Abstract:
Disclosed is a method of continuously raising and lowering an oilfield shaft drillstring using a double traveling slips device, wherein two sets of traveling slip mechanism form the two traveling slip mechanisms to form the two traveling slips device, the first set of traveling slip mechanisms and the second set of traveling mechanisms are respectively mounted on a pithead apparatus ( 10 ) to constitute a continuous raising and lowering system. In the process of raising and lowering an oilshaft drill-string, the slips ( 1, 4 ) of each set of traveling slip mechanisms alternately clamp or release the drillstring, ensuring a continuous raising and lowering motion for the drillstring ( 9 ) from beginning to end under the clamping of the slips, and achieving uninterrupted operation. Further disclosed is a double traveling slips device.

Description:
CROSS REFERENCE OF RELATED APPLICATION 
       [0001]    This is a U.S. National Stage under 35 U.S.C. 371 of the International Application PCT/CN2013/084585, filed Sep. 29, 2013, which claims priority under 35 U.S.C. 119(a-d) to CN 201210381451.5, filed Oct. 10, 2012. 
     
    
     BACKGROUND OF THE PRESENT INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention discloses a method for continuously running in and pulling out oil well pipe. The method can be applied to the repairing of wells, gas wells, injection wells, Pressure drilling operation, or other operations. The invention provides a double traveling slips device, which belongs to the technical field of oil field mechanical technology. 
         [0004]    2. Description of Related Arts 
         [0005]    In the technical field of oil field mechanical technology, the conventional snubbing units have both a stationary slip and a traveling slip which are operated in sequence to grip the pipe as it is snubbed into the well. The piston rod of the lifting hydraulic cylinder carries its single traveling slip to realize the reciprocating motion of running in and pulling out of the pipe. When a column is pulling out of a well, the upward stroke of the piston rod of the cylinder is a working stroke, and its downward stroke is an idle stroke; when a pipe is running into a well, the downward stroke of the piston rod of the cylinder is a working stroke, and its upward stroke is an idle stroke. The stroke&#39;s efficiency is less than 50%, along with additional power consumption. The traditional way of solving this problem is to speed up the idle stroke in order to reducing the time of the idle stroke, however, it does not really solve the problem about time wasted in the idle stroke. 
       SUMMARY OF THE PRESENT INVENTION 
       [0006]    The present invention discloses a method for continuously raising and lowering an oil well pipe. This method solves the problem about the waste of power and time in an idle stroke, and improves the efficiency of raising and lowering the oil well pipe. 
         [0007]    Further, the present invention provides a double-traveling slip device for implementing the above mentioned method for continuously raising and lowering the oil well pipe. 
         [0008]    The present invention further discloses a method for continuously raising and lowering an oil well pipe. The technical solutions are as follows: 
         [0009]    A technical solution of the method for continuously raising and lowering the oil pipe comprises following steps of:
       forming a double traveling slips unit by two groups of traveling slip mechanisms, respectively providing a first group traveling slip mechanism and a second group traveling mechanism on a wellhead equipment to form the double traveling slips unit which is a continuous raising and lowering system;   wherein in a process of raising and lowering the oil shaft drillstring, the slips of each set of traveling slip mechanisms alternately clamp or release the drillstring, so as to ensure a continuous raising and lowering motion for the drillstring from beginning to end under clamping of slips, and achieve uninterrupted operation.       
 
         [0012]    For both the first set of traveling slip mechanism and the second set of traveling slip mechanism, stroke of the piston rod of the slip-lifting hydraulic cylinder, the mounting distance between two hydraulic cylinders, the diameters of the cylinders, the diameters of the piston rods, and the mechanical behaviors are the same or equivalent. 
         [0013]    The present invention provides a double traveling slips device comprising a first set of traveling slip mechanism and a second set of traveling slip mechanism. The first set of traveling-slip mechanism comprises a first slip, a first upper crossbeam, two first slip-lifting hydraulic cylinders and a first lower support beam. The first slip is provided on the first upper crossbeam. The first upper crossbeam and the piston rod of the first slip-lifting hydraulic cylinder are fixed together and constitute a first gate-shaped frame lifting mechanism. The two first slip-lifting hydraulic cylinders, linked to the first lower support beam, are fixed on the pup joint of a wellhead equipment. The second set of traveling-slip mechanism comprises a second slip, a second upper crossbeam, two second slip-lifting hydraulic cylinders and a second lower support beam. The second slip is provided on the second upper crossbeam. The second upper crossbeam and the piston rods of the second slip-lifting cylinders are fixed together and constitute a second gate-shaped frame lifting mechanism. The two second slip-lifting hydraulic cylinders are fixed on the pup joint of a wellhead equipment via a second lower support beam. The pipe penetrates the internal holes center of the first slip and the second slip, and then is inserted into a wellhead equipment. The gate-shaped frame of the first set of traveling slip mechanism and the gate-shaped frame of the second set of traveling slip mechanism are crossing on the top and parallel on two sides, and form a revolving-gate-type structure. Another choice is to put the two first-slip-hydraulic cylinders of the first set of traveling-slip mechanism on a lateral of the two second-slips-hydraulic cylinders of the second set of traveling slips mechanism. The two first-slip-hydraulic cylinders and the second-slip-hydraulic cylinders are connected with a pup joint of a wellhead equipment and in parallel with two sides of the gates, and form paralleled rectangles with one outside the other on one vertical plane. 
         [0014]    The above two double-traveling slip mechanisms have the following characteristics: internal holes of both the first slip and the second slip are closed geometrical shapes such as an internal cylinder, an internal cone, an internal prism, or a pyramid. 
         [0015]    The gate-shaped frame of the first set of traveling slip mechanism and the gate-shaped frame of the second set of traveling slip mechanism can also be provided parallel in space to form a cuboid. The first lower support beam and the second lower support beam are fixed on pup joint of a wellhead equipment. The device has characteristics that the characteristic of the double traveling slips device: one side of the internal holes of both the first slip and the second slip are an open-mouth shape on one end. The width on the open-mouth end is greater than the diameter of the pipe. 
         [0016]    In the invention, the slips are fixed on the middle of the upper crossbeam. Two ends of the upper crossbeam are rigidly connected to two piston rods of the slip-lifting hydraulic cylinders. The slip-lifting hydraulic cylinders are fixed on wellhead equipment or on a supporting base platform with rigidity by lower support beam, which ensures lifting and pushing powers thereof. The slips, the upper crossbeam, and two hydraulic cylinders of the upper crossbeam constitute a gate-shaped frame mechanism for raising and lowering the pipe. The two slip-hydraulic cylinders are symmetrically arranged around the central line of the pipe and stand on the wellhead vertically. 
         [0017]    Beneficial effects of the present invention are as follows. 
         [0018]    Utilization of the double traveling slips device is capable of solving the problem of idle stroke produced by a conventional single-traveling slip device, and eliminating the pausing and waiting time during the idle stroke of the piston rod of the cylinder. If the short time that is spent to clip or release a pipe by turns is neglected, we can consider that the upward and downward movements of the pipe in the snubbing process are continuous, and thus the efficiency is almost doubled. The device increases the efficiency of a workover by two times. Idle strokes of the two slips do not take time alone. When one slip is at the idle stroke, the other one is at the working stroke. By this design, the device increases the work time and the efficiency by two times. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a three-dimensional structure schematic view of a double traveling slips device having a closed-mouth type of slips and gate-shaped frames crossing in space of the present invention. 
           [0020]      FIG. 2  is a first top schematic view of the double traveling slips device having a closed-mouth type of slips and gate-shaped frames crossing in space of the present invention. 
           [0021]      FIG. 3  is a first schematic view of the double traveling slips device having a closed-mouth type of slips and gate-shaped frames crossing in space of the present invention. 
           [0022]      FIG. 4  is a second schematic view of the double traveling slips device having a closed-mouth type of slips and gate-shaped frames crossing in space of the present invention. 
           [0023]      FIG. 5  is a second top schematic view of the double traveling slips device having a closed-mouth type of slips and gate-shaped frames crossing in space of the present invention. 
           [0024]      FIG. 6  is a third schematic view of the double traveling slips device having a closed-mouth type of slips and gate-shaped frames crossing in space of the present invention. 
       
    
    
       [0025]    Figure:  1 —first slip;  2 —first upper crossbeam;  3 —first slip-lifting hydraulic cylinder;  4 —second slip;  5 —second upper crossbeam;  6 —second slip-lifting hydraulic cylinder;  7 —first lower support beam;  8 —second support beam;  9 —pipe;  10 —wellhead equipment;  11 —pupjoint;  12 —internal holes on the first slip body;  13 —internal holes on the second slips body. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Example 1 
       [0026]    As shown in  FIG. 1 ,  FIG. 3 ,  FIG. 4 , and  FIG. 6 , a double traveling slips device mainly comprises a first set of traveling slip mechanism and a second set traveling slip mechanism. The first set of traveling slip mechanism comprises a first slip  1 , a first upper crossbeam  2 , two first slip-lifting hydraulic cylinders  3 , and a first lower support beam  7 . The first slip  1  is provided on the first upper crossbeam  2 . Two piston rods of the first slips-lifting hydraulic cylinders  3  are fixed on the first upper crossbeam  2  to constitute a gate-shaped frame lifting mechanism. The two first slip-lifting hydraulic cylinders  3 , are fixed on a pup joint  11  of a wellhead equipment  10  via the first lower support beam  7 . The second set of traveling-slip mechanism comprises a second slips  4 , a second upper crossbeam  5 , two second slip-lifting hydraulic cylinders  6  and a second lower support beam  8 . The second slip  4  is fixed on the second upper crossbeam  5 . The two piston rods of the second slips lifting cylinders  6  are fixed on the second upper crossbeam  5  to constitute a gate-shaped frame lifting mechanism. The two second slip-lifting hydraulic cylinders  6  are fixed on the pup joint  11  of a wellhead equipment  10  via the second lower support beam  8 . 
       Example 2 
       [0027]    As shown in  FIG. 1 ,  FIG. 2 , and  FIG. 3 , the first set of traveling-slip mechanism crosses above the second set of traveling-slip mechanism; In other words, the gate-shaped frame lifting mechanism formed by the two first slip-lifting hydraulic cylinder  3  and the gate-shaped frame lifting mechanism formed by the two second slip-lifting hydraulic cylinders  6  are crossing in space;
       both the second slips  4  and the first slips  1  provided on an up end of the second slips are sleeved on the pipe  9  separately;   both the second lower support beam  8  and the first lower support beam  7  provided on an up end of the second lower support beam  8  are fixed separately on a pup joint  11  of the wellhead equipment  10 . The pipe  9  penetrates internal hole centers  12 ,  13  of the first slips body  1  and the second slip body  4  and then is inserted into the wellhead equipment  10 .       
 
       Example 3 
       [0030]    As shown in  FIG. 4  and  FIG. 5 : in example 1, the gate-shaped frame of the first set of traveling slip mechanism and the gate-shaped frame of the second set of traveling slip mechanism are parallel on each side of the gates to constitute a cuboid structure. In other words, the two first slip-lifting hydraulic cylinders  3  and the two second slip-lifting hydraulic cylinders  6  are parallel. The first slip  1  holds the pipe  9 , while the second slip  4  releases the pipe  9  and is back to the idle stroke position. The first lower support beam  7  and the second lower support beam  8  are fixed on the pup joint  11  of the wellhead equipment  10  separately. 
       Example 4 
       [0031]    As shown in  FIG. 4  and  FIG. 5 , in example 3, the internal hole  12  of the first slips  1  body and the second slips  4  body are both open-mouth shapes on one end. A width on an open-mouth end is more than a diameter of the pipe  9 , which allows the pipe  9  getting into and out from the first slip  1  and the second slip  4  easily. 
       Example 5 
       [0032]    As shown in  FIG. 6 , in example 1, the gate-shaped frame mechanism of the first set of traveling slips and the gate-shaped frame mechanism of the second traveling slips are installed in parallel on one vertical plane. In other words, the two first slip-lifting hydraulic cylinders  3  are provided on a lateral of the two second slip-lifting hydraulic cylinders  6 ; and the two first slip-lifting hydraulic cylinders  3  are parallel with the two second slip-lifting hydraulic cylinders  6 . The first slip  1  is provided on an up end of the second slip  4 . Both the first slip  1  and the second slip  4  are respectively sleeved on the pipe  9 . The first lower support beam  7  and the second lower support beam  8  are connected to the pup joint  11  on the wellhead equipment  10  separately, so as to form the parallel rectangles by sharing the same central axis. 
       Example 6 
       [0033]    In example 2 and example 5, the internal holes  12  of the first slip body and the internal holes  13  of the second slip body are closed geometric shapes such as an internal cylinder, an internal cone, an internal prism, or inner pyramid. 
         [0034]    In example 1 and example 2, the operating movement status of the device mentioned above is as follows. 
         [0035]    (1) Operation of Lifting the Pipe Out of Well: 
         [0036]    At the beginning of the operation, the piston rods of the first slip  1  and the second slip  4  are both at the lowermost positions of the strokes. First, the first slip  1  clips the pipe, while the second slip  4  is at the release position. Then, the piston rod of the first cylinder  3  lifts the first clip  1 , which is clipping the pipe, to reach the uppermost position of its stroke. The preparation for pulling the pipe out from a well is thus over. 
         [0037]    At the beginning, the first slip  1  and the second slip  4  move on an opposite position: after the second slips clips the pipe, the first slips releases it immediately. Then, piston rod of the second slip-lifting hydraulic cylinders  6  lifts the second slips, which is clipping the pipe, to arrive at the middle position of its full stroke and piston rod of the first slip&#39;s cylinder  3  carries the first slip  1  to decrease to the middle position of the full stroke. Now, the first slips is at the end of its idling and reaches its working position on a condition that back and forth motions of the piston rods are at the same speed. 
         [0038]    Then the first slip  1  and the second slip  4  perform the divergent motion: after the first slip  1  clips the pipe, the second slip  4  releases the pipe immediately. The piston rod of cylinder  3  of the first slip, which is clipping the pipe, lifts the first slip  1 , to reach its uppermost position of the full stroke. The piston rod of the second slip-lifting hydraulic cylinders  6  carries the second slip  4  to reach the lowermost position of the full stroke. The second slips is at the end of the idle stroke and the beginning of the working position. Carried by the piston rods of the cylinders, the first slips  1  and the second slips  4  respectively finish a full stroke separately at the same time, and then begin to work on a next full stroke. 
         [0039]    The pipe is lifted by the lifting operations of convergent motion and the divergent motion of the first slips  1  and the second slips  4  alternately. 
         [0040]    When the first slip  1  releases the pipe and is at its downward idle stroke, the second slip  4  clips the pipe and is at its working stroke of lifting the pipe. When the second slip  4  releases the pipe and is at its downward idle stroke, the first slip  1  clips the pipe and is at its working stroke of lifting the pipe. If ignoring the switching time between clipping and releasing, we can consider the lifting of the pipe being continuous. During operation, the pipe is being clipped all the time, and the corresponding piston rods of cylinder of the clipped slip are at the upward working stroke. At the same time, the other slip releases, and its piston rod of the cylinder is at the idle stroke and getting ready for work. The idle stroke of each slip does not take time alone. It is companied by the working stroke of the other. While one slip releases, the other clips the pipe. The pipe is being clipped alternately and is in upward movement continuously. The movement of the pipe has no waiting and pausing time, and is continuous. 
         [0041]    The pipe is clipped by the first slips  1  and the second slips  4  sequentially and is pulled out from a well with the piston rods&#39; motions of the respective slips&#39; cylinders. 
         [0042]    (2) Operation of Lowering the Pipe into Well: 
         [0043]    When the pipe is inserted into a well, the first slip  1  and the second slip  4  are at the lowermost position. Firstly, the second slip  4  clips the pipe; the first slip  1  releases the pipe. When the first slip  1  goes up to the uppermost position of cylinder  3  of the slip, the preparation for operating the pipe down into the well is over. 
         [0044]    The convergent motion of the first slip  1  and the second slip  4  begins at the first. When the first slip  1  clips the pipe, the second slip releases the pipe rapidly. Then piston rod of cylinder  3  of the first slip carries the first slip  1 , which is clipping the pipe, to decrease to the middle position of the full stroke, while the piston rod of the second slip-lifting hydraulic cylinders  6  carries the second slip  4  to rise to the middle position of the full stroke on a condition that the back and forth motions of the piston rod are at the same speed. Then, the first slip  1  and the second slip  4  perform the divergent motion. When the second slip  4  clips the pipe, the first slip  1  releases the pipe immediately. The piston rod of the second slip-lifting hydraulic cylinders  6  carries the second slip  4 , which is clipping the pipe, to decrease to the lowermost position of the full stroke. At the same time, the piston rod of cylinder  3  of the first slip carries the first slip  1  to rise to the uppermost position of its full stroke, the first slip returns to an initial position with the idle stroke. In a similar way, they begin to work on the next full stroke. 
         [0045]    The pipe is clipped by the first slip  1  and the second slip  4  sequentially and is inserted into a well with motions of the piston rods of cylinders of the respective slips. The movement of the pipe while running into a well is the same as that of the pipe while being pulled out. The utilization on the stroke of piston rods from the two kind structures of slips lifting hydraulic cylinders are both 50%. 
         [0046]    Working conditions of the Example 3 and example 4 are as follows. As shown in  FIG. 4  and  FIG. 5 , when operating, not only the first set of traveling slip mechanism and the second set of traveling slip mechanism are running in vertical lifting motion, carried by the slip-lifting hydraulic cylinders, but also are moving in horizontal motions. This performance method allows the slips clip the pipe while moving forwards and releases it while moving backwards. Because of the characteristic of moving away from the working spot, two sets of traveling slip mechanisms do not interfere and block each other. Because the slip bodies of the first slip  1  and the second slip  4  have the open-mouth shapes, the slips can go forward to clip the pipe and go backwards to release the pipe. The best way of installing the two sets of slip mechanisms is to provide the first slip  1 , the first upper crossbeam  2 , the second slip  4  and the second upper crossbeam  5  on the same level with the two gate-shaped frame mechanisms parallel with each other (see  FIG. 4  and  FIG. 5 ). We can see: the motions of the first slip  1  and the second slip  4  are that the trails of the raising motion and the lowering motion are in parallel and are both parallel to the central axis of the pipe  9  clipped by the slips. The two slips begin to perform a convergent motion from the uppermost and lowermost positions, and then begin to perform a divergence motion after passing through the meeting spot. During the motion, the movement direction of two slips is kept unchanged from start to end, and has no turning point before reaching the uppermost and lowermost positions. Two sets of the traveling slip mechanisms do not interfere and block each other. The slips go forward to the central axis of the pipe  9  to clip the pipe during its working stroke. The slips back out from the central axis while releasing the pipe during its idle stroke in returning to its initial working position. In one full stroke, the working stroke and the idle stroke of two sets of traveling slip mechanism are alternating with each other and finish pulling out or running in of the pipe  9  continuously. With this device, the utilization on a stroke of the piston rods of the slip-lifting hydraulic cylinder is 100%.