Abstract

During the 80's a novel artificial lift method called slug gas lift was developed in-house in Lagoven (former affiliate of PDVSA), by a group of production engineers and it was applied to develop the first commercial phase of Urdaneta Offshore Lake Maracaibo Field between 1982 to 1984 that reached up to 50000 barrels per day with an average production per vertical well of 350 barrels per day of a 12°API heavy oil from depths between 6000 to 7000 feet.

Continuous gas lifting when applied to high productivity heavy oil reservoirs generate production problems caused by foam formation. Intermittent gas lifting on the other hand presents limitations for reservoirs such as Urdaneta-01 because a high productivity reservoir is capable of filling the production tubing with fluids and requires lifting from depths below 7000 feet. Slug gas lift was developed as alternative to continuous and intermittent gas lifting to deal with heavy oil reservoirs such as Urdaneta 01. This reservoir was discovered in 1946 and commercial exploitation started in 1982. Petroleum initially in place was estimated in 12 billion barrels with initial reservoir pressure of 3500 Psig and average depth of 8000 feet.

By applying slug gas lift the operator (Lagoven) was able to minimize foam formation by limiting the dynamic contact of gas and heavy oil liquid phases. The slug gas lift system is designed to prevent admission of liquids while gas is being injected at high pressure into the tubing, so condition for foam formation is eliminated.

Up until now there has not been any publication in SPE about this experience. The author was part of the production engineering group in charge of the Urdaneta field development project in 1982 and he also participated in the development and application of the slug gas lift model, This paper reviews the basis of slug gas lift, range of application and how it was applied in Urdaneta Field using the results from the first year of evaluation of a group of wells that constituted the first field pilot test.

It is likely that some heavy oil reservoirs located offshore worldwide could be potential candidates for application of slug gas lift.

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