| 摘要 |
An improved technique to more accurately calculate pore pressure of sedimentary rock due to subsurface fluid expansion. The technique is built upon a combination of known force balanced in situ loading limb mineralogical stress/strain relationships with locally variable unloading stress/strain relationships. In stress/strain space, the material properties governed loading limb is an upper limit for the many possible unloading limbs. A method for relating these different natural stress/strain paths and applying the correct path to calculate pore fluid pressure from in situ force balance is disclosed. This method preferably calibrated with in situ stress/strain data which allows for a lithologic sealing caprock to be identified and the locally prevailing in situ unloading limb stress/strain relationship to be estimated. The forced balance loading and unloading calibrations are applied to more accurately determine well casing depths using either wireline or real-time measured while drilling petrophysical data. Solidity (1.0-porsity) is the in situ strain parameter of choice which can be measured petrophysically in the borehole. Pore pressure is the fractions of the total external load which is borne by the fluids in the pore space of a sedimentary rock. The solid framework of a granular sedimentary rock bears the force balance remainder of the external confining load as effective stress. Loading and unloading power law linear stress/strain relationships are determined between effective stress and solidity for common sedimentary rocks.
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