Drilling fluid
Drilling fluid, commonly referred to as drilling mud, is a crucial component in the extraction of oil and natural gas. This mixture, which can be water-based, oil-based, synthetic, or gaseous, plays several vital roles during the drilling process. It helps keep the drill bit cool, removes rock debris, maintains well pressure to prevent blowouts, and supports well integrity until casing is installed. The formulation of drilling fluid is carefully monitored, as its density must be balanced to avoid fracturing the surrounding rock.
Historically, the use of drilling fluid began in the early 20th century and has evolved significantly, with specialized "mud engineers" overseeing its composition and application. A major part of drilling costs, drilling fluids are particularly critical in shale formations, where hydraulic fracturing techniques are employed to access deep gas reserves. While these fluids are essential for safe operations, they also raise environmental concerns, particularly regarding the toxicity of fracking fluids and the potential for groundwater contamination. The management of drilling fluid has been linked to significant industrial disasters, highlighting the importance of precise formulation and monitoring to ensure safety in drilling operations.
Drilling fluid
Used in the process of oil and natural gas extraction, drilling fluid—or, as it is often called in the industry, drilling mud—is a mixture of various liquids and gases that is used throughout the entire process of drilling boreholes in the ground. Drilling fluids may be water based, oil based, synthetic, or gaseous, and are a key component of any safe drilling operation, helping to prevent explosions. Some of the largest disasters on drilling rigs in history have identified mistakes made in drilling fluid mixtures as a contributing factor, including the Deepwater Horizon explosion in the Gulf of Mexico in 2010.
Background
Experts say that the use of drilling mud first began in the early twentieth century in Texas on a cattle farm, when a driller threw mud into a drilling hole to prevent it from collapsing. Its first official use was in 1913, and in the 1920s and 1930s, a number of companies in the United States began manufacturing and selling drilling fluid. At an oil or gas drilling site, drilling fluid serves a number of different purposes. It is used to keep the drill bit cool, clean, and lubricated; to remove rock fragments from the path of the drill and bring them back to the surface; to keep the pressure balanced in the well to prevent oil or gas from migrating into the well too early and causing a blowout (which is how explosions and blowouts at drill sites occur); and to prevent the well from collapsing after it is drilled and before the well casing is placed. The drilling fluid must be carefully mixed and monitored because it cannot be so heavy that it causes fractures in the rock. Experts consider drilling fluid to be an integral defense against blowouts.
Most drilling fluids are water based from either fresh or salt water, although oil-based fluids (or synthetic fluids meant to mimic the properties of oil) are also used. Less commonly used are gaseous fluids, which are air and foam based. Chemical additives are frequently mixed in to drilling fluids to serve a specific purpose at different types of wells. For instance, some fluids have weighting materials added, if a drilling site is highly pressurized. Other additives are intended to prevent corrosion in pipes; dispersants and flocculants help disperse rocks into particles in the borehole and bring them to the surface so they can be removed; biocides help to kill bacteria; and surfactants prevent foaming, among numerous other types of additives.
Drilling fluid enters the borehole along with the drill bit—in fact, it sprays out of nozzles on the drill bit while the bit is boring into the hole. Drill bits turn at 170 to 200 revolutions per minute, generating a great deal of heat that the drilling fluid helps to mitigate. As the fluid rises to the surface with the dispersed rocks and debris, it may be recirculated back down into the hole after the particles are removed. Drilling fluid can be used in up to ten different wells, and once it is no longer able to be used, it is dried up and taken to a landfill. The people who are responsible for maintaining, monitoring, and making the drilling fluid "recipe" on an oil or gas rig are called "mud engineers."
Topic Today
At oil and gas rigs around the world—but particularly in what are known as shale formations, sedimentary rocks deep in the earth that contain large reserves of natural gas—drilling fluid is the key component that makes the industry possible. Experts estimate that out of the total cost to drill a well, the cost for drilling fluid makes up one-quarter of it, and shale gas alone is a $100 billion industry. Growing in popularity in the United States, natural gas releases less carbon dioxide when it is burned compared to coal or oil. There are a number of shale gas resources within the United States, but the largest is known as Marcellus Shale, located mostly in northern Pennsylvania as well as in portions of Maryland, New York, and Ohio. Because shale gas is so deep in the earth, a special drilling process known as hydraulic fracturing (often known as fracking) is used. In fracking, a well is drilled vertically down to approximately 6,500 to 7,000 feet (some as far as 10,000 feet) before the well is turned horizontally and a unique type of drilling fluid, called fracking fluid—made up of millions of gallons of water, sand, and chemicals—is blasted into the hole at intense pressure. The pressure of this causes small fractures to form in the rock, releasing the natural gas and sending it flowing back up the well. Fracking fluid is highly toxic, and there are a number of environmental concerns that surround the hydraulic fracturing process, in particular regarding spills of fracking fluid and groundwater contamination. Hydraulic fracturing fluids are proprietary, and as a result, drilling companies are under no obligation to release information about the chemicals they contain.
Mistakes and accidents on drilling rigs are often related to drilling fluid and can be catastrophic, such as a natural gas well that exploded in the Gulf of Mexico in 2013 when miscalculations were made in the drilling fluid mix, or in the Deepwater Horizon explosion in 2010, also in the Gulf, that killed eleven people and spilled 4.9 million barrels of oil, the largest accidental oil spill in history. Mistakes in drilling fluid management were one of the contributing factors to that spill.
As pressure increases in the United States to divest from foreign oil sources, domestic oil and gas drilling will likely continue to be a significant industry, even as alternative sources of energy are sought. Ensuring that drilling operations are safe and environmental threats are minimized are key factors when considering the best ways to meet the energy needs of the United States in the coming years.
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