Effective pressure law for permeability of E-bei sandstones

• Published in: Journal of Geophysical Research: Solid Earth 2009-07, Vol.114 (B7), p.n/a
• Main Authors: Li, M., Bernabé, Y., Xiao, W.-I., Chen, Z.-Y., Liu, Z.-Q.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; effective pressure; Exact sciences and technology; permeability; sandstones
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2009JB006373

Laboratory experiments were conducted to determine the effective pressure law for permeability of tight sandstone rocks from the E‐bei gas reservoir, China. The permeability k of five core samples was measured while cycling the confining pressure pc and fluid pressure pf. The permeability data were analyzed using the response‐surface method, a statistical model‐building approach yielding a representation of k in (pc, pf) space that can be used to determine the effective pressure law, i.e., peff = pc − κpf. The results show that the coefficient κ of the effective pressure law for permeability varies with confining pressure and fluid pressure as well as with the loading or unloading cycles (i.e., hysteresis effect). Moreover, κ took very small values in some of the samples, even possibly lower than the value of porosity, in contradiction with a well‐accepted theoretical model. We also reanalyzed a previously published permeability data set on fissured crystalline rocks and found again that the κ varies with pc but did not observe κ values lower than 0.4, a value much larger than porosity. Analysis of the dependence of permeability on effective pressure suggests that the occurrence of low κ values may be linked to the high‐pressure sensitivity of E‐bei sandstones.