14 Dec 2021
There are approximately 2 million oil wells in operation worldwide and more than half of them use an artificial lift system to deliver oil to the surface in a controlled manner.
Gas lift is a method of artificial lift that uses gas to reduce the bottom hole tubing pressure so the existing formation pressure can lift the fluids in the well. Conventional gas lift systems use valves with pre-configured orifice sizes, installed into side pocket mandrels along the completion string. These increase production by injecting high-pressure gas from the casing annulus into the fluids in the production tubing. The injected gas reduces fluid density and hydrostatic pressure so the fluids can be lifted to the surface.
Fields with oil-producing reservoirs also often include a gas-producing stratum that can be used to provide gas lift. The gas is brought to the surface, separated from the liquids, chemically altered, compressed to an acceptable pressure, distributed to the oil production wells, and injected down their annuli.
However, this method requires two sets of wells: one set to produce the lift gas and another set to produce the oil. In addition, extensive and expensive surface infrastructure, such as compressors and pipelines are required. This creates a risk to personnel on-site and an increased environmental hazard both at the wellsite and in the locality through the transportation of plant and equipment.
An Alternative Form of Gas Lift
Where circumstances permit, natural, auto, or in situ gas lift can be a highly cost-effective alternative solution. With an in situ gas lift system, the gas and oil reservoirs have to be accessible from the same well. As a result, they are less commonly used than conventional systems.
Rather than lifting the gas to the surface, compressing it, and injecting it down the casing annulus of another well, in situ systems take the gas from a reservoir gas cap or zone and flow it directly into the production tubing. This means that each well taps into both the gas zone and the oil zone.
Regardless of whether the gas is above or below the oil zone, the entire in situ system is retained downhole. This eliminates the expense and environmental impact of surface infrastructure and certain equipment - such as a compressor - required by traditional gas lift. It also avoids unnecessary excess weight on offshore platforms. The gas reservoir itself acts as its compression and distribution facilities, while downhole metering and control serve as the surface choke and downhole gas lift valves.
More Control. Less intervention.
As the only functional component of the in situ gas lift system, success is contingent upon accurate control and metering of the gas flow from the gas formation into the oil production string. It is therefore important that the metering and control equipment used are both highly sensitive and flexible enough to rapidly adapt to changes in the oil or gas reservoirs to optimize the entire system.
In situ gas lift systems allow for control of the gas injection rate from a gas zone. Using technologies that can be adjusted remotely, such as the Silverwell digital intelligent artificial lift (DIAL), gas injection rates are changed without the need for well intervention.
DIAL uses just one tubing encapsulated cable (TEC) for all the gas lift and monitoring devices in the well. This avoids the need for multiple hydraulic lines. Back-check valves block the flow from the tubing to the annulus, ensuring the gas zones cannot be contaminated with fluids from the oil zones.
In situ gas lift systems are not applicable everywhere, but when deployed they can generate significant benefits for operators. The latest technologies to support in situ gas lift are extending those benefits even further by bringing new fields online at a faster rate, lowering carbon emissions, and enabling increased production.
Interested in how DIAL can bring the benefits of in situ gas lift to your well? Download our data sheet or get in touch with one of our experts.
For more information on how we can solve your gas lift challenges, contact our team.
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