van der Zwaag C H, Stallmach F, Skjetne T, Veliyulin E
SINTEF Unimed MR Center, 7465 Trondheim, Norway.
Magn Reson Imaging. 2001 Apr-May;19(3-4):543-5. doi: 10.1016/s0730-725x(01)00289-2.
Transverse (T2) NMR relaxation time at 2 MHz proton resonance frequency was measured on core plug samples from two different lithologies, sandstone and chalk, before and after exposure to selected drilling fluids. The results show that NMR signal response was significantly altered after displacing 50% of the original pore fluids, crude oil and water, by drilling fluid filtrate. Relaxation spectra of the rock samples invaded by water-based filtrate shift to significantly shorter T2-values. This shift yields an underestimation of the free-fluid volumes when selecting cut-off values of 33 ms and 100 ms for sandstone and chalk, respectively. In opposite, rock samples affected by oil-based filtrate respond with a signal indicating significantly larger free-fluid volumes than present before exposure. NMR-permeability calculated based on the Timur-Coates Free Fluid model altered in some cases by one order of magnitude.
在2兆赫质子共振频率下，对来自砂岩和白垩这两种不同岩性的岩心柱塞样品，在接触选定钻井液之前和之后测量横向（T2）核磁共振弛豫时间。结果表明，在用钻井液滤液取代50%的原始孔隙流体（原油和水）后，核磁共振信号响应发生了显著变化。被水基滤液侵入的岩石样品的弛豫谱向明显更短的T2值偏移。当分别为砂岩和白垩选择33毫秒和100毫秒的截止值时，这种偏移会导致对自由流体体积的低估。相反，受油基滤液影响的岩石样品的信号表明，自由流体体积比接触前显著更大。根据蒂穆尔-科茨自由流体模型计算的核磁共振渗透率在某些情况下改变了一个数量级。
