Classifying – separating – and assorting solids – Precedent preparation of items or materials to facilitate...
Reexamination Certificate
2000-11-28
2003-07-01
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Precedent preparation of items or materials to facilitate...
C209S017000, C209S070000, C209S281000, C175S066000, C175S206000, C175S207000
Reexamination Certificate
active
06585115
ABSTRACT:
SPECIFICATION
Field of the Invention
This is a continuation application of United Kingdom application 9913567.5 filed in the U.K., Jun. 11, 1999, now pending. Priority is claimed to PCT application No. GB 99/04097 filed Dec. 10, 1999.
This invention relates generally to handling of waste materials especially particulate solids. A method of transferring such materials from one location to another, and an apparatus suitable for performing the method, is described hereinafter. The invention finds particular utility in the oil and gas industry for disposal of well or drill cuttings (“hereinafter cuttings”) discharged from the solids control system on a well drilling site.
BACKGROUND OF THE INVENTION
Cuttings are typically pieces of rock, which have been chipped, ground or scraped out of a formation by a drill bit. Various types of drill cutting tools_are in use for this purpose and the invention hereinafter described is not limited to use of any particular type.
The drilling operation is conducted several hundred meters below the operation control point, which means that performance of the drill bit is critical to the operation. The effectiveness of the drill bit during a drilling operation relies upon the continual removal of cuttings; otherwise the drill would rapidly foul up due to accumulation of cuttings. Therefore, the cuttings are normally removed by delivery of a drilling fluid (often referred to as “drilling mud”) down to and around the drill bit in a recirculated manner by use of the drill string and annulus casing well established in the industry.
Accordingly the cuttings are commonly separated from the drilling fluid by devices such as a shale shaker, which captures cuttings and large solids from the drilling fluid during the circulation thereof. Basically, such a device has a sloping, close mesh, screen over which fluid returning from the hole being drilled passes. The screen may be typically of from 200×200 down to 30×30 mesh and is vibrated to facilitate separation of the majority of fluids from the solids. The solids captured on the screen travel down the sloping surface to be collected in the shaker ditch or cuttings trough. It is also desirable to recover as much of the expensive drilling fluids as possible. Therefore, other devices, which play a role in the separation of solids from drilling fluids, include cyclone separators, and centrifuges. The cuttings discharged from the shakers, cyclone's and centrifuges that are collected in the shaker ditch or cuttings trough are still highly contaminated with the drilling fluids and therefore form a slurry or heavy sludge. The slurry or sludge is very difficult to move or otherwise transfer in any conventional manner.
In some cases the cuttings slurry may be discharged directly into a cuttings box where space permits or vacuum collected, which under current practice means that the cuttings are sucked from the cuttings ditch or trough, by an applied vacuum, directly into a cuttings box for transport to an approved disposal site for re-claimation suggested in GB-A-2 286 615. However, in some cases in order to facilitate removal of the cuttings, a collection hopper may be used which allows a particular ground clearance typically of about 4 meters whereby the cuttings are discharged from the hopper by free-fall into open cuttings containers.
It is also proposed there to include another trough for intermediate collection of cuttings. A screw conveyor for lateral displacement of cuttings from beneath the intermediate trough is described. The screw conveyor pushes the cuttings, which fall into it from the trough towards a discharge trap door that opens under the weight of the cuttings to periodically allow the cuttings to fall into the holding tank.
The intermediate trough described remains under the influence of the suction pump to continue delivery of recovered fluid to a recycle system, whilst the screw conveyor below the trough shifts cuttings towards the trap door.
In a more recent operational system a vacuum cuttings hopper is provided including, a helical screw therein on a vertically arranged shaft driven by an overhead motor assists the delivery of the solids to the free-fall outlet for collection below the hopper, The cuttings are further subjected to compression by the helical screw prior to discharge thus extracting and recovering a substantial amount of the remaining fluids in the slurry. The extracted fluid is then withdrawn through a perforated casing around the screw under the action of a pump.
The problems associated with cuttings handling for disposal are familiar to all workers on a drilling installation and include the need for the presence of several storage containers to handle the volumes of cuttings produced and the time demands upon the installation's crane devoted to the shifting of a filled container to substitute an empty container close to the shaker station. This container “shuttling” routine is not only absorbing useful operational time for the crane but also presents additional physical hazards to workers involved in other tasks in close proximity to the cuttings containers. Furthermore, the cuttings recovery equipment and the containers themselves are usually accessed by workers scaling ladders, or scaffolding or the like staging up to heights often approaching 5 or 6 meters or thereabouts in order to open container lids or service the cuttings handling equipment. Of necessity the containers themselves must be sited close to the cuttings shaker station and be accessible by the crane. These factors have an impact on use of deck space, personnel mobility, and other task completion operations around the deck.
Further the filling and relocation of cuttings containers is dictated by the volume of cuttings being produced by the drilling operation in any given period of time. Therefore, it is essential that the cuttings handling apparatus and its methods of operation be capable of handling the volumes required to maintain production.
An object of the present invention is to provide improvements in cuttings handling for disposal and recovery of reusable drilling fluids and muds from the drill cuttings slurry thereby reducing cost of disposal and recycling. A
object fulfilled by aspects of the invention to be described hereinafter is to provide a drill cuttings recovery system of more compact or efficient design.
A still further object is to provide a more flexible disposal method allowing the operator greater degree of freedom in the options for handling the cuttings prior to disposal.
Generally the invention seeks to provide a system and method for handling of cuttings, which offers an improved alternative to current handling systems.
The invention, according to a first aspect, provides a method for handling cuttings that includes providing a system utilizing a screw pump to remove the cuttings from the cuttings trough and disperse them through a piping system to various disposal points.
The invention according to another aspect, provides a method for handling of cuttings, which method comprises providing a vessel adapted to sustain a reduced internal pressure with respect to external ambient atmospheric pressure, and external pumping means, said vessel and pumping means being operationally connected by means including a conduit, collecting cuttings from a drilling fluid/cuttings separation device in said vessel, removing cuttings from said vessel by means of said pumping means through said conduit whilst maintaining a reduced pressure, and selectively delivering removed cuttings by means of pumping to at least one of a variety of disposal points including a cuttings re-injection apparatus, removable transportable cuttings containers including a barge or the like for shipping to a remote disposal site.
According to another aspect of the invention there is provided an apparatus for handling of cuttings, comprising a vessel adapted to sustain a reduced internal pressure with respect to external ambient atmospheric pressure, and further provide a means for extracting fluids, the ap
Hollier Glynn M.
Reddoch Jeffrey
Baker Hughes Incorporated
Madan Mossman & Sriram P.C.
Miller Jonathan R
Walsh Donald P.
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