The drilling process uses a motor, either at the surface or downhole, to turn a string of pipe with a drill bit connected to the end. The drill bit has special “teeth” to help it crush or break up the rock it encounters to make a hole in the ground. While the well is being drilled, a fluid, called drilling mud, circulates down the inside of the drill pipe, passes through holes in the drill bit and travels back up the wellbore to the surface. The drilling mud has two purposes:
Water-based drilling mud is composed primarily of clay, water and small amounts of chemical additives to address particular subsurface conditions that may be encountered. In deep wells, oil-based drilling mud is used because water-based mud cannot stand up to the higher temperatures and conditions encountered. The petroleum industry has developed technologies to minimize the environmental effects of the drilling fluids it uses, recycling as much as possible. The development of environmentally friendly fluids and additives is an important area of research of the oil and gas industry.
Even with the best technology, drilling a well does not always mean that oil or gas will be found. If oil or gas is not found in commercial quantities, the well is called a dry hole. Sometimes, the well encounters oil or gas, but the reservoir is determined to be unlikely to produce in commercial quantities.
Technology has increased the success rate of finding commercial oil or gas deposits with less waste and a smaller impact on the surface. While conventional oil and gas wells are typically vertical, contacting only a limited amount of the target reservoir rock, horizontal wells look like a large “L.” The long horizontal wellbore, sometimes more than 4,000 feet long, contacts a large portion of the productive reservoir. The surrounding rock formation is then hydraulically fractured to release the oil or gas trapped inside. In hydraulic fracturing, massive trucks pump thousands of gallons of fluid into the rock at very high pressures in order to force the rock to crack. These cracks are then propped open with sand to allow a highly conductive passage through which the oil or gas can flow.
In shale fields, as many as 15 major fractures are placed along the horizontal wellbore, serving to connect all those small two-lane roads to wide boulevards and even larger, faster highways. Currently, the limits of this technology are being pushed back every day in order to unleash giant gas resources. In the future, this technology will have to go even farther to allow more fractures and longer horizontal wells. Advances in this area will undoubtedly transform our energy landscape.
Credits: energy4me.org
- To carry the small bits of rock, or cuttings, from the drilling process to the surface so they can be removed.
- To fill the wellbore with fluid to equalize pressure and prevent water or other fluids in underground formations from flowing into the wellbore during drilling.
Even with the best technology, drilling a well does not always mean that oil or gas will be found. If oil or gas is not found in commercial quantities, the well is called a dry hole. Sometimes, the well encounters oil or gas, but the reservoir is determined to be unlikely to produce in commercial quantities.
Technology has increased the success rate of finding commercial oil or gas deposits with less waste and a smaller impact on the surface. While conventional oil and gas wells are typically vertical, contacting only a limited amount of the target reservoir rock, horizontal wells look like a large “L.” The long horizontal wellbore, sometimes more than 4,000 feet long, contacts a large portion of the productive reservoir. The surrounding rock formation is then hydraulically fractured to release the oil or gas trapped inside. In hydraulic fracturing, massive trucks pump thousands of gallons of fluid into the rock at very high pressures in order to force the rock to crack. These cracks are then propped open with sand to allow a highly conductive passage through which the oil or gas can flow.
In shale fields, as many as 15 major fractures are placed along the horizontal wellbore, serving to connect all those small two-lane roads to wide boulevards and even larger, faster highways. Currently, the limits of this technology are being pushed back every day in order to unleash giant gas resources. In the future, this technology will have to go even farther to allow more fractures and longer horizontal wells. Advances in this area will undoubtedly transform our energy landscape.
Credits: energy4me.org
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