Boring or penetrating the earth – Processes – Boring with specific fluid
Reexamination Certificate
2000-01-03
2001-04-10
Tsay, Frank (Department: 3672)
Boring or penetrating the earth
Processes
Boring with specific fluid
C175S206000, C175S207000
Reexamination Certificate
active
06213227
ABSTRACT:
BACKGROUND OF THE INVENTION
In the drilling of oil and gas wells, a drill bit is used to dig thousands of feet into the crust of the earth. Oilrigs typically employ a derrick that extends above the well drilling platform and that can support joints of drill pipe connected end to end during the drilling operation. As the drill bit is pushed into the earth, additional pipe joints are added to the “string” of drill pipes. The drill string pipes each have an internal, longitudinally extending bore for carrying fluid drilling mud from the well drilling platform to a drill bit supported at the lower or distal end of the drill string.
Drilling mud lubricates the drill bit and carries away well cuttings generated by the drill bit. The cuttings are carried in a return flow stream of drilling mud through the well annulus and back to the well drilling platform at the earth surface. When the drilling mud reaches the surface, it is contaminated with small pieces of shale and rock known as well cuttings or drill cuttings.
In the past, well cuttings have been separated from the reusable drilling mud with commercially available separators that are known as “shale shakers.” Some shale shakers are designed to filter coarse material from the drilling mud while other shale shakers are designed to remove finer particles from the well drilling mud. After separating well cuttings, the drilling mud is returned to a mud pit where it can be supplemented and/or treated prior to transmission back into the well bore via the drill string to repeat the process.
The disposal of the separated shale and cuttings is a complex environmental problem. Drill cuttings contain not only the mud product, which would contaminate the surrounding environment, but also can contain environmentally hazardous oil, especially when drilling in a marine environment.
In the Gulf of Mexico for example, there are hundreds of drilling platforms that drill for oil and gas by drilling into the sea floor. These drilling platforms can be in many hundreds of feet of water. In such a marine environment, the water is typically crystal clear and filled with marine life that cannot tolerate the disposal of drill cuttings waste containing a combination of shale, drilling mud, and oil. Therefore, there is a need for a simple, yet workable solution to the problem of disposing of oil and gas well cuttings in offshore marine and other fragile environments. Traditional methods of cuttings disposal have been dumping, bucket transport, cumbersome conveyor belts, and washing techniques that require large amounts of water. Adding water creates additional problems of added volume and transport problems. Installing conveyors requires major modification to the rig area and involves many installation hours and very high cost.
SUMMARY OF THE INVENTION
The present invention provides an improved method and apparatus for removing drill cuttings from an oil and gas well drilling platform that uses a drill bit supported with an elongated, hollow drill string. Well drilling fluid (typically referred to as drilling mud) travels through the drill string to the drill bit during a digging of a well bore.
The method first includes the step of separating well drilling fluid from the drill cuttings on the drilling platform so that the drilling fluid can be recycled into the well bore during drilling operations. The drill cuttings fall via gravity from solid separators (e.g. shale shakers) into a materials trough. At the materials trough, cuttings are suctioned with an elongated suction line having an intake portion positioned in the materials trough to intake well cuttings as they accumulate.
Each suction line has an intake end that is positioned to suction cuttings from the materials trough. Each suction line communicates with a cuttings collection tank. A third tank (i.e. a vacuum tank) is positioned in between the vacuum means and the two collection tanks that communicate with the two materials collection lines. The third tank has dual inlets, each receiving a flow line from a respective collection tank. Each inlet is valved so that either one of the collection tanks can be shut off from the vacuum means. In this fashion, one collection tank can be filled at a time. The two collection tanks can be sequentially filled without having to shut the vacuum source down.
The drill cuttings are transmitted via a selected one of the suction lines to a selected one of the collection tanks.
A vacuum is formed within the selected collection tank interior using a vacuum means that is in fluid communication with the tank interior.
Liquids (drilling mud residue) and solids (well cuttings) are separated from the vacuum line at the selected collection tank before the liquids and solids can enter the vacuum means.
The vacuum means is powered with an electric motor drive to reach a vacuum of between about 16 and 25 inches of mercury. Each vacuum line is sized to generate speeds of between about 100 and 300 feet per second.
In one embodiment, two hoppers are positioned one above the other so that cuttings can be added to the first upper hopper via the suction line that communicates with the trough and then fed by gravity to the second lower hopper. A valving arrangement maintains vacuum within the interior chamber of at least one hopper at all times. The lower hopper discharges onto a shaker where drilling fluids are separated from drill cuttings. The separated drilling fluids are then saved in a storage tank for recycling into the well bore during drilling operations. The separated drill cuttings are then discharged into a holding tank for storage and transportation.
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