In tight reservoirs, as throat radius decreases to micro-nano scale, pore structure becomes more complex. The effect of interaction between seepage fluids and rocks increases, which changes flow characteristics in micro scale. In order to realize efficient development of tight reservoirs, the throat distribution and permeability needs new understanding.

In this paper, a device was established to measure water flow rate in microtubes, under different pressure gradient. The water was de-ionized and tubes were made of fused silica with radius of 1, 2.5, 5, 7.5, 10 and 15μm. The pressure gradient was set mainly 0.02~0.6MPa/m, close to that in oilfield, while previous published experiments focused on 1~80MPa/m. The results showed that experimental flow rate was lower than theoretical value calculated by Poiseuille equation. A stable boundary layer was formed near the solid wall, blocking the flow. Its thickness was calculated, ranging 29.6nm~ 1.08μm. As pressure gradient increased, the boundary layer declined and its effect vanished. This change led to nonlinear flow characteristics in micro scale. The thickness increased with throat radius increasing and reached a constant value when tube radius were larger than 15μm.

Based on experimental results, a boundary layer thickness function was regressed. The independent variables were pressure gradient, throat radius and viscosity. Considering boundary layer, the effective throat radius distribution was characterized, taking normal distribution as the original distribution. The results showed that the range of effective throat distribution was narrower than the original one and the peak value was higher. The sensitivity of the function was analyzed.

Based on the characterization of effective throat distribution, the formulas of Klinkenberg permeability and effective permeability were derived. The effective permeability formula was validated using data from Shiwu and Bohai oil reservoir. The deviation is lower than 6%.

The effective permeability of tight reservoir under different conditions was calculated and investigated. The larger the median radius and the range of the throat distribution, the higher the effective permeability. The effective permeability of a core is not determined only by its pore structure. It is also effected by pressure gradient and the properties of the fluids. When the pressure gradient increases, the effective permeability increases as the boundary layer declines. When the fluid viscosity increases, the effective permeability decreases.


Article metrics loading...

Loading full text...

Full text loading...


  1. BrutinD., TadristL.
    [2003] Experimental friction factor of a liquid flow in microtubes. Physics of Fluids (1994-present), 15(3), 653–661.
    [Google Scholar]
  2. CaoR., WangY., ChengL., et al.
    [2016] A New Model for Determining the Effective Permeability of Tight Formation. Transport in Porous Media, 112(1), 21–37.
    [Google Scholar]
  3. ChenZ.
    , [2011] Distribution Feature Of Micro-Pore And Throat And Evaluation Of Movable Oil In Extra-Low Permeability Reservoir: A Case Study In Yingcheng Formation, Shiwu Oil Field. Petroleum Geology & Experiment, 33(6), 657–661.
    [Google Scholar]
  4. ChengS.
    [1998] Numerical simulation of two dimensional two phase non Darcy slow flow. Petroleum Exploration & Development, 25(1), 41–43.
    [Google Scholar]
  5. CuiH, Z.Silberli, ZhuS.
    , [2004] Flow characteristics of liquids in microtubes driven by a high pressure. Physics of Fluids, 16(5), 1803–1810.
    [Google Scholar]
  6. DouH., YangY.
    [2012] Further understanding on fluid flow through multi-porous media in low-permeability reservoirs. Petroleum Exploration & Development, 39(5), 674–682.
    [Google Scholar]
  7. HuangY.
    , [1998] et al. Percolation mechanism of low permeability reservoir. Petroleum Industry Press, Beijing.
    [Google Scholar]
  8. HuangY., YangZ., HeY., et al.
    [2013] An overview on nonlinear porous flow in low permeability porous media. Theoretical and Applied Mechanics Letters, 3(2), 1–8.
    [Google Scholar]
  9. LiY., LeiQ., LiuX., et al.
    [2011] Non-linear seepage flow characteristics under micro scale. Petroleum Exploration and Development, 38(03), 336–340.
    [Google Scholar]
  10. LiZ., HeS.
    [2005] Influence of boundary layers upon filtration law in low- permeability oil reservoirs. Daqing petroleum geology and development, 24(2), 57–59.
    [Google Scholar]
  11. LiZ., RenX., ZhangY., et al.
    [2015] Experimental Study of Oil and Gas Permeability Measured Relationship on Low Permeability Reservoir. Journal of Liaoning Shihua University, 35(2), 50–54.
    [Google Scholar]
  12. LiuW., LiuJ., SunL., et al.
    [2011] Influence of Fluid Boundary Layer on Fluid Flow in Low Permeability Oilfields. Science & Technology Review, 29(22),42–44.
    [Google Scholar]
  13. MapxacинИ Л.
    [1987] The physical chemistry mechanism of reservoirs. Petroleum Industry Press, Beijing.
    [Google Scholar]
  14. TianX., ChengL., CaoR., et al.
    [2015] A new approach to calculate permeability stress sensitivity in tight sandstone oil reservoirs considering micro-pore-throat structure. Journal of Petroleum Science & Engineering, 133, 576–588.
    [Google Scholar]
  15. WangX, HaoM, HanY.
    [2013] Implication of the threshold pressure gradient and its application. Acta Petrolei Sinica, 34(1), 188–191.
    [Google Scholar]
  16. WeiX, LeiQ., GaoS., et al.
    [2009] Pseudo threshold pressure gradient to flow for low permeability reservoirs. Petroleum Exploration & Development, 36(2), 232–236.
    [Google Scholar]
  17. XuY., XuQ., GuoY., et al.
    [2006] The percolation mechanism of low permeability reservoir research and application. Petroleum Industry Press, Beijing.
    [Google Scholar]
  18. XuS., YueX.
    [2007] Experimental research on nonlinear flow characteristics at low velocity. J. China Univ. Petrol.(Nat. Sci. Ed.), 31(5), 60–63.
    [Google Scholar]
  19. XueY.
    [2001] Analysis of low velocity non-Darcy flow mechanism. Petroleum Exploration & Development, 28(5), 102–104.
    [Google Scholar]
  20. YangR.
    [2011] Numerical simulation of nonlinear seepage in ultra-low permeability reservoirs. Acta Petrolei Sinica, 32(2), 299–306.
    [Google Scholar]
  21. YangS.
    , [2006] WangZ., HeG., et al.Engineering fluid mechanics. Petroleum Industry Press, Beijing.
    [Google Scholar]
  22. YangZ, YuR, SuZ, et al.
    [2010] Numerical simulation of the nonlinear flow in ultra-low permeability reservoirs. Petroleum Exploration & Development, 37(1), 94–98.
    [Google Scholar]
  23. ZhangJ., JiangY., HuangK.,et al.
    [2014] Quantitative Characterization Of Permeability Based On Pore And Throat Distribution Constraint. Science & Technology Review, 32(22), 67–72.
    [Google Scholar]

Data & Media loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error