PrepTest 43, Section 4, Question 5
The accumulation of scientific knowledge regarding the environmental impact of oil well drilling in North America has tended to lag behind the actual drilling of oil wells. Most attempts to regulate the industry have relied on hindsight: the need for regulation becomes apparent only after undesirable events occur. The problems associated with oil wells' potential contamination of groundwater—fresh water within the earth that supplies wells and springs—provide a case in point.
When commercial drilling for oil began in North America in the mid-nineteenth century, regulations reflected the industry's concern for the purity of the wells' oil. In 1893, for example, regulations were enacted specifying well construction requirements to protect oil and gas reserves from contamination by fresh water. Thousands of wells were drilled in such a way as to protect the oil, but no thought was given to the possibility that the groundwater itself might need protection until many drinking-water wells near the oil well sites began to produce unpotable, oil-contaminated water.
The reason for this contamination was that groundwater is usually found in porous and permeable geologic formations near the earth's surface, whereas petroleum and unpotable saline water reservoirs are generally found in similar formations but at greater depths. Drilling a well creates a conduit connecting all the formations that it has penetrated. Consequently, without appropriate safeguards, wells that penetrate both groundwater and oil or saline water formations inevitably contaminate the groundwater. Initial attempts to prevent this contamination consisted of sealing off the groundwater formations with some form of protective barrier to prevent the oil flowing up the well from entering or mixing with the natural groundwater reservoir. This method, which is still in use today, initially involved using hollow trees to seal off the groundwater formations; now, however, large metal pipe casings, set in place with cement, are used.
Regulations currently govern the kinds of casing and cement that can be used in these practices; however, the hazards of insufficient knowledge persist. For example, the long-term stability of this way of protecting groundwater is unknown. The protective barrier may fail due to corrosion of the casing by certain fluids flowing up the well, or because of dissolution of the cement by these fluids. The effects of groundwater bacteria, traffic vibrations, and changing groundwater chemistry are likewise unassessed. Further, there is no guarantee that wells drilled in compliance with existing regulations will not expose a need for research in additional areas: on the west coast of North America, a major disaster recently occurred because a well's location was based on a poor understanding of the area's subsurface geology. Because the well was drilled in a channel accessing the ocean, not only was the area's groundwater completely contaminated, but widespread coastal contamination also occurred, prompting international concern over oil exploration and initiating further attempts to refine regulations.
The accumulation of scientific knowledge regarding the environmental impact of oil well drilling in North America has tended to lag behind the actual drilling of oil wells. Most attempts to regulate the industry have relied on hindsight: the need for regulation becomes apparent only after undesirable events occur. The problems associated with oil wells' potential contamination of groundwater—fresh water within the earth that supplies wells and springs—provide a case in point.
When commercial drilling for oil began in North America in the mid-nineteenth century, regulations reflected the industry's concern for the purity of the wells' oil. In 1893, for example, regulations were enacted specifying well construction requirements to protect oil and gas reserves from contamination by fresh water. Thousands of wells were drilled in such a way as to protect the oil, but no thought was given to the possibility that the groundwater itself might need protection until many drinking-water wells near the oil well sites began to produce unpotable, oil-contaminated water.
The reason for this contamination was that groundwater is usually found in porous and permeable geologic formations near the earth's surface, whereas petroleum and unpotable saline water reservoirs are generally found in similar formations but at greater depths. Drilling a well creates a conduit connecting all the formations that it has penetrated. Consequently, without appropriate safeguards, wells that penetrate both groundwater and oil or saline water formations inevitably contaminate the groundwater. Initial attempts to prevent this contamination consisted of sealing off the groundwater formations with some form of protective barrier to prevent the oil flowing up the well from entering or mixing with the natural groundwater reservoir. This method, which is still in use today, initially involved using hollow trees to seal off the groundwater formations; now, however, large metal pipe casings, set in place with cement, are used.
Regulations currently govern the kinds of casing and cement that can be used in these practices; however, the hazards of insufficient knowledge persist. For example, the long-term stability of this way of protecting groundwater is unknown. The protective barrier may fail due to corrosion of the casing by certain fluids flowing up the well, or because of dissolution of the cement by these fluids. The effects of groundwater bacteria, traffic vibrations, and changing groundwater chemistry are likewise unassessed. Further, there is no guarantee that wells drilled in compliance with existing regulations will not expose a need for research in additional areas: on the west coast of North America, a major disaster recently occurred because a well's location was based on a poor understanding of the area's subsurface geology. Because the well was drilled in a channel accessing the ocean, not only was the area's groundwater completely contaminated, but widespread coastal contamination also occurred, prompting international concern over oil exploration and initiating further attempts to refine regulations.
The accumulation of scientific knowledge regarding the environmental impact of oil well drilling in North America has tended to lag behind the actual drilling of oil wells. Most attempts to regulate the industry have relied on hindsight: the need for regulation becomes apparent only after undesirable events occur. The problems associated with oil wells' potential contamination of groundwater—fresh water within the earth that supplies wells and springs—provide a case in point.
When commercial drilling for oil began in North America in the mid-nineteenth century, regulations reflected the industry's concern for the purity of the wells' oil. In 1893, for example, regulations were enacted specifying well construction requirements to protect oil and gas reserves from contamination by fresh water. Thousands of wells were drilled in such a way as to protect the oil, but no thought was given to the possibility that the groundwater itself might need protection until many drinking-water wells near the oil well sites began to produce unpotable, oil-contaminated water.
The reason for this contamination was that groundwater is usually found in porous and permeable geologic formations near the earth's surface, whereas petroleum and unpotable saline water reservoirs are generally found in similar formations but at greater depths. Drilling a well creates a conduit connecting all the formations that it has penetrated. Consequently, without appropriate safeguards, wells that penetrate both groundwater and oil or saline water formations inevitably contaminate the groundwater. Initial attempts to prevent this contamination consisted of sealing off the groundwater formations with some form of protective barrier to prevent the oil flowing up the well from entering or mixing with the natural groundwater reservoir. This method, which is still in use today, initially involved using hollow trees to seal off the groundwater formations; now, however, large metal pipe casings, set in place with cement, are used.
Regulations currently govern the kinds of casing and cement that can be used in these practices; however, the hazards of insufficient knowledge persist. For example, the long-term stability of this way of protecting groundwater is unknown. The protective barrier may fail due to corrosion of the casing by certain fluids flowing up the well, or because of dissolution of the cement by these fluids. The effects of groundwater bacteria, traffic vibrations, and changing groundwater chemistry are likewise unassessed. Further, there is no guarantee that wells drilled in compliance with existing regulations will not expose a need for research in additional areas: on the west coast of North America, a major disaster recently occurred because a well's location was based on a poor understanding of the area's subsurface geology. Because the well was drilled in a channel accessing the ocean, not only was the area's groundwater completely contaminated, but widespread coastal contamination also occurred, prompting international concern over oil exploration and initiating further attempts to refine regulations.
The accumulation of scientific knowledge regarding the environmental impact of oil well drilling in North America has tended to lag behind the actual drilling of oil wells. Most attempts to regulate the industry have relied on hindsight: the need for regulation becomes apparent only after undesirable events occur. The problems associated with oil wells' potential contamination of groundwater—fresh water within the earth that supplies wells and springs—provide a case in point.
When commercial drilling for oil began in North America in the mid-nineteenth century, regulations reflected the industry's concern for the purity of the wells' oil. In 1893, for example, regulations were enacted specifying well construction requirements to protect oil and gas reserves from contamination by fresh water. Thousands of wells were drilled in such a way as to protect the oil, but no thought was given to the possibility that the groundwater itself might need protection until many drinking-water wells near the oil well sites began to produce unpotable, oil-contaminated water.
The reason for this contamination was that groundwater is usually found in porous and permeable geologic formations near the earth's surface, whereas petroleum and unpotable saline water reservoirs are generally found in similar formations but at greater depths. Drilling a well creates a conduit connecting all the formations that it has penetrated. Consequently, without appropriate safeguards, wells that penetrate both groundwater and oil or saline water formations inevitably contaminate the groundwater. Initial attempts to prevent this contamination consisted of sealing off the groundwater formations with some form of protective barrier to prevent the oil flowing up the well from entering or mixing with the natural groundwater reservoir. This method, which is still in use today, initially involved using hollow trees to seal off the groundwater formations; now, however, large metal pipe casings, set in place with cement, are used.
Regulations currently govern the kinds of casing and cement that can be used in these practices; however, the hazards of insufficient knowledge persist. For example, the long-term stability of this way of protecting groundwater is unknown. The protective barrier may fail due to corrosion of the casing by certain fluids flowing up the well, or because of dissolution of the cement by these fluids. The effects of groundwater bacteria, traffic vibrations, and changing groundwater chemistry are likewise unassessed. Further, there is no guarantee that wells drilled in compliance with existing regulations will not expose a need for research in additional areas: on the west coast of North America, a major disaster recently occurred because a well's location was based on a poor understanding of the area's subsurface geology. Because the well was drilled in a channel accessing the ocean, not only was the area's groundwater completely contaminated, but widespread coastal contamination also occurred, prompting international concern over oil exploration and initiating further attempts to refine regulations.
Based on the information in the passage, if a prospective oil well drilled near a large city encounters a large groundwater formation and a small saline water formation, but no oil, which one of the following statements is most likely to be true?
Groundwater contamination is unlikely because the well did not strike oil and hence will not be put in operation.
Danger to human health due to groundwater contamination is unlikely because large cities generally have more than one source of drinking water.
Groundwater contamination is likely unless the well is plugged and abandoned.
Groundwater contamination is unlikely because the groundwater formation's large size will safely dilute any saline water that enters it.
The risk of groundwater contamination can be reduced if casing is set properly and monitored routinely for breakdown.
Explanations
This question poses a hypothetical and asks us to play the thought experiment out correctly with one of the answer choices.
The hypothetical asks what would happen if we were drilling for an oil well, hit a groundwater formation and then a saline water formation, but never found oil.
We learned in the third paragraph that "Drilling a well creates a conduit connecting all the formations that it has penetrated. Consequently, without appropriate safeguards, wells that penetrate both groundwater and oil or saline water formations inevitably contaminate the groundwater."
Treat that like an if-then statement on an LR question. It means if we drill through groundwater and either saline water or oil (or both), and we don't properly safeguard the groundwater, then the groundwater gets contaminated.
I want an answer choice that follows those conditions. Let's see.
Nope. Contamination is certain unless we safeguard the groundwater.
No way. I have no evidence to support this answer. I know nothing about cities' water reserves keeping them safe from contaminants.
No, but so close. Yes, contamination is likely, but not unless we plug the well—unless we safeguard the groundwater.
Nope. Groundwater contamination is all but certain in this case, not unlikely.
Bingo. Even though contamination is very likely, we can limit the risks involved by properly safeguarding the groundwater and monitoring it. This is the answer.
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