Wells – Processes – Cleaning or unloading well
Reexamination Certificate
1993-08-24
2001-10-30
Britts, Ramon S. (Department: 3506)
Wells
Processes
Cleaning or unloading well
C166S173000, C166S222000
Reexamination Certificate
active
06308780
ABSTRACT:
FIELD OF THE INVENTION
The offered invention relates to the technical means applicable in removal of sludge, sand and other bridges occuring in operating wells in production of oil, gas or condenate.
DESCRIPTION OF THE PRIOR ART
In the course of well operation, sludge, sand or some other bridges may form in tubing that leads to loss of drilling mud circulation and, hence, to stoppage of product recovery.
Various methods and devices are used for regaining drilling mud circulation.
Known in the art are a method and a device for cleaning tubing. According to a known method a hydromechanical cleaner is run into the well on a pipe string to act on bridge and deposits on tubing walls by direct flow of drilling mud injected through the pipe string and a hydromechanical cleaner. The latter is moved down as the bridge and deposits are washed out and removed mechanically from tubing walls by rotating scraper elements of the hydromechanical cleaner. Products of cleaning are removed from the well by the ascending flow of the drilling mud. A device for embodiment of the known method has a branch pipe with an axial channel and a threaded element in its upper part for connection to a pipe string. A hydro mechanical cleaner is made in the form of scraper elements mounted on its body. The body, in its turn, is installed on the branch pipe concentrical to the latter so as to provide a possibility of rotating under the action of a drive. The body lower portion is furnished with jet nozzles arranged at different angles to the body's longitudinal axis and are hydraulically communicated with a branch pipe axial channel and fulfilling also the function of a drive rotating the body, as the body rotates under the effect of outflow of drilling mud through jet nozzles. There are a mechanism for displacement of the pipe string, a pump unit and a wellhead circulating head. Used in the given known technical solution is a continuous pipe string (U.S. Pat. No. 4,919,204).
Known in the art is a method for regaining drilling mud circulation in a well, comprising running of a hydromechanical cleaner into the well on a pipe string, jetting action on a bridge by direct flow of drilling mud forced through the pipe string and hydromechanical cleaner, motion of the latter as the dridge is washed out, mechanical removal of deposits from well walls by rotating scraper elements of the hydromechanical cleaner and disposal of products of cleaning from the well by; ascending flow of the drilling mud.
A device for embodiment of the known method includes a body with an axial channel and a threaded element in its upper portion to connect a pipe string, and a hydromechanical cleaner in the form of scraper elements installed on the body (USSR patent No. 1,465,545).
A drawback of the known method is its low efficiency, as rotation of scraper elements is effected by rotation of the whole pipe string. The process of removal of washed out bridge particles by the ascending mud flow is also complicated, because the scraper elements block the annulus and resist mud flow.
Known in the art is a method for regaining mud circulation, comprising running into a well of a hydromechanical cleaner on a pipe string, jetting action on wall deposits by direct flow of drilling mud pumped through the pipe string and the hydromechanical cleaner, motion of the latter as the bridge is destroyed and deposits are washed out, mechanical removal of deposits from well walls, breakage of the bridge by rotating scrpaer elements of the hydromechanical cleaner and removal of cleaned products from the well by the ascending flow of the drilling mud. A device for embodiment of the known method includes a hydromechanical cleaner in the form of scraper elements installed on its body, with the latter having its upper portion to connect a pipe string, a mechanism for moving the pipe string, a pump unit and a wellhead circulating head equipped with power slips and a sealing unit. There is means for making a pipe string from separate pipe sections when running it into a well and its breaking into separate sections when the pipe string is withdrawn from the well (U.S. Pat. No. 4,088,191).
A drawback of the known method is its low efficiency as it requires building up a significant pressure drop in mud, acros jet nozzles and rather high hydraulic resistance. Jetting action of the drilling mud on the bridge is not attainable. The bridge can be removed only by mechanical action of scraper elements. Furthermore, rotation of scraper elements is possible only by rotation of the whole pipe string. A device for embodiment of the known method is characterized by a complicated design and does not provide for performance of operations involved in regaining mud circulation under conditions of possible oil or gas formation exposure in removal of bridges, e.g., in tubing because of the design of the wellhead circulating head that does not allow holding of the string from its forcing out in the course of making connections.
Used as a prior art method is a method described in the USSR patent No. 1,465,545, and used as a prior art device is that described by the U.S. Pat. No. 4,088,191.
SUMMARY OF THE INVENTION
It is an object of the offered technical solution to develop an efficient method for regaining drilling mud circulation in a well by removal of sludge, sand and other bridges and deposits and to effect a device for embodiment of said method.
Realization of the offered technical solution makes it possible to enhance the efficiency of the known method due to more complete removal of cleaned products and higher quality of well wall cleaning or cleaning of tubing walls from deposits. Provision is also made to use the offered technical solution in case of deadling, both, with a pipe string formed of separate sections and with a continuous pipe string.
The method for regaining well mud circulation comprises running of a hydromechanical cleaner into a well on a pipe string; jetting action on the bridge by direct flow of drilling mud pumped through the pipe string and the hydromechanical cleaner; motion of the latter as the bridge is washed out; mechanical removal of deposited sludge from well walls by rotating scraper elements of the hydromechanical cleaner; and removal of products of cleaning by ascending flow of mud, whereby scraper elements of the hydromechanical cleaner are rotated to separate deposits from well walls by the ascending flow of drilling mud; and mechanical removal of deposits from well walls is accomplished during running of the hydromechanical cleaner into the well and its lifting out of the well.
The device for regaining well mud circulation comprises a hydromechanical cleaner in the form of scraper elements installed on the cleaner body provided with an axial channel and made so as to connect its top partion to a pipe string; a mechanism for motion of the pipe string; a pump unit for injection of drilling mud into the pipe string; and a wellhead circulating head; the scraper elements of the hydromechanical cleaer are made in the form of at least two cleaning heads with cutting knives on their outer surface installed so as to provide their free rotation in the opposite directions relative to each other in flow of mud.
Accomplishment of the object of the invention is promoted by the fact that a preferred embodiment of the device design comprises cutting knives of an involute profile which has in the upper portion of the cleaning head and the lower portion of the cleaning head cutting edges, and the height of each cleaning head is determined by the relation:
H=D/
2
tg&agr;
where H is the height of the cleaning head;
D is the diameter of the cleaning head; &agr; (is the angle of inclination of the cutting knife relative to the longitudinal axis of the cleaning head (angle of the knife).
In a preferred embodiment, the cleaning heads are installed on the body and supported in bearings, which are located in the end faces of cleaning elements and covered from the outside by means of protective skirts. The protective skirts between the lower end face of the up
Britts Ramon S.
Lilling & Lilling
Tsay Frank S.
LandOfFree
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