Offshore drilling poses serious risks to ocean ecosystems, air quality, and coastal communities. These risks span the entire lifecycle of an offshore operation, from the initial seismic surveys that drive marine mammals away to the abandoned wells that keep leaking methane decades after production ends. The problems fall into several categories: routine pollution during normal operations, catastrophic spill events, harm to marine life, and long-term contamination that can persist for 20 years or more.
Routine Pollution From Normal Operations
You don’t need a dramatic blowout for offshore drilling to contaminate the ocean. During everyday production, platforms discharge what’s known as “produced water,” the fluid that comes up from the well alongside oil and gas. EPA testing of offshore platform effluent found that every single platform discharged benzene, toluene, ethylbenzene, phenol, chromium, and lead in its treated wastewater. These aren’t trace amounts in untreated waste. They’re what remains after treatment.
In the Gulf of Mexico, treated effluent averaged 1.1 milligrams per liter of benzene, a known carcinogen. Lead concentrations ranged from 160 to 915 micrograms per liter across platforms, while chromium averaged 260 micrograms per liter. Nickel showed up at concentrations as high as 1,674 micrograms per liter on some platforms. Other heavy metals, including cadmium, copper, silver, zinc, and beryllium, appeared intermittently. Each platform continuously discharges this water into the surrounding ocean throughout its operational life, which can span decades.
On top of produced water, drilling operations dump spent drilling muds and rock cuttings onto the seafloor. These materials can bury bottom-dwelling organisms, introduce toxic compounds into sediment, and disturb communities when currents resuspend the particles. The effects ripple through the food chain from the seafloor up.
Greenhouse Gas Emissions Vary Wildly
Offshore drilling’s climate footprint is more complicated than most people assume. Deep-water operations in the federal Gulf of Mexico are actually among the lowest-emission oil production sources anywhere, with a carbon intensity of just 1.1 grams of CO2 equivalent per megajoule of energy produced. But shallow-water state operations in the same gulf produce emissions 40 times higher, at 43 grams of CO2 equivalent per megajoule. The difference is staggering, and it comes down almost entirely to methane leaking from aging infrastructure in shallow waters.
A University of Michigan study found that the actual climate impact of U.S. offshore production is double what official inventories estimate: 5.7 versus 2.4 grams of CO2 equivalent per megajoule. The gap exists because methane leaks from shallow-water operations are far worse than reported. Alaska’s Cook Inlet operations land at 22 grams of CO2 equivalent per megajoule, while California’s Santa Barbara Channel averages 7.2. The variation reflects differences in infrastructure age, water depth, and how carefully operators maintain their equipment.
Abandoned Wells Keep Leaking
When an offshore well stops producing, the problem doesn’t end. Globally, roughly 4.5 million abandoned oil and gas wells released an estimated 0.4 million tons of methane in 2022 alone. The United States has about 2 million of these abandoned wells, and many were never properly sealed. Unplugged offshore wells leak methane at eight times the rate of plugged ones. Onshore, the ratio is even worse, at 21 times higher. These wells will continue releasing greenhouse gases indefinitely unless someone pays to plug them, and for orphaned wells with no solvent owner, that cost falls on taxpayers.
Seismic Surveys Disrupt Marine Life
Before any drilling begins, companies conduct seismic surveys to map underground oil deposits. These surveys use arrays of airguns that blast compressed air into the water, generating sound waves that bounce off rock formations below the seafloor. The source levels from larger arrays reach around 260 decibels, and signals can be recorded up to 370 kilometers away.
Marine mammals are acutely sensitive to this noise. Harbor porpoises show avoidance behavior at sound levels below 145 decibels and have been observed fleeing from airguns at distances greater than 70 kilometers. Dall’s porpoises avoid areas above 181 decibels. Even gray whales, which appear less disturbed by the noise, alter their movement patterns during surveys. These disruptions can separate mothers from calves, push animals away from feeding grounds, and interfere with the echolocation that toothed whales and dolphins depend on to hunt.
Oil Spills and Dispersant Toxicity
The Deepwater Horizon disaster in 2010 remains the most vivid example of what can go wrong. The blowout preventer, the device designed as the last line of defense against an uncontrolled well release, failed for multiple reasons. The upper seal eroded under high-velocity flow. The blind shear ram, meant to cut through the drill pipe and seal the well, couldn’t close because the pipe had buckled off-center under pressure. The manufacturer had never even tested shearing an off-center pipe, and industry standards at the time didn’t address the scenario. A rubber sealing element later failed from prolonged heat exposure during the weeks-long blowout.
BP ultimately paid up to $8.8 billion in a natural resource damage settlement, the largest civil settlement ever awarded. That figure covers only ecological restoration, not the additional billions in cleanup costs, economic damages to fisheries and tourism, and legal fees.
What many people don’t realize is that the chemical dispersants used to break up spilled oil can be as harmful as the oil itself. Research on coral larvae exposed to Corexit 9500, the dispersant used extensively during Deepwater Horizon, found complete larval mortality at concentrations of 50 to 100 parts per million. Even at lower concentrations, coral settlement and survival dropped significantly. Since coral larvae are the mechanism by which reefs replenish themselves, dispersant exposure directly undermines reef recovery after a spill. The researchers concluded that dispersant chemicals pose a serious threat to coral recruitment, compounding rather than alleviating the ecological damage.
Subsea Pipelines Are Vulnerable
Getting oil from offshore platforms to shore requires networks of subsea pipelines, and these pipelines fail regularly. Analysis of North Sea operations from 1971 to 2000 found that external impact, primarily from ship anchors and other mechanical contact, caused 56% of all pipeline failures. European-wide data tells a similar story, with external interference accounting for roughly half of all transmission pipeline incidents. Corrosion, construction defects, material failures, and natural hazards make up the rest. Each failure risks releasing oil directly onto the seafloor, often in locations that are difficult and expensive to reach for cleanup.
Recovery Takes Decades
Once oil reaches sensitive coastal habitats, the damage persists far longer than most people expect. A long-term study of a catastrophic oil spill in a Panamanian mangrove ecosystem found that deep mud coastal habitats require 20 years or longer to recover from toxic oil exposure. Mangroves, salt marshes, and deep-sea coral communities all share this vulnerability. They grow slowly, reproduce slowly, and exist in environments where oil gets trapped in sediment rather than washing away.
Deep-sea corals are especially at risk because they grow at rates measured in millimeters per year and can live for centuries. A single spill event can destroy coral colonies that took hundreds of years to develop, and no restoration technology exists to speed their return. The combination of direct oil toxicity, dispersant exposure, and smothering by contaminated sediment means that some deep-water ecosystems damaged by a major spill may not fully recover within a human lifetime.