MINING METHOD FOR MULTI-LAYERED INHOMOGENEOUS OIL RESERVOIR Russian patent published in 2017 - IPC E21B43/18 E21B43/14 E21B43/267 

FIELD: mining engineering.

SUBSTANCE: method includes drilling of vertical injection wells and of a production well with a horizontal wellbore, identification of pay formations with different permeability separated by impermeable interlayers, fastening casing strings and their perforation, injection of displacement fluid and recovery of well products. One horizontal wellbore is drilled in the pay formation located in the middle of the oil reservoir perpendicular to the direction of the main stress σ_max. Then two vertical wellbores are drilled in the horizontal wellbore on the right and left side, drilling in all pay formations. The permeability of each pay formation is determined. The horizontal wellbore of the production well and the vertical wellbores of the injection wells are lined with casing strings. The perforation is done in vertical injection wells opposite each pay formation, and the perforation in the horizontal wellbore of the production well is done depending on the number of pay formations, perforated by the injection wells. Next, in each interval of perforation of the horizontal wellbore of the production well, interval hydraulic fractures are produced with the formation of fractures and their subsequent fixation by a proppant of a fraction corresponding to the permeability of each pay formation. To make a hydraulic fracture, a fracturing fluid with light proppant is injected into the lower pay formation. In order to make a hydraulic fracture within the pay formation where the horizontal wellbore is drilled, a fracturing fluid is injected without proppant. And in order to make a hydraulic fracture in the upper pay formation, a fracturing fluid is injected with a heavy proppant. To maintain hydraulic fractures, a carrying fluid with a 12/18 mesh proppant is pumped into a pay formation with a permeability of 0.01 to 40 mD, and a carrying fluid with a 20/40 mesh proppant is pumped into a pay formation with a permeability of 40 to 100 mD. A carrying fluid with a 40/80 mesh proppant is pumped into a pay formation with a permeability of 100 to 500 mD. Then, a pump is lowered into the horizontal wellbore of the production well, a displacement fluid is pumped through vertical injection wells into pay formations, the pump is started and the products are taken from the horizontal wellbore of the production well.

EFFECT: improved reliability of the method implementation.

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