METHOD OF OIL DEPOSIT DEVELOPMENT Russian patent published in 2003 - IPC

FIELD: development of oil deposits; applicable in development of water-encroached oil pools, particularly, oil recovery from formation roof zone. SUBSTANCE: method includes drilling of vertical and horizontal wells according to definite pattern. Water is injected and oil is recovered. At late stage of development with high water cutting of produced oil, centers of accumulation of oil residual reserves are determined in formation roof zone. Additional horizontal wells or branch horizontal wellbores are drilled from producing parent wells between vertical producing and injection wells in formation roof zone. Horizontal part of wells or wellbores are located perpendicular to lines of flow of formation fluids and at distance amounting up to 60-80% of distance from injection to vertical producing wells. Residual oil reserves are recovered at differential pressures allowing operation of horizontal wells or branch horizontal wellbores without dealing with cones of bottom water. EFFECT: increased oil recovery factor due to involving into development of unrecovered oil remaining between producing and injection wells in formation roof zone after primary displacement owing to action of gravitational forces. 2 dwg, 1 ex