scholarly journals Simulation Study of CO2 Huff-n-Puff in Tight Oil Reservoirs Considering Molecular Diffusion and Adsorption

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2136 ◽  
Author(s):  
Yuan Zhang ◽  
Jinghong Hu ◽  
Qi Zhang
Keyword(s):  
Molecular Diffusion ◽  
Co2 Storage ◽  
Oil Production ◽  
Oil Reservoirs ◽  
Co2 Injection ◽  
Tight Oil ◽  
Strong Basis ◽  
Well Production ◽  
Co2 Eor ◽  
Tight Oil Reservoirs

CO2 injection has great potentials to improve the oil production for the fractured tight oil reservoirs. However, Current works mainly focus on its operation processes; full examination of CO2 molecular diffusion and adsorption was still limited in the petroleum industry. To fill this gap, we proposed an efficient method to accurately and comprehensively evaluate the efficiency of CO2-EOR process. We first calculated the confined fluid properties with the nanopore effects. Subsequently, a reservoir simulation model was built based on the experiment test of the Eagle Ford core sample. History matching was performed for the model validation. After that, we examined the effects of adsorption and molecular diffusion on the multi-well production with CO2 injection. Results illustrate that in the CO2-EOR process, the molecular diffusion has a positive impact on the oil production, while adsorption negatively impacts the well production, indicating that the mechanisms should be reasonably incorporated in the simulation analysis. Additionally, simulation results show that the mechanisms of molecular diffusion and adsorption make great contributions to the capacity of CO2 storage in tight formations. This study provides a strong basis to reasonably forecast the long-term production during CO2 Huff-n-Puff process.

scholarly journals Simulation Study of CO2-EOR in Tight Oil Reservoirs with Complex Fracture Geometries

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Pavel Zuloaga-Molero ◽  
Wei Yu ◽  
Yifei Xu ◽  
Kamy Sepehrnoori ◽  
Baozhen Li
Keyword(s):  
Simulation Study ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Complex Fracture ◽  
Co2 Eor ◽  
Tight Oil Reservoirs

scholarly journals A Semianalytical Approach for Production of Oil from Bottom Water Drive Tight Oil Reservoirs with Complex Hydraulic Fractures

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Shuhui Dai ◽  
Chunqiang Chen ◽  
Hao Wang ◽  
Zhaohui Fu ◽  
Dameng Liu
Keyword(s):  
Bottom Water ◽  
Oil Production ◽  
Oil Reservoirs ◽  
Hydraulic Fractures ◽  
Tight Oil ◽  
Matrix Permeability ◽  
Cumulative Production ◽  
Tight Reservoirs ◽  
Tight Oil Reservoirs ◽  
Half Length

In order to improve the recovery rate, fractured horizontal wells are widely used in tight reservoirs. In general, a complex fracture system is generated in tight reservoirs to improve oil production. Based on the fractal theory, a semianalytical model is presented to simulate a complex fracture system by using the volumetric source method and superposition principle, and the solutions are determined iteratively. The reliability of this model is validated through numerical simulation (Eclipse 2011); it shows that the result from this method is identical with that from the numerical simulation. The study on influence factors of this model was focused on matrix permeability, fractal dimension, and half-length of main fracture. The results show that (1) the production increases with the increase of half-length of main fracture and matrix permeability during the initial production stage, but the production difference becomes smaller in different half-length of main fractures and matrix permeability in middle and later stages and (2) the cumulative production increases with the increase of fractal dimension, and the increments of cumulative production in different fractal dimensions gradually increase during the initial production stage, but the increments tend to be stable in middle and later stages. This study can be used for forecasting the oil production from bottom water tight oil reservoirs with complex hydraulic fractures. It can also guide in optimization of horizontal well fracturing design to improve oil production and oil recovery in bottom water tight oil reservoirs.

scholarly journals Performance Optimization of CO2 Huff-n-Puff for Multifractured Horizontal Wells in Tight Oil Reservoirs

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Mingqiang Hao ◽  
Songlin Liao ◽  
Guangming Yu ◽  
Xinhui Lei ◽  
Yong Tang
Keyword(s):  
Crude Oil ◽  
Horizontal Wells ◽  
Production Performance ◽  
Oil Reservoirs ◽  
Co2 Injection ◽  
Tight Oil ◽  
Production Parameters ◽  
Sensitivity Factors ◽  
Tight Oil Reservoirs ◽  
The Impact

In this paper, the sensitivity factors of CO2 huff-n-puff for multifractured horizontal wells (MFHWs) in tight oil reservoirs were investigated through an experimental test and numerical simulation. The pressure-volume-temperature (PVT) experiment and the slim tube experiment are used to understand the interaction mechanism between CO2 and crude oil, and the minimum miscibility pressure (MMP) of the CO2-crude oil system is 17 MPa. The single-well model was firstly established to analyze the sensitivity factors on production performance of MFHWs by using CO2 huff-n-puff. The controlling factors of CO2 huff-n-puff for MFHWs in tight oil reservoirs were divided into three categories (i.e., reservoir parameters, well parameters, and injection-production parameters), and the impact of individual parameter on well performance was discussed in detail. The range of reservoir parameters suitable for CO2 huff-n-puff of MFHWs is obtained. The reservoir permeability is from 0.1 mD to 1 mD, the reservoir thickness changes from 10 m to 30 m, and the reservoir porosity is from 7% to 12%. Based on the reservoir parameters of the target reservoir, the reasonable well and fracture parameters are obtained. The sensitivity intensity was followed by the horizontal well length, fracture conductivity, fracture spacing, and fracture half-length. CO2 injection-production parameters are further optimized, and the sensitivity intensity was followed by the single-cycle cumulative CO2 injection rate, the soaking time, the injection rates, and the production rates. It provides a reference for parameter optimization of CO2 huff-n-puff for MFHWs in tight oil reservoirs.

scholarly journals The Characteristics of Oil Migration due to Water Imbibition in Tight Oil Reservoirs

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4199
Author(s):  
Liu Yang ◽  
Shuo Wang ◽  
Zhigang Tao ◽  
Ruixi Leng ◽  
Jun Yang
Keyword(s):  
Clay Minerals ◽  
Oil Recovery ◽  
Oil Production ◽  
Inhibitory Effect ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Oil Migration ◽  
Water Imbibition ◽  
Migration Dynamics ◽  
Tight Oil Reservoirs

In tight oil reservoirs, water imbibition is the key mechanism to improve oil production during shut-in operations. However, the complex microstructure and composition of minerals complicate the interpretation of oil migration during water imbibition. In this study, nuclear magnetic resonance (NMR) T2 spectra was used to monitor the oil migration dynamics in tight oil reservoirs. The factors influencing pore size distribution, micro-fractures, and clay minerals were systematically investigated. The results show that the small pores corresponded to a larger capillary pressure and a stronger imbibition capacity, expelling the oil into the large pores. The small pores had a more effective oil recovery than the large pores. As the soaking time increases, the water preferentially entered the natural micro-fractures, expelling the oil in the micro-fractures. Subsequently, the oil in the small pores was slowly expelled. Compared with the matrix pores, natural micro-fractures had a smaller flow resistance and were more conducive to water and oil flow. Clay minerals may have induced micro-fracture propagation, which can act as the oil migration channels during water imbibition. In contrary to the inhibitory effect of natural micro-fractures, the new micro-fractures could contribute to the oil migration from small pores into large pores. This study characterized the oil migration characteristics and provides new insight into tight oil production.

scholarly journals Nanopore Confinement Effect on the Phase Behavior of CO2/Hydrocarbons in Tight Oil Reservoirs considering Capillary Pressure, Fluid-Wall Interaction, and Molecule Adsorption

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Zhixue Zheng ◽  
Yuan Di ◽  
Yu-Shu Wu
Keyword(s):  
Phase Behavior ◽  
Pore Size ◽  
Capillary Pressure ◽  
Confinement Effect ◽  
Oil Reservoirs ◽  
Co2 Injection ◽  
Tight Oil ◽  
Tight Reservoirs ◽  
Tight Oil Reservoirs ◽  
Nanopore Confinement

The pore sizes in tight reservoirs are nanopores, where the phase behavior deviates significantly from that of bulk fluids in conventional reservoirs. The phase behavior for fluids in tight reservoirs is essential for a better understanding of the mechanics of fluid flow. A novel methodology is proposed to investigate the phase behavior of carbon dioxide (CO2)/hydrocarbons systems considering nanopore confinement. The phase equilibrium calculation is modified by coupling the Peng-Robinson equation of state (PR-EOS) with capillary pressure, fluid-wall interaction, and molecule adsorption. The proposed model has been validated with CMG-Winprop and experimental results with bulk and confined fluids. Subsequently, one case study for the Bakken tight oil reservoir was performed, and the results show that the reduction in the nanopore size causes noticeable difference in the phase envelope and the bubble point pressure is depressed due to nanopore confinement, which is conductive to enhance oil recovery with a higher possibility of achieving miscibility in miscible gas injection. As the pore size decreases, the interfacial tension (IFT) decreases whereas the capillary pressure increases obviously. Finally, the recovery mechanisms for CO2 injection are investigated in terms of minimum miscibility pressure (MMP), solution gas-oil ratio, oil volume expansion, viscosity reduction, extraction of lighter hydrocarbons, and molecular diffusion. Results indicate that nanopore confinement effect contributes to decrease MMP, which suppresses to 650 psi (65.9% smaller) as the pore size decreases to 2 nm, resulting in the suppression of the resistance of fluid transport. With the nanopore confinement effect, the CO2 solution gas-oil ratio and the oil formation volume factor of the oil increase with the decrease of pore size. In turn, the oil viscosity reduces as the pore size decreases. It indicates that considering the nanopore confinement effect, the amount of gas dissolved into crude oil increases, which will lead to the increase of the oil volume expansion and the decrease of the viscosity of crude oil. Besides, considering nanopore confinement effect seems to have a slightly reduced effect on extraction of lighter hydrocarbons. On the contrary, it causes an increase in the CO2 diffusion coefficient for liquid phase. Generally, the nanopore confinement appears to have a positive effect on the recovery mechanisms for CO2 injection in tight oil reservoirs. The developed novel model could provide a better understanding of confinement effect on the phase behavior of nanoscale porous media in tight reservoirs. The findings of this study can also help for better understanding of a flow mechanism of tight oil reservoirs especially in the case of CO2 injection for enhancing oil recovery.

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