Emerging Environmental Impacts of ... - ACS Publications

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Chapter 7

Emerging Environmental Impacts of Unconventional Oil Development in the Bakken Formation in the Williston Basin of Western North Dakota Venkataramana Gadhamshetty,*,1 Namita Shrestha,1 Govinda Chilkoor,1 and Jejal Reddy Bathi2 1Civil

and Environmental Engineering, South Dakota School of Mines and Technology, 501 E. St. Joseph Street, Rapid City, South Dakota 57701, United States 2Global Systems International, LLC, 1114 Carriage Park Dr., Chattanooga, Tennessee 37421, United States *E-mail: [email protected]. Tel: +1-605-394-1997.

The Devonian and Mississippian Bakken formation in the Williston basin of western North Dakota (ND) contains the largest known source of unconventional oil in the United States (U.S.). Advanced drilling and fracturing technologies have enabled exponential increase in oil production from previously inaccessible (low-permeability) shale formations in the Bakken formation. The state of ND now ranks as a second largest oil producing state in the U.S. However, the abrupt increase in unconventional oil production and associated economic benefits may bring long-term negative environmental impacts. There is a dire need to engage both the public and research scientists with the emerging environmental impacts of oil development. This chapter provides a critical summary of the potential impacts of the Bakken oil development on the diverse subdomains of the environment.

© 2015 American Chemical Society In Hydraulic Fracturing: Environmental Issues; Drogos, Donna L.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


1. Introduction The recent “oil boom” has transformed the U.S. into one of the largest oil producers in the world. The crude oil is typically classified as conventional, transitional, and unconventional oil. The conventional oil that dominated the twentieth century is characterized with light (i.e., low molecular weight) oil that flows easily, and can be extracted with a typical well bore using primary, secondary, and tertiary methods. Transitional oil is similar to conventional oil, but is struck sin remote and impermeable sites including ultra-deep wells; sandstones; carbonates deep below the ocean floor; and tight plays (e.g. Bakken Shale). Its extraction requires unconventional techniques including multi-stage hydraulic fracturing, horizontal drilling, external heating and dilution with chemical solvents. Unconventional oil is characterized by high viscosity and high sulfur content; typical examples include heavy oil from oil sand (bitumen) and oil shale (kerogen). Unconventional oil requires huge energy for its extraction, processing and refining operations (1). In 2000, the United States Geological Survey (USGS) provided the first quantifiable assessment on the world’s crude oil resources (2). In the same year, the Energy Information Administration (EIA) has posed the following bold question: “When will the world physically run out of crude oil?” The EIA has speculated that the answer depends upon the technological advancements in the fields of renewable energy-sources (e.g. fuel cells) and unconventional oil sources (e.g. tar sands). However, the Colorado River Commission believed that the world’s petroleum reserves will deplete by the year 2102 (3). In the recent times, the unconventional drilling (a combination of horizontal drilling and hydraulic fracturing (HF)) has changed the oil landscape in the U.S by allowing the petroleum companies to access oil from the most remote and tight oil bearing formations. The U.S. sits on the brink of an oil boom due to a sudden increase in the oil production during the past decade. For example, oil production in the year 2008 was 7.5 million barrels per day (bbl/d) and increased to 11 million bbl/d by 2013 (4). The new trend in the oil production is expected to continue for coming several years, primarily due to the ability of oil companies to fracture deep pre-salt fields, tighter shales, and remote geographical sites (5). The transitional oil is currently being mined from Bakken (ND, Montana (MT), Saskatchewan, and Manitoba), Eagle Ford (Barnett) Permian basin (Texas and New Mexico), Cardium (Alberta), Miocene (Monterey), Antelope (California), Mowry-Niobrara (Wyoming and Colorado), Penn Shale (Oklahoma), Exshaw MT), Utica (Colorado, Wyoming, and New Mexico) with additional shales being explored in New York, Maine, Mississippi, Utah, and Alaska’s North Slope and Cook Inlet (1). This chapter will focus on the unconventional oil development, and the associated environmental impacts, in the Bakken at the Williston basin of western ND.

152 In Hydraulic Fracturing: Environmental Issues; Drogos, Donna L.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


1.1. Introduction to Bakken Shale A 2013 survey by the USGS has identified nearly 7.4 billion barrels of recoverable oil in the Bakken Formation and the Three Forks formation in the Williston basin. The use of horizontal drilling and multi-stage HF technologies has enabled the increase in the oil production from the Williston basin. The majority of this oil occurs in the state of ND. There are currently 12,000 active oil wells in the Bakken Play (6). ND is now ranked as the second largest crude oil-producing state in the nation (7). The Williston basin is a circular basin that extends into the states of ND, MT and South Dakota (SD) and the Canadian provinces of Manitoba and Saskatchewan; this basin houses the Devonian Three Forks Formations and the Devonian and Mississippian Bakken Formations (red line, Figure 1). The Bakken Total Petroleum System (TPS) includes the strata from the Devonian Three Forks Formation, Bakken Formation, and the lower part of the Mississippian Lodgepole Formation that may contain Bakken-sourced oil (Blue line, Figure 1) (8).

Figure 1. Williston basin province, Bakken total petroleum system (TPS). Adapted with permission from reference (8). Copyright 2013 U.S. Geological Survey. 153 In Hydraulic Fracturing: Environmental Issues; Drogos, Donna L.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


The Devonian and Mississippian Bakken Formation include the Pronghorn Member, lower shale member, middle member, and upper shale member (9). The upper and lower shale members are the primary source rocks for the Bakken TPS (9). As mentioned earlier, the shale members are present in parts of MT and ND and extend into the Canadian provinces of Saskatchewan and Manitoba. Approximately 450 million barrels of oil (MMBO) have been produced from the Bakken and Three Forks Formations in the United States since the 2008 assessment of the Bakken Formation (9). In the last decade, the Bakken experienced an overwhelming increase in the oil production, 150 thousand bbl/d in 2007 to 1350 thousand bbl/d in 2015 (10).

2. Hydraulic Fracturing The hunt for oil resources results in oil drilling closer to human populations (11). Oil companies use HF techniques to extract oil from formations. The pressurized fluid is injected into well bores to induce fractures, expand existing fractures, carry ‘proppants’ into fractures, and finally promote the flow of oil to the surface. The drillers in the Bakken found water-supplemented fluids (e.g. drilling mud or polymer) to be advantageous due to its effectiveness to: i) stimulate fractures, ii) send proppants into fractures, iii) pull back the excess proppants after stimulating the fractures, iv) offer low friction, v) suspend the proppants and vi) revert back to the low-viscosity fluid at end of the fracturing process. The HF fluids are supplemented with a range of chemicals (12) to promote the fracturing process in the Bakken (Table 1).

Table 1. Typical chemicals used to fracture formations in the Bakken. Reproduced with permission from reference (12). Copyright 2015 U.S. EPA. Addititive

Example

Purpose

Buffer

Sodium hydroxide,Potassium hydroxide

Adjust the pH of the base fluid

Biocide

Ammonium chloride, TetrakisHydroxymethylPhosphonium

Reduce microbial growth

Breaker Catalyst

Sodium Chloride

Degrade viscosity Holds open fracture to allow oil and gas to flow to well

Proppant Crosslink Agent

Hydrotreated Light, Ethylene Glycol, Potassium Metaborate

Crosslink Enhancer Surfactant

Delayed crosslinker for the gelling agent Non-delayed crosslinker for the gelling agent

Isopropanol, Naphthalene, Ethanol

Aids in recovery of water used during frac Continued on next page.



Table 1. (Continued). Typical chemicals used to fracture formations in the Bakken. Addititive

Example

Purpose

Base Fluid

water

Creates fractures and carries proppant, also can be present in some additives

Acid / Solvent

Hydrochloric Acid, Muriatic acid

Minimize mud build-up; dissolve minerals; initiates cracks in rock matrix

Clay Stabilizer

Potassium chloride, Tetramethyl ammonium chloride

Prevent clay particles from migrating in water-sensitive formations. Prevents precipitation of iron oxides during acid treatment

Organic Acid

Friction Reducer

Polyacrylamides, petroleum distillate

Allows fracture fluid to move down the wellbore with the least amount of resistance

Liquid Gel Concentrate

Guar Gum

Gelling agent for developing viscosity

Corrosion Inhibitor

Methanol

Prevents acid from causing damage to the wellbore and pumping equipment

The composition of the fracturing fluid is often maintained as a trade secret by oil companies. The drillers use a custom recipe to obtain a suite of fracturing chemicals to match hydro-geochemical characteristics of the shale play and the HF method. The HF chemicals should ultimately improve the oil flow through the fractures, and minimize the volume of fracturing fluid. In the Bakken, the operators use a series of “swell packers” along a liner that is inserted in a freshlydrilled horizontal well (11). Special fluids are injected to swell the packers in order to isolate the selected portions of horizontal wells. The nature of the environmental problems at fracturing sites depend upon the HF methods and the chemical and physical characteristics of HF fluids. In a hypothetical example, a potential leak in the flowback water transportation system (e.g. during the transportation from the oil fields to Class II injection wells) can contaminate the adjacent water sources and agricultural fields. There is increasing public concern about environmental impacts due to abrupt oil development in ND (13). A majority of these issues have been highlighted in newspaper articles (14, 15). Based on publicly available information, this article provides a critical summary of the environmental concerns related to fracturing in the Bakken formation in the Williston basin of western ND. This chapter will be organized under the following categories of environmental impacts: water stress and water contamination; oil spills; methane stranding – open flare of natural gas; and air pollution. 155 In Hydraulic Fracturing: Environmental Issues; Drogos, Donna L.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


3. Sources, Processes, and Hazards at Different Stages of Unconventional Oil Development Table 2 provides a summary of typical events relevant to oil extraction with horizontal drilling and HF. Each event has the potential to contaminate ground water, surface water, and air. For instance, heavy equipment for well pad construction can cause diesel emissions, noise and vibrations, and oil spills. The drilling and construction operations can release air pollutants related to drilling mud, rubber-based oil, synthetic oil, aluminum tristearate, choline chloride, aromatic and aliphatic hydrocarbons. The contaminants in the drilling muds (boric acid, borate salts, rubber-based oil, synthetic oil, aromatic and aliphatic petroleum hydrocarbons and inorganic chemicals; barium, strontium, bromine, heavy metals, salts and NORM (naturally occurring radioactive materials)) threatens ground water and surface water (16).

4. Impacts on Water Resources 4.1. Water Stress The HF puts immense stress on surface and groundwater sources, especially in the water-stressed regions of the U.S. For instance, during January 2011 to May 2013, the total water consumption for HF operations in six states (TX, PA, OK, AR, CO, and ND) exceeded 97 billion gallons of water (17) at the rate of a million gallon of fresh water per hydraulically fractured well (18). According to a recent report (17), nearly 50% of the unconventional oil wells that were hydraulically fractured since 2011 occur in regions with high or extremely high water stress; further, 55% of these wells are in regions experiencing droughts. The ‘region with extremely high water stress’ is defined as a region that allocated 80% of the available surface and groundwater for municipal, industrial, and agricultural uses (17). It can be speculated that water stress will be low in arid regions such as ND due to low population density and non-water-intensive agricultural practices. However, it is instructive to assess and evaluate the water-usage trends in an emerging oil play such as the Bakken. The water-usage-per-well in the Bakken play is typically higher than other shale oil-producing regions. Water consumption for horizontal oil wells in ND is at least two orders of magnitude higher than that for vertical wells in SD. Table 3 provides a comparison between the number of rigs, oil wells, and associated water consumption between the states of SD and ND (19).


Oil drilling event

Ground water pollution

Surface water pollution

Air pollution

Safety Hazards

Nonchemical hazards

Sources

Process

Large trucks

All

Diesel emissions

Spill and accidents

Noise, vibration

Heavy equipment

Well pad construction, drilling and well abandonment

Diesel emissions

Spill and accidents

Noise, vibration

Dust

Well pad construction, well abandonment

Diesel emissions including particulate matter

157


Table 2. Sources, processes, and hazards associated with oil exploration. Reproduced with permission from reference (16). Copyright 2014 American Chemical Society.

Drilling mud

Drilling

Drilling muds, e.g., boric acid, borate salts, rubber-based oil, synthetic oil

Fracturing fluid

Hydraulic fracturing, flowback

Fracturing fluids, e.g., lauryl sulfate, guar gum

Drilling muds, e.g., boric acid, borate salts, rubber-based oil, synthetic oil

Drilling Muds, Volatile, e.g., rubber-based oil, synthetic oil, aluminum tristearate, choline chloride

Fracturing fluids, e.g., lauryl sulfate, guar gum

silicaFracturing fluids, volatile: e.g., glutaraldehyde, ethylene glycol, methanol,, petroleum distillate

Spills

Continued on next page.

In Hydraulic Fracturing: Environmental Issues; Drogos, Donna L.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

158


Table 2. (Continued). Sources, processes, and hazards associated with oil exploration. Oil drilling event Sources

Process

Generators

Drilling, hydraulic fracturing

Produced water

Drilling cuttings



Air pollution

Safety Hazards

Diesel emissions

Drilling and construction, flowback

Drilling muds, e.g., boric acid, borate salts, rubber-based oil, synthetic oil,aromatic and aliphatic petroleum hydrocarbonsinorganic chemicals; barium, strontium, bromine, heavy metals, salts and NORM (naturally occurring radioactive materials)

Drilling muds, e.g., boric acid, borate salts, rubber-based oil, synthetic oil,aromatic and aliphatic petroleum hydrocarbonsinorganic chemicals; barium, strontium, bromine, heavy metals, salts and NORM

Drilling Muds, Volatile, e.g., rubber-based oil, synthetic oil, aluminum tristearate, choline chloridearomatic and aliphatic petroleum hydrocarbons

Drilling and construction



Diesel emissions, including particulate matterdrilling Muds, Volatile, e.g., rubber-based oil, synthetic oil, aluminum tristearate, choline chloride aromatic and aliphatic petroleum hydrocarbons


Nonchemical hazards

Noise

Spills

159


Oil drilling event Sources



Air pollution

Fracturing fluids, volatile: e.g., glutaraldehyde, ethylene glycol, methanol,, petroleum distillatearomatic and aliphatic petroleum hydrocarbons inorganic chemicals; barium, strontium, bromine, heavy metals, salts and NORM

Fracturing fluids, volatile: e.g., glutaraldehyde, ethylene glycol, methanol,, petroleum distillatearomatic and aliphatic petroleum hydrocarbons inorganic chemicals; barium, strontium, bromine, heavy metals, salts and NORM

Fracturing fluids, volatile: e.g., glutaraldehyde, ethylene glycol, methanol,, petroleum distillatearomatic and aliphatic petroleum hydrocarbons

Safety Hazards

Nonchemical hazards

Process

Flowback water

Flowback

Deep injection

Flowback

Gas venting

Drilling, flowback, production

Methanehydrogen sulfidearomatic and aliphatic petroleum hydrocarbons

Gas flaring

Drilling, flowback production

Carbon dioxidenitrogen oxides

Pigging

Production

Methanearomatic and aliphatic petroleum hydrocarbons

Seismic activity Accidents

Noise

Accidents Continued on next page.


Oil drilling event



Air pollution

Safety Hazards

Accidents

Sources

Process

Pipelines

Production

Methanearomatic and aliphatic petroleum hydrocarbons

Condensate tanks

Production

MethaneAromatic and aliphatic petroleum hydrocarbons

160


Table 2. (Continued). Sources, processes, and hazards associated with oil exploration.


Nonchemical hazards


Table 3. Comparison of oil production and associated water impacts in ND and SD. Reproduced with permission from reference (19). Copyright 2012 South Dakota Department of Environment & Natural Resources. SD

ND

Rig Count

1

>200

New oil Wells ( Per year)

12

>2000

Known oil reserves

Red river formation; Minnelusa wells

Bakken shale

Water consumption

0.015 million gallons/well

2-4 million gallons/well

Well Depth

8500 ft

10000 ft

Well cost

$2.5 million

$7.9 million

According to the ND State Water Commission, horizontally-drilled oil wells in ND consume nearly 4% of the total water consumption (12,629 acre feet surface) (Figure. 2). Water consumption for HF is almost equivalent to the total rural water consumption in ND. As per Cere’s report (17), oil development in ND consumed 5.5 billion gallons of water in 2012 alone. With an estimated development of 40,000-45,000 new oil wells in coming two decades, we can anticipate tremendous water stress in the region (20). The constant depletion of groundwater resources, coupled with limitations in surface water in the region, could increase competition among farmers, ranchers, shale energy producers and municipal users. Further, with increasing concerns for water depletion, obtaining a ground water permit will be a challenging task in the region. On a similar note, a regulatory dispute between the state of ND and the Army Corps of Engineers has restricted industrial water withdrawals from Lake Sakakwea (major reservoir of the Missouri River) (21–23). Nearly 78 percent of the water in the Bakken is obtained from six counties including McKenzie, Williams, Mountrail, Dunn, Richland, and Roosevelt. Figure 3 shows the highest water use counties in the Bakken and the corresponding stress category.



Figure 2. Consumptive water use in ND. Adapted with permission from reference (23). Copyright 2014 North Dakota State Water Commission.

Figure 3. Highest Water use counties in the Bakken by water stress Category. Adapted with permission from reference (17). Copyright 2014 CERES. 162 In Hydraulic Fracturing: Environmental Issues; Drogos, Donna L.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


4.2. Wastewater Management The HF in the Bakken generates two major types of wastewater (i.e., flowback and produced water). The flowback water is a portion of injected water that returns back to the surface, while the produced water is a naturally-occurring water that exists in the formation and is “produced” along with hydrocarbons throughout the lifetime of well. Both flowback and produced waters are contaminated with drilling muds, fracturing chemicals, methane, petroleum condensate, salts, metals, and naturally occurring radioactive materials (NORM). There are three options for managing wastewater generated during HF: i) Class II injection wells guided by Underground Injection Control regulations, ii) Water treatment facilities, and iii) Reuse opportunities within the oil field. The produced water and flowback water at Bakken are currently stored in surface pits prior to disposal in Class II injection wells. In ND, the wastewater is injected into Class II injection wells at a depth of one-half mile to one mile to prevent migration of fluids into adjacent formations and fresh water zones.

4.2.1. Type II Characteristics of Wastewater from the Bakken Oil Fields With nearly 12,000 unconventional oil wells in the Bakken Play, and each well consuming nearly 3-8 million gallons of water throughout its life time, the Bakken fields can be expected to generate an enormous amount of wastewater. The flowback water from Bakken is high in total dissolved solids (~300,000 mg/L) and includes a variety of fracturing chemicals introduced during the drilling operations. A majority of these chemicals can be associated with toxic, corrosive, and acidic characteristics. It is difficult to predict the overall hazard of wastewater due to unknown information for proprietary chemicals included in fracturing fluids. However, it may be conservative to state that the discharge of untreated wastewater from the Bakken oil fields can threaten surface water bodies and municipal water treatment plants. For instance, the produced/flowback water from the Bakken has the highest amounts of Total Dissolved Solids (TDS) of any producing U.S. region (24). Table 4 shows a typical composition of three samples collected from three wells which had a cumulative flowback water of 3,500 bbp. As shown in Table 4, the flowback water has the highest concentration of sodium (47,000 to 75,000 mg/L), followed by calcium (7,500 to 13,500 mg/L), and magnesium (600 to 1,750 mg/L). Among anions, chloride has the highest concentration (90,000 to 133,000 mg/L). The water pH was slightly acidic (

Emerging Environmental Impacts of ... - ACS Publications

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