Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
A Geomechanical Model for Gas Shales Based on the Integration of Stress Measurements and Petrophysical Data From the Greater Marcellus Gas System
The Pennsylvania State University
When an unconventional (i.e. gas shale) reservoir with a permeability < 1 μd is made economic by fracture stimulation, rock stress dictates fracture growth in terms of crack orientation, vertical and lateral dimension, breakdown pressure, closure pressure, aperture, and other characteristics. Because the greater Marcellus gas system hosts several prospective gas reservoirs, the engineering design of an efficient and economic fracture stimulation will account for stress-related issues including, for example:
- the reservoir-by-reservoir stress contrasts that may act to contain vertical growth in some situations and allow for further vertical growth in other situations
- the regional variation in breakdown pressures which are meaningful when identifying pump requirements
- the orientation of the local stress when trying to misalign horizontal laterals to promote higher production through generation of a complex network of interconnected fractures near the wellbore.
To this end, the objective of this project is to generate a geomechanical model for the Marcellus gas system through the integration of rock stress and petrophysical properties.
Description of the Project:
The heart of this project is a series of micro-frac stress tests in three vertical wells strategically placed in the two sweet spots of the Marcellus fairway. The data for this model will come from the Schlumberger MDT tool plus ancillary geophysical logs and petrophysical analyses of core. Four potential locations for the stress tests are from low stress envi-ronment to high: Marshall, Greene, Bradford, and Lycoming Counties. The goal is to develop an integrated, predictive geomechanical model for the Marcellus gas system that can be genera-lized for application in other shale plays.
A technology transfer by reports and papers in requisite journals that will document local and regional geomechanical characteristics of the Marcellus gas system.
Potential Impact of the Project:
Organization of industry in an open collaboration to understand one of the most important parameters, rock stress, in engineering the stimulation of horizontal wells for greater productivity. An open collaboration between industry and academia of this type is a real breakthrough for an industry that generally tends to be tight with sensitive data.
Terry Engelder & graduate student (Penn State), Bill Zagorski & Joe Frantz (Range Resources), Rick Svor & Jeff Miller (Chesapeake) plus Dick Plumb & George Waters (Schlumberger). This team is a collaboration of top notch engineers and geologists.
Principal Investigator: Prof. Terry Engelder