Swab hoist use thereof in conveying crude oil and natural gas

The invention relates to a swab hoist for use in conveying crude oil and natural gas having a cable drum and a driving motor for the cable drum. It is the object of the invention to provide a swab hoist of improved properties. This is achieved according to the invention by providing a hydraulic drive for the transmission of force from the driving motor to the cable drum. The hydraulic drive consists of a hydraulic pump driven by the driving motor, a hydraulic motor connected to the cable drum and a control means, in particular a pressure-reducing means, all connected to one another by means of pressure lines.

The invention relates to a swab hoist for use in conveying crude or mineral 
oil and natural gas having a cable or rope drum and a driving motor for 
said drum. 
The term swab hoist is used for devices by means of which a piston is 
lowered by means of a cable or rope into a drilled well filled with 
flushing water in the course of swabbing the well and is then hoisted up 
again in order to activate the well. In hoisting up the piston, its rate 
must be adjusted to the rate of the following jet of crude oil or natural 
gas, which means that the hoisting rate of the cable on the drum of the 
swab hoist must increase in proportion to the hoisting level of the piston 
in the well. 
In known swab hoists, the cable or rope drum is driven by means of a chain 
drive and a mechanical clutch by a diesel motor. The adjustment of the 
hoisting rate of the cable to that of the onrushing jet of mineral oil or 
natural gas is difficult and the construction of the chain drive requires 
that the diesel motor be arranged with its axis parallel to the axis of 
the drum. 
It is the object of the invention to avoid these disadvantages and to 
provide a swab hoist of improved properties. 
This object is achieved according to the invention in a swab hoist of the 
type initially mentioned by providing a hydraulic drive for the 
transmission of force from the driving motor to the cable drum. The 
hydraulic drive consists of a hydraulic pump driven by the driving motor, 
a hydraulic motor connected to the cable drum and a control means, in 
particular a pressure-reducing means, all connected to one another by 
means of pressure lines. 
SUMMARY OF THE INVENTION 
By use of a hydraulic drive for the cable drum, the rate of hoisting up the 
piston in the well can be infinitely varied so as to optimally adjust it 
to the onrushing jet of mineral oil or natural gas. Moreover, the position 
of the diesel motor can be selected independently of the position of the 
cable drum, so that if necessary, a diesel motor of higher capacity and 
thus larger dimensions can be used independently of the maximum length of 
the cable drum of 2.5 meters determined by the width of the roadway. By 
omission of the chain drive and the clutch, the entire width of the 
roadway of 2.5 meters can be used for the length of the cable drum, which 
means that more cable can be wound on the drum as compared to known swab 
hoists, so that the use of the swab hoist can be extended to deeper wells. 
According to an embodiment of the invention, the longitudinal axis of the 
driving motor is arranged essentially transversely in relation to the axis 
of the cable drum. This arrangement permits the use of a driving motor of 
any given dimensions, and thus capacity, independently of the length of 
the cable drum. 
It is further of advantage if the hydraulic motor serves as a bearing or 
support for the cable drum. This simplifies construction, on the one hand, 
and allows for a better utilization of the width of the roadway of 2.5 
meters maximum by the length of the drum, on the other hand. 
It is practical to provide a freewheel between the hydraulic motor and the 
cable drum. This allows for a saving in energy. Of particular advantage is 
the provision of a hydraulic motor provided with freewheel. 
According to a preferred embodiment of the invention, the pressure lines 
between the hydraulic pump and the hydraulic motor are provided with at 
least two hydraulic connections for further tools used in conveying 
mineral oil or natural gas, such as, for instance, tubing pliers or the 
like.

DETAILED DESCRIPTION 
FIG. 1 shows the swab hoist 1 comprising a cable or rope drum 2 and a 
driving motor 3 for the cable drum, at use in an oilfield. The rope or 
cable (wire) coming from the cable drum 2 runs over a guide pulley 5 of a 
mobile drilling rig 6 and supports on its free end a piston 7 which is 
lowered after cleaning the well 8 into the open well 8 filled with water, 
with a nonreturn valve provided in the piston 7 permitting the lowering 
into the well. For activation of the well, the piston 7 is then hoisted by 
the swab hoist by means of the cable 4, at this time, the nonreturn valve 
in the piston is closed. The water is removed from the well 8 by means of 
the top side of the piston and the crude oil streams up on the underside 
of the piston, with the pressure of the crude oil on the piston increasing 
in proportion to the hoisting level. The stroke rate of the piston 7 must 
be adjusted to the streaming rate of the crude oil jet as precisely as 
possible. 
FIGS. 2 to 4 are detailed illustrations of the swab hoist according to the 
invention. The cable drum 2 and the diesel driving motor 3 are arranged on 
a common, approximately rectangular frame 10. The width of this frame 10 
and the length of the cable drum 2 arranged transversely in relation to 
the frame amount to a maximum of 2.5 meters, so that the swab hoist can be 
conveyed from one drilling site to another on public roads. The axis of 
the diesel motor 3 extends parallel in relation to the longitudinal 
direction of the frame 10, which means transverse in relation to the axis 
of the cable drum 2, so that a correspondingly high driving capacity can 
be provided, which in a diesel motor of series construction known per se 
is approximately proportional to the length of the diesel motor, i.e. the 
number of cylinders. 
The transmission of force from the driving motor 3 to the cable drum 2 is 
effected by a hydraulic drive which bears the overall reference number 11. 
The hydraulic drive comprises a hydraulic pump 12 driven, i.e. entrained, 
in rotation, by the driving motor 3. The pump 12 is connected via a 
pressure line 13 and a control means 14 to a hydraulic motor 15 assembled 
with the cable drum and driving it. From the hydraulic motor 15, a 
pressure line 16 leads back to the hydraulic pump 12. The hydraulic pump 
and the hydraulic motor are preferably radial piston or axial piston 
construction units and the control means preferably comprises a 
pressure-reducing valve for adjustment of the hydraulic pressure. The 
control means can be actuated manually or be actuated automatically by 
means of a servo control 26 depending upon the pressure exerted on the 
piston. In the pressure lines 13, 16 between the hydraulic pump 12 and the 
hydraulic motor 15, two or more connections 17, 18 can be provided without 
difficulty for connecting further tools, such as tubing pliers or the 
like, used in conveying mineral oil or natural gas. 
FIG. 4 shows that the hydraulic motor 15 simultaneously serves as a bearing 
or support for the cable drum 2. The hydraulic motor 15 is attached to the 
frame 10 by means of a bracket 19. Thus, only one more lateral bearing 20 
is required for supporting the cable drum 2. 
This embodiment is much simpler than a known swab hoist driven by a chain 
drive and requires much less space in the axial direction of the drum. 
This is evident from the juxtaposition of FIGS. 4 and 5, the latter showing 
an analogous sectional view of a known swab hoist. In the known embodiment 
according to FIG. 5, the cable drum 2 is driven by means of a chain drive 
21 via a clutch 22, two more bearings 23, 24 being required in addition to 
the bearing 20. 
As already mentioned, the swab hoist according to the invention can be 
provided with a freewheel in order to save energy. It is particularly 
advantageous to use a hydraulic motor provided with freewheel 25 according 
to FIG. 4. The swab hoist according to the invention can also be driven in 
both rotating directions.