--> ABSTRACT: Predicting the Occurrence of Open Natural Fractures in Shale Reservoirs, by A. D. Decker and Alan L. Klawitter; #91019 (1996)

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Predicting the Occurrence of Open Natural Fractures in Shale Reservoirs

A. D. Decker and Alan L. Klawitter

Prolific oil and gas production has been established from naturally fractured shall reservoirs. For example, in the last few years over 4 Tcf of gas reserves have been established within the self-sourcing Antrim Shale of the Michigan Basin. Historically locating subsurface fracture systems essential for commercial production has proven elusive and costly. An integrated exploration approach utilizing available geologic, geophysical and remote sensing data has successfully located naturally fractured zones within th Antrim Shale.

It is believed that fracturing of the Antrim shale was a result of basement involved tectonic processes. Characteristic integrated stacked signatures of known fracture systems within the Antrim were built using gravity and magnetic data, structure maps, fracture identification logs, and Landsat imagery. Wireline fracture logs pinpointed the location and geometries of subsurface fracture systems. Landsat imagery was interpreted to reveal surficial manifestations of subsurface structures.

Data signatures were established in Antrim fracture fairways and outside of the fairways. Fracture fairways correlated to second derivative anomalies in the gravity, magnetic, and structure maps, the presence of northeast trending fractures in the Antrim and zones of concentrated and aligned northeast trending linear features interpreted from Landsat imagery. Similar signatures were encountered in Manistee County where subsequent drilling confirmed economic Antrim gas production. Further validation of the detection method will be tested by identifying new fracture trends, followed by drilling several Antrim wells in 1996.

The overall methodology described here is being applied in the San Joaquin Valley to establish validity of this approach for detecting and characterizing fractures in the Monterey Shale.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California