Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: Appalachian Basin

Sortuj według:

Ogranicz wyniki do:

Seismicity induced by hydraulic fracturing and wastewater disposal in the Appalachian Basin, USA: a review

Brudzinski Michael R., Kozłowska Maria

Acta Geophysica

2019

Vol. 67, no. 1

351--364

Eastern Ohio is an area of North America where a significant increase in seismicity rate was noted in the early 2010s. This increase has been associated with intensification of unconventional gas extraction performed in the Appalachian Basin and has been directly linked to two processes: hydraulic fracturing and disposal of the associated wastewater. In this paper, we review the recent seismicity in the Appalachian Basin including various episodes of induced seismicity that were temporally and spatially linked to operational activity, and we have performed some comparable analyses on the most recent sequences. The activities have not been as pervasive as other areas of North America, such that the cases are typically isolated and provide opportunities to study the seismogenic process in detail. The observed seismicity is concentrated in a narrow corridor that extends north–south in eastern Ohio and into central West Virginia, perhaps due to differences in operational targets and geologic variations. Ohio appears to have a higher prevalence of seismicity induced by wastewater disposal than surrounding states, but this is based on limited number of cases. Ohio also has an order of magnitude higher prevalence of seismicity induced by hydraulic fracturing than surrounding states, and prior work has suggested this is due to the targeting of the deeper Utica–Point Pleasant formation in Ohio that is closer to basement rocks than the Marcellus formation in West Virginia or Pennsylvania. In areas where hydraulic fracturing has induced seismicity, the percentage of stimulated wells that produce detectable seismicity is approximately 10–33%. Detailed studies of induced seismicity via double-difference relocation and focal mechanism analysis have revealed a series of linear fault segments, none of which correspond to previously mapped faults. Yet, the remarkable coherence in their orientation suggests these were preexisting, optimally oriented, and critically stressed. These fault orientations reveal a consistent regional stress field that only varies over a narrow azimuthal range from ~ 50° to 74°. The strongest observed seismic events in Ohio appear to occur in the Precambrian basement and indicate that these rocks have the maturity needed to produce M > 2 earthquakes and hence the greater potential hazard.

A tale of two shale units - petrophysical analysis and sequence stratigraphy of the Marcellus Shale and Utica Shale in the Appalachian Basin, USA

Carr T. R., McClain T., Wang G.

AGH Drilling, Oil, Gas

2013

Vol. 30, no. 1

315

Paleozoic organic-rich mudrock ("shale") units were deposited on the eastern margin of the United States of America from the initial Cambrian rifting to the assembly of Pangaea after the Devonian. Two of these organic-rich shale units the Ordovician Point Pleasant-Utica and Devonian Marcellus Shale of the northern Appalachian basin are some of the most active shale gas and liquids plays in the world, and a significant component in the United States energy market. Unconventional hydrocarbon plays are often referred to as statistical plays due to their high degree of heterogeneity, and present challenges for characterization and exploitation. Productivity depends upon an inter-related set of reservoir, completion and production characteristics. A key control on success is regional geology and sequence stratigraphy, in particular the geographic and stratigraphic distribution of organic matter, silica, and carbonate. The distribution of these key elements has been modeled at the basin and local scales. A 3-D mudrock lithofacies model is constructed using sequence stratigraphy to constrain mineral composition, rock properties and organic content. Core analysis and log data were used to calibrate the model from core scale to well scale and finally to regional scale. Geostatistical approaches were used to develop a quantitative relationship between conventional logs and lithofacies, and to model the distribution of mudrock lithofacies in three- dimensions. Controlled primarily by dilution, organic matter productivity, and organic matter accumulation distribution of organic-rich mudrock lithofacies was dominantly affected by water depth and distance to shoreline. The controls on mudrock reservoir quality are subtle and heterogeneity present in Utica and Marcellus results in regional and local well production variations. The proposed 3-D lithofacies modeling approach aids in recognizing geologic and engineering targets, designing horizontal well trajectories, targeting fracture stimulation strategies and understanding shale depositional environments and processes. The proposed approach can be extended to other organic-rich shale reservoirs.