| 摘要 |
<p>Systems and methods are described for calculating pore pressure in a porous formation such as shale gas having substantially disconnected pore spaces. In some described examples, an NMR logging tool with at least two depths of investigation (DOIs) is used. The deeper DOI can be used to sample the shale gas that has not been perturbed by the drilling process, for example, and contains the gas at connate pressure. The shallow DOI can be used to sample shale gas that has been perturbed, and has lost at least part of its gas content. The micro cracks that have been formed in the shallow location (closer to the borehole) allow for injection of gas into the formation at known pressures while measuring the NMR response. The connate pore pressure can then be calculated for the deeper location based on the NMR response to the known pressure increase.</p> |
