Method and system for pre-drill pore pressure prediction

Abstract

A method for pore pressure prediction includes obtaining a stress sensitivity coefficient, obtaining a compressional wave (P-wave) velocity and a shear wave (S-wave) velocity for a pre-drill location and obtaining a first predicted pore pressure. Further, the method includes iteratively performing calculating a total stress value associated with the pre-drill location using the first predicted pore pressure associated with the pre-drill location, and calculating a second predicted pore pressure associated with the pre-drill location using a stress-pressure relationship equation, a stress-velocity relationship equation, the stress sensitivity coefficient, a reference location, and at least one selected from a group consisting of the P-wave velocity and the S-wave velocity for the pre-drill location, and adjusting a drilling operation associated with the pre-drill location, based on the second predicted pore pressure.

Description

[0001] Cross References to Related Applications [0002] This application claims priority to U.S. Provisional Patent Application No. 60 / 595,814, filed August 8, 2005, by Colin Michael Sayers and Richard Anthony Birchwood, entitled "Sub-Salt Pore Pressure Prediction," which application is hereby incorporated by reference in its entirety as references. Background technique [0003] Some substances (such as salt, etc.) have low permeability, that is, they are not easy to pass through fluids. In some cases, the low permeability material may be on top of the material targeted by the drilling operation. [0004] Figure 1 shows a schematic diagram of a drilling operation. Those skilled in the art will understand that the drilling operations shown in Figure 1 are for illustrative purposes only and should not be construed as limiting the scope of the present invention. For example the drilling operation shown in Figure 1 is a subsea drilling operation, but the drilling operation may...

AI Technical Summary

Problems solved by technology

[0011] In addition, when drilling into overpressured formations, the number of casing strings (ie, the structural support inserted into the borehole) required may increase

In particular, without sufficiently accurate pre-drill pore pressure predictions, it is possible to prematurely insert additional strings of casing in order to prevent drilling control problems (such as influx of formation fluids) and / or drilling failure

Premature insertion of casing strings can delay drilling operations and / or reduce the size of the borehole, resulting in financial loss

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