Cleaning-up oil- and gas- wellbottom zones from sand/clay plugs by use of coiled tubing

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Purpose:

The technology is applied for cleaning-up oil- and gas-wellbottom zones from sand/clay plugs. 

Content:

The coiled tube (CT) with jet nozzle is run into hole without killing the well while the continuous circulation of process liquid is maintained.

To improve sand removal and provide required carrying capacity of the upward flow the two-phase liquids are used as flushing fluids. When flushing is performed by use of the coiled tubing the upward flow velocity in vertical and slanted sections with declination of up to 450 must exceed the settling rate of solid particles (that is also valid for any flushing). In less deviated and especially in horizontal sections of the well it is necessary to provide sufficient turbulence of upward flow.

In order to improve efficiency of the plug destruction process CT jet nozzles of various types and designs are used. Based on common principle of operation - water jet effect, they differ in number and directions of outlets. Pressure loss in jet nozzles may reach 17 МPа.

To avoid liquid absorption in the productive formation and clogging of its pore space it is required to thoroughly select the flushing liquid density that prevents the hydrostatic pressure rising above the formation pressure.  

Advantages:

  1. the cleaning-up of wellbottom zone from sand/clay plugs without killing the well. Due to that the lost circulation and clogging of the bottomhole formation zone are avoided;
  2. sand plug flushing is carried out within 1-3 days depending on work complexity and thickness of the sand/clay plug;
  3. due to small CT diameter a high injection speed as well as more efficient (total) removal of sand/clay sediments can be achieved;
  4. due to water jet effect and use of special flushing liquids the cleaning-up of the bottomhole formation zone from clogging and solvate sediments is ensured (skin-effect is eliminated). 

.Operation results on oil fields in Azerbaijan, Bulgaria, China, Cuba, Poland, Russia, Syria, Turkmenistan and Ukraine have shown that after the Company’s technologies application the oil production increases from 2 to 5 times and even more. After well workover the duration of well’s operation at increased level of yield is from 6 months to 2 years.

To find more details about the results of the technologies application, please see “Results” here or in the left menu.