Volumetric Formation Mechanical Property Characterization for Drilling Engineering Modeling Applications using the Rock Mechanics Algorithm (RMA)
Authors: Goodman H.E. , Perrin V.P. , Gregory D.H. 
Published: December 2007

A new analytical technique has been created that characterizes well design attributes volumetrically using 3D seismic data volumes and well control. The technique integrates seismic geophysics, open hole logs, drilling performance data and a new formation mechanical property model, the Rock Mechanics Algorithm (RMA). Oil and gas field development applications include formation drillability assessment for bit design, wellbore stability for extended reach and horizontal wells, sanding predictions for completion design, and formation stress profiling and elastic properties modeling for hydraulic stimulation design.

Leveraging the RMA program's strategy of defining elastic properties dynamically, the program's mathematical kernel has been encapsulated and integrated into readily available seismic processing software. This newly created RMA3D program enables the modeling of literally hundreds of thousands of proposed well locations using seismic data, generating mechanical property attributes throughout the seismic data volume in reasonable processing times, i.e. hours instead of days. These attributes are viewed in 3D, along with well data, as slices or "curtains", as projections onto geologic horizons, or semi-transparent "blobs" for comparison to proposed well paths. The new capability is now being linked to well planning tools that currently reside outside the RMA3D environment.

This paper will introduce the RMA program's mechanical property estimation technique, including physical principles used and the data input required. Two case histories will be presented summarizing a recent wellbore stability application for an extended reach well in the North Sea and a bit optimization project in the US mid-continent. Finally, a 3D volume cube of formation mechanical property data will be presented to demonstrate the feasibility of predicting drilling and completion performance over large field areas using a common earth model approach.

Introduction

Drilling and completion of oil and gas wells are being optimized with a new analytical technique that characterizes geomechanical properties using open hole geophysical logs and/or surface seismic data volumes. Chevron's Rock Mechanics Algorithm program uses the dynamic elastic equations to model formation mechanical properties. The RMA model's strategy of describing formation mechanical properties acoustically has enabled the program's engineering applications to be linked to geophysical technology.

Rank wildcat and step out drilling applications where offset well control is absent or extremely limited is augmented by the use of surface seismic data volumes to perform rock mechanical forward modeling for pre-drill well planning. Oil and gas field development applications include wellbore stability for extended reach and horizontal wells, formation drillability assessment for bit optimization, sanding predictions for completion design, formation stress profiling and elastic properties modeling for hydraulic stimulation design. The program's rock physics and formation acoustics forward modeling capabilities are also used for reservoir characterization applications, i.e. by-passed oil assessment and reservoir flood-out mapping.

In this paper, open hole wireline measured versus predicted formation dynamic rock properties are presented for two wells. One of these wells was also conventionally cored in order to measure compressive strength for calibration Finally, the RMA model's strategy of describing formation mechanical properties acoustically has enabled the program's engineering applications to be linked to geophysical technology. P. 169^