Zhanxi Pang

The study on classification methods for low production wells of thermal recovery and its applications

During the later period of steam injection, the oil production largely decreases to be a state of low production or low oil–steam ratio. In this article, a classification method of low production wells was established and some measures of improving oil production were researched for the low production wells during thermal recovery. Three visualization experiments were implemented to analyze the sweep efficiency and to measure the oil recovery factor during injecting different flooding agents. Then a novel diagram was introduced to guide us how to precisely choose the appropriate measures for the low production wells during thermal recovery in heavy oil reservoirs. According to the statistical results, the low production wells can be categorized into three types involving high degree of oil recovery, thermal disturbance (even steam channeling) among wells and dual factors. The results of visualization experiments showed that the injection of chemical agents can effectively increase the displacement efficiency in swept zone after steam injection. Temperature-resistant gel or foams can be used to decrease thermal disturbance and even steam channeling among wells during steam injection in heavy oil reservoir. The values of a new parameter can be employed to confirm the boundary of different improvement measures. Finally, a diagram was established to help choosing appropriate measures involving nitrogen injection, foam injection, gel injection and invalid measure.

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 (

Pore-Scale Experiment on Blocking Characteristics and EOR Mechanisms of Nitrogen Foam for Heavy Oil: A 2D Visualized Study

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

Enhance Oil Recovery for Steam Flooding: Low-Temperature Oxidative Decomposition of Heavy Oil with Air Injection

μo/μw) and relative permeability ratio

Flexibility Research of Hot-Water Flooding followed Steam Injection in Heavy Oil Reservoirs

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

A study of scaling 3D experiment and analysis on feasibility of SAGD process in high pressure environment

(krw/krnw) and increases with increasing average capillary back pressure and the difference in capillary back pressure. This work gives us a comprehensive insight into the spontaneous imbibition with TEO boundary condition.