Cornell Earth Source Heat Project: Technical Reports and Datasets
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Item Proof-of-concept for monitoring ground displacements in Tompkins County, NY using Persistent Scatterer Interferometric Synthetic Aperture Radar from the TerraSAR-X and Sentinel-1 satellitesMolan, Yusuf E.; Pritchard, Matthew E.; Lohman, Rowena B. (2022-04-27)Underground mining and the pumping of fluids, such as the proposed Cornell University Earth Source Heat Project (ESH), can result in observable displacement of the Earth’s surface that we can use to better understand the effects of those subsurface activities. Such surface movements can be monitored by ground surveying, but the process is labor intensive, limited in spatial extent, and potentially expensive. Here we test whether the established satellite monitoring of surface movements called Interferometric Synthetic Aperture Radar (InSAR) can be used in Tompkins County, NY as part of the ESH project with the goal of achieving a precision of a few mm/year over the areas of interest. We used data from two types of satellites: the TerraSAR-X and TanDEM-X (TSX) satellites of the German Space Agency ( X-band, 3.1 cm radar wavelength) and the Sentinel-1 (S1) satellites of the European Space Agency (C-band, 5.6 cm radar wavelength). We find that both data can be used to detect sub-centimeter/yr deformation rates using Persistent Scatterer Interferometry (PSInSAR). We assess the precision of the inferred rates through comparisons with limited ground survey data and between satellites. PSInSAR selects only reliable pixels, aka persistent scatterers (PS), to be analyzed at the full spatial resolution of the data. Generally, man-made objects, buildings, pipes, roads, etc., are persistent scatterers whereas vegetation cover, fields, bare soil are excluded from further analysis. An analysis with snow-/rain-free TSX data showed that while removing snow covered and rainy images increases the PS population up to two times, the points are concentrated at locations that already have denser PS points. Further, snow-/rain-free images estimate almost the same deformation behavior as the full-stack data set does. In an area of known ground subsidence above an underground mine in Lansing, NY, our analysis revealed that TSX provides more PS points compared to S1. Although both datasets show inter-annual deformation rates that agree with the in situ observations, S1 possessed a higher noise level. With this lower precision level, S1 can be a reliable monitoring tool in the ESH area if the expected deformation is larger than 4-5 mm/yr and if the deforming area extends to at least 300 meters around the drilling site. Otherwise, TSX data should be considered for ground surface monitoring in the area. Based on our comparison with ground control points, we can expect to measure deformation rates of 1-2 mm/yr with TSX PSInSAR.Item Analysis of Cornell University’s Seismic Networks for the Earth Source Heat InitiativeSuhey, Jane; Katz, Zachary; Zhang, Maia; Ferris, Aaron; Pritchard, Matthew; Salerno, Jeremy; Hubbard, Peter; Gustafson, J. Olaf (2021-03-21)As part of efforts to achieve campus carbon neutrality by 2035, Cornell University launched the Earth Source Heat (ESH) project in 2007, to research the possibility of using deep geothermal heating to heat the campus. To effectively explore the availability of geothermal resources and the feasibility of extracting such resources, an accurate understanding of geologic features and regional seismicity is required. However, national and regional seismic networks do not have sufficient sensitivity to record seismicity in Tompkins County, NY. Thus, two seismic networks were installed to study the background seismicity in Tompkins County in advance of any proposed drilling as part of ESH. The first network (CorNET16) operated between 2015-2016 with 12 seismometers, while the current network installed from July 2019-present (CorNET21) includes 17 seismometers over a larger area. The installation of CorNET21 and analysis is completed under contract with Weston Geophysical Group with assistance from Cornell students, staff, and faculty. Preliminary analysis indicates about 359 seismic events in Tompkins County between August 2019-January 2021, including impulsive ground vibrations such as drilling, mine blasts, construction activities, as well a natural events such as microearthquakes. About 70 events were reviewed by a seismologist and a more accurate location was determined. Some natural microearthquakes have been observed, and efforts to separate these from the human-caused seismic events are ongoing. Events as small as magnitude negative 2 have been detected, but further work to assess the magnitudes and what small magnitude events might be missed is in progress. Re-analysis of the CorNET16 data using the same techniques used for CorNET21 finds about 20 seismic events in Tompkins County between 2015-2016 with the number of events and locations focused near or under Cayuga Lake similar to previous work. We suspect that more events were found by CorNET21 because of its increased sensitivity as well as change in the nature of seismic events. CorNET21 indicates dozens of seismic events each year within 10 km of the proposed geothermal drill site not visible in the national and regional seismic networks. Thus CorNET21 provides important information not otherwise available about local seismic events.Item Hydrologic challenges to heating Cornell using Earth Source Heat (ESH) and a strategy for meeting themCathles, Lawrence (2020-05-28)To reduce carbon emissions Cornell proposes to heat its campus by producing >60°C brine from 2 to 3 km depth. Twenty percent of its heating needs can be met by producing at 364 gpm. Demonstrating production and reinjection at this rate constitutes Cornell’s ESH pilot project. The standard hydrologic analysis reported here shows that a transmissivity of >0.26 D m is required. Only in specific locations in specific strata is the transmissibility under Cornell likely to be this high. Production and injection over 20 years will draw fluids and change pressures to distances of 4 to 33 km from the wells. This raises concerns that injected fluids might short-circuit to the production well and cool its produced fluids, and that increased fluid formation pressures could trigger earthquakes. The short-circuiting risk can be eliminated and the earthquake risk reduced by taking advantage of the stratigraphically layered nature of the Cornell subsurface and producing below while injecting above an interval of impermeable strata. A strategy of first finding the most permeable targets with 3D seismic and Fracture Seismic surveys, and then drilling to determine if these locations have sufficient permeability for production and injection to be separated stratigraphically in this fashion is suggested.Item FINAL REPORT: Potential Field Surveys, Analyses, and Interpretation for Cornell’s Earth Source Heat ProjectHorowitz, Frank (2020-02)This work was contracted to look for geological structures that might be proximal to the proposed drilling sites for Cornell University’s Earth Source Heat (ESH) project. I used geophysical gravity and magnetic (collectively: potential field or PF) surveys as the underlying data from which I primarily formed my interpretations. PF surveys offer a relatively low-cost means of identifying underground geological structures in an area of interest. While they certainly can not attain the resolution available from seismic reflection surveys, their low-cost affords a method of covering a much larger map area of interest than would be economical via 2D or 3D reflection seismic surveys. Here, I report on results and interpretations derived from two independent PF surveys. First, during July 2018 – with the help of field assistants – a gravity survey was performed in the region using a rented Scintrex CG5 gravity meter. Second, a commercial aeromagnetic survey – flown on speculation during exploration activity for the Trenton-Black River gas play in 1999 – was purchased for Tompkins county from geophysical service company EDCON-PRJ. Both of these data sets were analyzed using a Poisson wavelet multi-scale edge analysis of potential fields, informally known as the ‘worm’ technique. This technique uses gravity and magnetic fields to detect lateral contrasts (“edges”) in mass density or magnetization strength, respectively. There are several geological structures found by this work. Some of them are previously known or have been inferred, while several of them are new. The gravity survey found one strong and apparently deep structure of interest to the south of the Cornell campus. The structure strikes roughly E-W and dips about 60° to the north. The analysis of the aeromagnetic data shows another strong and deep feature in roughly the same area, with a similar strike but the opposite sense of dip. The limited precision inherent in these measurements, along with multiple possible explanations for the inferred lateral contrasts in bedrock properties, do not allow us to reach specific conclusions regarding the nature of the geologic structures present. However, these data complement the seismic reflection data to further illuminate the deep bedrock structure near the Cornell campus, and will provide context for planned cutting and core sample analysis during installation of the initial test well.Item Earthquakes in an Aseismic Region: Local Seismic Network Results for Central New York An AVF InvestigationMcLeod, Lauren; Brown, Larry; Quiros, Diego; Gustafson, J. Olaf (2020-01)Twelve seismographs were deployed on or near the campus of Cornell University in the fall of 2015 to record seismic activity in an area under consideration for development of geothermal wells. This area is notable for its lack of recorded and historic seismic activity. The CorNET network operated from October 15, 2015 until November 2, 2016. Preliminary examination of the recorded seismograms has identified 90 events, 64 of which are likely to be earthquakes in central New York. The magnitudes of these events are all less than m = 3.7. However, only four of these likely earthquakes were located within Tompkins County, within which the proposed drill sites lie. The lack of apparent alignment of these events suggests that none of the geological faults known or suspected near the campus are active at present. None of these local events are reported in the national and regional catalogs produced by permanent networks operating in the area, supporting the speculation that the apparent aseismicity of the Ithaca area is an artifact of the detection limits of conventional networks rather than complete lack of natural seismic events. No events were found in the immediate vicinity of the proposed drilling sites for Earth Source Heating. Although the locations of events well beyond the limits of the CorNET array are poorly constrained, most occur within the Finger Lakes region to the northwest of the array. Additionally, 13 events were detected that seem to occur near an active salt mine. Some of these events display a distinctive waveform and temporal clustering, suggesting that they are artificial events rather than tectonic.Item Seismic Studies in Support of Earth Source Heating at Cornell University: Stratigraphy in the Vicinity of ESH Candidate Drill Sites from Multichannel Seismic Reflection Profiling in 2018May, Daniel; Brown, Larry; Gustafson, Olaf; Khan, Tasnuva (2019-12)Multichannel seismic reflection surveys using vibroseis sources and nodal seismic recorders were carried out on and near Cornell University’s Ithaca campus in support of the ongoing Earth Source Heat Project (ESH). These data were collected over a two-week period in September of 2018 with the help of student volunteers and subsequently processed to produce seismic reflection images of the subsurface near proposed geothermal drill sites. Although systematic noise from surface waves was found to be pervasive in the nodal recordings, basic stratigraphy in the immediate vicinity of the proposed well sites were delineated and identified with geological formations based on correlations with regional seismic surveys previously collected for gas exploration and available well data. Local structural disruptions in the dominant layer-cake stratigraphy at the target depths for geothermal drilling were found to be few and relatively minor in terms of offset geological units. These seismic images did not reveal any features that would preclude exploratory drilling for geothermal characterization at the drill sites under consideration.Item Geological evaluation of subsurface features near Ithaca, NY: interpretations of seismic reflection profiles collected by the petroleum industryJordan, Teresa (2019-12)To provide background geological information with which to assess some of the technical and environmental risks of a Cornell Earth Source Heat (ESH) project in Ithaca, NY, this report describes the geological features below Tompkins and easternmost Chemung counties that are revealed by approximately 150 km (94 miles) of 2D hydrocarbon-industry seismic reflection profiles. Details of subsurface features near the Cornell campus are presented on maps, and also described. Such data were not previously available in any publicly available reports, and therefore the analysis presented is a major step forward in documentation of subsurface features near Cornell. The vertical distribution of sedimentary rocks known from deep hydrocarbon boreholes was used as the basis for the approximate sedimentary unit identification of packages of seismic reflections to a depth of about 3 km (10,000 ft). The lower limit of sedimentary rocks, which overlie a crystalline basement, can be identified readily in only a minority of the seismic profiles; in most of the data, there is a large uncertainty on position of the basement contact. Sedimentary units with possible interest as geothermal reservoirs are expected within the lowest 300-600 m (1000 to 2000 ft) of sedimentary rocks near Cornell. These data allow tentative identification of a unit of sedimentary rocks with favorable reservoir potential immediately overlying the basement in paleovalleys near campus. Disruptions to the positions or continuities of these reflective sedimentary rock units are identified as either folds, which are smooth undulatory waveforms of the rocks, or faults, which are breaks in the units. Two classes of faults, one sub-vertical and one sub-horizontal (i.e., thrusts) are differentiated such that their different roles in technical and environmental risk can be individually evaluated. The seismic profiles reveal five categories of structural deformation, two of which were not expected based on publicly available reports for Tompkins and neighboring counties. Among the three expected categories of structural deformation, folds of the uppermost sedimentary layers are widespread; these should impact an ESH project only by making predictions of depths to horizons of interest slightly more uncertain. Folds and thrusts within the Syracuse and Vernon Formations are highly likely to occur under the Cornell campus region and plausible ESH project sites, in a depth range of 750-1200 m (2500-4000 ft). These widespread features are not shown in the executive summary illustration, yet they are detailed in the report. Standard practices exist in central New York for drilling through and isolating this interval of deformed, weak rocks. The seismic reflection profiles reveal that the third expected category, sub-vertical faults known by the hydrocarbon industry as “Trenton-Black River” (TBR) structures, occurs in some sectors of Tompkins County. A Trenton-Black River fault cluster is not expected near the Cornell campus (see summary figure). An uncertain individual TBR-type fault is located about 1.4 km (0.9 mi), and a more reliable single fault about 3.4 km (2.1 miles), north of the Palm Drive area. The first unexpected category of structures is a widespread set of sub-horizontal thrust faults within the Cambrian and Ordovician sedimentary rocks, in an interval of rocks predicted from boreholes to be about 350 m (1150 ft) thick at Cornell’s campus. The near-Cornell industry- quality seismic reflection profiles reveal thrust faults in these sedimentary units (see summary figure). A seismic depth model with high uncertainty implies that these thrusts may be as shallow as 2.1 km (6900 ft) or as deep as 3.0 km (10,000 ft) near the east end of campus. Because of their sub-horizontal disposition, these disruptions may have more relevance to analyzing reservoir potential than to seismic hazard analysis. The second unexpected category of structures is of greater uncertainty than any of the other features described here. Within Tompkins County, there are a small number of fold-forms in the deepest well-imaged sedimentary units. There is a significant degree of uncertainty that some or all of these fold-forms are physically real parts of the rocks. Conventional geological wisdom suggests that these undulations may be associated with faults that are not imaged by the seismic reflection data. Hypothetically, either of two markedly different types of faults could be related to deep folds: near-vertical faults (like the TBR faults) that offset rocks in the basement, or sub-horizontal thrust faults within the poorly imaged deeper sedimentary rocks or at the sedimentary rock-basement contact. I recommend that additional modeling and analyses of the seismic reflection data be considered, in efforts to reduce the uncertainty on the fold-forms near the base of the sedimentary rocks, to improve estimates of the depth to reflectors, and to learn whether more useful information about the crystalline basement can be extracted. This study, supplemented by the Vibroseis survey collected in 2018 by Professor Brown and students, has illuminated relatively well the nature of the sedimentary rocks near the eastern edge of the Cornell campus development. Because sub- vertical faults projecting down toward the basement are not revealed close to campus, it is my opinion that investments in future geophysical studies should focus on extracting information about the crystalline basement rather than about the sedimentary rocks. Perhaps the best designs for further geophysical studies will involve instrumentation within a pilot borehole that complements instrument deployments across the land surface.