Microseismic Monitoring to Determine Fracture Height Growth during Hydraulic Fracturing at NETL's Marcellus Shale Test Site in Greene County, Pennsylvania

Hammack, Richard W.; Harbert, William; Sams, James; Siriwardane, Hema

This study presents the results of microseismic monitoring to evaluate fracture height growth during the hydraulic fracturing of six horizontal Marcellus Shale wells at NETL's Marcellus Test Site in Greene County, Pennsylvania.

The Marcellus Shale Test Site comprises eight Marcellus Shale wells (six horizontal wells and two vertical wells) at 8100-8200 ft total vertical depth. All six horizontal wells were drilled from one pad: three wells were drilled northwest and three were drilled southeast. Two existing vertical Marcellus Shale wells were optimally located to serve as microseismic monitoring wells during hydraulic fracturing; one vertical well was located amidst the three northwestern horizontal wells while the second vertical well was located amidst the three southeastern horizontal wells. During hydraulic fracturing, eight wireline geophone tools spaced 100 ft apart were deployed in the vertical Marcellus Shale well that was nearest to the horizontal wells being completed. The two lowermost geophones were located in the Hamilton Formation, above the Marcellus Shale but below the Tully Limestone; the upper six geophones were located in shale formations above the Tully Limestone. Microseismic data were acquired during the pumping of 56 stages; more than 10,000 microseismic events were located.

This study's objective is to examine the upward growth of fractures during hydraulic fracturing and is primarily focused on microseismic events located above the Tully Limestone. Such events were observed during the pumping of all stages of all wells. Most events above the Tully Limestone were observed during the pumping of the northwestern wells where events were clustered along two near-vertical planes with azimuths of about 10° and 50°. Microseismic event clusters attained a maximum height of 1920 ft above the Marcellus Shale, which coincides with the maximum height of faults in the area as interpreted from 3-D surface seismic. For the southeastern wells, microseismic events above the Tully Limestone were infrequent and scattered; no event clusters were observed. Microseismic results indicate a maximum fracture height growth of about 1900 ft upward to a depth of about 6200 ft at this location. More than 5500 ft of strata separate the uppermost created fracture from the nearest drinking water aquifer.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013