Small-Diameter Gas Lift Systems -A ViableTechnical Solution for Transport of FluidsFrom Low-Pressure Reservoirs

摘要

Production of fluids from low-pressure reservoirs requires acontinuous or an intermittent artificial lifting technology. If theshut-in fluid level is less than 20%of the depth of the wellfinding a suitable and economic artificial lifting technology is achallenging task. Depending on local conditions andeconomics, gas or steam lifting alone or associated with other artificiallifting technologies is selected.Within a limited range of gas-liquid flowrates, use of small-diameter gas lifting technology is better suited than the gaslifting using conventional tubing to produce liquids from low-pressure reservoirs.Laboratory investigations dedicated to small-diameter gaslifting operations have been so far limited to fluid transferoperations requiring maximum 10-20 m. This study responds tothe industry need for a better evaluation of depth – diameterflowrates limitations in view of assessing the potential field application of gas lifting for very low reservoir pressures andrelatively small liquid flowrates. Production of oil and gas from pressure-depleted reservoirs, recovery of methane from coalbed reserves, and efficientdrainage of heavy oil and saturated high-temperaturecondensate produced under steam-assisted gravity methods, where reservoir pressure is marginally low, require a re-visiting of conventional artificial lifting technologies. For example, there are thousands of dormant gas wellswhere bottom water aquifers of 50 m or less impede gasproduction. Similar conditions are often found in the coalbedmethane reservoirs. Use of submersible electric pumps for low-pressure, low liquid production reservoirs is rarely aneconomic or a viable technical option. The availability of gas and the relatively small amount ofliquid to be transferred suggest gas lifting as a potentialstrategy for producing the reservoir water and releasing thegas. However, conventional gas lifting (using tubes with adiameter D>1 in. )is not possible due to the extreme low