Abstract
N2 injection process is a potential technique to control the water coning behavior in heavy oil reservoirs. In this paper, by using the methods of experiment and numerical simulation, the N2 injection process for controlling the edge water coning behavior is investigated. First, through a visual fluid flow experimental device, the flow behavior of N2-water in porous media is discussed. Also, the effects of temperature, pressure, and injection rate were studied. Then, based on the experimental results, aiming at an actual edge water heavy oil reservoir, a reservoir simulation model is developed. Thus, the water coning behavior of edge aquifer is systematically studied. Also, two novel indicators are proposed to evaluate the water coning behavior. Then, a series of numerical models are developed to investigate the performance of N2 injection process in edge water heavy oil reservoirs after water coning, and the adaptability and the optimal operation parameters are analyzed. Results indicate that under the effect of porous media, N2 can cut into a series of small gas bubbles. It is a typical dispersed phase and can effectively plug the water coning path. Compared with pressure and injection rate, temperature is a more sensitive factor to affect the plugging performance of N2. From the simulation results, it is observed that the permeability, water/oil ratio, and distance between well and aquifer can significantly affect the performance of water coning behavior. N2 injection process can effectively control the edge water coning and improve the CSS performance. Furthermore, from the simulation results, it is found that the optimal operation parameters for a N2 injection process is that the total N2 injection volume should be higher than 6,000 m3 within one operation cycle and the optimal N2 injection rate should be lower than 700 m3/day. This investigation further clarifies the mechanisms of N2 injection process to control the water coning behavior in heavy oil reservoirs. It can provide a useful reference for the EOR process of the heavy oil reservoirs with edge water.
Highlights
Heavy oil reservoir is an important type of petroleum resources (Meyer et al, 2007; Liu et al, 2019)
The slope for the curve of ratio of cumulative-edge-water to cumulative-water (REWW) versus time will used to evaluate the strength of water coning and to design the suitable injection volume of plugging agent
From the two new indicators, the water coning behavior of edge water heavy oil reservoirs after CSS process will be discussed
Summary
Heavy oil reservoir is an important type of petroleum resources (Meyer et al, 2007; Liu et al, 2019). It refers to the petroleum reservoir whose oil viscosity is higher than about 50 mPa·s at reservoir condition. Considering the diversity of the type of heavy oil reservoirs, the three classic thermal recovery processes usually have the optimal screening criterion. It indicates that for some special or complicated heavy oil reservoirs, the conventional steam injection process is usually not effective (Dong et al, 2019)
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