STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to handling well bore tubulars. More particularly, the present invention relates to a system for handling and storing the tubulars as they are inserted into and removed from a well bore.
2. Description of the Related Art
Drilling an oil or gas well involves two main operations: drilling and tripping. To commence the drilling procedure, a drill string composed of drill pipe and terminating with a drill bit is positioned within a drilling rig. A rotating drive mechanism rotates the drill string to bore the drill bit into the ground. The components of the drill string, such as drill collars and drill pipe, are threaded for interconnection. Depending on what type of drive system is being used, the uppermost length of drill pipe in the drill string is connected to the drive mechanism. As the drill bit advances and the top of the drill string approaches the working platform or drill floor of the drilling rig, additional lengths of drill pipe must be added to the drill string in order to advance the drill string further into the ground. Pipe is added by temporarily supporting the top of the drill string using “slips” and disconnecting the drive mechanism from the top of the drill string. The rig's elevating system then lifts a new section of drill pipe into position and the new section of pipe is connected to the top of the drill string. The drive mechanism is then reconnected to the drill string, and drilling operations resume until it is again necessary to add more sections of drill pipe.
Tripping is a necessary but unproductive part of the overall drilling operation, and involves two basic procedures. The first procedure is extracting drill pipe from the well (referred to as “pulling out of hole” mode, or “POH”), and the second is replacing drill pipe in the well (“running in hole” mode, or “RIH”). Tripping may be necessary for several reasons, such as for replacement of worn drill bits, for recovery of damaged drill string components, or for installation of well casing.
In POH mode, the drive mechanism is removed temporarily, the drill string is connected to pipe elevators, and the drill string is pulled partially out of the hole as far as the hoisting mechanism and geometry of the drilling rig will permit. The slips then support the drill string so that the section or sections of the drill pipe exposed above the drill floor may be disconnected or “broken out” and moved away from the well. The elevators then reengage the top of the drill string so that more of the drill string may be pulled out of the hole. This process is repeated until the desired portion of the drill string has been extracted. The procedure for RIH mode is essentially the reverse of that for POH mode.
Whatever type of rig is being used, drilling operations require a convenient storage area for drill pipe that will be either added to or removed from the drill string during drilling or tripping. On many rigs, drill pipe is stored vertically, resting on the drill floor and held at the top in a rack known as a “fingerboard.” This system typically requires a “derrickman” working on a “monkey board” high up in the rig, to manipulate the top of the drill pipe as it is moved in and out of the fingerboard. Other rigs use a “pipe tub”, which is a sloping rack typically located adjacent to and extending below the drill floor. Drill ships and ocean-going drilling platforms often provide for vertical or near-vertical storage of drill pipe in a “Texas deck” located under the drill floor, with access being provided through a large opening in the drill floor.
When sections of drill pipe are being added during drilling or in RIH mode during tripping, the pipe must be transported into position from the pipe storage area. The opposite applies in POH mode during tripping, when pipe removed from the drill string must be transported away from the well and then to the storage area. With most if not all known drilling rigs, these pipe-handling operations cannot be conveniently performed using the rig's main hoist, because the main hoist typically is centered over the well hole, and cannot be moved laterally. The pipe has to be moved laterally using either manual effort or auxiliary machinery. In addition, drilling a well bore requires pipe joints of different size and different maximum tool-end upsets. The placement and sizing of the pipe handling devices must take into account the range of sizes of pipes and their maximum too-end upset so as to contact the pipe body only and not the pipe ends.
It can readily be seen that the efficiency and economy of a well-drilling operation will increase as the amount of time and effort required for handling drill pipe is decreased. Drill pipe is typically manufactured in standard-length “joints.” One common length for a pipe “joint” is 31 feet. Many known rigs handle “stands” made up of two joints (“doubles,” in industry parlance) or three joints (“triples”), and such rigs are typically thought to provide significant operational cost savings over rigs that can handle only single joints of pipe.
Multiple-joint rigs have significant disadvantages, however. To accommodate doubles and triples, they must have taller masts. For instance, if the rig is to handle triples that are 93 feet long, the hoist must be able to rise 100 feet or more above the drill floor and the mast has to be even higher than that. Because of the increased height, the mast will obviously be heavier and therefore more expensive than a shorter mast, even though the maximum hoisting loads that the mast must be designed for might be the same in either case. A taller mast's weight and cost will be even further increased by the need to design it for increased wind loads resulting from the mast's larger lateral profile. A larger mast also requires a larger base to support the higher structure. The larger the size of the base, or “footprint”, the greater the overall cost of the well.
Tall, heavy rigs also have particular drawbacks when used on ocean-going drill platforms or drill ships. Each floating platform or drill ship has its own particular total weight limit, made up of dead weight plus usable load capacity. Every extra pound of rig weight adds to the dead weight and reduces the usable load capacity correspondingly. Extra dead weight not only increases fuel costs for transportation, but also increases expenses for supply ships, which must make more frequent visits because the platform or drill ship has less available load capacity for storage of supplies. Moreover, ocean-going rigs generally need to be even taller than comparable land-based rigs. The additional height is needed compensate for vertical heave of up to 15 feet or more to keep the drill bit working at the bottom of the hole under an essentially constant vertical load when the platform or drill ship moves up or down due to wave action.
Another shortcoming of tall rigs is that the center of gravity of the rig, as well as that of the entire drilling platform, generally rises higher as the mast becomes taller. This is especially true for rigs that have heavy hoisting equipment mounted high in the mast. In stormy conditions, drilling and tripping operations can become impractical, unsafe, or both. This risk increases as the rig's center of gravity rises, such that a tall rig generally will have to be shut down to wait out bad weather sooner than a shorter rig in the same weather. Downtime due to weather conditions, known as “waiting on weather” time (or “WOW” time) in drilling parlance, is extremely expensive. Experience in drilling operations has been that WOW time averages as much as 10% of total rig deployment time. Because the total expense of operating an offshore rig is commonly in the range of $150,000 or more per day, it is readily apparent that the pipe-handling economies made possible by offshore rigs with tall masts can be offset significantly by a corresponding risk of increased WOW time.
Another disadvantage of high mast rigs involves the transportation of mobile rigs from site to site. Typically, portable rigs are loaded onto trucks and moved to different locations. The cost and difficulty of transportation of the rigs can increase as the size of the rig increases. Transporting rigs can also involve travel over narrow roads and bridges and travel in hazardous weather. Thus, large rigs can provide obstacles as to the conditions and locations in which they can be transported.
Additionally, traditional rigs require certain manual intervention in handling the drill pipes at various stages of the drilling process. The process of manually moving pipe or manually operating equipment used to lift and or rotate pipe can be tedious and dangerous. Humans are sometimes required to load pipe onto pipe racks, roll pipe across the racks, pull single pipes to the rig floor, screw the threaded connections together, and stand pipe in combinations of two or three joints into the fingers of the racking board of a conventional derrick.
For all the reasons outlined above, there is a need in the well-drilling industry for a drilling rig: (1) that via automation and other means, provides for a safer work environment than that of a conventional rig; (2) that delivers significant cost savings derived from transporting drill pipe to and from a pipe storage area automatically so as to eliminate or minimize the need for time-costing manual labor; (3) that is light and easily movable to facilitate rig moves; and (4) that can work on narrow well centers and have a very small footprint.
SUMMARY OF THE EMBODIMENTS
In one embodiment, the pipe handling system comprises a pipe magazine, a pipe conveyor system, and a pipe arm for use in automatically handling pipes in conjunction with a drill rig for drilling a well bore. Alternatively, the pipe handling system includes multiple pipe magazines, each with conveyor systems that transport the pipe from one pipe magazine to another until the pipe is delivered to the pipe arm.
In operation, the pipe handling system runs in two modes, RIH mode where pipe is delivered from the magazine and POH mode where pipe is delivered to the magazine.
In the RIH mode, the pipe magazine delivers joints of pipe to the pipe conveyor system. The pipe conveyor system receives the joint of pipe from the magazine and then delivers the joint of pipe to the pipe arm. Clamps on the pipe arm then clamp around the pipe joint and hold it as the pipe arm pivots from a horizontal position to a vertical position. The pipe arm then presents the pipe joint over the well hole center where elevators on the rig latch on to the pipe. Once the elevators latch on to the pipe, the clamps on the pipe arm open and the pipe arm pivots back to its horizontal position.
The POH mode executes the opposite process from the RIH mode. Once the pipe elevators latch on to a pipe joint and the connection is broken from the drill string, the clamps on the pipe arm clamp around the pipe. The elevators then unlatch, release the pipe, and are raised out of the way of the pipe arm. The pipe arm then pivots back down to the horizontal position to deliver the pipe to the pipe conveyor system. “Kickers” on the pipe arm push the pipe onto the pipe conveyor system. The pipe conveyor system then delivers the pipe to the pipe magazine for loading and storage.
The entire system is alternatively automated and sequenced via electronic sensors and signals that measure the location of pipe at specific intervals. The entire system is also alternatively integrated with software and a general-purpose computer to ensure the pipe is passed from one machine to the next as seamlessly as possible.
The embodiments thus provide a pipe handling system for a drilling rig that provides for a safer work environment than that of a conventional rig. The system also delivers significant cost savings derived from transporting drill pipe to and from a pipe storage area automatically so as to eliminate or minimize the need for time-costing manual labor. The pipe handling system is also light and easily movable to facilitate rig moves. Finally, the pipe handling system is part of a drilling rig that can work on narrow well centers and have a very small footprint.
Thus, the embodiments comprise a combination of features and advantages that enable them to overcome various shortcomings or problems associated with prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments and by referring to the accompanying drawings.