Baroid Technology, Inc.

Nl Industries

Philip W Holbrook

William B Bradley

Sanjeev Mittal

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.

Method for determining sedimentary rock pore pressure caused by

An improved technique to more accurately calculate pore pressure of sedimentary rock due to subsurface fluid expansion where 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, including that in stress/strain space, the material properties governed loading limb is an upper limit for the many possible unloading limbs; also, 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 such that the method is 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, where the forced balanced loading and unloading calibrations are applied to more accurately determine well casing depths using either wireline or real-time 'measured while drilling' petrophysical data; and also solidity (1.0--Porosity) is the in situ parameter of choice which can be measured petrophysically in the borehole, where pore pressure is the fraction of the total external load which is borne by the fluids in the pore space of a sedimentary rock, and the solid framework of a granular sedimentary rock bears the force balance remainder of the external confining load as effective stress; so that loading and unloading power law linear stress/strain relationships are determined between effective stress and solidity for common sedimentary rocks.

Hardware, software and methods for controlling the usage of well drill bits and other aspects of well drilling plans. At least a portion of a given well is drilled with a given drill bit. An abrasive-wear-affecting variable (drilling strength) for the lithology which has been most recently drilled with the bit is continually evaluated. The current abrasive wear of the bit by the total lithology which has been drilled thereby is continually calculated, based on the abrasive-wear-affecting variable. Continued use or retirement of the bit is controlled in accord with the wear calculation. Relative pore pressure at the current site of the drill bit is a useful by product which can be independently used to control other aspects of the well drilling plan, e.g. mud weight and the setting of casing.

System and method for controlling drill bit usage and well plan

The potential for failure of a formation is predicated by using standard logging apparatus and techniques to monitor the change in a formation characteristic over an extended time period. Changes in this characteristic are attributed to absorption of fluid by the formation which could lead to a possible breakdown of the structural integrity of the formation.

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Houston, TX, United States of America

Philip W Holbrook