METHOD DEVELOPMENT OF SHALY CARBONATE OIL PAYS Russian patent published in 2017 - IPC E21B43/27 

FIELD: oil-and-gas industry.

SUBSTANCE: invention relates to oil industry. Technical result is increased oil recovery of thick shaly carbonate oil pays. The method of development of shaly carbonate oil pays comprises drilling of the horizontal wells, annulus cementing in the horizontal bore between casing string and pay, secondary opening of the pay with oriented direction of the perforated holes to single row, multistage hydraulic fracturing (MHF), packers use to separate horizontal bores to sections, product recovery from the horizontal wells. Wherein the carbonate pay with average thickness H > 50 m and average absolute permeability is below 2 mD is selected, a pair of horizontal wells is drilled parallel to each other in vertical plane. The horizontal bore of the injection well is located above the horizontal bore of the production well at distance h = (0.5-0.9)·H, length of each horizontal bore is equal to l ≥ 4·h. In top injection well the perforating holes row is oriented downward, and in bottom production well - upward, in both wells acid MHF is performed with distance between stages 50 m maximum, wherein position of each next MHF stage in the production and injection wells coincide in structural plan view. Speed and volume of the injected acid are determined depending first of all on creation of structure for carbonates dissolution in for of branched cavities, and secondly on cracks height a, wherein a^p_n+aⁱⁿ_n=(1.0-1.1)·h, where indices p and in relate to the production and injection wells, respectively, n is No. of MHF stage. After MHF the production well is developed and put into production, upon each oil yield decreasing in the production well below the economically profitable value in the injection well large-scope acid treatments are performed, wherein prior to acid injection water is injected in the injection well with total mineralization not exceeding 1 g/l and suspended particles stable to action of the applied acids, with diameters exceeding average diameter of porous channels in the pay. Water with particles is injected till the moment when injection pressure will rise by 5 times minimum, so the shaly pay is developed under mode of acid-gravity drainage (AGD).

EFFECT: method of development of shaly carbonate oil pays increasing the oil recovery.

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