Three-dimensional physical modeling of waterflooding in metamorphic fractured reservoirs

To understand water-oil displacement characteristics and the mechanism of improving waterflood efficiency in metamorphic fractured reservoirs, taking JZ251S oil field as an example, a large-scale physical simulating model which meets the geometric similarity, kinematic similarity, dynamic similarity and dual media characteristic parameters similarity based on the theory of scaling criteria was designed to simulate the development of the reservoir by horizontal wells. The mechanism of water displacing oil in dual media reservoirs, the factors affecting fluid flow and waterflood characteristics, and the enhanced oil recovery (EOR) features of different water injection patterns were studied by experiments. The results show that: (1) Capillary imbibition is the main mechanism of enhancing matrix oil recovery in a dual media reservoir which is controlled by waterflooding; (2) whether or not there is crude oil draining from matrix, the water cut trend after water breakthrough can be divided into two stages, the first stage is quick rise stage of water cut in early water breakthrough period and the second stage is slow rise stage of water cut in mid-high water cut period; (3) displacement rate is the main factor controlling water-free production period, water cut trend and ultimate recovery; (4) compared with continuous injection, intermittent injection can give full play to the function of oil-water gravity segregation, reducing the water cut and improving the production rate of initial stages greatly.