C&P: "The Geo-mechanics of a Clay Rich Formation in Southern Chile"
Building a basis of design for completing and fracture stimulating conventional wells requires developing a profile with depth of in-situ stress, Young's Modulus, and leak-off coefficient. In these reservoirs, it is fairly straightforward. For unconventional reservoirs, it requires additional knowledge of the rock, its mineralogy, geo-mechanics, and the state of stress as well.
This presentation provides insight into the development of the basis of fracture design for the Glauconite Formation in a remote and logistically challenged area of Southern Chile. This formation is comprised of an average of over forty percent clay, thirty four percent feldspar, and twenty three percent quartz with some pyroclastic tuff mixed in. A truly unconventional reservoir where the use of dipole sonic logs to develop an in-situ stress and modulus profile hasn't worked effectively. These logs indicate that the Glauconite Formation has a low Young's Modulus and is a very "ductile" formation. As a result and because this data appeared inconsistent, a significant data collection effort was undertaken. This effort included an extensive core analysis program including mineralogy, ultrasonic and tri-axial compression tests, un-propped crack tests, and embedment tests. Additionally, the data collection efforts included the use of Diagnostic Fracture Injection Tests (DFIT's) and mini-frac tests on every well. These data collection efforts have shown the Glauconite to be a relatively high Young's Modulus and "brittle" formation totally refuting the dipole sonic log analysis and its use in developing a fracture design basis.
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