Using Microseismic Monitoring to Better Understand Completion of the Medina - Whirlpool Formations: A NYSERDA - Sponsored Project

Abstract

The Medina is a group of Silurian-age sandstone formations that have been dependable gas producing zones in Western New York since the late 1800's. Most of the production from the Medina has come from a combination of the Whirlpool and Grimsby formations. The method of how to most effectively complete these two formations is an ongoing topic of debate. The formations are separated by the Cabot Head shale formation that ranges in thickness from less than 5 feet to more than 70 feet in some places. One of the main questions with regard to completion of these formations is whether to 1) stimulate the Whirlpool and the Grimsby with separate treatments to ensure effective stimulation of both layers; or 2) stimulate both formations with one hydraulic fracture treatment, at a lower cost, that grows from the Grimsby through the Cabot Head and into the Whirlpool.Microseismic monitoring of hydraulic fracture treatments is now a proven technique used to analyze hydraulic fracture geometry and azimuth. The New York State Energy Research and Development Authority funded a project in Chautauqua County, New York to use this technology to monitor a hydraulic fracture treatment in a Grimsby/Whirlpool well for the purpose of understanding hydraulic fracture development in these formations. This paper uses the microseismic results obtained from the study to validate a hydraulic fracture model of the Grimsby/Whirlpool formations. A sensitivity analysis was then performed using this hydraulic fracture model to give direction as to when the Grimsby and Whirlpool formations should be stimulated simultaneously and when a two-stage completion would be more beneficial to obtain an effective stimulation in both zones.

Water Pollution Risk Associated with Natural Gas Extraction from the Marcellus Shale

“…( 43 ) Proponents of hydraulic fracturing posit that there is no known mechanism by which fractures and fluid can propagate through over 1,000 m of sedimentary strata; some recent data even suggest that Marcellus Shale wells should be more closely spaced due to shorter effective fracture lengths than originally estimated. ( 44 ) In reply, critics say that several potential mechanisms cannot be ruled out: ( 10,45 ) unexpected vertical fracturing through overlying strata, ( 46,47 ) and fracturing fluid preferentially traveling through naturally occurring fractures and faults. ( 44,48 ) Besides, critics argue, current conventional fracturing models are not appropriate for shale gas reservoirs, ( 49 ) and the interpretation of microseismic data used to monitor hydraulic fracturing is still controversial.…”