The problem of life extension for drowned wells

The important problems concerning the mature development of gas and oil and gas condensate fields (OGCF) is the depletion of reservoir natural energy and water encroachment of producing deposits which result in the loss of productivity and spontaneous well shut-in. Because the reservoir pressure declines and the stock of operating wells reduces it's necessary to find technical and technological solutions in order to extend the life of these wells. Such solutions are found due to systematic work with the well stock that is conducted to define highly drowned wells which are in and out of operation and also due to use of different lift methods for high-volume production.

Methods of life extension

The authors propose that artificial lift methods can be used in order to revive and then operate highly drowned gas wells [1]. The following methods are used in the Vuktylskoye field for this purpose:

  • with application of jet pumps (ejectors);

  • with application of intermittent gas lift (drowned wells with high reservoir pressure);

  • combined system - gas lift installation for cyclic well operation with gas-liquid ejector (GLICWO)

Some results related to the development and testing of the last two methods that were applied in the Vuktylskoye field on the initiative of and with the direct participation of the authors are presented below.

Test objects

Two drowned wells No. 197 and 26 were chosen as the objects for field tests to evaluate the efficiency of artificial lift methods applicable for lifting drowned wells. Wells No. 197 and 26 located at the southern dome of the Vuktylskoye OGCF were out of operation for a long time and were even planned to be abandoned.

Monitor-observation well (former development well) No. 197 - Vuktylskaya having the depth of artificial bottom hole 3239m is supplied with the underground equipment for the cyclic gas lift designed to lift hydrocarbon fluids from drowned gas wells [1–4]. This well was chosen as a test object to show the efficiency and reliability of cyclic gas lift technology at the most difficult operating conditions (lack of conditions for wells to flow and to apply the most common methods of gas lift operation).

The operating principle of cyclic gas lift installation is the step-like lifting of water-cut hydrocarbon production (gas, condensate, oil) by injection gas with the cycles of liquid accumulation in the well followed by the cycles of its displacement to the surface. Depending on mining and geological conditions of well operation this installation can operate in two basic modes:

  • constant liquid outflow to the surface at continuous injection of external gas to the well;

  • cyclic lifting of liquid that is performed by stages, i.e. by intermittent gas injection into the annulus through alternate opening and closing automatically operated valve that is installed at the gas- supply pipeline [1–4].

In the Vuktylskoye field high pressure gas (HPG) from gas main pipeline branches is used as the working agent for gas lift well operation. The gas main pipeline branches - HPG reservoirs are available at each gas treatment facility.

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