Development of Vietsovpetro fields is characterized by decreasing oil production and increasing water cut. The increase of stream water cut reduces the productive capability of gas lift and increases the bottomhole pressure. Appearance of leaks in the downhole equipment complicates the situation and leads to the enhanced consumption of the compressed gas. Gas lift efficiency depends on many factors: layout, actuating pressure and size of gaslift valves, compressed gas consumption rate, downhole equipment leak integrity, etc. During the operation, equipment wearing increases and leak integrity fails, leading to gaslift gas leaks and efficiency reduction down to the fill stop of the equipment. Restoration of well performance requires the workover operations with replacement of the downhole equipment which is a cost demanding activity under the offshore conditions. Alternative to the downhole equipment replacement may be found in deploying the special inserted isolating assemblies to eliminate the leaks. To perform the pilot tests on eliminating the leaks in the downhole equipment, Vietsovpetro has chosen the technology of Tubing Pack-off due to the following factors: applicability in the existing geophysical conditions, simplicity and safety of implementation, equipment and services costs. Tubing Pack-off assemblies represent the module units, ran to the target depth and installed in the designated interval by wireline techniques. These assemblies consist of separately adjustable elements which ensure the leak integrity of the isolated interval with the possibility to install a small-sized mandrel with gaslift valve to deepen the compressed gas injection point. Application of Tubing Pack-off allows increasing the well current production rates by eliminating the leaks of the downhole equipment, multiply reduce the workover costs, improve the gas lift operation efficiency and optimise the operational costs by lowering the compressed gas injection volume. The article includes the defined application criteria of Tubing Pack-off system for Vietsovpetro wells and specified perspectives for improving Vietsovpetro gaslift wells diagnostics technology.
References
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