Abstract

In 2009, OJSC "Samotlorneftegas" began performing two-stage fracture stimulations in newly drilled and sidetracked wells. The wells were treated zone-by-zone, with frac fleets doing two or more frac jobs. Slotted filter intervals were treated first. Then they were plugged off with bridge plugs or proppant for the next interval to treat. After two frac jobs, the bottom-holes were cleaned and the wells were started.

The success of the method consisted in an increased oil production at an early stage of production (around 40 tons per day from newly drilled wells) and in a slower decline in flow rates throughout the first year of production (around 35%) as compared to directional wells. There was only one disadvantage - a longer shut-in period (up to 60 days), which, with low formation pressures, can lead to a lower oil increment due to saturation of the formations with flush fluids.

In mid 2011, the multistage stimulation technologies did not find improvement for a number of reasons:

  1. No multistage fracturing equipment on the market. No such equipment was built in Russia and oil companies showed little interest in a large-scale application of purpose-built multistage fracturing completion systems;

  2. Lack of multistage fracturing experience;

  3. Significant geological and technological risks involved, when using these technologies to improve production to expected levels and enhance the cost effectiveness of these projects;

  4. Little experience in horizontal drilling with the drilling conditions being difficult to make large enough holes to accommodate multistage fracturing systems (MSFS). No effective annular isolation techniques.

In the first half of 2011, special ball-activated sleeves were delivered to the Russian market from abroad. However, OJSC "Samotlorneftegas" continued using an interesting multistage fracturing technique employing the use of burst port collars and cup-to-cup (C2C) tools.

The technology was being improved for 4 years. Owing to the improvement efforts, a unique 29-stage frac job was performed at the beginning of 2016.

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