Theoretical Investigation of Nonlinear-Diffusion Countercurrent Imbibition for Porous Medium with Micro-/Nanopores

Self Cite

Spontaneous imbibition is an essential method to enhance recovery during fracturing shut-in of tight reservoirs. However, most of the investigations are primarily focused on the mechanism of water imbibition to enhance recovery; the mechanism of fracturing fluid to enhance recovery and the lower limit of imbibition flow are remained insufficiently investigated. This paper identifies the pore structure characteristic of tight reservoirs, the fracturing fluid imbibition, and the lower limit of imbibition flow by combining nuclear magnetic resonance and high-pressure mercury intrusion methods, clarifying the mechanism of fracturing fluid recovery enhancement. The core-scale super diffusion model of fracturing fluid was established, and the sensitivity analysis of imbibition-influencing factors was conducted. The experimental results indicated that high interfacial tension increased the driving force and decreased the lower limit of imbibition flow, while low interfacial tension decreased the crude oil flow resistance and increased the lower limit of imbibition flow. The imbibition recovery improved with the increase of matrix permeability and decreased with the increase of crude oil viscosity. The degree of mobilization of micropores decreases and the degree of mobilization of mesopores with macropores increases with decreasing interfacial tension. The increase in matrix permeability elevated the degree of mobilization of each pore, while the increase of crude oil viscosity decreased the reduction of each pore. The simulation results fitted well with the experimental data, verifying the reasonableness of the model. The results indicated that the imbibition recovery was positively correlated with the characteristic parameters of the capillary force and negatively correlated with the core length and the viscosity of the fracturing fluid. The investigation in this paper provides a new theoretical basis for the improvement of recovery in tight reservoirs.

Section: Introductionmentioning

confidence: 99%

“…They developed a microscale model that takes into account advanced diffusion, according to the findings of the experiment. Additionally, they performed a comprehensive sensitivity analysis of the relevant factors …”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Imbibition Diffusion and Recovery Enhancing of Fracturing Fluids in Tight Reservoirs

Zhang,

Yu,

Tang

et al. 2024

Self Cite

“…On the other hand, polymer microspheres are usually micrometer-sized and not suitable for low-permeability and tight reservoirs . Due to the complexity of the low-permeability and tight reservoir pore structure and strong heterogeneity, the flow and plugging mechanism of microspheres are different from those of a conventional reservoir, which needs further investigation. − …”

Section: Introductionmentioning

confidence: 99%

A Systematic Method to Investigate the EOR Mechanism of Nanospheres: Laboratory Experiments from Core to Micro Perspective

Wang

Yang

et al. 2023

Self Cite

Nanospheres have been used as an available plugging material to solve the problem of water intrusion, which is of crucial importance to enhanced oil recovery (EOR). However, the microflow of nanospheres in a lowpermeability reservoir is complex, and its plugging performance and EOR mechanism need to be further investigated by a variety of experiments. In this paper, the expansion experiments were given priority to explore the water absorption and salt tolerance of nanospheres. The displacement experiments were conducted to investigate the plugging performance of nanospheres at the core scale. The flow characteristic and EOR mechanism of nanospheres at the microscale were revealed by nuclear magnetic resonance (NMR) experiments and microfluidic experiments. Expansion and displacement experiments results demonstrate that high salinity inhibits the expansibility and agglomeration of nanospheres, and the formation damage and plugging performance of nanospheres should be comprehensively considered. The suitable particle size of nanospheres should be optimized for field application. As for the microscale, NMR experiments revealed that nanospheres would first enter the large pore and then enter the middle and small pores. In microfluidic experiments, the oil recovery increased by 23.02% original oil in place after the injection of nanospheres. The systematic and comprehensive investigations of expansion property, plugging performance, flow characteristic, and EOR mechanism of nanospheres were conducted from core to microscale, which yielded significant insights into preventing water intrusion and enhancing oil recovery.

“…Although this visual experiment method can directly observe the apparent phenomenon of the huff-n-puff process, it cannot measure and analyze the in situ oil/gas distribution and oil recovery in the core. At present, CT scanning , and nuclear magnetic resonance (NMR) have become important methods of in situ visual analysis of fluid distribution and seepage laws in cores, which are conducive to further research on the in situ recovery mechanism of gas huff-n-puff. Francisco D. Tovar et al employed X-CT imaging technology to monitor the experimental production process and tracked the saturation change in core samples through the conversion relationship between the CT number and density.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the CO₂ Effective Distance and CO₂-EOR Storage for Tight Oil Reservoir

Xie

et al. 2022

Self Cite

CO 2 underground storage is an important approach to reduce carbon emissions; meanwhile, the combination of CO 2 storage and economic benefits can further promote the long-term development of carbon neutrality. Global tight oil reserves are abundant, but the depletion development of most tight reservoirs is unsatisfactory. Therefore, it is crucial to utilize CO 2 storage combined with enhanced oil recovery (EOR) for tight reservoir development. At present, there are few experimental studies on the CO 2 effective distance and CO 2 -EOR storage of huff-n-puff in tight reservoirs. In this paper, the CO 2 effective distance and the evolution of saturation profiles in tight cores are first investigated, and CO 2 -EOR storage is quantitatively evaluated for CO 2 huff-npuff in tight reservoirs based on CT and nuclear magnetic resonance technology. Meanwhile, the influences of oil composition and permeability on the effective distance and CO 2 -EOR storage are further investigated. The results indicate that the increase of CO 2 effective distance gradually slows down with time, and the decrease of permeability significantly reduces the effective distance. Increasing amount of oil is mainly produced in larger pores, which is more than twice of that in smaller pores. CO 2 -EOR storage experiments quantify that the CO 2 storage ratio for a 0.22 × 10 −3 μm2 core is up to 72.31% under different depressurization conditions (12, 8, and 0.1 MPa). With the decrease in production pressure, oil recovery gradually increases, while the CO 2 storage ratio decreases, indicating that there is a collaborative optimization to maximize the oil production and CO 2 storage ratio. Comparison experiments reveal that the oil composition (replaced by fluorocarbon oil) has little influence on the effective distance and CO 2 -EOR storage, while the influence of permeability is significant. The CO 2 effective distance determines the sweep efficiency, so increasing effective distance is essential to enhance oil recovery and CO 2 storage. This research is of great significance for CO 2 utilization and CO 2 storage in tight reservoirs.