Qingbang Meng

Three-dimensional physical modeling of waterflooding in metamorphic fractured reservoirs

Abstract 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.

Mechanism simulation of oil displacement by imbibition in fractured reservoirs

Abstract The mechanism model of both static and dynamic imbibition considering capillary pressure and gravity was presented based on the imbibition mechanisms and seepage theory. The validation of the model was performed using published experiment data. Then, this model was employed to study the impacts of oil viscosity, matrix permeability, core size, interface tension, and displacement rate on imbibitions. The results show that, the recovery decreases as oil viscosity increases, and the initial imbibition rate is much faster for lower viscosity oil. Imbibitions recovery is positively related to matrix permeability, the differences of oil recovery for low-permeability to tight oil reservoirs are obvious. Imbibitions effect is negatively related to core size. If the interface tension is low, imbibitions cannot occur without consideration of gravity. But it can occur even in very low interface tension scenario with consideration of gravity. On the whole, the recovery first increases and then decreases as the interface tension decreases. The gravity and capillary play different roles at different ranges of interface tension. There exists an optimal value range of displacement rate in fractured reservoir, which should be optimized with a sufficient oil production rate to achieve higher recovery.

Asymmetry Characteristics of Oil Production by Spontaneous Imbibition from Cores with Two Ends Open

Spontaneous imbibition experiments with two ends open (TEO) boundary condition showed that oil production from each open face of core is asymmetrical while the invasion of water is symmetrical. Investigating the asymmetry characteristics of oil production is helpful to understand the imbibition displacement mechanisms. In this paper, a mathematical model considering the difference in capillary back pressure for TEO imbibition is established by assuming piston-like advance of the imbibition front. Based on the model, the reason for asymmetry in oil production is discussed and the effect of the viscosity ratio, relative permeability ratio, average capillary back pressure and the difference in capillary back pressure on the asymmetry in oil production is investigated as well. The simulated results show that asymmetry in oil production depends on the ratio of the difference in capillary back pressure to the pressure drop in oil between the imbibition front and the open face of the core. As capillary driving pressure dissipated in oil is very small, a small difference in capillary back pressure will cause a significant asymmetric production of oil. Furthermore, the asymmetry in oil production decreases with increasing viscosity ratio (

Entrapment of the Non-wetting Phase during Co-current Spontaneous Imbibition

\mu _{\mathrm{o}}/ \mu _{\mathrm{w}})

Effect of Viscosity on Oil Production by Cocurrent and Countercurrent Imbibition From Cores With Two Ends Open

μo/μw) and relative permeability ratio

Experimental and Numerical Study on Cyclic Water Injection in Stress-Sensitive Reservoirs: A Case Study

(k_{\mathrm{rw}}/k_{\mathrm{rnw}})