Fossil's Drilling Process Video

Preparation for Drilling

A lot of people think that drilling for oil amounts to finding a spot where "bubbling' crude" oozes from the soil a'la Jed Clampet -- drilling a hole and waiting for the black sludge to come squirting to the surface like Old Faithful. It's not quite that way. Drilling for oil today is a complex, scientific process of coaxing oil that's deeply embedded in sandstone or limestone, not like a gusher, but more like a leaking faucet -- drop by drop.

Fossil Oil Company's engineers and workers use a combination of sciences including seismology, geology and physics. Once geologists have determined that an area may contain oil, dirt work begins at the drilling site to prepare a suitable location for the drilling rig. A drilling rig, complete with a 90-foot derrick (mast) is erected at the site.

Once the engines are assembled on the site and the rig is up, drilling for surface casing begins. The surface casing is usually set below any fresh water formations, often approximately 300 to 400 feet deep. The casing itself comes in 40-foot sections, which are threaded at both ends. Workers, or "roughnecks" attach the sections with a "collar" which also is threaded. Chains are used to spin the pipe into the threaded collar. The roughnecks then tighten the collar with a large pipe wrench. Once the surface casing has been run into the hole, a special cement is pumped in. The cement seals the area between the surface casing and the side of the hole protecting all fresh water formations from contamination as the well is drilled deeper. Then, drilling commences once again.

The drill bit and 30-foot sections of drill pipe are used to drill deeper toward the potentially oil-bearing formation. A liquid consisting of fresh water and bentonite is mixed (on the fly) to a gelatin-like consistency and is pumped into the hole to carry the drill cuttings to the surface. This liquid is called "drilling mud."


Once the hole reaches the desired depth, logging begins. Logging is the process of determining which of the formations between the surface and the bottom of the well contain oil and gas and which formations contain merely water. An electrical cable and a "logging tool" are lowered into the hole, and the tool sends electrical charges into the formation. Logging contractor employees prepare to lower the 20-foot logging tool into the hole. 5000' of drill pipe is standing beside them. The tool then sends this geological information to the "logging" truck where a computer processes the information. The information which can be derived from logging includes rock type, porosity, and resistivity (oil resists electricity; water conducts it).

Once this information is gathered and studied, a decision is made to either plug or complete the well. This is called the "casing point decision." Once the decision to complete the well has been reached, enough casing is lowered into the hole to reach the bottom (often over 5000 feet). A worker, called a "stabber" makes sure the casing is "stabbed" straight into the joint of each piece of casing. Power tongs screw the pipe together until it reaches the proper torque. Cement is then pumped into the hole through the casing. When it hardens, the cement forms a seal between the outside of the casing and the wall of the hole itself. The last joint

The rig and derrick are removed, and a service rig moves in to complete the well. A perforating gun blows holes through the casing and cement into the rock using shaped explosive charges. The perforating gun blows a hole about every three inches down the hole with a computer telling the gun when to shoot. These holes or "perforations" then allow the oil to seep into the casing. However, another step must be taken to improve the quantity of oil seeping into the casing.

This next step involves "loosening" the oil that is trapped in the porous rock using a process called "fracing" (pronounced fracking). This is accomplished by pumping water at extremely high pressure into the hole until a crack develops in the rock formation. Water and sand are then pumped into the crack, which often extends as far as 1200 feet. Once pumping is ceased, the sand holds the cracks open and is a great deal more porous than the rock which contains the oil. Once all this is accomplished, the oil begins to escape the fractured rock and flows into the casing. The service rig is then utilized to run another string of pipe into the well (inside the casing). This string of pipe is called the "tubing." A pump is also installed in the bottom of the well. A "roustabout" crew then assembles the pumping unit and installs the pipelines which transport the oil and natural gas which have been pumped out of the formation to a separation facility. The gas and oil are separated. The gas flows into a gas pipeline, and the oil is stored in tanks. The oil is then trucked or shipped via pipeline to

NOTE: The steps for producing oil and gas as outlined above are typical . Producing oil and gas in different geographic areas and for different productive formations can be significantly different.