Wells – Brushing – scraping – cutting or punching-type cleaners – On tubing or casing
Reexamination Certificate
1998-07-29
2001-01-16
Bagnell, David (Department: 3672)
Wells
Brushing, scraping, cutting or punching-type cleaners
On tubing or casing
C166S311000
Reexamination Certificate
active
06173771
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to apparatus for cleaning well tubular members downhole, and more particularly to a downhole cleaning tool having a rotary milling head with fluid discharge nozzles for cleaning deposits from the tubular bore.
BACKGROUND OF THE INVENTION
Downhole rotating jetting heads have been used to remove deposits from well tubular members. Fluid jetting heads driven by impulse motors, such as offset nozzles or turbines, tend to generate low drive torque. This makes the heads susceptible to stalling by deposit cuttings or by deposit bridges. Further, when the head stalls, no signal is given to surface that the head is not rotating. Further, jetting heads are most efficient when cleaning radially rather than axially, particularly for drilling through deposit bridges. Therefore, multiple runs into a well are often required to fully remove the deposits; first running a positive displacement motor (PDM) with a milling head to remove bridges followed by a run with a radial jetting tool to remove wall deposits.
U.S. Pat. No. 4,705,107 dated Nov. 10, 1987 shows a rotating cutting tool driven by a fluid turbine motor with fluid nozzles to assist in removing deposits from the tubular bore. However, spend fluid used for driving the turbine motor is utilized for the fluid nozzles and a flexible connection is provided between the cutting head and the fluid turbine motor which substantially limits the torque transmitted to the cutter. Further, no blades or cutting elements are provided on the lower end of the cutting tool for penetrating any bridge deposits.
It is desired that a milling head rigidly connected to the motor be provided with milling elements projecting downwardly from the lower end of the head along the axis of rotation for penetrating deposits bridging the tubular bore.
Further, it is desired that fluid jets be provided adjacent the upper end of the milling elements on the milling head to assist in the cleaning of the deposits from the tubular bore after milling with unspent power fluid being available for the fluid jets.
SUMMARY OF THE INVENTION
The present invention is directed to a downhole cleaning tool having a rotating milling head with fluid jet nozzles receiving power fluid. The power fluid is discharged radially from jet nozzles on a combined fluid jetting and milling head (jet/milling head) adjacent milling elements projecting from the head and removes deposits outside the hole drilled by the milling head. The milling elements on the milling head extend along the lower end of the milling head across the axis of rotation for drilling a hole through a deposit bridging the tubular bore and the fluid jet streams discharged from jet nozzles above the milling elements are highly effective in removing any deposits remaining after the milling action. Additional fluid jets may be provided adjacent the lower end of the milling head.
A fluid motor is utilized for rotating the jet/milling head and a major portion of the power fluid is normally directed to the fluid motor for rotating or driving the fluid motor. The remainder of the power fluid flows unimpeded to the jet nozzles for discharge radially at a relatively high velocity against the inner periphery of the adjacent tubular member. The spent fluid which was diverted to the fluid motor for rotation of the jet/milling head rejoins the power fluid downstream of the fluid motor for discharge from the jet nozzles with the power fluid.
Normally, if the jet/milling head is not stalled or milling, the pressure drop through the fluid motor is relatively low (100 psi) and the remainder of the pressure drop across the tool is across the nozzles. In the event the head begins to stall or to mill, the pressure drop across the fluid motor increases to about 400 psi, for example, providing an increase in total tool pressure drop at a constant flow rate. This gives a stall indication at surface and the flow rate may be reduced to acceptable levels. The increased pressure drop across the fluid motor develops significant torque, such as at least about 50 ft.-lbs., which should free the stuck head (followed by a pressure drop across the tool) or allow milling of a bridge.
Coiled tubing is normally used for servicing of wells to remove scale and other downhole deposits on the wells of the well tubular members. The cleaning fluid is injected in the coiled tubing and flows downwardly to the bottom hole assembly or tool which includes the fluid motor and jet/milling head. The power fluid is split between flow through the motor and flow through a bypass port through the rotor thereby giving improved speed control. The two split flows combine downstream of the motor and flow to the jetting nozzles. The amount of bypass flow is controlled by using properly sized orifices in the bypass passage to the motor. In the event the head stalls due to jamming or encountering a bridge, the available pressure drop across the motor (and therefore the torque) is limited by the pressure drop through the bypass port caused by the increased flow through the bypass port after stall.
The jet/milling head of a generally frusto-conical shape includes milling elements or inserts projecting from the outer surface of the milling head including the rounded lower end of the head and are particularly effective in breaking through a bridge across the tubular bore. Radially directed fluid discharge nozzles are positioned on the jet/milling head adjacent the upper ends of the milling elements for the radial discharge of high pressure cleaning fluid directly against the deposits in the tubular member after the milling elements have contacted the deposits. Fluid discharge nozzles are provided on the lower rounded end of the jet/milling head for the downward discharge of high velocity fluid against the deposits prior to engagement of the deposits by the milling elements. The lower nozzles are effective also for the transport of milled cuttings upwardly above the fluid jetting and milling head.
It is an object of the invention to provide a cleaning tool for cleaning deposits from a downhole tubular member which has a combined fluid jetting and milling head with high velocity jet nozzles positioned above projecting milling elements for removing the deposits from the tubular bore of the tubular member.
Another object of the invention is to provide a cleaning tool having a lower fluid jetting and milling head with milling elements projecting from the rounded lower end of the head and fluid discharge nozzles adjacent the lower end of the milling elements for the discharge of high velocity cleaning fluid directly against the deposits prior to engagement of the deposits by the milling elements.
A further object is to provide such a cleaning tool having a fluid motor for rotating the jet/milling head with the power fluid divided between a passage for driving the motor and a bypass passage through the rotor of the fluid motor thereby permitting power or unspent fluid to flow to the jet nozzles.
Other objects, features, and advantages will be apparent from the following specification and drawings.
REFERENCES:
patent: 812361 (1906-02-01), Pickles et al.
patent: 1705451 (1929-03-01), Taricco
patent: 4705107 (1987-11-01), Council et al.
patent: 4919204 (1990-04-01), Baker et al.
Eslinger David M.
Leising Lawrence J.
Bagnell David
Hawkins Jennifer M
Nava Robin C.
Schlumberger Technology Corporation
Vick John E.
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