Mud engineer
Encyclopedia
A mud engineer works on an oil well
or gas well drilling rig
, and is responsible ensuring the properties of the drilling fluid
, also known as drilling mud, are within designed specifications.
, 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.
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.
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.
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.
Company), Baroid Drilling Fluids (Halliburton
Oilfield Services), and Baker Hughes
Drilling Fluids. 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.
Oil well
An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
or gas well drilling rig
Drilling rig
A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
, and is responsible ensuring the properties of the drilling fluid
Drilling fluid
In geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often 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. Liquid drilling fluid...
, also known as drilling mud, are within designed specifications.
Use of mud
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 bitDrill bit
Drill bits are cutting tools used to create cylindrical holes. Bits are held in a tool called a drill, which rotates them and provides torque and axial force to create the hole. Specialized bits are also available for non-cylindrical-shaped holes....
, 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
Non-Newtonian fluid
A non-Newtonian fluid is a fluid whose flow properties differ in any way from those of Newtonian fluids. Most commonly the viscosity of non-Newtonian fluids is not independent of shear rate or shear rate history...
of variable viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher 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
Bentonite
Bentonite is an absorbent aluminium phyllosilicate, essentially impure clay consisting mostly of montmorillonite. There are different types of bentonite, each named after the respective dominant element, such as potassium , sodium , calcium , and aluminum . Experts debate a number of nomenclatorial...
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.
Barite
Barite
Baryte, or barite, is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main source of barium...
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
Blowout (well drilling)
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....
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
Drilling fluid
In geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often 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. Liquid 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 Job
The mud engineer (or drilling fluids engineer) may be a university, college, or technical institute graduate, or may have no tertiary education at all, having gained experience working on rigs which could be over 10 years. 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.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
Mud logging
Mud logging, also known as hydrocarbon well logging, is the creation of a detailed record of a borehole by examining the bits of rock or sediment brought to the surface by the circulating drilling medium . Mud logging is usually performed by a third-party mud logging company...
technician) about progress through the geological zones, and will make regular physical and chemical checks on the drilling mud. In particular the Marsh funnel
Marsh funnel
The Marsh funnel viscometer is a simple device for measuring viscosity from the time it takes a known volume of liquid to flow from the base of a cone through a short tube...
viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
and the density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
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.
Important Fluid Properties
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 hydrocarbonHydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
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
Blowout (well drilling)
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....
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
Borehole
A borehole is the generalized term for any narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water or other liquid or gases , as part of a geotechnical investigation, environmental site...
walls.
Drilling Fluids Companies
Drilling fluids operations are often contracted to service companies, a trend commonly observed in the oil industry for most of it operations. The largest three companies for mud services are M-I SWACO (A SchlumbergerSchlumberger
Schlumberger Limited is the world's largest oilfield services company. Schlumberger employs over 110,000 people of more than 140 nationalities working in approximately 80 countries...
Company), Baroid Drilling Fluids (Halliburton
Halliburton
Halliburton is the world's second largest oilfield services corporation with operations in more than 70 countries. It has hundreds of subsidiaries, affiliates, branches, brands and divisions worldwide and employs over 50,000 people....
Oilfield Services), and Baker Hughes
Baker Hughes
Baker Hughes Baker Hughes provides the world's oil & gas industry with products and services for drilling, formation evaluation, completion, production and reservoir consulting. Baker Hughes operates in over 90 countries worldwide mainly based in countries with a mature petroleum industry as is...
Drilling Fluids. 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.
Further reading
- ASME Shale Shaker Committee (2005) The Drilling Fluids Processing Handbook ISBN 0-7506-7775-9
- Kate Van Dyke (1998) Drilling Fluids, Mud Pumps, and Conditioning Equipment
- G. V. Chilingarian & P. Vorabutr (1983) Drilling and Drilling Fluids
- G. R. Gray, H. C. H. Darley, & W. F. Rogers (1980) The Composition and Properties of Oil Well Drilling Fluids
See also
- BoringBoring (earth)Boring is drilling a hole, tunnel, or well in the earth.-Earth boring:Boring is used for a wide variety of applications in geology, agriculture, hydrology, civil engineering, and oil and natural gas industries...
- DerrickhandDerrickhandThe Derrickhand or Derrickman position varies greatly from one drilling rig to another. He almost always reports directly to the driller. The name derrickman comes from the position that he normally occupies, which is at the top of the derrick...
- Drilling mud
- Drilling rigDrilling rigA drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
- Marsh funnelMarsh funnelThe Marsh funnel viscometer is a simple device for measuring viscosity from the time it takes a known volume of liquid to flow from the base of a cone through a short tube...
- Oil wellOil wellAn oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
- Society of Petroleum EngineersSociety of Petroleum EngineersThe Society of Petroleum Engineers is a not-for-profit professional organization whose mission is to collect, disseminate, and exchange technical knowledge concerning the exploration, development and production of oil and gas resources and related technologies for the public benefit and to provide...