Abstract

The integration of core based rock mechanics with the open hole log and seismic geophysics technologies, has created added value through operational costs savings for Chevron's world-wide drilling and completion holdings. Early development of this integrated technology focused on supplementing core measured rock property data with open hole log measurements to obtain rock mechanical property estimates throughout the horehole. Log derived mechanical property estimates have lead to the development and worldwide use of the following applications:

  1. formation drillability assessment for bit optimization and performance prediction,

  2. wellbore stability for extended reach and horizontal wells,

  3. sanding predictions for completion design, and

  4. formation stress profiling and elastic properties modeling for hydraulic stimulation design.

The characterization of rock mechanical properties, in the absence of core, hinges upon the newly created capability of predicting formation shear wave propagation velocities. This breakthrough technique was first developed to estimate formation shear wave velocities for single well (1D) mechanical property predictions using conventional open hole measurements- (compressional wave velocity and bulk density). The technique was then enhanced to utilize surface seismic data sets in a 1D sense to predict formation mechanical properties at undrilled prospect locations. The links to the seismic world have proven particularly valuable for rank wildcat and step out drilling applications where offset well control is absent or extremely limited.

The latest innovation has been to characterize volumetric (3D) formation mechanical properties from 3D seismic data cubes. Volumetric rock properties currently determined include Poisson's ratio, horizontal stress magnitude, borehole breakdown pressure gradient, pore pressure gradient and unconfined compressive strength.

This paper summarizes the shear wave velocity estimation technique and presents several examples. Field examples will also be shown that demonstrate successful applications of log derived mechanical properties for rock strength and minimum horizontal stress profiling applications for fracture stimulation design. A full set of volumetric formation mechanical property cubes will then be presented, demonstrating the feasibility of using 3D seismic data for well planning.

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