Gas Drilling-Associated Compounds

The oil & natural gas exploration and development process involves multiple activities, each of which has the potential for adverse impacts to human health and to the environment.  Potential adverse impacts may occur in any media, including groundwater, surface water, air and soil.  In particular, recent focus has been on the hydraulic fracturing for unconventional natural gas development.  This is certainly of concern; however, all activities need to be considered.  This webpage focuses on summarizing oil & natural gas exploration and production activities, along with the associated compounds of concern.  We also provide links to other websites and sources of information.

Table I, presented below, summarizes the oil & gas drilling activities and some of the most commonly associated compounds.  It should be noted that some of those listed do occur naturally, underscoring the importance of having a water quality baseline conducted prior to oil & gas drilling-related activities.

TABLE I - Summary of Oil & Gas Drilling Activities & Commonly Associated Compounds

 Compounds SeismicWell Pad ConstructionOil & Gas Well Drilling & Installation Hydraulic Fracturing Drilling Waste Storage & Disposal
 Volatile Organic Compounds     
 - Unchlorinated (e.g. benzene, toluene, ethylbenzene, xylenes, others) X X X X X
 - Chlorinated (e.g. PCE, TCE, other degreasers) X X X X X
 Natural Gases     
 - Methane, Ethane, Propane, Butane   X X X
 - Aluminum   X X X
 - Antimony   X X X
 - Arsenic   X X X
 - Barium   X X X
 - Boron   X X X
 - Cadmium   X X X
 - Calcium   X X X
 - Chromium   X X X
 - Cobalt   X X X
 - Copper   X X X
 - Hexavalent Chromium   X X X
 - Iron   X X X
 - Lead   X X X
 - Lithium   X X X
 - Magnesium   X X X
 - Manganese   X X X
 - Molybdenum   X X X
 - Nickel   X X X
 - Potassium   X X X
 - Selenium   X X X
 - Silver   X X X
 - Sodium   X X X
 - Strontium   X X X
 - Thallium   X X X
 - Titanium   X X X
 - Vanadium   X X X
 - Zinc   X X X
 - Gross Alpha/Gross Beta   X X X
 - Radium 226   X X X
 - Radium 228   X X X
 - Radon   X X X
 - Acid, Caustic   X X X
 - Acid, Hydrochloric  
 X X
 - Alkalinity   X X X
 - Ammonia   X X X
 - Biochemical Oxygen Demand (BOD)   X X X
 - Biocides (e.g. glutaraldehyde, others)    X X
 - Breakers (e.g. magnesium peroxide, sodium chloride)    X X
 - Bromide   X X X
 - Carbon Dioxide (air emissions)  X X X X
 - Carbon Monoxide (air emissions)  X X X X
 - Chemical Oxygen Demand (COD)   X X X
 - Chloride   X X X
 - Clay Stabilizers (e.g. sodium chloride, others)    X X
 - Corrosion Inhibitors (e.g. acetaldehyde)    X X
 - Crosslinkers (e.g. carrier fluids, viscosity stabilizers)    X X
 - Friction Reducers (e.g. methanol, petroleum distallates)    X X
 - Gelling Agents (e.g. guar gum)    X X
 - Hydrogen Sulfide (air emissions)   X X X
 - Iron Controls (e.g. acetic acid)    X X
 - Nitrate   X X X
 - Nitrite   X X X
 - Non-Emulsifiers (e.g. lauryl sulfate)    X X
 - Oil & Grease X X X X X
 - pH   X X X
 - pH Adjusting Agents (e.g. sodium hydroxide)    X X
 - Scale Inhibitors (e.g. sodium polycarboxylate)    X X
 - Specific Conductivity   X X X
 - Sulfate   X X X
 - Sulfide   X X X
 - Surfactants (MBAS)  
 X X
- Total Dissolved Solids (TDS) X X X X X
 - Total Organic Carbon (TOC)   X X X
 - Turbidity, Total Suspended Solids (TSS) X X X X X
 - Total Coliform   X X X

In addition to considering those compounds that are closely associated with oil & gas drilling activities, water quality baselines also need to take into account a compound's mobility and toxicity.  For example, most of the volatile organic compounds are both highly mobile and toxic in groundwater.  Benzene has a federal maximum contaminant level (MCL) of 5 ug/L.  This amounts to approximately 5 drops in an olympic-size swimming pool!  Many other volatile organics have similarly low standards.  Needless to say, we strongly recommend that the full list of volatile organics be a part of every water quality baseline.  Many of the metals also have health-related standards and are commonly a part of oil & gas drilling-derived contamination.  These too should be included as a minimum.

The following references provide a substantial amount of information regarding oil & gas drilling activities and associated compounds of concern.  We strongly recommend that parties interested in this subject matter review these sources.

Sources of Additional Information

FracFocus, Chemical Disclosure Registry,  Description:  Website provides information on hydraulic fracturing compounds, including their use, types, regulations and general information.

Schlumberger Limited; Houston, Texas;  Description:  Website provides complete formulations of their OpenFRAC fluids, used for hydraulic fracturing.

The Endocrine Disruption Exchange (TEDX); Paonia, Colorado;  Description:  Homepage of The Endocrine Disruption Exchange, which provides extensive information on endocrine disruptors, associated with natural gas development.

U.S. Department of Energy et al.  (2009)  Modern Shale Gas Development in the United States: A Primer, DE-FG26-04NT15455,  Description:  Document provides technical information and summarizes unconventional natural gas development.