Chapter 5 - Drilling and Completion: Onshore Flashcards
Each onshore well is sited within a what?
Drilling Spacing Unit (DSU)
In recent historical practice, a DSU was a what? PAST.
A DSU was a square encompassing 40 or 80 acres, within which only one well was drilled
Why was the DSU constraint established?
The DSU constraint was established in the 1930s in the United States to prevent exploitation of a field with excessive drilling and production rates.
Based on advances in geologic evaluation and drilling technology, what has happened to the DSU?
Tighter spacing is being used, depending on such factors as formation permeability and heterogeneity, and drilling costs. A 10-acre DSU is not uncommon. In addition, operators can now drill as many as two dozen wells in a spoke pattern from a single surface location (pad).
After the legal and environmental issues are settled, the crew goes about preparing the drill site. For an onshore site, this entails the following steps:
1) Land is cleared and leveled, and access roads are built if needed.
2) A water well is drilled if necessary to provide the significant volumes of water used in oil and gas drilling operations.
3) A reserve pit is dug and lined with plastic, to hold rock cuttings and drilling mud generated during the drilling process. In environmentally sensitive areas, the cuttings and mud are trucked off-site instead of being placed in the pit.
Once the lad has been prepared, the crew digs several holes to make way for the rig and main hole. What is a cellar?
A rectangular pit, called a cellar, is dug around the point where drilling will take place. The cellar provides a workspace around the hole and room for auxiliary equipment that will be located below the floor of the pain drilling platform.
For Onshore Drilling, define the main hole.
The crew then drills the main hole, often with a small drill truck rather than the main rig. The first part of the hole is larger in diameter than, and not as deep as, the main portion will be and is lined with a large-diameter conductor pipe.
The first commercial oil well drilled in the United States-in 1859 at Titusville, Pennsylvania-used what type of rig?
Cable Tool Rig
Define Cable Tool Rig
Cable tool rigs drilled all wells in all U.S. fields discovered during the 1800s, as recently as 1953. In simple terms, a cable tool rig repetitively raises and drips a solid steel rod (about 5ft long with a chisel point on its lower end) to pound, rather than drill, a hole into the ground. Progress was very slow with the Cable Tool Rig, about 25ft/day. Also, the inability to control subsurface pressure meant that blowouts were frequent.
Define Rotary Drilling.
Virtually all oil and gas wells-onshore and offshore-are drilled using a system called a rotary drilling rig, which can drill several hundred to several thousand feet per day. This system turns a long length of steel pipe with a sharp bit on its lower end to cut the wellbore.
A basic rotary drilling system consist of four groups of components:
1) Prime Mover (one or more engines)
2) Hoisting equipment
3) Rotating equipment
4) Circulating equipment
In Rotary Drilling, define Prime Mover.
Most rotary rigs use from one to four diesel engines, generating as much as 3,000 horsepower. This prime mover powers the rotating equipment, the hoisting equipment, and the circulating equipment as well as associated lighting, water-pumping, and compression equipment.
In Rotating Drilling, define Hoisting Equipment.
The hoisting equipment raises and lowers what goes into or comes out of the wellbore. The most visible part of the hoisting equipment is the derrick, or mast, a tower like structure up to 200 feet tall. The floor of the derrick is typically built on a framework that raises it 10-30 feet above the ground, to allow space for installation of wellhead equipment.
In Rotating Drilling, of the Hoisting Equipment, define Drawworks.
A strong hoisting line (braided steel wire wound on a fiber or steel core) is spooled around a frame, called the drawworks, on the derrick floor. The prime mover drives the drawworks to wind and unwind the hoisting line.
In Rotating Drilling, of the Hoisting Equipment, define Traveling Block.
From the drawworks, the line goes up to the top of the derrick and attaches to a set of large pulleys (bolting to the derrick) in a block-and-tackle arrangement. Below the block (called the traveling block) is a large hook, from which a swivel hangs. As the drawworks reels in or pays out the hoisting line, the equipment hanging from the hook moves up or down.
In Rotating Drilling, of the Rotating Equipment, define Kelly, Kelly Bushing, & Rotary Table..
A key component-hanging directly from the hook described above-is a very strong pipe called the Kelly. Made of high-grade molybdenum steel, it is a standard length (40 or 54 feet) and has four or six flat sides. Those flat sides allow the kelly’s lower end to fit into (but slide up and down within) a special fitting (the Kelly bushing) that is attached to a circular device on the derrick floor called the rotary table.
In Rotating Drilling, what is the configuration after the Rotary Table.
At the very start of a drilling operation, one section of round drill pipe is screwed tightly to the bottom end of the Kelly. That first section-with a shart drill bit attached to its lower end-is then lowered through the bushing and rotary table until the flat sides of the lower end of the Kelly are seated securely in the Kelly bushing.
What is each drill pipe section called? Specs?
Joint. Made of heat-treated alloy steel, each section can be from 8 to 45 feet long (commonly 30 feet), with an outside diameter ranging from 3 to 5.5 inches.
Define the Drill String.
Collectively, the downhole drill pipe, the bit, and related equipment comprise the drill string.
Special sections can be added to the drill string to serve what functions?
Drill Bit, to add weight, vibration absorption, stabilization, changing drill pipe diameter and threads
How large are Drill Bits?
Typically, range in diameter from about 4 to 26 inches.
What is the most common drill bit?
The most common type is the rotary cone bit, and the general design that uses three rotating cones is called a tricone bit. As the drill string turns, the three cones also rotate, and teeth or buttons on the cones either flake or crush rock at the bottom of the well. Typical rotation speeds range from 50 to 100 rpm.
Touch on tricone bit designs of drill bits.
There are hundreds of different tricone bit designs, generally classified as either milled-teeth or inset bits. The former are more suitability for rock of soft or medium hardness; the latter are more effective on hard rock.
Touch on drill bits and the use of industrial diamonds.
A different drill bit design uses industrial diamonds to shear away the rock. Its metal cutters are studded with chips of diamond (rather than milled teeth or tungsten carbide insert buttons). The diamond drill bit has no moving parts (unlike the rotating cones in the tricone design). It simply turns at the same speed as the drill pipe to which it is attached.
What is a common drill bit diamond configuration?
A common configuration is the polycrystalline diamond compact (PDC) drill bit. Although a PDC bit is expensive, it can last several hundred hours and drill more footage than other types.
Touch on the lubrication and cooling of the drill bit.
The structure that connect a drill bit to the drill string above it contain channels. These enable the flow of drilling mud to lubricate and cool the drill bit and flush rock cuttings from the face of the bit.
Touch on the weight of the drill string pressing down on the drill bit.
The weight of the drill string pressing down on the drill bit is controlled from above the drawworks and is hoisting line, as well as by the number of sections added to the drilling string. Typically, 3,000-10,000 pounds per square inch (psi) of pressure per inch of bit diameter is applied.
Define ‘tripping’ during drilling.Define ‘tripping’ during drilling.
In a time-consuming process called tripping, drilling is halted while the entire drill string is pulled from the wellbore. The drill pipe sections are unscrewed in sequence (sometimes three sections at a time) and are stored temporarily on a special rack on the drilling platform.
Define ‘bit breaker’ in drilling.
A device called a bit breaker is attached to the rotary table to grip and unscrew the bit when it reaches the surface.
Touch on the pressure and temperature changes as we drill deeper.
As a drill bit moves downward, it encounters increasing temperature and pressure. On average, temperature rises by about 1-2F for every 100 feet of depth below the surface.
In drilling define the ‘circulation system’, specifically ‘mud’.
The circulating system consists of a range of equipment that works together to move drilling fluid (called mud) into and out of the hole being drilled. This drilling mud serves several purposes: it cools and lubricates the drill bit; it flushes cuttings and debris away from the face of the drill bit; and it coats the walls of the well to stabilize them.
What is a very critical function of drilling mud.
Another critical function of the circulating system is to help control pressure within the well. The weight of the drilling mud can be adjusted to exert greater pressure on the bottom of the well than the pressure exerted by the fluids (oil, gas, and water) in the surrounding rock. This control is necessary to prevent uncontrolled fluid flow into the well and to prevent the well walls from caving in, trapping equipment downhole.
What common mixtures can drilling mud consist of?
- Water (fresh or saline) and clay (commonly bentonite)
- Oil (diesel, mineral, or synthetic) and clay
- Water with 10% oil, plus clay (emulsion)
- A synthetic organic material and water
Define the ‘annulus’ of a well.
The walls of the well
What happens to drilling mud when it returns to the surface?
At the top of the well, the mud moves into the mud return line and then through a series of devices that remove well cuttings, sand, silt, and even dissolved gases. This “clean” mud goes back into the mud tanks, ready for recirculation into the well, while removed solids are directed into a reserve pit.
What is done with the mud after a well has been drilled?
After a well has been drilled, the mud cannot be reused. If made with freshwater, the mud can be spread on nearby land to fertilize crops. Other types must be moved by truck or barge to an approved disposal site.
What is a blowout during drilling?
A blowout is the uncontrolled flow of oil or gas up the drill string or wellbore annulus. This is triggered when the formation pressure (exerted by gas or oil in the formation around or at the bottom of the well) exceeds the pressure created by the drilling mud. A blowout can seriously injure workers and damage the drilling rig.
What is a blowout preventer?
A BOP (blowout preventer) – designed and built to rigorous standards set by API – typically consists of several stacked components. At the top is an annular preventer – a rubber-and-steel doughnut that can be rapidly compressed hydraulically to close around the equipment of any size or shape still in the well. The aim is to completely seal the annulus.
In a blowout preventer – what is a blind ram?
If the annular preventer cannot stop the flow-and if there is no drill string or other equipment in the wellbore-then a series of large still plates are rapidly pushed together to completely seal off the top of the well. The first of these is called a blind ram and is mounted immediately below the annular preventer.
In a blowout preventer – what is a pipe ram?
If the blind ram is ineffective (or cannot be used), then a pipe ram (mounted below the blind ram) is activated. The pipe ram also is composed of two large blocks of steel, but each has a semicircular cutout in tis mating surfaces. These cutouts allow the ram to close around, but not damage, the drill string (in the same manner as the annular preventer) while simultaneously sealing the annulus.
In a blowout preventer – what is a blind shear ram?
A blind shear ram consists of two sliding stell plates with intersecting blades. As the plates come together, the angled blades cut the drill string, then , the plates in which they are mounted move into place to seal both the drill string and the annulus.
In a blowout preventer – what is a choke manifold?
A final BOP-related component is the choke manifold, a set of flow lines, valves, and chokes connected to the BOP stack. It is routinely used for nonemergency routing of drilling mud from the well to various onsite equipment. However, if the BOP has been activated, it can also be used to relieve well pressure and to circulate heavier drilling mud into the well.
