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Yao T.,China University of Petroleum - East China | Huang Y.,CAS Institute of Porous Flow and Fluid Mechanics | Li J.,Geological Scientific Research Institute of Shengli Oilfield Co.
Lixue Xuebao/Chinese Journal of Theoretical and Applied Mechanics | Year: 2012

The research on flow mechanism and productivity evaluation of shale gas is still in its infancy. Based on the complex pore structure of shale gas reservoir, slip flow and adsorption-desorption of shale gas, Darcy model is modified. Compared with the Darcy model in production steady case, the bottom hole pressure based on non-Darcy flow model is higher than that from the Darcy flow; the pressure from the Darcy flow model decays more exaggerated and than predicted well life was shorter. The modified flowing model can describe and characterize shale gas flowing process more accurately. The results can provide basic parameters for the operation and management of the shale gas reservoir.

Yao T.,China University of Petroleum - East China | Huang Y.,CAS Institute of Porous Flow and Fluid Mechanics | Li J.,Geological Scientific Research Institute of Shengli Oilfield Co.
Lixue Xuebao/Chinese Journal of Theoretical and Applied Mechanics | Year: 2012

The gas flow characteristic in an adsorbent bed is a vital problem for further studying the mechanics of gas separation process. In this paper, a comprehensive mathematical model of gas flow and adsorption in an adsorbing bed, which based on mass and momentum conservation law, is established. A typical cyclic process of an axial-flow rapid pressure swing adsorption is numerically studied. The flow patterns in different cyclic period for pressurization, adsorption, depressurization, desorption and purge, are obtained. The flow characteristics and their difference from the gas flow in an empty bed and a no-adsorption bed are also studied.

Qin J.,Petrochina | Zhang K.,CAS Institute of Porous Flow and Fluid Mechanics | Chen X.,Petrochina
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2010

Aiming at problems of low or no efficiency of water flooding in high water cut reservoirs or stagnant zones, the present paper studied the mechanism of supercritical CO2 miscible flooding, migration characteristics of oil film and the mass transfer process between CO2 and oil by using a high-speed, advanced and visualized camera micro-simulation model, by which the displacement mechanism of transient blind side was observed, and the film migration phenomenon and the mixed phase were also seen. The results have shown that the wax in crude oil continues to be deposited at pore throats and chock up throats, while supercritical CO2 can surpass water hindrance in pores and further flood the residual oil away in the form of both the cylindrical and columnar flow. Supercritical CO2 has a strong ability to dissolve oil due to the occurrence of molecular aggregation within it. What is more, it could extract not only light hydrocarbon components but also certain heavy hydrocarbon components from crude oil. Thus, supercritical CO2 is a kind of good miscible agents for flooding crude oil.

Zhang K.,CAS Institute of Porous Flow and Fluid Mechanics | Qin J.S.,Petrochina
Petroleum Science and Technology | Year: 2011

With the technical development of enhanced oil recovery (EOR), the alkali/surfactant/polymer (ASP) compound flooding technique has been the necessary choice in Daqing oilfield. Compared to average polymer flooding, ASP compound solution decreases the interfacial tension (IFT) between water and crude oil; however, the viscosity and viscoelasticity of ASP solution were performed by surfactant and alkali, both of which could affect the polymer moleculal structure and the oil recovery of ASP flooding. Considering practical requirements in oilfield development, much effort has been focused on the effect of alkali and surfactants on polymer solution by laboratory experiment and theoretical analysis. The results indicate that alkali and surfactants cause the interfacial tension decrease; at the same time, the molecular structure of the polymer is changed and the viscosity and viscoelasticity of polymer solutions are decreased. In addition, alkali neutralizes with negative ion on polymer molecular and causes the polymer molecular chains to curl up, forming a band molecular structure. Those actions could make viscoelastic behavior and rheological property of ASP solution weak. Copyright © Taylor & Francis Group, LLC.

Yang Z.,CAS Institute of Porous Flow and Fluid Mechanics | Yu R.,CAS Institute of Porous Flow and Fluid Mechanics | Su Z.,CAS Institute of Porous Flow and Fluid Mechanics | Zhang Y.,Petrochina | Cui D.,Petrochina
Shiyou Kantan Yu Kaifa/Petroleum Exploration and Development | Year: 2010

At present, ultra-low permeability reserves occupy a very large proportion in the proved and undeveloped reserves in China. So, it is necessary to research the law of the nonlinear porous flow in low permeability reservoirs. In this paper, on the basis of characteristics of low permeability formation and seepage flow mechanics in ultra-low permeability reservoirs, a nonlinear flow model which can better describe the characteristics of low permeability reservoirs is established. Based on this mathematical model, a new nonlinear mathematical model of numerical simulation is proposed. And by using the developed numerical simulation software of ultra-low permeability reservoir, the Shu 322 block in the Yushulin ultra-low permeability field is studied by means of numerical reservoir simulation. It is showed that pseudo-linear seepage flow only took place in a small range around the wellhead while nonlinear seepage flow dominated in a large scale of the formation. Therefore, taking nonlinear seepage flow into account is more suitable than only considering linear seepage flow and pseudo-startup pressure gradient.

Xiu J.,CAS Institute of Porous Flow and Fluid Mechanics | Yu L.,Petrochina
Applied Mechanics and Materials | Year: 2012

To successfully simulate the anaerobic metabolic process of Indigenous Microbial Enhanced Oil Recovery (IMEOR) and reduce the risk of practice test, a new mathematical model was established for porous flow field-microbial field coupling in anaerobic metabolic process according to the study on anaerobic microbe chain composed of fermentative bacteria, nitrate reducing bacteria, sulfate reducing bacteria and methanogen, and the solution of this model was given. The effect of IMEOR in anaerobic metabolic process relies on the regulation of microbe community. Equations about porous flow field affected by microbe in the model not only elaborate the impacts of microbe and three primary metabolic products (bio-surfactant, bio-polymer, bio-gas) on physical parameters, but also reflect the main mechanisms (emulsification, profile modification and viscosity reduction) for microbial enhanced oil recovery. Equations in microbial field influenced by fluid flow could indicate the substance distribution decided by fluid flow and the collaborative metabolism relationship on biological chain formed by microbe community. The coupling of porous flow field and microbial field should be solved together. The model supplies theoretical basis for the study on IMEOR mathematical model software. © (2012) Trans Tech Publications, Switzerland.

Xu Q.,CAS Institute of Porous Flow and Fluid Mechanics | Liu X.,CAS Institute of Porous Flow and Fluid Mechanics | Yang Z.,CAS Institute of Porous Flow and Fluid Mechanics | Wang J.,CAS Institute of Porous Flow and Fluid Mechanics
Journal of Petroleum Science and Engineering | Year: 2011

Low permeability reserves occupy a large proportion in the remaining reserves all over the world. So it is urgent to research intensively the law of the seepage in the low permeability reservoirs. Fluid flow in the low permeability reservoirs deviates from the classic Darcy's law and instead conforms to the one of nonlinear seepage. According to this characteristic, a nonlinear seepage numerical simulation software has been developed. Unlike most mature commercial numerical simulation softwares at the present stage, the influence caused by the nonlinear seepage is specially considered. In this paper, a nonlinear seepage mathematical model is proposed. In addition, on the basis of practical field and laboratory experiment data, an ideal model of diamond inverted nine spot well pattern is also established. Under the same reservoir condition, the nonlinear simulation, conventional Darcy simulation and the simulation of threshold pressure gradient are also conducted. The simulation result shows that: in the low permeability reservoirs, nonlinear seepage dominates in a large scale of formation and the nonlinear simulation result shows excellent agreement with the production data. Therefore taking the nonlinear seepage into account is more suitable to reflect the percolation mechanism and development performance of low permeability reservoirs. © 2011 Elsevier B.V.

Wang J.,CAS Institute of Porous Flow and Fluid Mechanics | Yu L.,China National Petroleum Corporation | Huang L.-X.,China National Petroleum Corporation
Petroleum Science and Technology | Year: 2011

The feasibility of enhancing oil recovery in Qinghai oilfield with hypersalinity was studied. The results showed that main microbial populations in the reservoir were saprophytic, hydrocarbon-oxidizing, fermentative, nitrate-reducing bacteria and methanogens. The indigenous microorganisms preferentially used nitrogen sources for emulsification, the gas-liquid ratio was 0.20, pressure reached 0.27 MPa; saturated hydrocarbon was catalyzed selectivity. The species isolated were confirmed as Oceanobacillus sp. and Staphylococcus sp.; the oil recovery was 8.42%, which shows great potential to enhance oil recovery. Copyright © Taylor & Francis Group, LLC.

Yang P.,University of Regina | Guo H.,CAS Institute of Porous Flow and Fluid Mechanics | Yang D.,University of Regina
Energy and Fuels | Year: 2013

The NMR relaxometry measurements have been designed and applied to quantitatively determine residual oil distribution during waterflooding in tight oil formations. A tight core sample is first saturated with water to measure its NMR transverse relaxation time (T2) spectrum. NMR T2 spectrum is then measured for the core sample after it has been displaced with the fluorinated oil. Subsequently, the core sample is displaced with water until residual oil saturation is achieved, and the NMR T2 spectrum is measured again at the end of the displacement. Subsequently, the constant-rate mercury injection method is used to experimentally measure the size of the pore and throat in the core sample. The residual oil saturation is determined as a function of pore size by comparing the difference between the first and last NMR T2 spectrum. It is found from four core samples with permeability of 0.04-1.70 mD that the average pore size is in a range of 129-145 μm, and the pore throat has a radius of 0.17-0.89 μm. The original oil saturation is found to be 76-83%, whereas the oil recovery factor is 36-62%; 4-27% of the original oil is distributed in pores larger than 100 μm, 50-54% in pores from 10 to 100 μm, and 21-46% in pores and throats smaller than 10 μm. Residual oil saturation is 1-2% in pores larger than 100 μm, 29-64% in pores from 10 to 100 μm, and 34-69% in pores and throats smaller than 10 μm. © 2013 American Chemical Society.

Xia W.-J.,CAS Institute of Porous Flow and Fluid Mechanics | Dong H.-P.,CAS Institute of Porous Flow and Fluid Mechanics | Yu L.,CAS Institute of Porous Flow and Fluid Mechanics | Yu D.-F.,CAS Institute of Porous Flow and Fluid Mechanics
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

Biosurfactant produced by Pseudomonas aeruginosa, Bacillus subtilis and Rhodococcus erythropolis that isolated from the formation water of Chinese petroleum reservoir has been compared in surface abilities and oil recovery. Maximum biosurfactant production reached to about 2.66. g/l and the surface tension of liquid decreased from 71.2 to 22.56. mN/m using P. aeruginosa. Three strains exhibited a good ability to emulsify the crude oil, and biosurfactant of P. aeruginosa attained an emulsion index of 80% for crude oil which was greater than other strains. Stability studies were carried out under the extreme environmental conditions, such as high temperature, pH, salinity and metal ions. Results showed an excellent resistance of all biosurfactants to retain their surface-active properties at extreme conditions. It was found that the biosurfactants from three isolated bacteria showed a good stability above pH of 5, but at lower pH (from 1 to 5) they will harmfully be affected. They were able to support the condition up to 20. g/l salinity. P. aeruginosa biosurfactant was even stable at the higher salinity. Regarding temperature, all produced biosurfactants demonstrated a good stability in the temperature up to 120°C. But stability of three biosurfactants was affected by monovalent and trivalent ions. Oil recovery experiments in physical simulation showed 7.2-14.3% recovery of residual oil after water flooding when the biosurfactant of three strains was added. These results suggest that biosurfactants of these indigenous isolated strains are appropriate candidates for enhanced oil recovery with a preference to biosurfactant of P. aeruginosa. © 2011 Elsevier B.V.

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