydrate formation, excess water (e.g. seawater) can be added. It is also possible to adjust the hydrate slurries viscosity by adjusting the amount of water. Anti-agglomerants and other additives might be necessary to control the hydrate crystal size and prevent solid blockage in these systems. Where possible, it is proposed to use a " Loop?? concept which allows circulating the liquid phase (totally or partially) and its associated additives. The recycled fluid acts as carrier fluid, transferring produced hydrocarbons to their destination (e.g. platform). In this case, all or part of the additives including anti-agglomerants (AAs) can be recycled, hence reducing the operational costs and potential environmental impact. This paper presents the latest results of development of the HYDRAFLOW technology, including hydrate growth and kinetic for different systems (low and high GOR) and effect of salts (e.g. from reservoir brines or added seawater). Introduction Progressively, oil and gas production and transportation are extending to deeper water, mature fields and long tiebacks. These conditions, which involve low temperatures combined with high pressures, high water cuts and longer transfer times, are well inside hydrate risk zone and a major challenge in deep water field development to ensure unimpeded flow of hydrocarbons. It also means that existing flow assurance techniques - which have limitations on preventing hydrate formation - are becoming less practical and economic. Therefore, the industry needs new and improved ways of tackling this problem. This has resulted in the introduction of novel techniques where hydrates are not prevented, but managed to prevent their agglomeration and pipeline blockage. These techniques are generally regarded as cold flow, which have several common characteristics, including,no heating or insulation,hydrates are not prevented but allowed to form andtheir agglomeration is avoided by various techniques. Several research groups are working on various cold flow concepts, most notably SINTEF-BP (Wolden et al., 2005, Larsen et al., 2001, Lund et al., 2000) and NTNU (Gudmundsson, 2002). IFP has also studied hydrate slurries in flowing conditions and particularly in multiphase flow lines (Peysson et al., 2003). CSIRO/IFP are also investigating hydrate transport in continuous gas phase.

The expanding demand for primary energy has pushed exploration and production activities towards more challenging environments, such as the north slope of Alaska, Siberia and deeper oceans. In many cases associated gas could be a limiting factor in the field developments. While stabilised oil could be transported by pipelines and/or tankers, the options for gas and associated gas is rather limited and/or not economical. There are strict limitations on flaring due to environmental/economical concerns, and most of the available options for gas utilisation (e.g. gas to liquid, gas to wire, compressed natural gas…) require considerable CAPEX. Recently, we have proposed HYDRAFLOW, which is a Cold Flow solution for avoiding gas hydrate problems. This could provide a solution for gas transportation. The concept of HYDRAFLOW is based on allowing/encouraging gas hydrate formation, but preventing their agglomeration and pipeline blockage by using chemicals and/or mechanical means. The aim is to eliminate/minimise the gas phase by converting it into hydrates and dispersing hydrates in oil and/or aqueous phase. Water could be added to maximise gas conversion into hydrates and/or adjusting the slurry viscosity. Furthermore, a loop concept has been developed where part of the liquid phase could be recycled, minimising chemical discharge to the environment. As HYDRAFLOW basically converts gas into hydrates and transport it as slurry in a liquid phase, it could provide a solution for gas utilisation for fields where the ambient temperature and pipeline pressure are inside the hydrate stability zone. In this communication, after introducing the HYDRAFLOW concept, the latest results of laboratory tests at subzero conditions are presented as well as an economical evaluation and a pipeline transportation simulation on one of the West Siberian oil fields. These simulations demonstrate that the concept is viable, and suggest that HYDRAFLOW technology could offer significant benefits over existing flow assurance strategies, providing a novel low CAPEX/OPEX solution for gas utilisation. Introduction The rising trend in global energy demand and high price of the oil has led to production from reserves previously considered uneconomic and/or less practical. There are many challenges in production from these reserves due to various reasons such as:–The field is remote and/or located in deepwater (e.g. stranded gas).–The gas field is too small to justify a gas pipeline for long-term production (marginal)–Ambient temperatures are very low such as the north slope of Alaska, Siberia and deeper oceans.–There are restrictions on flaring associated gas. In many cases associated gas could be the limiting factor in the field developments. While stabilised oil could be transferred by pipeline and/or tankers, the options for gas and associated gas are rather limited and/or uneconomic. Worldwide, governments are restricting/limiting flaring associated gas. In many cases these restrictions could limit oil production rates. According to statistics [1], approximately 113 billion m3 (4 trillion cubic feet) of natural gas is being flared annually and close to 142 trillion m3 (5,000 trillion cubic feet) of natural gas (either associated with crude oil, or non-associated) is stranded worldwide. However, there is a high demand for natural gas in global market and considerable effort is being made throughout the industry to reduce the costs for natural gas transportation. There are a number of methods of exporting gas energy from an isolated field for use elsewhere such as pipelines, liquefied natural gas (LNG), gas to liquid (GtL), Gas to commodity (GtC), gas to wire (GtW), compressed natural gas (CNG) and gas to solids (GtS), i.e. hydrate (NGH).

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