Abstract:

The development of the reservoirs with narrow oil ring, gas cap, and bottom water is often challenged by water coning, gas channeling, and complex remaining oil distribution. This paper discusses the well location optimization and potential tapping strategy for horizontal well development in the Bohai Bay basin. In the basic well pattern arrangement stage, in plane, horizontal wells are arranged perpendicular to the structural lines and penetrating multiple layers for enhancing the recovery of reserves, and the separated-layer production string with intelligent sliding sleeve is equipped to alleviate inter-layer contradiction; vertically, horizontal wells are arranged parallel to the fluid interface and at 1/3 of the oil column height from the water-oil contact for gas channeling prevention and water control. In the comprehensive adjustment stage, according to the numerical reservoir simulation, the remaining oil is enriched in inter-well retention zone in plane in the middle-late development stage, and is vertically enriched in the upper part of the reservoir due to the subsequent dominance of water drive in the late stage. Comparing the oil increment indexes under the schemes of inter-well sidetracking, gas reinjection into the gas cap, and barrier water injection, the former two schemes are preferred for tapping the potential remaining oil. Ineffective and inefficient wells are sidetracked to the zones at high positions between wells, with the expected net oil increment of 3.4×10⁴-4.2×10⁴ m³ per well. For gas reinjection into the gas cap, existing gas production wells are converted for gas reinjection to replenish the energy of the gas cap, so as to displace the remaining oil in the upper part of horizontal wells and enhancing the oil recovery, with the expected net oil increment of 5.2×10⁴ m³ per well.

Key words: gas cap, bottom water, narrow oil ring, well pattern arrangement, comprehensive adjustment, remaining oil, inter-well sidetracking, gas reinjection, barrier water injection