Characterization of Fracture Patterns in the Marcellus Formation of New York State: Applications to CO2 Sequestration and Natural Gas Extraction
Michael J. LaGamba¹,², Robert D. Jacobi¹,², Alex O’Hara¹,², and Anna Hrywnak¹,²
¹The University at Buffalo Rock Fracture Group, Buffalo, NY
²The University at Buffalo Shale Resources and Society Institute (SRSI)
The Devonian aged Marcellus Formation can be found from eastern New York, through Pennsylvania, and into West Virginia and Ohio. In New York State, the Marcellus Formation has been described as carrying two regional joint sets (J1 and J2), although local variations in orientation have been shown to occur. Data characterizing about 1400 fractures from 40 outcrops were recorded from across the Marcellus outcrop belt of New York State. The outcrops where data were measured consisted of primarily the Marcellus Formation (Union Springs, Cherry Valley, Oatka Creek, Cardiff) and adjacent units such as the Onondaga Formation, which underlies the Marcellus Formation, and the Mottville Shale, which overlies the Marcellus. For each fracture, eight characteristics were measured: strike, dip, spacing, height, length, trend (curvilinear or planar), abutting relationship and sedimentary unit description. Results show that the orientations of J1 (Set III) joints in the Marcellus Formation are not consistently oriented throughout the state. J1 joint strikes are commonly ENE in the western part of the state but the strikes rotate clockwise in the middle of the state, and range from 65° to 100° in the eastern part of the state. The entire range of J1 joint orientations in the Marcellus varies from 53° to 100°. Complicated abutting relationships vary across the state as well and are inconsistent in some areas. This reflects a relatively long history of fracture set generation where J1 joints to the west appear to have propagated later than J1 joints in eastern NYS, consistent with Lash and Engelder’s proposal. The fracture frequency of both J1 and J2 joints vary inversely with the height above the base of the Marcellus where TOC values decrease upsection (as had been observed for other units by Lash and others). Frequencies of J1 joints also vary directly with organic-rich thickness (> 1.5%) and TOC feet (organic-rich thickness x % TOC) of the basin. Greater TOC feet yield a higher potential for elevated fracture frequency. Low TOC units have similar fracture frequencies for J1 and J2 joints. The presence of faults can affect fracture generation. Faults can be associated with FIDs (fracture intensification domains) and open faults can create local stress field anomalies that can deviate the strike of propagating joints.
AAPG Search and Discovery Article #90154©2012 AAPG Eastern Section Meeting, Cleveland, Ohio, 22-26 September 2012