Horizontal wells in the Middle East are mainly completed with 6-inch open hole, and some wells are put into the screen in the horizontal section. This kind of wellbore structure can meet the production demand in the early stage. But it is not conducive to the later fracturing or acid fracturing, because the open hole section cannot be effectively segmented, and the targeted injection control or segmented production control cannot be carried out after stimulation.

In order to realize the segmented stimulation of the open hole, the secondary completion string is run in on the premise of keeping the existing string unchanged, which is used for segmented fracturing and segmented injection or production control after fracturing. The string consists of open hole packers, switchable sliding sleeves, toe anchor, etc. Each part is connected with 4-1/2 inches’ base pipe. All sliding sleeves are closed when they are lowered, and are opened through soluble rubber plugs. After fracturing operation, the sliding sleeve can be opened by coiled tubing with switch tools and the horizontal pipe string remained as the production pipe string.

Through the laboratory test, the switchable sliding sleeve and open hole packer can be used under the conditions of no more than 180 °C and pressure difference no more than 60MPa, and are resistant to hydrogen sulfide and carbon dioxide corrosion. From 2012 to 2020, the switchable sliding sleeve has been used in 187 wells in the eastern oilfield of China, including 36 vertical wells and 151 horizontal wells, with a total of 1449 sets of sliding sleeves. The maximum pumping rate of hydraulic fracturing is 12 m³/min with up to 21 fracture stages. The maximum temperature is 135°C with up to 12989 m³ of fracturing fluid and 1018 m³ of sand injected into a single well. The maximum well depth is 4995 m (MD) and the maximum vertical depth is 4200 m (TVD).

The technology realizes the segmented stimulation of low permeability reservoirs in the Middle East under the existing horizontal open hole completion conditions, realizes the segmented control of water injection wells and segmented production of production wells, saves the operation cost and prolongs the life cycle of old wells. However, in order to reduce fracturing investment, casing completion is still recommended for new wells with low permeability reservoirs.

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