National Subsea Research Initiative Gas disposal; What are the options for small pools? Christer Fjellroth 2016 www.nsri.co.uk
Overview • Generic Technology Overview • Benefits • Potential Technology Suppliers • Potential Specific Solutions • Concluding Remarks • Recommended Further Work • Appendix www.nsri.co.uk
Generic Technology Overview In exploiting the UK Small Pools, a prevalent problem will be what to do with the produced gas in primarily oil producing wells. Given the size of each individual reservoir, it could be uneconomical to put processing and export infrastructure in place that will only be in use for a relatively short period of time. As it stands the main solutions to this problem are flaring and re-injecting the gas. There are a number of technologies for capturing low pressure gas at source or in an offshore processing plant. These include: • Flare Gas Recovery Systems • Water Alternating Gas (WAG) • Offshore Methanol Production • Offshore Power Generation • Methane to Plastic • Gas to Liquid (GTL) • Micro Liquid Natural Gas (LNG) www.nsri.co.uk
Benefits With all the options listed, there is potential to monetise a waste product while reducing environmental discharge of CO2 and methane at the same time. The benefit of using these solutions in small pools is that it will eliminate the need for a gas export line. www.nsri.co.uk
Potential Technology Suppliers Flare Gas Recovery Systems Power Generation Wartsila Power Barge Corp. Zeeco John Zink Methane to Plastic Transvac University of Munich Water Alternating Gas Gas to Liquid Shell SBM Offshore Eni Compact GTL Statoil Velocys Offshore Methanol Production Micro LNG Waller Marine LNG BOC www.nsri.co.uk
Flare Gas Recovery Systems According to the Global Gas Flaring Reduction Initiative (GGFR), “more than 140 billion cubic metres (4.9 trillion ft3) is flared annually and the same amount is probably vented.” There is a trend in the oil and gas industry to reduce flaring and utilise Flare Gas Recovery Systems (FGRS). It is possible to retrofit these technologies to existing plants. Statoil have installed FGRSs on Gullfaks A and estimate they have saved 20 million NOK (£1.6M) in Carbon Dioxide tax. Gullfaks A has used the gas as fuel or for gas injection. FGRS are field proven and pressure to reduce flaring could potentially make this technology commonplace. The drawback of this method is that gas still needs to be exported, used for power generation or reinjected. www.nsri.co.uk
Flare Gas Recovery Systems Transvac have developed ejectors which safely and economically compress waste and surplus gas back into the production process. Ejectors are ideally suited to this application because they employ either the available high- pressure gas or liquid energy to entrain and compress waste and surplus gas to a pressure where the gas can be recovered into production or used as fuel gas. The ejectors have no moving parts and require no maintenance. Other Vendors of FGRSs include: Wartsila • Zeeco • John Zink • www.nsri.co.uk
Water Alternating Gas Water alternating gas (WAG) process has been used to improve the mobility of the flooding system resulting in better sweep efficiency and improvement in oil recovery efficiency. WAG injection has been widely applied since the late 1950s and usually uses CO2. The gas represents a large fraction of the total cost where surplus gas is not available. Utilizing this method where gas disposal is an issue could increase rate of recovery and dispose of gas in an environmentally friendly way. www.nsri.co.uk
Water Alternating Gas This technique has been used by many operators including Statoil and Eni. Statoil have stated that the challenges related to WAG are: Mechanisms: understanding microscopic effects, particularly in cases • where three-phase flow and hysteresis are important for the improved oil recovery effect. Capillary phenomena and wettability are important properties for low-permeable rock and may be taken advantage of or manipulated for IOR gains. Predictions. • Use of foam (foam-assisted WAG or FAWAG). • Gas costs: gas injection is usually seen as supplementary to an on- • going waterflood, and finding technical and commercial ways to reduce gas costs would prove beneficial. The problem with this solution is that it requires an injection well and topside compressor as well as a flowline/riser etc. For small pools, this might be too expensive. www.nsri.co.uk
Offshore Methanol Production Methanol production has been considered a feasible alternative to flaring associated gas for development of marginal gas fields. The advantage of the methanol process over other possible ways of converting natural gas to a commercial product are the relative simplicity of the process and the ease in handling the methanol. The conversion of natural gas to methanol usually requires a pre-treatment stage to remove any hydrogen sulphide which would poison the catalysts used in the conversion process. The desulphurized gas is then passed with high pressure steam over a nickel catalyst in the reformer to produce a gas consisting of hydrogen, carbon monoxide and dioxide. This gas is then compressed and passed over a catalyst in radial flow converters to produce methanol and water. www.nsri.co.uk
Offshore Methanol Production This method has been discussed since the 1980’s but very little has been done to develop the idea. Waller Marine has a concept for a Methanol Plant that would take the form of a semisub. This area needs more R&D. If a Methanol Plant could be made compact enough to fit on an FPSO, the product could then be transported in the same way as the crude oil. This method is around 5 years from being commercial. Note: Waller Marine was contacted for information concerning volume of gas required for this facility but no response was given. August 2016 www.nsri.co.uk
Offshore Power Generation The concept of offshore power generation is, in its simplest form, a consolidation of existing technologies. Offshore production facilities currently generate electricity for their own consumption. Commercial floating generation plants have been employed in various locations, typically near shore or dockside. High voltage electrical power is transmitted by subsea cable. www.nsri.co.uk
Offshore Power Generation Power Barge Corporation already produces these and they are operating in locations in the Gulf of Mexico. To be cost effective, these barges need to take on 50MMSCF of gas. In Small Pools this may require several developments tied back to a power barge. With more renewables developments in the UKCS, it may be possible to export excess power to the renewables power grid infrastructure to sell power back to the grid. This could make use of the produced gas profitable. www.nsri.co.uk
Methane to Plastic Johanes Lercher and colleagues at the Technical University of Munich have found a means of producing methyl chloride, a key plastics-industry chemical, from gas which is usually flared. This technology is still in the experimental stage. The technique could have one drawback, it uses chlorine, a toxic gas. The researchers' plan includes recycling the hydrogen chloride and repeatedly using it for the reaction. "In the vision we're playing with, the chlorine would not ever get on a boat," says Eric Strangland, a chemistry and catalysis researcher at Dow and a co-author of the 2007 paper on the subject. Transporting plastic could prove difficult and energy companies would need to find new customers for these plastic products. Time to market is likely 10 years. www.nsri.co.uk
Gas to Liquid (GTL) SBM Offshore and Compact GTL have developed a concept for an FPSO with an integrated GTL plant for small field developments. The concept is ready for field specific FEED. Velocys have developed a small scale GTL and have estimated that an offshore facility could process 1,000 bpd (assumptions such as GOR for this figure were unavailable) and take up approximately 20% of total deck space on an FPSO. Velocys have so far only manufactured onshore GTL facilities. www.nsri.co.uk
Gas to Liquid (GTL) Information from Compact GTL suggests for the Small Pools, this could be the most economical method however they had not considered re-injection in their comparison. Cost effective GTL would require 30-50MMSCF/day of gas. This may require several small pools to be tied back to a main facility. Estimated cost for a module is between £35-40 Million, this module could service several developments to spread the cost. www.nsri.co.uk (Trillion Cubic Feet)
Micro LNG LNG – BOC have a Micro LNG plant in a remote location in Tasmania. This plant exports LNG to tanks mounted on trucks and is transported by road to where needed. This plant produces 50 tonnes of LNG per day and runs 24 hours a day. This size of plant could be fitted to an offshore platform, in order to transport the LNG the platform could have removable tanks which are swapped out and transported back to shore. LNG is currently the cheapest way to transport gas, a problem is that the natural gas has to be transported at pressure in the liquid state. www.nsri.co.uk
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