 and gas in California. One day, Bob, a geologist, and his young friends, Cindy and Jack, were walking near the La Brea Tarpits in Los Angeles. Suddenly, do you know what that is, Jack, asked Bob? Sure, said Jack, an old puddle of oil. You probably don't know how old or how important either, Bob said. Why don't we sit down and tell you and Cindy about oil. Cindy, your blouse is nylon, right? Nylon's made from oil. Jack, the buttons on your shirt are made of plastic. Plastic's made from oil. The food you eat grew with the help of fertilizer made from oil and natural gas. The electricity in your house, oil and gas help to make it. The asphalt pavement roads is made from oil. The gasoline in your car is, too, and I could go on. Wow, that really is interesting, said Jack. You said oil is old? Just how old is it and where does it come from? I'm glad you asked, said Bob. This oil was formed underground. Let me explain. Everywhere you go, you're on top of rock. In some places in California, you can be on top of about 20 miles of rock. Mount Everest is a mass of rock about six miles high, so rock 20 miles deep would reach over three times as far. That's a lot of rock, and that's what you're on. Most rock-containing oil begins as tiny grains of sand, silt or clay, just like the soil in your yard. Through the years, wind and rain roll these small grains around. Eventually, they come to low spots and settle. Often, the low spots are underwater in rivers, lakes and seas. Some plants and animals live in the water. Most are too small to be seen without a microscope. Many are diatoms, which are tiny one-cell plants. Sand, silt and clay grains sink in the water, covering up dead diatoms and other dead plant and animal life, most just as small. Water is trapped between the grains as well. Soon, the grains themselves are covered by more dead plant and animal life. The process is repeated over and over as layers of mud, sand and water thousands of feet thick build up. You know how, when things get piled up, sometimes the things on the bottom get squashed by the weight of the things on the top? Well, this is what happens to the layers of sand, mud and water and dead plant and animal life. As they are covered up on the river, lake and sea bottoms, the pressure on them becomes greater and greater. As they are buried deeper and deeper, they also get hotter. Finally, after millions of years and the right amounts of heat and pressure, the mud and sand grains harden into rock. The rock looks like brown or gray cement. As the dead plant and animal life decay, oil and natural gas are formed. Most oil and gas come from decayed microscopic plants and animals. Exactly how the oil and gas form isn't known, but heat, pressure and bacteria all are important. The oil and gas were formed in shallow seas, which covered much of the state that is now above water. Most of our oil and gas fields are found where these seas once were. About four and a half billion years ago, the earth was a mass of swirling gases. Four billion years ago, the earth's crust hardened. Most California oil is considered young by geologists, as it's about 23 million years old, which is still pretty old. Because of its youth, most California oil is heavy and thick, like the oil on the right. It often contains a lot of nitrogen, metals and sulfur. This makes California oil harder to take from the ground and harder to make into gasoline and other products. Once oil and gas form, they don't stay still. Like you and me, they travel. Where do they go? asks Cindy. They rise, said Bob. The oil, gas and water are found between rock grains. Because they are lighter than the water, the oil and gas move to the top of the water. Sometimes they pass into the cracks in the earth, called faults. At times, the oil and gas reach the surface along these faults. At the surface, the oil and gas is called a seep. California has hundreds of seeps, mostly in areas close to the state's oil and gas fields. The oil puddle you just stepped in, Jack, is a small natural seep. Indians and pioneers used oil from seeps for many things, such as waterproofing baskets and greasing wagon wheels. Luckily, some oil and gas are trapped before they reach the surface. This happens when oil and gas reach a rock bed they cannot flow through, called a cap rock or another barrier. When a lot of oil and gas collect there, an oil and gas reservoir is formed. A typical oil and gas reservoir in California is sandstone, made from sand grains. The oil or gas is in small spaces between the sand grains, not in a big open pool. Reservoirs are very important. Oil and gas companies hire geologists like me to find the reservoirs. How do they find them? asks Jack. Well, it's not easy, said Bob. Most reservoirs are very deep and cannot be seen directly from the surface. Geologists look for clues like outcrops, which are parts of rock beds appearing at the surface. Geologists study outcrops, mapping the locations, thicknesses and angles. From this and other information, geologists try to determine sites and shapes of rock beds beneath the surface, and where oil and gas reservoirs may occur. Just as you thump on a watermelon and listen to find out whether the fruit is ripe, sometimes geologists try to decide what is underground by vibrating the ground, often using a steel plate on a special truck. Then they study the reflected sound waves on records called seismograms, which are different for every type and structure of rock. Other tests are used as well. One measures how magnetic the rock layers are. To do this, a plane or helicopter flies over the rock with a small instrument called a magnetometer hanging from the aircraft. These tests help to locate traps or rock structures that may contain oil and gas. When geologists decide where to drill, oil and gas companies pay landowners for permission to drill on their land. Then the companies apply for drilling permits from the California Department of Conservation's Division of Oil and Gas, and when necessary, from other governmental agencies. When it's time to drill, a drilling rig is centered over the spot where the well will be. The tall derrick supports long lengths of drill pipe that are fastened to the drilling bit. The bit is turned as it presses against the rock. As it turns, rock is cut away. Drilling fluid, also called drilling mud, is pumped through the drill pipe. At the bottom of the well, the drilling mud flows out through the drilling bit and returns to the surface between the outside of the drill pipe and the well wall. Drilling mud is very important. It brings the rock chips back to the surface, cools the drilling bit, and cakes the sides of the well. The mud cake helps keep the well from caving in until steel pipe is put in place when the well is completed. The weight of the drilling mud stops any oil, gas, or water in the rocks from gushing out through the well to the surface. Today, drilling oil and gas wells is very safe. Laws enforced by the Division of Oil and Gas and other agencies protect underground and surface areas. About one exploratory well in seven is a good well. A good well means that any oil or gas that is found can be produced at a profit. When a well is not good, it is filled with cement and mud and carefully sealed off under the supervision of the Division of Oil and Gas. At a producing oil well, oil is piped from the well to holding tanks nearby. Usually, a pump must be placed in a well to uplift the oil to the surface. After gas and water are removed from the oil, the oil is taken to a refinery by trucks, trains, or pipelines. At the refinery, the oil is made into many different products such as gasoline, diesel fuel, furnace oil, jet fuel, lube oil, grease, asphalt, solvent, and thinner. Refined materials are later converted at petrochemical plants into products such as rubber, medicine, paint, nylon, and plastic. How much oil does California produce? asked Jack. About 50 million gallons a day in 1985, said Bob. California is the fourth largest oil-producing state. Only Texas, Alaska, and Louisiana produce more. Even so, we need to buy 33 million gallons of oil a day from other states and countries. Some wells produce only gas. At a producing gas well, gas flows from the well into buried pipelines, often owned by utility companies, which distribute the gas to homes and businesses. How much gas does California produce? asked Cindy. About 1.4 billion cubic feet a day in 1985, said Bob. Still, we need to buy 5.6 billion cubic feet of gas a day from other states and countries. In California, we depend on oil and natural gas for over 90% of our energy needs to fuel our cars, run our factories, and heat our homes. But what we have won't last forever. We must continue to search for new oil and gas fields. When we find them, we must develop them carefully and use the resources wisely.