kelly hose drilling definition in stock

A large-diameter (3- to 5-in inside diameter), high-pressure flexible line used to connect the standpipe to the swivel. This flexible piping arrangement permits the kelly (and, in turn, the drillstring and bit) to be raised or lowered while drilling fluid is pumped through the drillstring. The simultaneous lowering of the drillstring while pumping fluid is critical to the drilling operation.

A kelly hose is a piece of mining equipment. Specifically, it refers to a piece of equipment used in the mining of fluid or semi-fluid resources, such as oil and natural gas. The main purpose of a kelly hose is to allow the drill string to be raised and lowered at the same time that drill fluid is being pumped through it. This is important, as drill fluid is critical to the mining process.

In most cases, a kelly hose is classified as a large-diameter hose. This means that the inside diameter is usually between 3 and 5 inches (about 7.6 cm and 12.7 cm). This wide diameter allows for a significant rate of flow and reduces the likelihood of a blockage occurring in the hose.

The kelly hose must also be able to withstand large amounts of pressure. This applies primarily to the pressure of the fluid flowing through the hose. For this reason, it is often made of highly durable material and is generally reinforced with steel.

In a derrick or drilling rig, the kelly hose connects the standpipe, which is the rigid metal shaft that delivers the mining fluid, to the swivel, which is the piece that supports the weight of and controls the rotation of the drill string. Its purpose is to provide a flexible drilling fluid conduit, as a rigid conduit would be unable to move with the swivel and would therefore disallow movement of the drill string and, subsequently, the bit.

The drilling fluid, sometimes called drilling mud, carried by a kelly hose is critical to operations in several ways. It keeps the bit cool, which helps reduce friction and failure. It also cleans the bit and carries away drill cuttings so they cannot damage the drill assembly. Some varieties are used for additional purposes, such as preventing corrosion and providing hydrostatic pressure. Drilling fluid is not necessarily fluid, but may, in fact, be a solid, liquid, gas or other combined form.

The kelly hose is so named because of its connection with the kelly, the actual mechanical piece that ejects the drilling fluid over the drill string. It may alternatively be called a mud hose or a rotary hose. Failure can occur, despite the rugged construction of the hose. Such failure can lead to damage to the rig or a failure to operate. Failed kelly hoses must be repaired or replaced before mining operations can safely and effectively resume.

The kelly provides a connection between the rotary table, also called the kelly bushing, to the drill string that allows the drill string to turn around its longitudinal axis and move up and down along its length. The hole in the kelly is matched by a hole in the kelly bushing that allows for the passage of drilling fluid into the bore. A kelly is used in fluid or oil assisted bore projects.

Flexible drilling rubber hoses play an important role in petroleum extraction. They should suffer high operating pressure, extreme operating temperature, abrasion and other inferior elements. Our special compounded synthetic rubber has been proven an effective and economical way to reject these problems. All our oilfield drill hoses are manufactured as API 7K or other related specifications.

Steel cable reinforcement loads most working pressure up to 15,000psi. The wires are usually zinc-plating or copper platting to improve steel wire resistant against rust and corrosion. Due to the thick reinforcement, the hoses should be handled or stored in correct way to avoid kicking or crushing. They will substantially decrease their rated operating pressure.

Rotary hose, Kelly hose, cement hose, mud hose, jumper hose and vibrator hose and choke & kill hoses are the most popular oilfield rubber hoses. They convey high-pressure drilling fluid from one place to another. Many end fittings are provided to satisfy different applications. Most end fittings are made according to API standards. Special order is also available.

This is the brief explanation of a Kelly rotating system on the rig. Kelly rig is on an old style rigs and  nowadays it is mostly used on land operations. For offshore operation, a top drive system is used instead.

The upper end of the drill pipe is screwed onto the saver sub. The saver sub is used to protect and minimize wearr and tear on the threads at the bottom of the Kelly. The Kelly is about 40 ft in length with a square or hexagonal shape and it is hollow throughout in order to transport the drilling mud.  Kelly moves freely through a Kelly bushing even though the drill stem is rotated.

A Kelly cock valve is located at the top of a Kelly and it is a safety valve which can be closed to stop back pressure from coming back to damage other surface equipment.

A swivel attached to the hook does not rotate, but at the bottom part it supports the Kelly which is being rotated while drilling.  Drilling mud is pumped from a mud pump to a stand pipe manifold, Kelly hose and then to a gooseneck connection at a swivel.

A rotary table rotates a Kelly bushing and it simultaneously rotates a Kelly and a drill string and a drill bit. A rotary table has two main functions. The first one is to provide rotation to a drill stem and a bit and the second function is to hold slip in order to support the weight of a drill stem when it is not connected to a Kelly.

A master bushing severs its function as a rotary motion transmission from a rotary table to a Kelly. Additionally, it is a link between a slip and a rotary table.

A Kelly bushing (some people call “rotary Kelly bushing”) engages a master bushing via four pins and rollers inside a Kelly bushing to allow a Kelly to move up or down freely while it is rotated or in a static mode.

The IADC Lexicon is © IADC. However, the documents from which the definitions were drawn may be copyrighted by the original sources, and may not be used without express permission of the copyright holders. IADC expressly recognizes the copyrights of contributors to this Lexicon, including API, OGP, ISO, NORSOK and DNV.

The equipment included in the drilling fluid circulating system of a rotary rig. Basically, the components consist of the mud pump, rotary hose, swivel, drill ...

The complete, circuitous path that the drilling fluid travels. Starting at the main rig pumps, major components include surface piping, the standpipe, the kelly (rotary) hose, ...

One or more valves installed at the wellhead to prevent the escape of pressure either in the annular space between the casing and the drill pipe or in open hole (for example, hole with no drill pipe) during drilling or completion operations. See annular blowout preventer and ram blowout preventer.†

The arrangement of piping and special valves, called chokes, through which drilling mud is circulated when the blowout preventers are closed to control the pressures encountered during a kick.†

A centrifugal device for removing sand from drilling fluid to prevent abrasion of the pumps. It may be operated mechanically or by a fast-moving stream of fluid inside a special cone-shaped vessel, in which case it is sometimes called a hydrocyclone.†

A centrifugal device, similar to a desander, used to remove very fine particles, or silt, from drilling fluid. This keeps the amount of solids in the fluid to the lowest possible level.†

The hoisting mechanism on a drilling rig. It is essentially a large winch that spools off or takes in the drilling line and thus raises or lowers the drill stem and bit.†

The cutting or boring element used in drilling oil and gas wells. Most bits used in rotary drilling are roller-cone bits. The bit consists of the cutting elements and the circulating element. The circulating element permits the passage of drilling fluid and uses the hydraulic force of the fluid stream to improve drilling rates.†

The heavy seamless tubing used to rotate the bit and circulate the drilling fluid. Joints of pipe 30 feet long are coupled together with tool joints.†

A wire rope hoisting line, reeved on sheaves of the crown block and traveling block (in effect a block and tackle). Its primary purpose is to hoist or lower drill pipe or casing from or into a well. Also, a wire rope used to support the drilling tools.†

A device fitted to the rotary table through which the kelly passes. It is the means by which the torque of the rotary table is transmitted to the kelly and to the drill stem. Also called the drive bushing.†

A series of open tanks, usually made of steel plates, through which the drilling mud is cycled to allow sand and sediments to settle out. Additives are mixed with the mud in the pit, and the fluid is temporarily stored there before being pumped back into the well. Mud pit compartments are also called shaker pits, settling pits, and suction pits, depending on their main purpose.†

A trough or pipe, placed between the surface connections at the well bore and the shale shaker. Drilling mud flows through it upon its return to the surface from the hole.†

A diesel, Liquefied Petroleum Gas (LPG), natural gas, or gasoline engine, along with a mechanical transmission and generator for producing power for the drilling rig. Newer rigs use electric generators to power electric motors on the other parts of the rig.†

A hole in the rig floor 30 to 35 feet deep, lined with casing that projects above the floor. The kelly is placed in the rathole when hoisting operations are in progress.†

A mud pit in which a supply of drilling fluid has been stored. Also, a waste pit, usually an excavated, earthen-walled pit. It may be lined with plastic to prevent soil contamination.†

The hose on a rotary drilling rig that conducts the drilling fluid from the mud pump and standpipe to the swivel and kelly; also called the mud hose or the kelly hose.†

The principal component of a rotary, or rotary machine, used to turn the drill stem and support the drilling assembly. It has a beveled gear arrangement to create the rotational motion and an opening into which bushings are fitted to drive and support the drilling assembly.

A series of trays with sieves or screens that vibrate to remove cuttings from circulating fluid in rotary drilling operations. The size of the openings in the sieve is selected to match the size of the solids in the drilling fluid and the anticipated size of cuttings. Also called a shaker.†

A vertical pipe rising along the side of the derrick or mast. It joins the discharge line leading from the mud pump to the rotary hose and through which mud is pumped going into the hole.†

A rotary tool that is hung from the rotary hook and traveling block to suspend and permit free rotation of the drill stem. It also provides a connection for the rotary hose and a passageway for the flow of drilling fluid into the drill stem.†

The top drive rotates the drill string end bit without the use of a kelly and rotary table. The top drive is operated from a control console on the rig floor.†

n: a small, usually truck-mounted rig, the purpose of which is to drill ratholes for regular drilling rigs that will be moved in later. A rathole rig may also drill the top part of the hole, the conductor hole, before the main rig arrives on location.

n: a tool used in drilling to smooth the wall of a well, enlarge the hole to the specified size, help stabilize the bit, straighten the wellbore if kinks or doglegs are encountered, and drill directionally.

n: a set of controls, usually placed on the rig floor, or elsewhere on location, that is manipulated to control the amount of drilling fluid being circulated through the choke manifold. This procedure is necessary when a kick is being circulated out of a well. See choke manifold.

n: the course of drilling fluid downward through the annulus and upward through the drill stem, in contrast to normal circulation in which the course is downward through the drill stem and upward through the annulus. Seldom used in open hole, but frequently used in workover operations.

n: the machine used to impart rotational power to the drill stem while permitting vertical movement of the pipe for rotary drilling. Modern rotary machines have a special component, the rotary or master bushing, to turn the kelly bushing, which permits vertical movement of the kelly while the stem is turning.

n: a drilling method in which a hole is drilled by a rotating bit to which a downward force is applied. The bit is fastened to and rotated by the drill stem, which also provides a passageway through which the drilling fluid is circulated. Additional joints of drill pipe are added as drilling progresses.

n: a worker on a drilling or workover rig, subordinate to the driller, whose primary work station is on the rig floor. Sometimes called floorhand, floorman, rig crew member, or roughneck.

n: a length of pipe whose bottom edge is serrated or dressed with a hard cutting material and that is run into the wellbore around the outside of stuck casing, pipe, or tubing to mill away the obstruction.

Kelly hose is used to connect the standpipe to the swivel. It allows the drill string to be raised and lowered while the drill fluid is pumped through it. Kelly line usually contains two layers of plated steel cables to reach 5000 psi operating pressure. Inside tube is made of special NBR to improve abrasion and corrosion capability. Rubber cover is compatible with the ozone, sunlight and oils for a long time. It is supplied with multiple end fittings – API flanges, threads, butt-welded union and other as specified.

The rotary system includes all of the equipment used to achieve bit rotation. Originally, the main driver in the system of all rigs was the rotary table. The main parts of the rotary system with a rotary table are the swivel, kelly, and drillstring.

The rotary swivel (Fig. 1)serves two important functions in the drilling process. It is a connecting point between the circulating system and the rotary system. It also provides a fl uid seal that must absorb rotational wear while holding pressure. The upper section of the swivel has a bail for connection to the elevator hook, and the gooseneck of the swivel provides a downward-pointing connection for the rotary hose.

The kelly is the fi rst section of pipe below the swivel. The outside cross section of the kelly is square or (mostcommonly) hexagonal to permit it to be gripped easily for turning. Torque is transmitted to the kelly through kelly bushings, which fi t inside the master bushing of the rotary table. The kelly thread is right-handed on the lower end and left-handed on the upper end to permit normal right-hand rotation of the drillstring.

During drilling operations, in every connection, a new pipe is added below the kelly. To avoid premature wear in the kelly’s threads, a kelly saver sub is used between the kelly and the fi rst joint of drillpipe. Kelly cock valves are located on either end of the kelly.

Modern rigs use a topdrive to replace the kelly, kelly bushings, and rotary table. Drillstring rotation is achieved through hydraulic or electric motors. One type of topdrive is shown in Fig. 2

Topdrives are suspended from the hook and can travel up and down the derrick. This will allow drilling to be done with stands of pipes, instead of single joints, which will save considerable time. Comparing with the conventional process, where a new pipe must be added to the drillstring after the length of just one joint has been drilled, using a topdrive system, a new connection will occur only after the length of one stand (two, three, or four pipes) has been drilled.

Range 2 drillpipe is used most commonly. Since each joint of pipe has a unique length, the length of each joint must be measured carefully and recorded to allow a determination of total well depth during drilling operations.

The BHA is the lower section of the drillstring. Even though a BHA may have many different tubulars depending on the complexity of the operation, most of the BHA is composed of drill collars (Fig. 3c). The drill collars are thick-walled, heavy steel tubulars used to apply weight to the bit. The buckling tendency of the relatively thinwalled drillpipe is too great to use it for this purpose. The smaller clearance between the borehole and the drill collars helps to keep the hole straight. Stabilizers (Fig. 4)often are used in the drill collar string to assist in keeping the drill collars centralized. Other types of tubulars used include shock absorbers and drilling jars. In addition, heavyweight drillpipes, a type of drillpipe with thicker walls, are commonly placed on top of the BHA to make the transition between the heavier drill collars and the drillpipes.

AUTHORIZATION FOR EXPENDITURE (AFE)A document used to estimate the cost of drilling a well or installing major equipment facilities in an oil field. The AFE is submitted to management and/or industry partners in the activity for their authorization and approval of the expenditure. The AFE is a budgetary device; when the project is complete, the operator collects invoices of actual work done and compares it to the AFE, should the project come in under budget, he refunds the balance. If the project has cost overruns, the operator submits additional invoices to the participants.

DEVELOPMENT DRILLING– A development well is generally a well drilled as an additional well to the same oil and gas reservoir as other producing wells and not more than one location away from a producing well.

DRILLING MUD –A special mixture of clay, water, and chemical additives pumped down hole through the drill pipe and drill bit. The mud cools the rapidly rotating drill bit; lubricates the drill pipe as it turns in the well bore; carries rock cuttings to the surface; and serves as plaster to prevent the wall of the bore hole from crumbling or collapsing. Drilling mud also provides the weight or hydrostatic head to prevent extraneous fluids to entering the well bore and to control down-hole pressures that might be encountered.

DRY-HOLE COST –The cost of drilling the well; also known asDRILLING COST. Completion costs are in addition to drilling costs but only come due if the well locates producible oil or gas.

FARM OUT AGREEMENT– A form of agreement between oil operators whereby the owner of a lease who is not interested in drilling at the time agrees to assign the lease or a portion of it to another operator who wishes to drill the acreage. The seller may or may not retain an interest (Royalty or production payment) in the production.

FLANGE-UP– Oil-field slang meaning to finish the job. Derived from work with pipe having flanges (rims) on the ends; this pipe is bolted together at those flanges; the pipe can carry liquids once it is “Flanged Up.”

GAS-CUT MUD– Drilling mud aerated or charged with gas from formations down hole. The gas forms bubbles in the drilling fluid. Gas-cut mud may indicate commercial quantities of gas present in the formation.

GAS KICK– Pressure from down hole in excess of that exerted by the weight of the drilling mud, causing loss of circulation. If the gas pressure is not controlled by increasing the mud weight, a kick can violently expel the column of drilling mud resulting in aBlow-out.

INFILL DRILLING –Wells drilled to fill in between established producing wells on a lease to increase production from the lease. SeeDevelopment Drilling.

INTANGIBLE DRILLING COSTS –Expenditures made by an operator for labor, fuel, repairs, hauling and supplies used in drilling and completing a well for production. Intangible drilling costs include also the construction of derricks, tanks, pipelines on the lease, buildings, and preparation of the drill site but does not include the cost of materials or equipment. A rule of thumb is: do the items for which expenditure were made have any salvage value? If not, they qualify under the tax laws as intangible drilling costs.

INTERMEDIATE STRING– SeeCasing. There may be several strings of casing in a well, one inside another. The first casing put in a well is called Surface Pipe which is cemented into place and serves to shut out and protect shallow water formations and also as a foundation or anchor for all subsequent drilling activity. Extremely deep wells will often have an “intermediate string” cemented in place to protect and preserve the well bore as the remaining hole is drilled and completed.

JACK–KNIFE RIG– A mast-type derrick whose supporting legs are hinged at the base. When the rig is to be moved, it is lowered or laid down intact and transported by truck.

JOINT– A length of pipe, casing, or tubing usually from 20 to 30 feet long. On a drilling rig, drill pipe and tubing are lowered into the hole the first time one joint at a time. When pulled from the hole and stacked in the rig, they are usually pulled two, three, or four at a time. These multiple-joint sections are calledStands.

KELLY– The first and sturdiest joint of the drill column; a thick-walled, hollow steel forging with two flat sides and two rounded sides. When fitted into the square hole in the rotary table will rotate the kelly joint and thence the drill column and drill bit. Attached to the top of the kelly is the swivel andmud hose.

KELLY HOSE or MUD HOSE –This is a flexible, steel-reinforced, rubber hose connecting the mud pump with the swivel and kelly joint on the drilling rig. Mud is pumped through the mud hose to the swivel and down through the kelly joint and drill pipe to the drill bit at the bottom of the hole.

LOSS OF CIRCULATION– A condition that exists when drilling mud pumped into the well through the drill pipe does not return to the surface. This serious condition results from the mud being lost in porous formations, a crevice or cavern penetrated by the drill bit.

LOST CIRCULATION MATERIAL –Material that is added to the drilling mud when circulation is lost to assist in plugging the breached area of the well bore.

MUD –A special mixture of clay, water, and chemical additives pumped down hole through the drill pipe and drill bit. The mud cools the rapidly rotating drill bit; lubricates the drill pipe as it turns in the well bore; carries rock cuttings to the surface; and serves as plaster to prevent the wall of the bore hole from crumbling or collapsing. Drilling mud also provides the weight or hydrostatic head to prevent extraneous fluids to entering the well bore and to control down-hole pressures that might be encountered. SeeDrilling Mud and Blow Out.

MUDLOG –A progressive analysis of the well-bore cuttings washed up from the bore hole by the drilling mud. Rock chips are retrieved and examined by the geologist. Modern drilling operations include an electronic evaluation of the mud itself that indicates the presence of hydrocarbons in the mud along with the analysis of the well-bore cuttings.

MUD PITS –SeeRESERVE PITS. Excavations near the rig into which drilling mud is circulated. Mud pumps withdraw the mud from one end of the pit as the circulated mud, bearing rock chips from the bore hole, flows in at the other end. As the mud moves toward the suction line, the cuttings drop out leaving “clean” mud ready for another drip down the well bore.

ONE-THIRD FOR A QUARTER– A term used by independent oil operators who are selling interests in a well they propose to drill. An industry partner who agrees to the one-third for a quarter deal will pay one-third of the cost of the well to some point and receive one-fourth of the well’s net production. When the operator sells three of these one-third for a quarter interests, his industry partners will have paid the cost of drilling the well to casing point.

OPERATOR– A person or entity engaged in the business of exercising direct responsibility and supervision over drilling, completion, operation, maintenance, and production from an oil/gas well.

PAYOUT– The recovery from production of the costs of drilling, completing and equipping a well. Sometimes included in in the costs is a pro-rata share of lease costs.

RAT HOLE –A slanted hole drilled near the well’s bore hole to hold theKellyjoint when not in use. The kelly is unscrewed from the drill string and lowered into the rat hole as a pistol into a scabbard.

RESERVE PIT –SeeMud Pits. An excavation connected to the working mud pits of a drilling well to hold excess or reserve drilling mud; a standby pit containing already-mixed drilling mud for use in an emergency when extra mud is needed.

ROYALTY a.k.a. ROYALTY INTEREST (R.I.)A share of the minerals (oil and gas) produced from a property by the owner of the property. Originally, the right of the king to receive a percentage of the minerals taken from the mines of his realm. (Silver, gold, salt, copper, etc) Entitles the owner to a share of gross proceeds which is free of expense of drilling, completion and production, but having no control over field activities.

SCOUT TICKET– a standard form of information about activities on a drilling location or well. The information includes dates, well’s depth, formations encountered, well logs and tests run. Completion information is briefly described as is the fate of the well, whether put in production or plugged.

SPUD– To start the actual drilling of a well. The first section of the hole is drilled with a large-diameter spudding bit down several hundred feet to accommodate the surface pipe which may be 8 to 20 inches in diameter, depending upon the depth to which the well will ultimately be drilled. The surface pipe is cemented into this hole to protect the surface formations which might contain potable water.

STEP-OUT WELL – a.k.a. Offset Well– A well drilled adjacent to a proven well but located in an unproven area; a well located a “step out” from proven territory in an effort to determine the boundaries of a producing formation. SeeDevelopment Drilling.

TURNKEY CONTRACT– A contract to drill, complete and equip an oil or gas well for a set, predetermined price. The turnkey format is designed to limit the liability of an industry partner to the amount of their capital contribution for drilling and completion.

WORKING INTEREST (W.I.)– The operating interest entitling the holder, at his or its expense, to conduct drilling and production operations on the property and to receive the net revenues from such operations.

Hello, this is Marvin Glotfelty, here with another in NGWA: Industry Connected video. I am a hydrogeologist from Arizona and also a licensed well driller. And a lot of the workshops I’ve given on different drilling techniques, and I’ve talked in this video series previously about dual rotary drilling. There’s a lot of different types. But another couple of the standard types that are pretty universal are direct rotary drilling. There’s direct mud rotary and direct air-rotary. Oh, I want to show you some of the slides here. I’m going to share my screen, show you some information that we can then consider.

First with mud rotary drilling, it of course has advantages and disadvantages, just like all drilling types. So the advantage is, while we’re drilling, we are keeping the borehole full to the brim, full to the land surface, with drilling fluid, also called drilling mud. So what does that do? That stabilizes the borehole. It keeps it from caving in on us, even if it’s loose, unconsolidated material. And we can adjust the properties of this drilling fluid to make sure that that happens. And so that also means that we’re going to collect good, reliable cuttings and other data from the borehole as we go. That’s important.

And we can address problems with, like I said, adjusted drilling fluid. If we have swelling clays, if we have lost circulation where our drilling fluid is seeping into a porous formation. If we have hard drilling and all these different things, if there’s different properties in the formation, which there will be, we can just change the drilling fluid to address them.

So what are the downsides? The downsides is, these drilling fluids are not given away for free, they cost some money. So as long as we can manage that, the overall cost will not be exorbitant, but it is an additional cost because it’s a consumable material that we require during the drilling in mud rotary. And the other thing is we can’t tell where the water table is because the borehole’s full to the brim, not until we’ve completed and isolated a portion of the aquifer from the land surface.

So that’s okay. Here’s a cartoon of the drilling fluid circulation. So you can see that we have a mud pump shown on the back of this truck, and of course the silly colors on the truck are just so we can point out different parts of the rig. I don’t think anybody would ever paint a rig like this. But we can pull the drilling mud up through the mud pump, up through the stand pipe, the Kelly hose, and down to the drill bit. And then as it circulates up the borehole outside of the drill pipe, it’s going to carry the cuttings with it which can be deposited in that mud pit.

Now the mud pit can be below ground as shown, or it can be above ground. Either way, it’s the same difference. So this means that we can control our properties and collect our cuttings and really have a lot of good information as we go. So the big part of this though, is the drilling fluid, being able to control that and change it.

So let’s consider what that drilling fluid does. If we look close there’s in, at the microscopic level, there’s a bunch of platelets that are like little tiny sheets of paper, that are the bentonite clay. They’re not shaped like a little ball, they’re shaped like a little sheet of paper. And so if they’re dispersed, they’re floating around in the fluid mixture, in the water, and there’s a little bit of soda ash and things like that mixed in there with other chemicals perhaps.

But then when they flocculate, they stick together. And that means that the thickness, the viscosity, of the drilling fluid can be higher, even though we didn’t add additional bentonite, that’s cost some money. So that means that we can carry cuttings out of the borehole better and things like that. So that’s, when you hear people talking about the benefits of flocculation of drilling fluid, this is what we’re talking about. It had the property where it can pick it up, so at the same uphole velocity we can carry more cuttings out of the borehole, which is what we want to do.

The other thing that happens with drilling fluid is some of the water seeps out of the drilling mud and leaves behind these clay partlets stuck to the borehole wall, and this is how we form a wall cake. What we like is to have a little bit of water, not too much flow out to their formation, and make a relatively thin and hard wall cake. If we have a thin, hard wall cake, it’ll be very stable and easy to remove later on when we’re going to develop the well and finalize it. If it’s a thick, fluffy wall cake, it’s the opposite. It won’t be as stable and it’ll be more difficult to remove.

So this is a property of the drilling mud, not a property of the formation, so we can control it. And so it’s one of the things that we measure, one of many things. And I’ve got photos of how we measure things. In the upper left is a mud scale, so we’re just measuring the weight of the drilling mud. Usually, of course, water weighs about 8.3 pounds per gallon. Drilling mud might weigh 8.8, maybe nine pounds per gallon. But if we get it real heavy, like 9.4, 9.5 pounds per gallon, unless we’re intending that, and sometimes we are, but unless we’re intending that, that means that what we’re doing is recirculating solids. Fine solids that are the native silts and clays from the formation, and we’re not getting them removed as we recirculate and recirculate this drilling fluid.

That’s bad because that means our wall cake, for one thing, will be getting not as thin and hard as we’d like it. To measure that amount of water that goes out, called filtrate or water loss, that’s what’s shown in the device in the center there with the green frame. That’s a filter press, so we’re just measuring how the drilling fluid responds. And then on the right, you see the young lady with a marsh funnel measuring the viscosity or thickness of the drilling fluid.

So the mud engineer can come to the drilling site, as you see on the lower left, with a pickup truck or some sort of a vehicle to check all these things and some others too. In addition to the weight and viscosity, the mud engineer can look at chemical properties, such as pH, maybe calcium content, chloride content, things like that. They have titration devices and so they can measure these things. They can measure the rheology, the flow properties called plastic viscosity, yield point, gel strength, things like that. So there’s a lot of stuff that’s kind of exotic, but the mud engineer can tell all the folks and the parties involved whether that’s a problem or not.

And then the filtrate, that’s what we’re measuring with the filter press in the middle of the screen. And the solids content can be directly measured with a small Imhoff cone, but also is reflected by how heavy the drilling mud is. So all that stuff is good, that means we have control to some extent, as we interact with mother nature as we’re drilling in the well. And that’s a good thing, so this is a good … That’s why direct mud rotary is a very commonly used approach and it’s very successful.

But there’s other alternatives with almost the same drilling rig, such as direct air-rotary. What if we’re drilling at a place where we want … We’re going to have a stable borehole, no matter whether we have drilling fluid or not, and we’d like to give the advantages of air rotary. So with air rotary, we have a very rapid penetration rate compared to other drilling types, and we have quick bottoms-up time.

So that means, to the geologist, that when we drill cuttings at say a thousand feet, they will be at the land surface almost immediately, very quickly. So we don’t have to wonder how long it’ll take or calculate how long it’ll take for the drilling fluid to bring them to the surface. This happens very fast with compressed air. And we can identify where the water table is as we drill, can’t do that with mud rotary but we can do it air rotary.

And of course the wall cake in this case, it’s only really there because of some soap and because of natural formations, not because of any introduced material. And so it’s thin and basically minimal. So the disadvantages, I’ll show you in a cartoon that’s coming up next why it’s not feasible in some unconsolidated or unstable formations. We have to switch to mud in some cases. Or if the borehole makes water faster than the air compressor can remove it, well, then it keeps the bit from adequately turning on that formation rock. And so it makes it a problem called water logging or flooded out bit where we’ve got too much water coming in. Good problem to have, but it can be a limitation to this type of drilling.

So here’s what the cartoon looks like. Very similar to the mud rotary rig you noticed, except that instead of being … Once we label things are a little bit different. This brown device on the back of our drill rig is now an air compressor instead of a mud pump. So we blow compressed air through our stand pipe and Kelly hose, directly down the bit to remove the cuttings. And they come up and now, instead of we’re calling our discharge line a flow line, we just rename it as the blewie line.

And so notice that the borehole is not full of fluid to the land surface. This is the water table somewhere down here. And so we can fill this with foam, but we can’t fill up with water because we’re drilling with compressed air. So that means that if the upper borehole is wanting to cave in on us, that’s when we might have to switch to mud. But there are a number of things we can do to generally stabilize the bore hole while we drill, and it is a good and efficient way. And of course, I’m showing a rotary tricone drill bit cartoon on the bottom, but we can also use a down-the-hole hammer and have a pneumatic hammer type drilling, which in a hard or brittle formation is really effective.

So we have these different levels of viscosity, even in air-rotary drilling, that we can do. And once we’ve added some foam, some detergent, we’re going to have a little bit of a surfactant surface on that borehole wall. It’s going to slightly stabilizes. We have some help there, and so if it’s a hard rock formation, no problem. But if it’s a unconsolidated formation, depending on the nature, we may or may not be able to drill.

Either way, I really advocate both mud rotary and air rotary for drilling. It’s just a good way to go. I’m sharing my screen there. So with that, that’s a primer, mud and air rotary drilling 101 for you. So I hope you have a great day and we’ll talk to you next time. Thanks.