Based on the features of microemulsion flooding in low-permeability reservoir, a three-dimension three-phase five-component mathematical model for microemulsion flooding is established in which the diffusion and adsorption characteristics of surfactant molecules are considered. The non-Darcy flow equation is used to describe the microemulsion flooding seepage law in which the changes of threshold pressure gradient can be taken into account, and the correlation coefficients in the non-Darcy flow equation are determined through the laboratory experiments. A new treatment for the changes of threshold pressure and the quantitative description of adsorption quantity of surfactant and relative permeability curves are presented, which enhance the coincidence between mathematical model and experiment results. The relative errors of main development indexes are within 4%. A software is programmed based on the model to execute a core-level small-scale numerical simulation in Chaoyanggou Oilfield. The fitting relative errors of the pressure, flow rate, and moisture content are 3.25%, 2.71%, and 2.54%, respectively. The results of laboratory experiments and numerical simulation showed that microemulsion system could reduce the threshold pressure gradient by 0.010 MPa/m and injection pressure by 0.6 MPa. The biggest decline in moisture content reaches 33%, and the oil recovery is enhanced by 10.8%.
Daqing Oilfield is now at the stage of extra-high watercut after 48 years of development. Since 1996, the field scale polymer flooding has been targeting major reservoirs with thick pay zones and high permeability, and the commercial polymer in Class ?? reservoirs (the effective thickness is 1~3m and the effective permeability is higher than 100×10-3 µm2) also started. In order to increase the recovery factor of Class ??? reservoir and to improve the development effect of mature oilfield, the study on polymer flooding in Class ??? reservoir (the effective permeability is less than 100×10-3 µm2, the effective thickness is smaller than 1m) and corresponding pilot test were performed. The objectives were to enhance oil recovery efficiency, increase recoverable reserves of Class ??? reservoir, and determine potential target layers for field scale polymer flooding. In this work, based on the detailed geological information, optimal polymer injection parameters were designed based on the coreflood tests and numerical simulation. The coreflood results indicated that the compatibility between the molecular size of polymer and pore structure of Class ??? reservoir is very important. Physical properties of reservoir, well log data, sealed coring data, the polymer injection parameters were also selected for the design. Six sets of polymer flood plans were calculated and compared. The results showed that the novel separate-layer injection with different molecular weights obtained higher oil recovery. The polymer injection in pilot test started in March 2007. The field application results of initial stage of polymer flooding are very promising. Introduction Daqing oilfield, the largest oilfield in China, is a typical example of polymer flooding, even chemical flooding, in the world petroleum industry(Pu et al. 2008). Field scale polymer flooding has been successfully applied in Daqing oilfield since 1996, the annual oil production by polymer production has exceeded 10 million tons (Wang and Liu, 2006). It has become an important supporting technology for the high and stable production of Daqing (Pu et al. 2008). Polymer flooding in major reservoirs, which are the best quality reservoirs in Daqing, is almost finished. On the basis of mature polymer flooding technology in major reservoir, the research on the polymer flooding in Class ?? reservoir was conducted. Based on the understanding of polymer flooding in Class ?? reservoir by laboratory investigation, the field test of polymer flooding in Class ?? reservoir was carried out. For example, in 2002, polymer flooding in low quality reservoirs was performed in northern part of Sazhong area, providing technical experience in developing polymer flooding in low quality reservoirs (Cheng et al., 2007). The industrial scale polymer flooding in Class ?? reservoir has been implemented. Because the physical properties of target zone are poor, the oil saturation is low, and the residual oil distribution is highly dispersed, it is not economically feasible to further drill infill wells in Class ??? reservoir. In order to increase the recoverable reserves and to increase the recovery factor, the feasibility study on polymer flooding in Class ??? reservoir was performed. Through the laboratory experiments and reservoir numerical simulation study, the optimal polymer injection plan was obtained. La 8–182 wellblock of Lamadian oilfield in northern Daqing was chosen to carry out pilot test of polymer flooding in Class ??? reservoir. The polymer injection started in March 2007. To date, the desirable pilot performance of polymer flooding is achieved, the lessons learned and experience gained in the initial stage of polymer flooding in low permeability reservoirs are invaluable to apply polymer flooding in other reservoirs.
Based on mass conservation, foam total amount balance thought and foam properties characterization model, a foam flooding mathematical model with three-phase and five components is established and numerically solved. The explicit is used to solve the saturation equation and the implicit is used to solve the pressure equation in this model. By fitting the results of foam plugging capacity experiments and numerical calculation, the correctness of the model is verified. On this basis, the conceptual model is established to simulate and evaluate the sensitivity of influencing parameters of foam flooding plugging ability. The results show that: the plugging ability of foam system increases with the increase of foaming agent concentration. When the concentration of foaming agent is more than 0.3%, the resistance coefficient tends to steady; when gas-liquid ratio is 2:1, the foam plugging ability is the strongest. The plugging ability of foam system increases with the increase of permeability showing good permeability selectivity. If the permeability in the reservoir is higher than the profile, control capability will also be stronger.
It is very risky and difficult to develop low-permeability reservoirs, but reservoir development can be guided by the development potential of different low-permeability reservoirs. In this study, natural cores of the Daqing Oilfield were used as the research objects. The throat radius distributions of the different low-permeability cores were determined by the constant velocity mercury injection method, the movable fluid distribution characteristics were determined by nuclear magnetic resonance, and the nonlinear fluid flow characteristics were analyzed via fluid flow experimentation. From these data, the development potential for low-permeability reservoirs was determined. The results show that when the permeability is 1×10−3 μm2, the average throat radius is only approximately 0.9 μm and throats with radii less than 0.1 μm account for approximately 30% of the throats. The throats with an average radius less than 1 μm, especially throats with radii less than 0.1 μm, are the main factor restricting the fluid flow in these cores. The movable fluid is only approximately 20% of the fluid in a core, and the threshold pressure gradient reaches 0.15 MPa/m when the permeability is 1×10−3 μm2, indicating that it is more difficult to develop reservoirs with permeabilities less than 1×10−3 μm2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.