D-optimal design for Rapid Assessment Model of CO2 flooding in high water cut oil reservoirs

Abstract After a sandstone oilfield enters the high water-cut period, the viscosity of crude oil has an important influence on remaining oil distribution and waterflooding characteristics under the same factors of, e.g., reservoir quality and development methods. Based on a comprehensive interpretation of the waterflooded layers in new oil wells, physical simulation experiments, and reservoir numerical simulations, we analyzed the waterflooding laws of a high water-cut sandstone reservoir with different oil viscosities in Kazakhstan under the same oil production speed, and we clarified the remaining oil potential of reservoirs with different viscosities and proposed corresponding development measures. The results show that low-viscosity oil reservoirs (1 mPa s) have uniform waterflooding, thick streamlines, small waterflooding areas, and low overall waterflooding degrees because of their homogeneous oil–water viscosities. However, within waterflooded areas, the reservoirs have high oil displacement efficiencies and high waterflooding degrees, and the remaining oil is mainly concentrated in the unwaterflooded areas; therefore, the initial production and water cut in new oil wells vary significantly. High-viscosity oil reservoirs (200 mPa s) have severe waterflooding fingering, large waterflooding areas, and high overall waterflooded degrees because of their high oil–water mobility ratios. However, within waterflooded areas, the reservoirs have low oil displacement efficiencies and low waterflooding degrees, and the remaining oil is mainly concentrated in both the waterflooded areas and the unwaterflooded areas; therefore, the differences in the initial production and water cut of new oil wells are small. Moderate-viscosity oil reservoirs (20 mPa s) are characterized by remaining oil distributions that are somewhere in between those of the former two reservoirs. Therefore, in the high water-cut period, as the viscosity of crude oil increases, the efficiency of waterflooding gradually deteriorates and the remaining oil potential increases. In the later development, it is suggested to implement the local well pattern thickening in the remaining oil enrichment area for reservoirs with low viscosity, whereas a gradual overall well pattern thickening strategy is recommended for whole reservoirs with moderate and high viscosity. The findings of this study can aid better understanding of waterflooding law and the remaining oil potential of reservoirs with different viscosities and proposed corresponding development measures. The research results have important guidance and reference significance for the secondary development of high water-cut sandstone oilfields.

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Research Method of Phase Behavior in Gas-Crude System and the Application in L Block with HP/HT

10.2523/iptc-21267-ms ◽

2021 ◽

Author(s):

Tongwen Jiang ◽

Daiyu Zhou ◽

Yiming Wu ◽

Lunjie Chang ◽

Liming Lian ◽

...

Keyword(s):

Phase Behavior ◽

Relative Error ◽

High Water ◽

Mixing Rules ◽

Mixing Rule ◽

Co2 Flooding ◽

High Water Cut ◽

Water Cut ◽

Behavior Models ◽

Speed And Accuracy

Abstract This paper provide improved phase behavior models, trying to mitigate the problem that phase behavior of gas-crude system is difficult to describe in L block with low permeability and high water cut in China. This situation leads to a series of problems in CO2 flooding process and lower recovery up to expectations. The models is evaluated to possess both high calculation speed and accuracy compared with existing others. Characteristics of CO2-crude systems had been considered into repulsion-attraction type EOS (equation of state) based on the analysis of repulsion parameter and attraction parameter in EOS, and the improved EOS had been applied in developing calculation method of MMP (minimum miscible pressure). No ideality of CO2-crude systems had been considered into mixing rules of CO2-crude systems based on analysis of mixing rules of repulsion-attraction type EOS. Promotion had also been put into the obtain methods of parameters in phase behavior, including density, viscosity, MMP, critical parameters of plus components etc. All these methods are applied in L Block. The phase behavior models of CO2-crudes system promoted in this paper mainly include EOS, mixing rule and viscosity model and have been applied in CO2 flooding process in T Reservoir. The relative error of density calculation is reduced from 7% ∼ 20% to less than 1%and the modified EOS is applied to predict the MMP of the CO2-crude systems from 8 different blocks in T reservoir. The modified EOS also works well for the relative error of MMP prediction is reduced from 20% ∼ 70% to less than 5%. Compared with the existing mixing rules, the modified mixing rule is with higher calculation speed and accuracy. The relative error of components mole fraction calculation is reduced from 30% ∼ 80% to less than 10%. Compared with the existing viscosity models, there are large improvements of the modified viscosity model in accuracy. The relative error of viscosity simulation is reduced from more than 50% to about 5%. According to the simulation results, C2∼C15 are the key hydrocarbons with positive effect on the miscibility of CO2-crude systems, while C16+ are the key hydrocarbons with negative effect. The recovery of the pilot has increased by 23% by these methods. The improved phase behavior models provided in this paper possess as good performance as existing models in calculation speed, and accustom a big step forward in simulation accuracy. The modified components of the models also partially complete physical meaning in describing phase behavior of CO2-crude system. All the models mentioned above are finally applied in L block with HP/HT and high water cut and obtained an increase in recovery by 19.2%.

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Effects of Bottom Aquifer on the Productivity of Chemical Flooding Applied to Multi-Layered Heterogeneous Reservoirs

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.316-317.791 ◽

2013 ◽

Vol 316-317 ◽

pp. 791-794

Author(s):

Byung In Choi ◽

Moon Sik Jeong ◽

Kun Sang Lee

Keyword(s):

Bottom Water ◽

High Water ◽

Oil Reservoirs ◽

Chemical Flooding ◽

Accurate Assessment ◽

Heterogeneous Reservoirs ◽

High Water Cut ◽

Water Cut ◽

Reservoir Simulator ◽

Unfavorable Condition

Complex geological properties of oil reservoirs affect productivity of chemical flooding. Presence of bottom-water aquifer combined with heterogeneous reservoirs has been regarded as a problem which brings out reduction of recovery factor and high water-cut. A numerical reservoir simulator is used to investigate effects of aquifer on the performance of chemical flooding. By including the effects of bottom-water aquifer, productivity decreases significantly compared with that from non-aquifer case. Results from this study emphasize the importance of an accurate assessment of performance before implementing chemical flooding, especially in unfavorable condition such as bottom-water aquifer.

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A novel method for improving recovery of heavy oil reservoirs with high water cut based on polymer gel-assisted CO2 huff and puff

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-021-01232-z ◽

2021 ◽

Author(s):

Haiwei Lu ◽

Zhenyuan Wang ◽

Tong Peng ◽

Jiapeng Zheng ◽

Xiaoliang Yang ◽

...

Keyword(s):

Heavy Oil ◽

Apparent Viscosity ◽

Retention Rate ◽

High Water ◽

Salt Resistance ◽

Oil Reservoirs ◽

Polymer Gel ◽

Heavy Oil Reservoirs ◽

High Water Cut ◽

Water Cut

AbstractA novel enhanced oil recovery (EOR) method based on polymer gel-assisted carbon dioxide (CO2) huff and puff was developed aiming to improve the development effect of heavy oil reservoirs with high water cut. The polymer gel prepared using partially hydrolyzed polyacrylamide (HPAM), hexamethylenetetramine, phenol, resorcinol, oxalic acid, and thiocarbamide as raw materials had a special network structure to overcome the challenge of significant heterogeneity in heavy oil reservoirs. The strength of polymer gel reached the maximum value 20,000 mPa·s within 22 h. The temperature resistance and salt resistance of polymer gel directly determined the plugging effect. The polymer gel was placed for 190 days at 85 ℃, and its apparent viscosity retention rate was 66.4%. The salt resistance experiments showed that the apparent viscosity retention rate of this polymer gel at 1.8 wt % NaCl, 0.045 wt % CaCl2, 0.045 wt % MgCl2 was 71.3%, 78.5%, 71.4%, respectively. Huff and puff experiments confirmed that this method could be used to increase the sweep volume and improve the oil displacement efficiency of heavy oil reservoirs with high water cut. Furthermore, the EOR of this method was better than that of water huff and puff, polymer gel huff and puff or CO2 huff and puff.

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Enhanced heavy oil recovery and CO2 storage in a reservoir with high-water-cut: laboratory to field

10.5194/egusphere-egu21-10495 ◽

2021 ◽

Author(s):

Xiang Zhou ◽

Yongsheng Tan ◽

Qi Jiang

Keyword(s):

Oil Recovery ◽

Heavy Oil ◽

Co2 Storage ◽

High Water ◽

Production Performance ◽

Water Flooding ◽

Heavy Oil Recovery ◽

Co2 Flooding ◽

High Water Cut ◽

Water Cut

<p>In this study, in order to enhance heavy oil recovery in the heavy oil reservoir with a high-water-cut after water flooding process, experimental and numerical simulation studies are conducted. In the experimental studies, firstly, the properties of the heavy oil-CO2 system were measured under different saturation pressures at the reservoir temperature. Secondly, to mimic the high-water-cut condition in the real reservoir, water flooding process was conducted for each core; then four long core experiments insist of one CO2 huff `n` puff process and three CO2 flooding processes were implemented. The CO2 huff `n` puff process is conducted to compare the production performance with that in the CO2 flooding process to optimize the method. Regarding the CO2 flooding process, different gas (pure CO2, flue gas) and different production categories (constant production pressure, pressure depletion) were applied to study the heavy oil production performance in the heavy oil reservoir with high-water-cut. The experimental results indicate that, the CO2 flooding coupling with pressure depletion process is the best choice to reduce the water-cut and enhance the heavy oil recovery, which is 41.84% of the original oil in place and the water-cut reduced to lower than 70%. In the numerical simulation studies, the WinProp module in CMG is applied to simulate the properties of the heavy oil-CO2 system, which is generated by recombining CO2 into heavy oil, and high agreement simulation results were obtained. Then the results of the optimized experiment were history matched using GEM module. Finally, the upscaling studied was conducted. The CO2 flooding processes are carried out in the studied reservoir to maximum the heavy oil recovery factor. Moreover, the CO2 storage ratio is studied using GEM model.</p>

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