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A mud engineer (correctly called a drilling fluids engineer, but most often referred to as the "mud man" [1] [2] ) works on an oil well or gas well drilling rig, and is responsible for ensuring the properties of the drilling fluid, also known as drilling mud, are within designed specifications.
Mud is a vital part of drilling operations. It provides hydrostatic pressure on the borehole wall to prevent uncontrolled production of reservoir fluids, lubricates and cools the drill bit, carries the drill cuttings up to the surface, forms a "filter-cake" on the borehole wall to prevent drilling fluid invasion, provides an information medium for well logging, and helps the drilling by fracturing the rock from the jets in the bit. To fulfill these tasks effectively, the mud contains carefully chosen additives to control its chemical and rheological properties.
Drilling mud is usually a shear thinning non-Newtonian fluid of variable viscosity. When it is under more shear, such as in the pipe to the bit and through the bit nozzles, viscosity is lower which reduces pumping-power requirements. When returning to the surface through the much roomier annulus it is under less shear stress and becomes more viscous, and hence better able to carry the rock cuttings. Bentonite is commonly used as an additive to control and maintain viscosity, and also has the additional benefit of forming a mud-cake (also known as a filter cake) on the bore-hole wall, preventing fluid invasion. [3]
Barite is commonly used to "weight" the mud to maintain adequate hydrostatic pressure down-hole. This is critical in a drilling operation to avoid a kick and ultimately a blowout from uncontrolled production of formation fluids. The "mud-pits" at the surface have their levels carefully monitored, since an increase in the mud level indicates a kick is taking place, and may require shutting in the well and circulating heavier weighted drilling mud to prevent further formation fluid or gas production.
Drilling fluid must be chemically compatible with the formations being drilled. Salinity must be chosen so as not to cause clay swelling or other problems. Mud can be "oil-based" or "water-based". In many areas oil-based muds are being phased out, as they are less environmentally friendly, although in some formations they are necessary because of chemical compatibility issues. Offshore rigs typically use synthetic oil based mud.
The mud engineer (or drilling fluids engineer) may be a university, college, or technical institute graduate, having gained experience working on rigs. [4] On land, this experience would come from being a derrick hand, and offshore, the experience would come from being a pump man. Prior to working on his own, he has been on a special training course, known as "mud school", and often spends time working with a senior mud engineer to gain experience.
Before the mid-1940s, the driller dealt with drilling mud; but specialization occurred with the increasing complexity and overlapped more with the geologist. [1]
Prior to drilling a well, a "mud program" will be worked out according to the expected geology, in which products to be used, concentrations of those products, and fluid specifications at different depths are all predetermined. As the hole is drilled and gets deeper, more mud is required, and the mud engineer is responsible for making sure that the new mud to be added is made up to the required specifications. The chemical composition of the mud will be designed so as to stabilize the hole. It is sometimes necessary to completely change the mud to drill through a particular subsurface layer.
As drilling proceeds, the mud engineer will get information from other service providers such as the mud logger (mud logging technician) about progress through the geological zones, and will make regular physical and chemical checks on the drilling mud. In particular the Marsh funnel viscosity and the density are frequently checked. As drilling proceeds, the mud tends to accumulate small particles of the rocks which are being drilled through, and its properties change. It is the job of the mud engineer to specify additives to correct these changes, or to partially or wholly replace the mud when necessary. He or she must also keep an eye on the equipment which is used to pump the mud and to remove particles, and be prepared if the geologists' predictions are not entirely correct, or if other problems arise.
It is sometimes necessary to stabilize the wall of a borehole at a particular depth by pumping cement down through the mud system, and the mud engineer is sometimes in charge of this process.
The mud engineer is well supported by the mud supply company with computer aids and manuals dealing with all known problems and their solution, but it is his or her responsibility to get it right in a situation where mistakes can be very costly indeed.
A mud engineer's job may involve long shifts of over 12 hours a day. Typical offshore and foreign work schedules are four weeks working and four weeks off.
One of the most important mud properties is the mud weight (density). If the mud weight exceeds the fracture pressure of the formation, the formation may fracture and large quantities of mud are lost to it, in a situation referred to as lost circulation. These cracks can also cause water to seep into the well bore or into a hydrocarbon bearing zone, which would likely impede the ability of the formation to produce oil (or require the separation of large quantities of water).
Conversely, if the mud weight is too low it will have a hydrostatic pressure that is less than the formation pressure. This will cause pressurized fluid in the formation to flow into the wellbore and make its way to the surface. This is referred to as a formation "kick" and can lead to a potentially deadly blowout if the invading fluid reaches the surface uncontrolled.
Other important mud properties to be maintained are the YP (Yield Point) which determines the carrying capacity of the mud to carry the drill cuttings to the surface. Mud should be capable of forming a thin "mud cake" which forms a lining of the borehole walls.
Drilling fluids operations are often contracted to service companies, a trend commonly observed in the oil industry for most of it operations. The largest four companies for mud services are M-I SWACO (A Schlumberger Company), Baroid Drilling Fluids (Halliburton Oilfield Services), Baker Hughes Drilling Fluids, and Weatherford International Drilling Fluids and Drilling Waste Management. There are, however, many smaller companies providing drilling fluid services as well. Independent companies can provide a localized knowledge, and quality services and mud products. ANA Industries Limited is also the largest independent drilling fluids company presently in West Africa
Well drilling is the process of drilling a hole in the ground for the extraction of a natural resource such as ground water, brine, natural gas, or petroleum, for the injection of a fluid from surface to a subsurface reservoir or for subsurface formations evaluation or monitoring. Drilling for the exploration of the nature of the material underground is best described as borehole drilling.
An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may be termed a gas well. Wells are created by drilling down into an oil or gas reserve that is then mounted with an extraction device such as a pumpjack which allows extraction from the reserve. Creating the wells can be an expensive process, costing at least hundreds of thousands of dollars, and costing much more when in hard to reach areas, e.g., when creating offshore oil platforms. The process of modern drilling for wells first started in the 19th century, but was made more efficient with advances to oil drilling rigs during the 20th century.
In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Essentially, it is the process of "recognizing a commercial well when you drill one".
Directional drilling is the practice of drilling non-vertical bores. It can be broken down into four main groups: oilfield directional drilling, utility installation directional drilling, directional boring, and surface in seam (SIS), which horizontally intersects a vertical bore target to extract coal bed methane.
Well logging, also known as borehole logging is the practice of making a detailed record of the geologic formations penetrated by a borehole. The log may be based either on visual inspection of samples brought to the surface or on physical measurements made by instruments lowered into the hole. Some types of geophysical well logs can be done during any phase of a well's history: drilling, completing, producing, or abandoning. Well logging is performed in boreholes drilled for the oil and gas, groundwater, mineral and geothermal exploration, as well as part of environmental and geotechnical studies.
Well control is the technique used in oil and gas operations such as drilling, well workover and well completion for maintaining the hydrostatic pressure and formation pressure to prevent the influx of formation fluids into the wellbore. This technique involves the estimation of formation fluid pressures, the strength of the subsurface formations and the use of casing and mud density to offset those pressures in a predictable fashion. Understanding pressure and pressure relationships is important in well control.
Casing is a large diameter pipe that is assembled and inserted into a recently drilled section of a borehole. Similar to the bones of a spine protecting the spinal cord, casing is set inside the drilled borehole to protect and support the wellstream. The lower portion is typically held in place with cement. Deeper strings usually are not cemented all the way to the surface, so the weight of the pipe must be partially supported by a casing hanger in the wellhead.
In geotechnical engineering, drilling fluid, also known as drilling mud, is used to aid the drilling of boreholes into the earth. Used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells.
A drilling rig is used to create a borehole or well in the earth's sub-surface, for example in order to extract natural resources such as gas or oil. During such drilling, data is acquired from the drilling rig sensors for a range of purposes such as: decision-support to monitor and manage the smooth operation of drilling; to make detailed records of the geologic formations penetrated by a borehole; to generate operations statistics and performance benchmarks such that improvements can be identified, and to provide well planners with accurate historical operations-performance data with which to perform statistical risk analysis for future well operations. The terms measurement while drilling (MWD), and logging while drilling (LWD) are not used consistently throughout the industry. Although these terms are related, within the context of this section, the term measurement while drilling refers to directional-drilling measurements, e.g., for decision support for the wellbore path, while LWD refers to measurements concerning the geological formations penetrated while drilling.
Mud logging is the creation of a detailed record of a borehole by examining the cuttings of rock brought to the surface by the circulating drilling medium. Mud logging is usually performed by a third-party mud logging company. This provides well owners and producers with information about the lithology and fluid content of the borehole while drilling. Historically it is the earliest type of well log. Under some circumstances compressed air is employed as a circulating fluid, rather than mud. Although most commonly used in petroleum exploration, mud logging is also sometimes used when drilling water wells and in other mineral exploration, where drilling fluid is the circulating medium used to lift cuttings out of the hole. In hydrocarbon exploration, hydrocarbon surface gas detectors record the level of natural gas brought up in the mud. A mobile laboratory is situated by the mud logging company near the drilling rig or on deck of an offshore drilling rig, or on a drill ship.
A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well or gas well after pressure control systems have failed. Modern wells have blowout preventers intended to prevent such an occurrence. An accidental spark during a blowout can lead to a catastrophic oil or gas fire.
A derrickhand or derrickman is the person who sits atop the derrick on a drilling rig. Though the exact duties vary from rig to rig, they almost always report directly to the driller. Their job is to guide the stands of the drill pipe into the fingers at the top of the derrick. Other duties might include monitoring pH and calcium levels, viscosity and the mud weight (density), adding chemicals and oil based fluids, and being responsible for the shale shakers and mud pump.
In drilling technology, casing string is a long section of connected oilfield pipe that is lowered into a wellbore and cemented. The purpose of the casing pipe is as follows:
Petroleum is a fossil fuel that can be drawn from beneath the earth's surface. Reservoirs of petroleum are formed through the mixture of plants, algae, and sediments in shallow seas under high pressure. Petroleum is mostly recovered from oil drilling. Seismic surveys and other methods are used to locate oil reservoirs. Oil rigs and oil platforms are used to drill long holes into the earth to create an oil well and extract petroleum. After extraction, oil is refined to make gasoline and other products such as tires and refrigerators. Extraction of petroleum can be dangerous and have led to oil spills.
Underbalanced drilling, or UBD, is a procedure used to drill oil and gas wells where the pressure in the wellbore is kept lower than the static pressure of the formation being drilled. As the well is being drilled, formation fluid flows into the wellbore and up to the surface. This is the opposite of the usual situation, where the wellbore is kept at a pressure above the formation to prevent formation fluid entering the well. In such a conventional "overbalanced" well, the invasion of fluid is considered a kick, and if the well is not shut-in it can lead to a blowout, a dangerous situation. In underbalanced drilling, however, there is a "rotating head" at the surface - essentially a seal that diverts produced fluids to a separator while allowing the drill string to continue rotating.
In the oil and gas industry, coiled tubing refers to a long metal pipe, normally 1 to 3.25 in in diameter which is supplied spooled on a large reel. It is used for interventions in oil and gas wells and sometimes as production tubing in depleted gas wells. Coiled tubing is often used to carry out operations similar to wirelining. The main benefits over wireline are the ability to pump chemicals through the coil and the ability to push it into the hole rather than relying on gravity. Pumping can be fairly self-contained, almost a closed system, since the tube is continuous instead of jointed pipe. For offshore operations, the 'footprint' for a coiled tubing operation is generally larger than a wireline spread, which can limit the number of installations where coiled tubing can be performed and make the operation more costly. A coiled tubing operation is normally performed through the drilling derrick on the oil platform, which is used to support the surface equipment, although on platforms with no drilling facilities a self-supporting tower can be used instead. For coiled tubing operations on sub-sea wells a mobile offshore drilling unit (MODU) e.g. semi-submersible, drillship etc. has to be utilized to support all the surface equipment and personnel, whereas wireline can be carried out from a smaller and cheaper intervention vessel. Onshore, they can be run using smaller service rigs, and for light operations a mobile self-contained coiled tubing rig can be used.
Oilfield terminology refers to the jargon used by those working in fields within and related to the upstream segment of the petroleum industry. It includes words and phrases describing professions, equipment, and procedures specific to the industry. It may also include slang terms used by oilfield workers to describe the same.
In oil or gas well drilling, lost circulation occurs when drilling fluid, known commonly as "mud", flows into one or more geological formations instead of returning up the annulus. Lost circulation can be a serious problem during the drilling of an oil well or gas well.
Oil well control is the management of the dangerous effects caused by the unexpected release of formation fluid, such as natural gas and/or crude oil, upon surface equipment of oil or gas drilling rigs and escaping into the atmosphere. Technically, oil well control involves preventing the formation gas or fluid (hydrocarbons), usually referred to as kick, from entering into the wellbore during drilling or well interventions.
Well cementing is the process of introducing cement to the annular space between the well-bore and casing or to the annular space between two successive casing strings. Personnel who conduct this job are called "Cementers".