The exploitation and exploration of the environment date back to the early days of human existence on earth (Ajilowo et al., 2011). Such activities reveal sophisticated implications amid improvements in process technologies. Hydrocarbon (oil and gas) exploration processes are commonplace across different regions of the world.
Such activities have triggered adverse environmental impacts, including habitat destruction in different ecosystems. In this context, the term ‘environment ‘refers to humans’ immediate surroundings and includes both biological and natural resources (Ajilowo et al., 2011). Within the framework of human activities and surroundings, the environment comprises the atmosphere (with multiple layers) and biophysical components, such as air, water, and land.
Hydrocarbon exploration is the process of mining or extracting fuel minerals from land using technological resources (Ajilowo et al., 2011). Exploration activities extend to the processing, shipment, and storage of petroleum products. Diverse materials are discharged into the environment during oil and gas exploration, and they include fluids used to stimulate production, drilling mud, drill cuts, and oil mineral separation and anticorrosion chemicals.
While safety precautions are often put in place to ward off disasters, accidental leakages may occur during the exploitation and drilling of crude oil. Such leakages are caused by human error and equipment failure. Research postulates that there is a negative correlation between environmental quality and exploration activities (Ajilowo et al., 2011). This assertion has become more relevant to hydrocarbon exploration in inter-regional perspectives.
In Nigeria alone, oil and gas exploration activities accounted for 1,426 million barrels of crude oil discharged into the environment between 1976 and 1983 (Tyokumbur, 2014). This review will specifically investigate whether or not there is a general trend (track record or history) of environmental degradation by hydrocarbon exploration techniques. Issues To establish whether or not there is a general trend in environmental degradation due to hydrocarbon exploration techniques, a few issues will be addressed.
Foremost, the review will investigate how oil exploration could harm the environment, in the context of oil spills and greenhouse gas (GHG) emissions, and human health impacts. With reference to petroleum exploration techniques such as hydraulic fracking, the study will establish whether or not such methods will create a general trend towards negative environmental impacts. The study will explicitly focus on three core issues: water pollution, GHG emissions, and human health impacts.
Scope and Limitations The scope of the review will be limited to the effects of hydrocarbon exploration on the environment, as other types of energies such as renewable energies will not feature in the discussion. To the extent possible, the review will discuss the environmental impacts of oil exploration and will exclude the oil impacts on the economy. P
erspective Ordinarily, the ecosystem becomes disrupted when subjected to fluctuating pollution over a considerable period of time. In particular, the spillage of petroleum and its derivatives to the marine environment may predispose aquatic organisms and birds alike, to toxic exposure.
Such organisms exhibit a bioconcentration of hydrocarbons in their tissues. Equally, chronic water contaminants from the oil exploration process could potentially harm human beings. The aspects of water pollution and human health impacts are based on such premises (Ajilowo et al., 2011). Generally, the aquatic ecosystem exists in a complex state of flux, albeit a balanced one.
However, a perturbation in the form of an excessive impact, or a stressor agent, could potentially disrupt this state of balance beyond the system’s ability to restore equilibrium. Simply, recovery efforts could prove problematic when certain tolerance thresholds are exceeded. Effects of Hydrocarbon Exploration on Water Pollution Ajilowo et al. (2011) document the environmental impacts of hydrocarbon exploration along the offshore and onshore regions of the Niger Delta. The effects of oil spills were devastating in different ways, depending on the physical geography of the affected area, the type of oil, climatic conditions, and pollutant dosage.
The most productive biological regions along the mangrove swamps were severely contaminated by oil spill incidents that occurred between 1976 and 1980. A few months after the spillages, the mangrove plants withered in the contaminated waters. Further, the massive death of aquatic organisms, including mollusks and crabs was reported. Two years later, about 1.51× 105 m2 of water tables were affected due to re-pollution of the underlying soil layer.
Clearly, petroleum exploration-related activities, be it crude oil discharge or spillage of refined petroleum, depict a consistent trend of environmental degradation in numerous ways. Further, the study raises concerns about the handling of drill cuttings and drilling mud within the prohibited areas of discharge. In an earlier study, the environmental problems of petroleum exploration appeared to be well articulated by the inhabitants of the Niger-Delta region (Ikporukpo, 1988, cited in Ajilowo et al., 2011).
Water pollution emerged as the most disturbing consequence of oil exploration due to poor handling of drill cuts as well as poor sampling and analysis techniques. By the year 2011, oil and gas exploration activities along the coastal areas of Ondo State, Nigeria, led to landscape destruction and shoreline erosion. Worth noting, the Earth’s crust from productive oil wells, despoiled the surrounding agricultural land, thus degrading the environment.
Oil spillages in the region accounted for the premature death of humans and marine life due to the consumption of oil-contaminated water. While I would have loved to see Ajilowo et al. (2011) describe the contribution of Persistent Organic Contaminants (POC) to environmental degradation, it would have been more realistic to quantify their bioaccumulation in the affected shellfish species, which were already toxic to human health.
Notwithstanding, the study has vividly captured the health impacts of plant smelters and surface water acidification in the region. In 2014, the ecological effects of petroleum exploration along the Niger-Delta region were also investigated by Tyokumbur (2014). The study examined the effects with respect to upstream (oil well) and downstream (refinery and transportation) exploration activities. Even with proper guidelines, advanced technologies, safety precautions, and personnel training, the environmental impacts of hydrocarbon exploration still appear to be far-reaching.
For instance, downstream exploration (transportation of petroleum products via rail, road, or waterways) activities have led to the death of flora and fauna. A practical example is the Valdez ship accident that occurred in the early 1980s. The spillage caused irreparable damage to the affected marine ecosystem (Tyokumbur, 2014). The indiscriminate dumping of naphthalene, a crude oil refinery product, is posed to pollute the environment. It also clogs the respiratory system of aquatic organisms and diminishes fishing activities.
Prospecting, that is, the identification of potential oil drilling sites, alters the top soil layers and, thereby, creates room for infiltration of chemicals into aquifers. The cumulative effect of such activities is ecosystem degradation or water pollution. In addition, oil extraction processes (such as drilling around wellheads, drilling mud, and disposal of chemicals) tend to pollute the natural aquatic ecosystems.
Other regular sources of environmental pollution include material failure along transportation pipelines and valve failures along oil flow stations (Tyokumbur, 2014). By 2015, hydrocarbon pollution was noticeably high along selected areas in the Niger-Delta region. As shown in Table 1 below, hydrocarbon pollution was more pronounced towards the tidal areas (Tyokumbur, 2014). As is often the case along the shoreline, the pollution pattern was phenomenal when the tide was onshore and the source was offshore.
In fact, human mortalities are reported to correlate with the degree of water pollution. In addition, Tyokumbur (2014) has shown that the heat emitted from gas flaring activities can cause respiratory problems in humans. Other health impacts of hydrocarbon exploration include inflammation of the skin due to inappropriate handling of chemicals or oil spills, carcinogenesis, disabilities arising from accidental fires or explosions, and extreme colds or heat.
From the chronology of events reported by Ajilowo et al. (2011) and Tyokumbur (2014), one can conclude that there is a concrete trend between oil exploration activities and oil spills, and water pollution. Effects on Greenhouse Gas (GHG) Emissions Recently, high volume hydraulic fracking (HVHF) or fracturing, coupled with horizontal drilling, gained widespread adoption in the construction of shale gas reservoirs in different parts of the world and more so, in the United States (Zhang and Yang, 2015).
This technique utilizes hydraulic stimulation to develop a sophisticated fracture network that reduces the permeability of the extracted mineral, thus, enhancing its flowing potential. During gas exploration, large volumes of chemical additives, proppants, and water are injected into the formation. In particular, HVHF makes it possible to extract gas and oil from geological formations such as tightly compacted shale where conventional methods are not applicable.
However, concerns about the negative environmental impacts of fracking have been raised. Other than contaminating ground and surface waters, hydraulic fracking is feared to pollute the environment and intensify water supply stress, given the water-intensive nature of the process. Zhang and Yang (2015) argue that ‘the environmental costs of shale gas extraction are too high, considering the inevitable risks of water contamination and methane leakage’ (p.875).
Fluid leakage during shale gas development can either occur along the damaged casing, which creates the leaking channel or between the formation and the casing due to faulty cementing, thereby contaminating shallow aquifers (Zhang and Yang, 2015). Worth noting, methane is a primary greenhouse gas that could lead to global warming. During natural gas exploration via HVHF, CO2 from diesel engine combustion and methane leakage during extraction account for the GHG emissions. These, combined with volatile compounds from storage ponds, can cause air pollution.
Previously, Howarth et al. (2011, cited in Zhang and Yang, 2015) showed that gas leaks in shale gas wells, which occur during flowback and hydraulic fracking, release significant volumes of methane to the atmosphere. Sometimes, the volume can be as high as 8% of the total gas extracted. In tandem, Zhang and Yang (2015) postulate that the carbon footprint of a shale gas well could be significantly higher than that of a conventional gas and oil well over a 2 decade-long horizon.
Clearly, these independent analyses depict a consistent trend of GHG emissions arising from hydraulic fracking. However, from the end user’s point of view, one can conclude that coal and gasoline exhibit relatively higher, GHG life-cycle emissions than shale gas exploration. More often, GHG emission footprints are subject to uncertainties due to the complexity of predicting well recovery and the fracturing fluid’s flow back ratio.
Therefore, measures aimed at minimizing gas leakages should be adopted on site (Zhang and Yang, 2015). More recently, Hoffmann (2018) explored the effects of hydrofracking on the environment and human health. The study was based on the Williston Basin in the state of Montana, where deep fracking is still in its early stages of development compared to other states in the U.S. The study observes that the greatest concern about hydraulic fracturing is methane (CH4) pollution, which negatively impacts on climate change.
As the primary constituent of natural gas, CH4 exhibits a higher heat-trapping potential in the atmosphere than CO2; its carbon footprint is 25 times higher than that of CO2. Recently, the National Oceanic and Atmospheric Administration (NOAA) claimed that hydrofracking wells discharge 4% of CH4 into the atmosphere (Hoffmann, 2018). Quite surprisingly, the carbon footprint from gas wells in the Weld County was comparable to the carbon emissions of 2 -3 million automobiles.
Aligned with the previous observations by Zhang and Yang (2015), Hoffmann (2018) mentions that ‘methane, a by-product of natural gas exploration, is among the most destructive greenhouse gasses’ So far, research has portrayed a general trend of environmental degradation (GHG emission) by hydrocarbon exploration techniques. Effects on Human Health Over the years, hydrofracking has been a controversial subject due to its perceived health effects. While drilling the well site, disposing the wastes, and transporting equipment or materials, several air contaminants are released into the environment.
These pollutants include, but not limited to: metalloids from the combustion of diesel, formaldehyde, carbon monoxide (CO), oxides of nitrogen (NOx), ozone (O3), photochemical smog, particulate matter, and benzene (Hoffmann, 2018). Both long and short-term exposures can lead to birth defects (in expectant women), system disorders, carcinogenesis, and death. Within the same period, Wright and Muma (2018) examined the human health impacts of hydraulic fracking.
In their comprehensive, peer review, the authors observed that most human toxins and carcinogens are either present or exist as byproducts of the hydraulic fracturing process. The study has identified a number of compounds that are commonly used in fracking. The damaging effects of these compounds (arsenic in water wells, benzene, and indoor radon) on human health are well-known. The common symptoms exhibited by patients in HVHF areas include fatigue, nasal irritation, and headaches.
However, symptoms such as eye itches were reported to be seasonal. As established earlier, oil spillages in the Niger-Delta region accounted for the premature death of humans and marine life alike, due to the consumption of oil-contaminated water (Ajilowo et al., 2011; Tyokumbur, 2014). Undoubtedly, Hoffmann (2018), together with Wright and Muma (2018), have shown a general trend in human health impacts arising from hydrocarbon exploration. Conclusion This literature review has analyzed a collection of recent studies on the environmental impacts of hydrocarbon exploration.
The focus was narrowed down to three core issues, that is, the effects of petroleum exploration on water pollution, global warming emissions, and health impacts. With regards to water pollution and human health impacts, oil spills tend to impregnate soils surrounding water bodies with hydrocarbons and POCs, which bioaccumulate in the tissues of fish populations. Toxic exposure levels cause the death of aquatic organisms. Hoffmann (2018) has also shown that some additives are incorporated in the drilling fluid, mud, and slurry.
Oil wells account for a significant volume of toxic fluids that stem from both the chemical additives and naturally occurring brine water, metalloids, liquid hydrocarbons, and radioisotopes. The fracking process creates fissures, which serve as pathways for groundwater pollution. Some of the chemical additives using during oil drilling percolate into aquifers, thus polluting ground waters. Previously, Ajilowo et al. (2011) and Tyokumbur (2014) showed that oil spillages in the Niger-Delta region accounted for the premature death of humans and marine life due to the consumption of oil-contaminated water.
Equally, byproducts of the hydraulic fracturing process (benzene, CO, or particulate matter) can cause serious health effects when inhaled. In addition, petroleum exploration methods, especially horizontal well drilling and hydrofracking in shale gas mining, tend to aggravate GHG emissions in the form of methane leakage. The review has also shown that hydraulic fracking contaminates both ground and surface waters, and intensifies water supply stress.
Overall, the evidence gathered from the literature indicates a general trend of environmental degradation, arising from hydrocarbon exploration. Future Works Going forward, future works should quantitatively investigate the environmental impacts of hydrocarbon exploration from multiple facets, including earthquake excitation and water supply, which were obviously beyond the scope of this review.
While traces of methane leakage have been detected in some oil wells within the United States, the baseline data is still insufficient, making it difficult to draw definitive, region-specific conclusions as to whether the fracking fissures will cause methane leakage or channel it to the shallow aquifers. In addition, future works should examine the possibility of duplication bias in peer-reviewed journals. This will enable researchers to establish the extent to which a publication represents research findings in this field.