Gas Lift Systems

WHAT IS GAS LIFT?

Gas lift is a field-proven artificial lift method that dates back at least five decades. It relies on external high-pressure gas injected into the wellbore to stimulate and lift produced fluids to the surface for separation and further processing. The lift principal reduces fluid density within the casing and scrubs the liquids to help separate them from the well’s solids content. Gas lift can be used with either intermittent flows or continuous service. Further, it can extract well fluids either with injection of high-pressure gas down the tubing for annular lift or down the annulus for conventional tubing lift. It is perhaps the industry’s best lift method for handling sand and heavy solids residue, succeeding without any negative impact to its production like experienced with electrical submersible pumps (ESPs).

THE MAIN COMPONENTS OF GAS LIFT SYSTEMS

MANDRELS, VALVES & PACKERS The total gas lift assembly includes mandrels, valves and a packer to provide a seal between the tubing OD and the casing ID. Depending on the depth of the producing zone, multiple gas lift valves can be set on the mandrels inserted into the wellbore inside or outside the tubing. The spacing is established using a computer design program based on projected bottom hole pressures, temperatures and desired production. Continuous flow gas lift is used primarily in high volume wells and is dependent on an adequate gas supply which can either be compressed or available in high pressures. This method is utilized offshore in conventional drilled wells or, increasingly, onshore in both conventional and unconventional horizontal wells. Intermittent lift is usually implemented when bottom hole pressure is low and when there is a ‘slug’ or situation within the well where flow is impeded. This method is not as common as continuous and can be problematic with surface gas surges or high sand content.

ADVANTAGES OF GAS LIFTS

Gas lift methodology has several advantages, especially in the early stages of a well’s production when IP is critical for optimized financial returns. Because of its relatively simple design with few moving parts, gas lift normally has low operating costs and is uncomplicated to operate. Gas Lift is cost-effective with few maintenance or repair issues regardless of sand or produced solids. Annular gas lift is usually more impactful during the early well production stage. The annulus diameter allows for increased flow area to assist in unloading the well during initial production. Gas flows through internally-mounted mandrels during this phase. As the unloading continues and the effective bottomhole pressure diminishes, there is a need to change over from annular flow to conventional tubing flow. This has historically been a disadvantage of gas lift. Because of the internal position and diameter of the mandrel, and the normal protrusion of the gas valve in the tubing string to produce annular lift, there is often insufficient clearance to change the configuration without pulling the entire tubing string and mandrels. Consequently, a workover rig must be used. This is expensive and time consuming, resulting in a production shutdown, use of specialized equipment and increased manpower for this operation. A configuration using less intrusive side pocket mandrels is available, but that assembly is also an expensive alternative.

ENTER HYRATE™ - LIBERTY LIFT’S EFFECTIVE GAS LIFT SOLUTION

This is the problem our patent-pending gas lift system solves with valves included in the externally-mounted capsule mandrel assembly which allows both annular and conventional flow through the tubing.