High-Precision Numerical Simulation on the Cyclic High-Pressure Water Slug Injection in a Low-Permeability Reservoir

Abstract

The paper presents a novel waterflooding technique, coupling cyclic high-pressure water slug injection with an asynchronous injection and production procedure, to address the inefficient development of low-permeability oil reservoir in Shengli Oilfield, a pilot test with 5-spot well pattern. Based on the first-hand data from the pilot test, the reservoir model is established. With an in-depth understanding of the mechanism of the novel waterflooding technique, different simulation schemes are employed to screen the best scheme to finely investigate the historical performance of the pilot test. The production characteristics of the pilot test are both qualitatively and quantitatively investigated. It is found that the novel waterflooding technique can provide pressure support within a short period. And the formation around the injector is significantly activated and deformed. Once passing the short stage of the small elastic deformation, the reservoir immediately goes through the dilation deformation accompanied with the opening of microfractures so that the reservoir properties are significantly improved, which leads to better reservoir performance. With the multicyclic dilation-recompaction geomechanical model, the impact of pressure cyclic evolution on the reservoir properties and performance under the novel waterflooding mode of cyclic high-pressure water slug injection is taken into consideration. The historical data of the pilot test is well matched. In the study, a high-precision simulation scheme for the novel waterflooding technique in low-permeability reservoirs is proposed, which provides significant technical support for further optimization of the pilot test and large-scale application of the novel waterflooding technique.

Well Pattern and Well Spacing Optimization of Large Volume Water Injection in a Low-Permeability Reservoir with Pressure Sensitivity

“…Compared with conventional flowgeomechanical coupling models [22], where complex coupling schemes, expensive computational cost, and massive input data, such as rock mechanical data and in situ stress data, get involved, the methodology employed in the study characterizes the dominating mechanism of the physical process while keeping the modeling and computational cost low. The methodology has been applied and validated by previous work to both accurately and efficiently simulate the process [9,[23][24][25][26].…”

“…The dilation-recompaction model finely depicts the relation between the porosity and reservoir pressure as a piecewise and path-dependent function, illustrated in Figure 2 [9,[27][28][29]. Different value is given to the compressibility according to the range of reservoir pressure.…”

“…But water injection is still the primary method to improve the performance of low-permeability reservoirs [5][6][7][8]. Shengli Oilfield proposes an innovative waterflooding scheme with large volume injection to further improve the low-permeability reservoir performance in Block X, which has been depleted for years with low productivity [9]. There are two factors accounting for the improvement of reservoir performance.…”

The Seepage Mechanism of Micro Remaining Oil During Cyclic Waterflooding in Low-permeability Reservoir

“…According to practices in mines in China and foreign countries, cyclic waterflooding is one of the effective means to improve the exploitation effect of low-permeability oilfields [4], and it is advantages for a small investment, quick effects and simple operation [5][6] . It can relieve the rising rate of the aquifer in the low-permeability reservoir and increase the final waterflooding recovery efficiency to some extent [7] . At present, there are many studies on reasonable working systems of cyclic waterflooding [8][9] , cyclic waterflooding parameter optimization [10] , nonlinear percolation of cyclic waterflooding [11] , and macroscopic yield-increasing mechanism of cyclic waterflooding [12] in China and abroad.…”

Numerical Investigation on EOR in Porous Media by Cyclic Water Injection with Vibration Frequency

“…Although the reliability of the CWI on EOR has been proved by core flooding experiments, field development and numerical simulations, the EOR performances reported by the researchers vary from 3% to 20%, indicating that diverse frequencies trigger various EOR effects. Moreover, few studies have found a critical frequency for the optimal EOR by CWI from a pore-scale perspective; therefore, the correlation between the frequency of water injection and the EOR is still to be revealed [30,31]. In addition, for operability, the field site generally sets the water injection frequency constant based on the engineering experience, rather than the critical frequency of the optimal EOR at the present residual oil saturation.…”