National Geographic : 1974 Dec
Getting offshore It takes time. The Exxon gasoline you're filling up with today may have come from an oil field we started looking for 8 years ago. Geological survey. Eight years ago, Exxon began to ex plore a piece of acreage 75 miles out in the Gulf of Mexico. Our geologists examined rocks from the bottom of the Gulf and along the shoreline. They used special devices to locate possible oil-bearing rock thou sands of feet below the seafloor. From this information, they cre ated a vertical "picture" of the rock layers to find strata that looked promising. These studies can take very lit tle time, or up to six years. This one took four. In 1970, convinced that the chances of finding oil were good, Exxon bought the rights to drill exploratory wells. This was the only way we'd find out for sure if there really was oil there. Exploratory drilling. We started drilling foroil in mid-1971. To do it, we used a mobile drill ing rig. The cost of leasing and operating this rig was $24,500 a day. Working round the clock, it took us 25 days to drill the first well. It was 8,500 feet deep-and we discovered gas, but no oil. We then drilled a second hole. Fortunately, we hit oil. To find out how big the field was, we drilled several more wells. They outlined the size of the field and confirmed that oil was down there in commercial quantities. Exploratory drilling can often take as long as five years. We were lucky. It had taken us just two years. The next step was to design and construct the oil-producing platforms which would replace the mobile rig. These huge plat forms would be anchored to the seafloor directly over the field. Platform construction and in stallation. We started building the twin drilling and production platforms in 1972. Construction took 16 months. Each offshore platform has to be built specifically for the area it will work in. You have to take into account water depths, wind and wave action, earthquake pos sibilities, and other factors. This is why an offshore platform built for the relatively calm Gulf will be different from one built for the fierce North Sea. Our next step was to tow the steel structures out into the Gulf. We then sank them in place in 235 feet of water, and anchored them with pilings driven into the seafloor. Then we added the platform decks.These included the crew's quarters as well as facilities for producing the oil.