SOLID CARBONATE OIL DEPOSITS DEVELOPMENT METHOD Russian patent published in 2017 - IPC E21B43/26 E21B43/27 

FIELD: oil and gas industry.

SUBSTANCE: invention can be applied to develop powerful solid carbonate oil deposits using multistage hydraulic fracturing (MHF) into acid-gravity drainage mode (AGD). The method includes drilling of wells with horizontal tailing-in (WHT), cementing of an annular space between a production casing and a reservoir in a horizontal bore, secondary deposit penetration with the orientation direction of perforations in one row, carrying out of multistage hydraulic fracturing, packers application for separation of horizontal shaft into sites, and product extraction from the horizontal wells. According to the invention, a deposit is selected with an average thickness of the oil-saturated reservoir H ≥ 50 m and an average absolute permeability not more than 2 mD, the deposit is drilled with pairs of WHT, whose bores are arranged parallel in the vertical plane at a vertically distance h=(0.5-0.9)⋅H, with the upper WHT being completed with two horizontal bores parting at angle β=30-60°, the lower WHT is completed with one horizontal bore directed perpendicular to the vector of the main maximum collector voltage and being the bisector of the angle β in the plan. The length of each horizontal bore is made equal to l≥4⋅h. At the top of the WHT at each horizontal, bore perforations are oriented downward, and the horizontal bore of the lower WHT - upward. All wells are subject to the acid multistage hydraulic fracturing with the distance between the stages of no more than 50 m. Moreover, the location of each corresponding multistage hydraulic fracturing in the upper and lower wells does not match structurally. The rate and volume of injected acid is determined from the conditions, firstly, of forming a carbonate dissolution structure, being branched cavities, secondly, fractures half-length a=(0.2-1.0)⋅l⋅sin(β/2) and fractures height c=(0.5-1.0)⋅h. After MHF, the lower WHT are completed and started up for production. With each decrease in the oil production rate of the lower production wells below the economically viable value, in the respective upper injection wells, large-volume acid treatments are carried out. Wherein, prior to acid feeding, in the injection well, water is pumped with total mineralization of not more than 1 g/l and particles resistant to used acids impact, with diameters greater than the average diameter of pore collector channels, water with particles is injected as long as the injection pressure does not grow at least five times, thus, the deposit is developed in AGD mode.

EFFECT: enhanced oil recovery of powerful solid carbonate oil deposits.

2 dwg