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21 Cards in this Set
- Front
- Back
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Different types of foreign contracts
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Multinational companies can negotiate several types of contracts with foreign governments. The 3 phases of operations include exploration, exploitation, and production. Exploration involves the drilling of exploratory wells, exploitation involves the development of newly discovered fields, and production occurs during oil and gas production.
-Concession agreement: multinational company is granted an exclusive concession and bears all the costs of exploration, exploitation, and production. The host country is paid bonuses, taxes, and royalties on production. In an alternative concession agreement, the multinational company will still bear the risks and cost of exploration, but the host company will share the cost of exploitation. -Production sharing contract: the multinational company is granted a concession to explore during a specific contract time during which they bear the entire cost of exploration and drilling. If commercial amounts of oil and gas are not found during this time, then the contract is terminated and the company loses the costs of exploration and drilling. If commercial amounts are found, then an agreed upon share of the gross oil and gas production goes to the company to sell and recover the costs of exploration, exploitation, and production. After the costs have been recovered, the remaining oil, called profit oil, is split by an agreed-upon formula between the multinational company and the host government. -Service contract: provides a contractor with a fee for specific services such as exploration and production. -Production contract: A contractor takes over an existing or underdeveloped field and improves production. The contractor is paid a portion of the increased production. |
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AFEs
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Before a well is drilled, an Authority for Expenditure is completed. The form estimates the cost of drilling and completing the well, both as a dry hole and a producer. Costs such as drilling intangibles, completion intangibles, and equipment are listed. Intangibles are salaries, services, and equipment that cannot be salvaged after the well is drilled. The AFE includes the cost of the drilling rig, mud, logging, testing, cementing, casing, well stimulation, prime movers, pumps, tubing, separator, and other services and expenses. It is used to economically evaluate the well before it is drilled. The operator and any other financial contributors to the well approve the AFE. The operator then uses the AFE as a guideline for expenditures.
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Six types of support agreements
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A support agreement can be used to encourage and support drilling a well.
-Dry-hole agreement: A party agrees to make a cash contribution if the well being drilled by another party is a dry hole. In return that party receives the geological and drilling information from that well whether or not the well is a dry hole. -Bottom-hole contribution agreement: A party agrees to make a cash contribution to the party drilling a well to a certain depth in return for geological and drilling information on that well. -Acreage contribution agreement: A party contributes leases or interests to another party who is drilling a well in that area in return for geological and drilling information on that well. -Seismic farmout: paying another company to perform seismic in exchange for information. -farmout: a lease given to another company for drilling in return for a consideration such as a royalty. -buying a lease: |
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types of wells
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-wildcat or exploratory: a well drilled to discover a new oil or gas reservoir. It can be drilled in an area that has no production (new-field exploratory well) or to test a new reservoir rock that has no current production in a producing area (new-pool exploratory well) that is either shallower (shallower pool test) or deeper (deeper pool test) than current production. An exploratory well can also be drilled to significantly extend the limits of a discovered field or to significantly extend the limits of a discovered reservoir (outpost or extension test, or step-out well).
-rank wildcat: a well drilled at least 2 miles away from any known production. -Discovery well: if the well discovers a new field, the size of the field must be determined ASAP. If it is private fee land, it must be determined which leases need to be drilled to maintain the leases and which can be abandoned. If this is an offshore field or in a remote area or foreign country, the size of the field needs to be determined to compute the amount of oil and gas that can be produced (reserves). This will determine if the size of the field is large enough to economically justify further development. -Step-out, delineation, or appraisal wells: determine field size by drilling to the sides of the discovery well. If the oil-water or gas-water contact can be made on all four sides of the discovery well, the area of the field can be determined. -Developmental wells: wells drilled in the known extent of the field. -Infill wells: wells drilled between producing wells in an established field to increase the production rate. |
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drilling rig hoisting systems and elements
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-The hoisting system is used to raise and lower and to suspend equipment in the well. The derrick or mast is the steel tower directly above the well that supports the crown block at the top and provides support for the drillpipe to be stacked vertically as it is pulled from the well. If the tower comes on a tractor-trailer and is jacked up as a unit, it is a mast. All land rigs use masts. On a cantilevered mast rig, the mast is transported in sections, assembled horixontally and then pivoted up to a vertical position using the traveling block and drawworks on the rig. Masts are stabilized by guywires that radiate out from the top of the mast to anchors in the ground. If the tower is erected vertically on the site, it is a derrick. All offshore rigs use derricks. Derricks and masts are commonly 80 to 187' tall to accommodate 2, 3, or 4 joints of vertical drill pipe in a stand. They have a square cross section with 4 vertical legs made of structural steel. The horizontal structural members between the legs are called girts. The diagonal members are braces. An inverted, V-shaped opening in the front of the derrick or mast called the V-door allows drillpipe and casing to be pulled up the pipe ramp onto the drill floor. Derricks and masts are rated for maximum drillpipe load and also for wind load. The base of the mast or derrick is a flat, steel surface called the drill, derrick, or rig floor, where most of the drilling activity occurs. Two substructures made of a steel framework 10 to 30' high can be used to raise the drill floor above the ground. This is done to provide space for wellhead equipment below the drill floor such as the blowout preventers when drilling a deep well.
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the rotating system
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The first type of rotating system is the Kelly. The Kelly is 4 or 6 sided pipe that can be gripped and turned by the rotary table. The rotary table is a circular table in the derrick floor which is connected to the engines so the Kelly can be rotated. The Kelly fits into the Kelly bushing, which fits into the master bushing in the rotary table. All the pieces turn to the right as a unit. The top drive rotating system is used by modern drilling rigs because it is safer and faster. It is a large electrical or hydraulic motor. The top drive is hung from the hook on the traveling block and turns a shaft into which the drillstring is screwed. It moves up and down the derrick or mast while drilling.
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the circulating system
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The circulating system pumps drilling mud in and back out of the well hole. Drilling mud is stored in several mud tanks on the ground beside the rig and is kept mixed by the mud agitator or mud gun. Large pumps driven by the prime movers, called mud hogs, use pistons in cylinders to pump the drilling mud from the mud tank. The mud flows from the pumps through a long rubber tube, the mud hose, and into the swivel. The drilling mud then flows down through the follow, rotating drillstring and jets out through the holes in the drilling bit on the bottom of the well. The drilling mud picks the cuttings off the bottom of the well and flows up the well in the space between the rotating drillsting and well walls. At the top of the well, the mud flows through the BOPs, along the mud return line and on to a series of vibrating screens made of woven screen cloth in a steel frame called the shale shaker. The shale shaker is located on the mud tanks and is designed to separate the coarser well cuttings from the drilling mud. The mud then flows through other solid control devices such as cone-shaped desanders and desilters that centrifuge the mud to remove finer particles. The mud then flows back into the mud tanks to be recirculated down the well.
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BOPs
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BOPs are used to close off the top of the well and control subsurface pressure to prevent blowouts. A typical BOP stack has an annular preventer at the top with one or more rams in line below it. If the annular preventer is not effective, the rams are thrown. Between the rams and the annular preventer are the drilling spools.
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the four major drilling problems
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-fishing: When something breaks or falls down into the well, drilling is suspended and a fishing tool is used to grapple for the fish.
-stuck pipe: When the drillstring is stuck in a well and the drillstring adheres to the well walls due to suction, drilling mud is used to decrease the suction. -lost circulation: If a very porous zone is encountered and an excessive amount of drilling mud is lost, then a control agent is mixed with the drilling mud and is pumped into the well. -abnormal high pressure: this occurs when fluid pressure is higher than hydrostatic pressure at a certain depth. It can be fixed by the driller's method which is when the killmud is already prepared and a second circulation is pumped to replace the original mud with kill mud, and also by the wait-and-weigh method which is when the well is shut in as the kill but id being prepared. |
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steerable downhole assemblies
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A steerable downhole assembly is used to drill deviated wells. The bent sub is a short section of pipe with an angle of 0.5 to 3 degrees in it. The downhole mud or turbine motor is driven by drilling mud flowing down the center of the drillstring. The mud strikes either a spiral shaft or blades in the motor, causing it to turn the drillbit. It can be turned on or off from the rig floor. A diamond or PDC bit is usually used with a downhole mud motor. Stabilizers are subs that centralize the assembly.
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deviated or directional types and their purposes
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-Offshore: An offshore field is best developed using one large production platform with numerous deviated wells that radiate out to the sides.
-Shoreline: An oilfield in very shallow waters can often be more economically developed by deviation drilling from the beach. -Relief: If a well is on fire, a relief well can be drilled a safe distance from the well. The relief well does not have to intersect the wild well in the subsurface but just come close. It drills into the high pressure zone and the pressure is relieved by producing the gas. Then heavy drilling mud is pumped from the relief well through the subsurface rocks and into the wild well to control it. -Sidetracking: Drilling a deviated well out from a straight hole is common if something breaks off and cannot be fished out. The sidetracked well can be drilled around the fish. -Multiple zones: Drilled to test several potential reservoirs. -Inaccessible site: drilled to avoid a poor drilling location |
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horizontal wells and their elements
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A horizontal well is a deviated well that is drilled along the pay zone, or target, parallel to the reservoir. There are 2 build angle sections separated by a tangent section. The entry point is where the well first penetrates the target. The horizontal part of the well is called a lateral or horizontal section. The toe is at the end and the heel is at the start of the lateral. The lateral is drilled out from the motherborg, the original vertical well. Horizontal wells are described by their build angle, the rate of change in degrees per unit length as the well goes from vertical to horizontal. They can be classified as short radius, medium radius, and long radius.
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well logging procedures, types and purposes
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Wells are tested with well logs which are records of rocks and their fluids in the well. Gamma ray logs measure radioactivity in the rocks along the wellbore. A drilling-time log is a record of the rate of drill bit penetration through the rocks. Electrical logs measure resistivity. Neutron logs measure the porosity of rocks in wells.
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drill stem tests
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A drillstem test is a temporary completion of a well, during which pressure on the fluid flowing into the drillstem is continuously measured and recorded on a pressure buildup curve. The pressure records help calculate formation permeability, reservoir fluid pressure, and the extent of any formation damage. Though they can be expensive, they can also save a company money in the long run.
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why wells are cased
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A well is always cased to complete the well. Casing stabilizes the well and prevents the sides from caving into the well, protects freshwater reservoirs from the oil, gas, and saltwater brought up the well during production, and prevents the production from being diluted by waters from other formations in the well.
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why tubing is used
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Tubing is small-diameter pipe which is run into the well to just above the bottom to conduct the water, gas, and oil to the surface. Tubing protects the casing from corrosion by the produced fluids.
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bottom-hole completions
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The bottom of the well is completed with either an open-hole or cased-hole completion. An open-hole completion is made by drilling down to the top of the producing formation, and then casing the well. The well is then drilled through the producing formation, leaving the bottom of the well open. This completion is used primarily in developing a field with a known reservoir and reduces the cost of casing. An open-hole completion cannot be used in formations that might cave into the well because the casing is set before the pay is drilled and cannot be salvaged if the pay is unproductive. In a cased-hole completion, casing is cemented into the producing reservoir and perforations are shot through the casing and cement and into the reservoir.
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hydrocarbon lifting devices
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Gas wells flow to the surfaces by themselves. Some oil wells have enough pressure to produce by themselves for a while, but while eventually need an artificial lifting device. The sucker rod pump is the most common and uses a sucker-rod pump on the bottom of the tubing string, a beam-pumping unit on the surface, and a sucker-rod string that runs down the well to connect them. It also has a traveling valve which lifts the oil and water up the tubing. In gas lift, a compressed, inert gas in injected into the annulus in the well between the casing and the tubing. An electric submersible pump uses an electric motor that drives a centrifugal pump with a series of rotating blades on a shaft on the bottom of the tubing. A hydraulic pump is like a sucker-rod pump except it is driven by hydraulic pressure from a liquid pumped down the well.
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separators
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Most oil wells produce saltwater, gas, and oil at the same time. They are separated in a steel tube called a separator. Two-phase separators separate gases from liquids and three-phase separators separate gas, oil, and water.
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oil and gas measurement and sales
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The amount and quality of gas in a tank is measured by a gauge tape with a brass weight on the end, and also a thief with a stopper that is lowered into the tank. The temperature is measured with a shake-out machine. Turbine meters are also used to measure the volume of oil being transferred. Positive displacement tanks measure the volume of oil in separate, equal tanks. When the oil is transferred from a tank to a pipeline, 3 run tickets are made by a gauger and witnessed by a pumper. A copy goes to the purchaser because it is the legal instrument by which the purchaser is paid.
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sonde
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a logging tool used in a well during a wireline test
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