April 11, 2013 │ Pittsburgh, Pennsylvania
SAFER PA conducted its initial Shale Gas R&D Technical Briefing on April 11, 2013. This event gathered technical leaders to present and discuss the latest research from shale gas related projects in Pennsylvania. The meeting was well attended and robust dialogue accompanied the technical presentations. Links to the slides and abstracts are provided below.
- Oil & Gas R&D Initiatives: NORM, AMD, and Shale Network
Radisav D. Vidic, PhD, PE, Department of Civil and Environmental Engineering, University of Pittsburgh
Abstract: NORM in Flowback/Produced Water: Public and regulatory agencies are becoming increasingly concerned about the fate of NORM in flowback/produced water during storage in surface impoundments, reuse for hydraulic fracturing with or without treatment and different final disposal alternatives. When flowback/produced water is placed in an impoundment, dissolved 226Ra2+ as the most dominant NORM component, would react with suspended solids and bottom sediments. Adsorption and lattice replacement (or coprecipitation) reactions are the controlling mechanisms for 226Ra2+ uptake by the solids that may be present in impoundments. The importance of the difference between these two mechanisms lies in the difference in radium release from these solids due to changes in ambient conditions, which may produce differences in environmental impacts. When flowback/produced water is treated prior to reuse, this is typically done to control Ba, Sr, and Ca and both sulfate and carbonate precipitation may be needed to accomplish the treatment objective. Despite the low solubility product for species like RaSO4 (Ksp = 10-10.26), pure Ra solids (e.g., RaSO4) tend not to precipitate because Ra2+ concentrations in flowback water are too low to reach the saturation limit. However, Ra can co-precipitate with barium, strontium and calcium as sulfates and carbonates. Ra-BaSO4 lattice replacement reaction is the dominant pathway for the removal of 226Ra2+ in the presence of sulfate ions. Any radium incorporated into barite will be so tightly bound that even pH 0.5 solution will not be able to extract it. However, this is not true for 226Ra2+ incorporated in carbonate solids. Abstract: Use of Abandoned Mine Discharge for Hydraulic Fracturing: Abandoned mine discharges (AMDs) are located throughout the state of Pennsylvania, and in the vicinity of many Marcellus shale gas development sites. These discharges offer an abundance of water that may be considered as makeup water for hydraulic fracturing as part of the overall management strategy that focuses on reusing flowback water and minimizing water footprint and environmental impacts of unconventional gas development. Mixing of flowback waters and carefully selected AMDs was studied by following the reaction kinetics and analyzing the crystallography of the precipitates that formed in this system. The ratio of flowback water and AMD in these experiments (15% flowback and 85% AMD) was based on the percent of frac fluid recovery with the assumption that the only make up for subsequent fracturing operations would be the AMD source that is located in the vicinity of the flowback water storage. Barium and strontium precipitation kinetics were determined for different supersaturation ratios that will result after the addition of AMD as makeup water. Complete removal of barium in solution can be achieved in less than 30 min when the initial barite supersaturation is above 50, while slow precipitation occurs for supersaturation of 10. Barium sulfate crystals exhibited different shapes depending on the flowback water tested, and hence the initial barium concentration. The crystals were fairly monodisperse in size (around 3 _m). In most cases, Ba-Sr-SO4 solids are the dominant solids in solution, except in the case of the net alkaline AMD when significant calcite formation can be observed. Both conventional coagulation-flocculation and ballasted sand flocculation processes are capable of producing the finished water with very low turbidity (less than 5 NTU). Careful blending of flowback and AMD is needed to achieve a desired level of sulfate in the finished water. Abstract: Shale Network and Water Quality Database: The rapid pace of Marcellus shale natural gas development in the northeastern United States has prompted many scientists and citizens to begin monitoring water resources. The Shale Network’s intent is to acts as an “honest broker” and facilitate compilation of these disparate data into a database that enables scientists and citizens alike to investigate surface and ground water quality in areas of shale gas extraction. This includes flowback water produced after hydraulic fracturing and production water extracted during well use. The Shale Network is compiling data collected by watershed groups, government agencies, industry stakeholders and universities; as well as organizing and uploading the data for online publication. The mission of the Shale Network is to create a sustainable network among these groups and to develop a database that can be used to establish background concentrations and to assess impacts across extraction regions of shale plays. By doing so, we will generate knowledge from the collected water chemistry and flow data. Funded by the National Science Foundation, the Shale Network is a collaboration of members from Pennsylvania State University, University of Pittsburgh, Dickenson College, Pitt University, and the Consortium for Universities for the Advancement of Hydrologic Sciences, Inc. (CUAHSI).
Abstract: The goal in hydrofracturing and stimulation of gas and oil wells is maintaining high permeability paths for resource recovery over the life of the well. This is commonly achieved by introducing a slurry of surfactants, corrosives, and ceramic aggregates under pressure to induce and maintain fractures emanating from the well bore. The aggregates are pinned by closure stresses after the hydrofracturing pressure has been relieved, and “prop” the fracture open, thereby providing a permeable pathway for oil and gas to migrate to the well bore for subsequent extraction. Hence, the aggregates are commonly referred to in the industry as proppants.State of the art proppants are derived from sintered aluminosilicates, such as kaolin and bauxite. Worldwide demand for proppants exceeds 6 billion pounds per year, and is expected to exceed that by an additional 40-60% by 2011 as new natural gas plays such as the Marcellus shale are developed. Concurrently, the demand for high alumina content aluminosilicates for competing uses, such as in primary aluminum metal production and industrial refractories, has increased nearly six-fold worldwide in the past three years, thereby resulting in a significant shortage and an increase in cost and availability of high strength proppants.
This presentation summarizes our work on the development of high strength, high performance proppants from alternative raw materials derived from industrial/domestic waste streams. Proppants manufactured from mixed glass cullet, single- and double-ion exchanged glass beads, doped low-grade alumina-bearing ores, and rhyolite-, andesite-, and basalt-based glass-ceramics have been developed. These non-traditional materials have been shown to rival commercially available sintered bauxite-based materials with regard to strength, hardness, specific gravity and behavior in ISO standard conductivity tests. Our studies on the role of dopants for controlling microstructure, specific strength, specific gravity, electromagnetic properties, and catalytic activity in sintered bauxite and kaolin based proppants have been transitioned to manufacturing. Related technology for achieving enhanced fracture resistance of glass based proppants through ion exchange treatments and/or controlled devitrification in rhyolite-, andesite-, and basalt-based proppants has been developed. The ability to manufacture high performance proppants from these inexpensive indigenous raw materials, closer to the site of application, offers significant potential for reducing the cost of hydrofracturing operations.
This work has been funded by the U.S. Department of Energy and a number of manufacturers and end-users of proppants worldwide.
Abstract: In Tioga County, Pennsylvania, the surface and near-surface geology is characterized by Paleozoic rocks exposed at the surface overlain in some areas by Pleistocene glacial outwash sediments. Between 20 - 40 percent (depending on area) of pre-drill baseline groundwater samples in northeastern Pennsylvania are found to contain pre-existing methane. Pre-existing methane occurring in freshwater aquifers of northeastern Pennsylvania can be attributed to both geologic and anthropogenic factors. Upper Devonian gas-bearing sandstones of the Bradford Group (Lock Haven and Catskills formations) occur at or near the surface across most of Tioga County. In many cases old oil and gas wells (drilled in this region since the late 1800s) were not constructed to modern well design and zonal isolation standards. Decades-old derelict oil, gas, and water wells have deteriorated in place or were pulled out of the ground for reuse. These historical practices have in some cases resulted in vertical conduits for movement of methane from gas-bearing organic-rich shales and sandstones into freshwater aquifers. Methane, that in past decades was re-injected into the Oriskany Sandstone for storage by pipeline companies, has also been detected by USGS researchers in freshwater aquifers. Finally, in the case of recently drilled gas wells, imperfect zonal isolation by the surface and intermediate casing and cement intervals can result in a potential conduit for methane getting into groundwater.In August 2011, Shell contracted with NEOS to conduct a remote sensing survey of our Tioga County operating area in Pennsylvania. A fixed-wing aircraft was used to collect band-specific hyperspectral, magnetic, gravity, electromagnetic and radiometric data over all of Tioga County. In addition, a helicopter system was used to collect high-resolution band-specific hyperspectral, magnetic, electromagnetic and radiometric data over a project specific area. Key project objectives were:
Detection of surface hydrocarbon seeps and potential indirect hydrocarbon indicators.
- Detection of abandoned / derelict oil and gas wells not found in state agency or commercial databases.
Mapping of resistivity anomalies in the near-surface to provide an indication of potential aquifer salinity variations and locations of shallow gas sands in the Upper Devonian Bradford Group.
Definition of surface lineaments and fracture corridors, and identification of fault networks that can be extended from the surface into the subsurface when integrated with 3D and 2D seismic.
Developing a hyperspectral-derived image of surface geo-hazards and geo-botanical variations.
Abstract: Chesapeake Energy has conducted sampling of over 14,000 water wells from 2009 to the present, from shale-gas development areas across Pennsylvania, Ohio, and West Virginia. Sampling was conducted prior to Marcellus/Utica Shale-related exploration, drilling, and production activities in the vicinity of these water wells. The pre-drill samples have been analyzed for methane, ethane, and propane as well as many inorganic parameters. This presentation will explore the occurrence and distribution of methane in groundwater prior to unconventional gas development. GIS-based mapping and statistics will be used to evaluate the geographic distribution and relationship to bedrock geology. The relationships between methane and other parameters can also help explain methane occurrence, including parameters such as ethane and propane, alkalinity, TDS and major ions, barium, etc. Better understanding of methane in shallow groundwater will lead to better decision-making when evaluating potential impacts of shale-gas development on water supplies and stray gas occurrence.
Long-term Methane Variability in Domestic Water Wells in Northeast Pennsylvania
Charles B. Whisman, PE, Denise Good, PE, and Richard Wardrop, PG of Groundwater & Environmental Services, Inc.
Bert Smith, PG, Debby McElreath, and Charles Olmsted, PG, CPG of Chesapeake Energy
Abstract: Naturally-occurring methane is present in many domestic water wells in northeast Pennsylvania. A significant amount of data is currently being collected by the oil and gas industry as a result of sampling efforts and investigations, much of which is from pre-drilling (“baseline”) sampling conducted prior to any drilling activity. However, gaps remain in understanding and quantifying the natural temporal variation in methane concentrations in these wells. This is of significant importance in assessing claims of gas migration when there is nearby anthropogenic activity. This presentation will discuss a research project developed and implemented to gain an understanding of the long-term variability of methane in domestic water wells.Real-time remote monitoring and data trend analyses are being utilized to understand natural dissolved methane fluctuations in groundwater and correlations between methane headspace concentration in the well annulus and other physical and chemical parameters which could correlate to changes in headspace concentration. Significant efforts were made to select, evaluate, and prepare the wells for the study including borehole geophysics, well equipment upgrades, and installation of water-treatment systems. Descriptions of the customized real-time remote monitoring equipment, array of well headspace and water-quality sensors utilized, and equipment setup will be presented, as well as the associated challenges and logistics. Barometric pressure, water use, water quality, well recharge, water-level fluctuations, and pump cycling are examples of the variables monitored.Results from the on-going study will be presented, including discussion of well construction, geologic settings, water quality, initial trends and findings, and real-time display of data. The usefulness of the data and the accuracy/precision of sensors will be discussed. The long-term study will provide further information to better understand the occurrence and potential causes of methane fluctuations in groundwater and associated water well quality issues in northeast Pennsylvania.
A Geochemical Context for Stray Gas Investigations in the N. Appalachian Basin: Implications of Analyses of Natural Gases from Quaternary-through-Devonian-Age Strata
Fred Baldassare, ECHELON Applied Geoscience Consulting
Mark McCaffrey, PhD, Weatherford Laboratories
John A. Harper, PhD, Pennsylvania Geological Survey
Abstract: As the pace of drilling activity to the Marcellus Formation in the northern Appalachian Basin has increased, so has the number of alleged incidents of stray natural gas migration to shallow aquifer systems.Prior to the present study, the occurrence and origin of natural gas in the strata above the Marcellus Formation in the Northern Appalachian basin has not been well defined. More than 2,300 gas and water samples were analyzed in the present study for (1) molecular composition, (2) stable carbon and hydrogen isotope compositions of methane and (3) stable carbon isotope composition of ethane. The samples are from Quaternary to Middle Devonian-age strata in a five-county study area in northeastern Pennsylvania. Gas and water samples were collected from (1) 234 gas wells during Mudgas Logging (MGL) programs for wells being drilled to the Marcellus Shale Formation, and (2) 67 private water supply wells during baseline groundwater water-quality testing programs. Regional and local geologic conditions were evaluated from core analyses and published studies.Evaluation of this geochemical database reveals that microbial, mixed microbial/thermogenic, and thermogenic gases occur in some shallow aquifer systems, and that the gas occurrences predate Marcellus Formation drilling activity. The isotope data reveal that thermogenic gases in the Quaternary and Upper Devonian strata are typically distinct from gases from deeper Middle Devonian strata (including the Marcellus Fm.).
Significantly, however, a more detailed review of the geochemistry at the site-specific level also reveals a complex thermal and migration history with gas mixtures indicated by partial isotope reversals (δ13C1>δ13C2) in some areas throughout the stratigraphic section above the Marcellus Formation.
Defining a specific source for stray natural gas requires the investigation and synthesis of several data types at the site-specific level. Molecular and isotope geochemistry provide evidence of gas origin and evidence of secondary processes that may have affected the gases. Such data provide focus for investigations where the potential sources for stray gas include multiple naturally occurring and anthropogenic gases. Additional investigation to delineate migration pathways and the mechanism of migration are necessary to further constrain and identify specific stray gas source(s).