Benefit of using Ejector Technology for Enhanced Recovery
- No operating costs
- No maintenance costs
- No carbon footprint
- Low project costs compared to compressors
- Low weight & compact size allows for production upgrades
- Patented Design
- Fast-track installation available for short-term well opportunities
- Minimal disruption to existing production operations
- Ideal solution for topside, subsea or FPSO installations
Restart shut-in or liquid loaded gas wells
Ejectors offer an attractive solution for generating extra production from LP wells and in the process extending field life. Most commonly, shut-in or liquid loaded wells can be revived, as well as satellite or stranded wells deemed too expensive to recover with ‘traditional’ techniques. In this example, gas from HP wells was being choked to a lower pressure to meet downstream process conditions. Wasting ‘usable’ energy in this way offers no added value to production. Instead, the HP gas was used to ‘drive’ an Ejector, which not only delivered the HP gas at a suitable lower pressure to meet downstream conditions, but also lowered the back-pressure on the nearby LP wells, bringing them back to life.
The ‘Universal Design’ Ejector allowed for new internals to be fitted as HP well pressures declined over time, keeping the Ejector operating at the optimal design point and, as such, keeping production steady.
- Extra 32MMscfd of gas produced from shut-in wells
- New ejector internals fitted as well pressures declined to maximise production
- New internals were fitted in less than one shift
- The new internals increased production of well by 17.7MMscfd
- Ejector has no running costs, as it utilises motive gas energy which is normally wasted across a choke valve
- Ejector requires no maintenance and produces no emissions
- Universal design allowed manufacture of new Ejector internals to be delayed until new HP well was drilled, thereby reducing project risk
Boost production using compressor recycle gas
Many older production facilities have compressors operating in constant recycle as conditions have changed from design point and the compressors themselves are less efficient. Gas is compressed from low to high pressure then some of this is let-down and fed back into the compressor to maintain operating throughput. By making use of this available energy to ‘drive’ an Ejector, back-pressure on LP wells can be reduced by the Ejector to increase production or even restart shut-in wells. This method of boosting production is achieved ‘for free’ by making use of otherwise wasted energy. In many instances significant capital savings are also made by eliminating the need for modifications of, or secondary, mechanical compressors.
- Total gas production increased by 91MMscfd
- Changeable Ejector internals allowed production to be maximised as wellhead pressure declined
- Replaced requirement for compressor re-wheeling, saving capital and accelerating the benefit
- Requirement for 1st stage compressor eliminated saving the client over £10m capital cost
Using available water to enhance recovery - with high compressions
Transvac’s Research and Development team have made huge advances in the efficiency and capability of liquid motivated Ejectors. Offering compression ratios of up to 150:1, these latest designs open the door to a wealth of new Ejector applications throughout the Upstream and Downstream Oil & Gas Industry. The below diagram shows just one way in which operators can make use of this technology for enhanced recovery.
Typically, injection water or produced water is employed to motivate the Ejector, thus making use of existing facilities - perfect for brownfield developments. The Ejector can entrain and compress gas from a number of sources including a separator, manifold or individual well. The resultant reduction of backpressure on the upstream process delivers a boost to production and promotes steady flow where liquid loading is an issue, particularly in long tiebacks.
- High gas compressions can be achieved
- Existing facilities (e.g.injection water) can be used to 'drive' the Ejector
- Existing separator capacity can be used
Maximise Production from Multi-phase Wells
Multi-phase production can be enhanced using this simple technique to reduce separator pressure. The Ejector can be 'driven' using energy from compressor recycle gas, HP well gas, or even HP water (such as injection water, although introducing a liquid would require downstream separation). By lowering separator pressure, it is simply reducing the backpressure (resistance) on upstream production process, which increases production
This technique has been sucessfully used to offer flow assurance in a 50km subsea tieback, which had been suffering from lumpy production due to liquid/condensate loading. The resulting pressure drop in the separator increased the specific volume of the gas in the tieback, resulting in steady, increased recovery for a number of years. As compressor recycle gas was used, no 'new' energy was required, making the project a win on many levels.
Replacing a 1st stage compressor
Ejectors can be used to completely replace existing mechanical compressors. With no maintenance and utilising available energy, this approach can often be justified on lower CAPEX and OPEX alone. In this example, high pressure gas from the 1st stage separator is used to power the Ejector, boosting the pressure of the 4th stage separator gas.
The Ejector discharges at the required inlet pressure for the 2nd stage compressor, thus completely eliminating the need for the expensive mechanical 1st stage compressor.
- Flare Gas of 2 MMscfd at 1bara captured and delivered at the suction pressure of 2nd stage compressor
- Used energy that was already available
- 1st stage compressor was removed from service. It simplified system operation and reduced maintenance costs
- Gas no longer burned to power this compressor
Gas Reinjection for Enhanced Oil Recovery
Transvac's 'liquid driven' Ejectors offer a suitable method of compressing produced gas for reinjection down-hole for enhanced recovery techniques. In many cases this can also eliminate the need for flaring where gas export is not viable. Existing injection water pumps can often be used to supply high pressure water to the Ejector which entrains and compresses the gas. The Ejector then discharges the compressed gas/HP fluid back down-hole for resevoir flooding and other common EOR techniques such as SWAG (Simultaneous Water and Gas Injection).