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(11) | EP 0 083 961 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Improved jar tool for drill strings |
| (57) A jar tool for use in a drill string for use in dislodging a drill bit or well-tools
trapped in well bores. The tool comprises an outer housing adapted to move longitudinally
with respect to an inner spline mandrell. A piston assembly is acted on by a piston
actuator and hydraulic fluid restricts the movement of the piston assembly and, therefore,
the movement of the mandrell relative to the housing while the piston assembly is
within a narrower portion of a hydraulic cylinder. When the piston assembly reaches
a larger diameter portion of the cylinder, the hydraulic fluid rushes past the piston
assembly which allows a knocker connected to the spline mandrell to collide with the
outer housing. A compression spring returns the piston assembly to its rest position
abutting a shoulder on the outer housing. Provision is made for a valve to be inserted
in the piston assembly so that the system can be temperature compensated and more
desirable hydraulic fluids can be used. |
[0001] Jar tools are extensively used in the oil drilling industry to dislodge drill bits, drill string sections, or other well tools trapped in well bores. An example of such a jar tool is disclosed in U.S. Patent 3,716,109 (Griffiths) entitled ROTARY JAR and owned by the applicant. U.S. Patent 3,716,109 discloses a jar tool which has been in satisfactory use for a number of years.
[0002] Problems have remained with the patented apparatus, however, which have resulted in improvements being made which are the subject of this application.
[0003] U.S. Patent 3,716,109 discloses a jar tool having a spline mandrell and an outer housing, the mandrell and the housing being able to move longitudinally relative to each other. A knocker is connected to the mandrell and it collides with an anvil which is connected to the housing. The collision or impact between them causes the jar on the drill string and it should be appreciated that the impact is violent and the operating conditions under which the tool is used are extreme. This impact is created by the sudden release of entrapped hydraulic fluid which is allowed to rush by a piston assembly travelling from a relatively narrow diameter of a hydraulic cylinder into a relatively larger diameter where the fluid flow past the piston is largely unimpeded.
[0004] To actuate the piston assembly; a piston actuator is used. This piston actuator includes resilient fingers extending from the actuator and towards the piston. The fingers engage a resilient part on the piston assembly when contact is made and provide a "pulling" action on the piston assembly to return it to its home position following the jar. The technique of using these fingers and the necessary costs entailed in using them and complementary parts on the piston assembly is expensive and complicated.
[0005] Further, it was considered desirable to improve the metering system. The use of the metering system, required fluids that, although having viscosity characteristics more constant under different operating temperatures, did not have desirable lubricating qualities. The metering system could be improved by selecting temperature compensable valves within the metering system and pressure relief valves. The metering and pressure relief valves may be used in various combinations to achieve desirable operating characteristics.
[0006] The use of a metering system which allows for the changes in fluid viscosity and density as the temperatures within the drill hole vary, allows for the use of more desirable fluids from a lubriction view point.
[0007] According to one aspect. the invention provides a jar tool for use in a drill string, said jar tool comprising:
A jar tool for use in a drill string, said jar tool comprising:
a mandrell adapted to be connected at one end to an adjacent piece of drill pipe;
a housing surrounding the major portion of said mandrell and defining therein a passageway for drilling fluid and an annular chamber for hydraulic fluid, said annular chamber having first, second and third sections, said first section being of relatively smaller diameter and located adjacent to said second section and said third section being located adjacent said first section;
coupling means between said mandrell and said housing, said coupling means acting to transmit torque between said mandrell and said housing and to allow longitudinal relative movement between said housing and said mandrell between closed and open positions;
respective pairs of abutment faces between said housing and said mandrell to define said closed and open positions of said tool;
a piston assembly mounted within said annular chamber and around said mandrell, said assembly being adapted to move longitudinally relative to said housing and mandrell between said first section and said second section and acting to seal said third section from said first section, said third section being located adjacent said first section on the end of said piston assembly opposed from said second section, said first section being adapted to closely receive said piston assembly;
shoulder means in said annular chamber between said first and third sections defining a rest position for said piston assembly, said piston assembly further defining a metering passageway for hydraulic fluid;
piston actuation means mounted on said mandrell in said third section and acting to actuate and move said piston assembly from said first section to said second section as said tool moves from said closed to open positions;
spring means within said housing acting on said piston assembly to retain said assembly on said shoulder means whereby, as said tool moves from said closed to said open position, said piston actuation means moves said piston assembly from said first section to said second section as said fluid flows through said metering passageway wherein in said second section, said fluid freely flows past said piston allowing said abutment faces on said mandrell and housing to collide and impart shock to said drill string; and wherein said spring means acts to return said piston assembly to said shoulder position when said tool moves from said open to said closed position.
[0008] An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a broken cross-sectional view of the jar tool in its entirety;
Figure 2 is a cross-sectional enlarged view of the area II-II in Figure 1 and depicts the piston of the jar tool just prior to the jar being initiated;
Figure 3 is a cross-sectional enlarged view of the area III-III in Figure 1;
Figure 4 is an enlarged cross-sectional view similar to Figure 2 and depicts the piston of the jar tool in a fully open position;
Figure 5 is a view showing the relief and metering valves in a parallel configuration;
Figure.6 is an enlarged cross-sectional view of the piston showing the relief and pressure valves in a combination parallel and series configuration;
Figure 7 is an enlarged cross-sectional view of the piston showing the relief and pressure valves in a series configuration; and
Figure 8 is an enlarged cross-sectional view of the piston showing only the pressure relief valve configuration.
[0009] Referring now to the drawings, a jar tool is shown generally at 100 in Figure 1. The jar tool 100 comprises a spline mandrell shown generally at 101 and an outer housing shown generally at 102.
[0010] Spline mandrell 101 comprises a threaded socket 103 adapted to receive an adjacent piece of drill pipe (not shown) within the head portion 104 of the spline mandrell 101.
[0011] Hexagonal splines 105 extend longitudinally along spline mandrell 101 to threaded portion 106. A knocker 107 is connected to the threaded portion 106. An impact ring 108 is mounted between knocker 107 and a shoulder 109 on the spline mandrell 101. Knocker 107 has an opposed threaded end 110. A piston mandrell 111 is threadedly connected to knocker 107 at threaded end 110. Knocker 107 also includes O-rings 112, which act as seals between knocker 107, spline mandrell 101 and piston mandrell 111.
[0012] A washpipe 113 is mounted to piston mandrell 111 on threaded connection 114. The washpipe 113 extends longitudinally from the end of piston mandrell 111 and terminates at end 115.
[0013] A piston actuator 116 (see also Figure 2) is connected to washpipe 113 by a threaded connection 117. 0-ring 118 provides a seal between piston mandrell 111 and washpipe 113.
[0014] The outer housing 102 comprises a sealing housing l19 extending from head portion 104 of spline mandrell 101 to a threaded connection 120. Polypak 121 in sealing housing 119 acts as a seal between sealing housing 119 and head portion 104 of spline mandrell 101. A bearing bushing 122 is provided in the sealing housing 119 as well as a cylinder fill plug 123. The fill plug 123 is used for adding hydraulic fluid to the jar tool 100. A spline housing 124 has threads complementary to those at threaded connection 120 to join with sealing housing 119 and further threads 125 located at its opposed end. A knocker housing 126 is connected to spline housing 124 by threads 125. It extends longitudinally from spline housing 124 to threaded connection 127. 0-rings 128 at opposed ends of spline housing 124 act between sealing housing 119 and knocker housing 126, respectively. A cylinder fill plug 129 in knocker housing 126 acts as a port for adding hydraulic fluid to the upper chamber 130 in the jar tool 100.
[0015] A packing sub 131 is connected to knocker housing 126 at threaded connection 127. Packing sub 131 has an opposed threaded connection 132 where it is attached to hydraulic cylinder 133. O-rings 134 at opposite ends of packing sub 131 act as seals between the packing sub 131, knocker housing 126 and hydraulic cylinder 133, respectively.
[0016] Packing sub 131 has an internally formed shoulder 134 and an inner diameter which changes from a maximum area at 135 to a minimum area at 136. Packing sub 131 also includes a further threaded connection 137 where it is connected to an upper gland nut 138.
[0017] Hydraulic cylinder 133 extends from the packing sub 131 to a threaded connection 139 and includes two cylinder fill plugs 129 in its periphery. The inside of hydraulic cylinder 133 is formed into three main areas having diameters 140, 141 and 142 with a transition portion 146 existing between diameters 140 and 141. A shoulder 147 is formed on hydraulic cylinder 133 between the areas having diameters 141 and 142.
[0018] A washpipe housing 148 is connected to hydraulic cylinder 133 at threaded connection 139. It extends longitudinally to threaded connection 149. An O-ring 150 acts as a seal between hydraulic cylinder 133 and washpipe housing 148.
[0019] The various apparatus which are located between the several sections comprising the outer housing 102 and the several sections comprising the spline mandrell 101, respectively, will now be described.
[0020] A knocker gland 156 is mounted between the knocker 107 and packing sub 131 in upper chamber 130. Knocker gland 156 contains four polypak rings 157 which act as seals between the knocker gland 156, knocker housing 126 and piston mandrell lll, respectively.
[0021] o-ring gland 158 is seated against shoulder 159 of packing sub 131. O-ring gland 158 includes four O-rings and back up rings 160 which act between the packing sub 131 and piston mandrell lll. A female junk ring 166 abuts O-ring gland 158 and V-rings 167 are inserted between female junk ring 166 and male junk ring 168. A packing spring 169 is inserted between male junk ring 168 and upper gland nut 138. Upper gland nut 138 is threadedly connected to packing sub 131 at threaded connection 137 as described. It includes a wiper ring 170 acting between the upper gland nut 138 and the piston mandrell lll.
[0022] A second female junk ring 176 is positioned together with V-rings 177 and male junk ring 178 on shoulder 134 of packing sub 131 in the area 136 betweeen the packing sub 131 and piston mandrell 111. One end of a piston return spring 179 abuts male junk ring 178 and the other end of piston return spring 179 is in contact with a piston assembly 180.
[0023] Piston assembly 180 (see also Figure 2) abuts shoulder 147 of hydraulic cylinder 133 in its rest position and is shown more clearly in Figures 2 and 3 in positions displaced from its rest position. There are close tolerances between piston assembly 180, the diameter of the piston mandrell 111 and hydraulic cylinder 133. The piston assembly 180 includes a piston cup 181 and a metering valve 182 which is removable from the piston assembly 180. Metering valve 182 may be replaced with other suitable valves depending on the operating conditions under which the jar is used. Metering valves manufactured by the Lee Company, Arlington, Texas, are particularly appropriate for these applications.
[0024] A filter cage 186 (Figure 2) is installed within the piston assembly 180 to remove contaminants in the hydraulic oil prior to passing through the metering and/or valve system. Piston return spring 179 acts to retain piston assembly 180 against shoulder 147 and also acts to retain the V-rings 177, male junk ,ring 178 and female junk ring 176 (Figure 1) in the position depicted.
[0025] An 0-ring gland 187 is inserted between washpipe housing 148 and washpipe 113. The 0-ring gland 187 contains four O-rings and back up rings 188 which act as seals between the O-ring gland 187, washpipe housing 148 and washpipe 113, respectively.
[0026] A gland nut 189 is connected to washpipe housing 148 by a threaded connection 190. A retaining ring 196 retains the gland nut 189 in the position depicted.
[0027] Referring now to Figure 5, an enlarged view of the piston assembly 180 is shown in which alternative embodiments of the invention are described. In a first alternative embodiment, the piston assembly 180 is provided with a metering valve 182 as well as a pressure relief valve 197 which is inserted in the piston assembly 180 in a configuration parallel to that of the metering valve 182.
[0028] Referring to Figure 6, an enlarged view of the piston assembly 180 is shown in which a second alternative embodiment of the invention is described. In this embodiment, the piston assembly 180 is provided with a metering valve 182 and a pressure relief valve 197 in series on one side of the piston assembly 180 and a pressure relief valve 198 only is provided on the opposite side.
[0029] Referring to Figure 7, an enlarged view of the piston assembly 180 is shown in which a third alternative embodiment of the invention is described. In this embodiment, the piston assembly 180 is provided with a pressure relief valve 197 and a metering valve 182 only.
[0030] Referring now to Figure 8, an enlarged view of the piston assembly 180 is shown in which a fourth alternative embodiment of the invention is described. In this embodiment, the piston assembly 180 is provided with a pressure relief valve 197 only.
[0031] In operation, it will be assumed the jar tool 100 is originally in the position shown in Figure 1. The driller applies a tension force which tends to lift the drill string in the direction indicated by the arrow and, in so doing, force will be applied between the spline mandrell 101 and the outer housing 102. The head portion 104 of the spline mandrell 101 will begin to move away from sealing housing 119 at their abutting faces 199 such that interface 200 becomes exposed. As spline mandrell 101 moves relative to outer housing 102, piston actuator 116 will move leftwardly with piston mandrell 111. When piston actuator 116 contacts piston assembly 180, piston assembly 180 will move away from shoulder 147 under the influence of the piston actuator 116 as seen in Figure 2 since the counter-acting force against piston assembly 180 by piston return spring 179 is relatively smaller than the force from the piston actuator 116. Hydraulic cylinder 133, however, contains hydraulic fluid 201 and the oil cannot pass from the area at diameter 141 of hydraulic cylinder 133 to area 142 without passing through metering valve 182. Accordingly, the relatively slow passage of hydraulic fluid 201 through metering valve 182 restricts the speed at which the spline mandrell 101 and outer housing 102 can move relative to each other until the piston assembly 180 reaches the position shown in Figure 2. This builds up fluid pressure within the area 140 which creates a large potential tensile force between the two ends of the jar tool 100.
[0032] When the piston assembly 180, including piston cup 181 however, passes into area 140 under the continued influence of piston actuator 116, hydraulic fluid 201 is free to pass around the piston assembly 180 and into the areas of diameters 141, 142 with the result that the spline mandrell 101 and outer housing 102 suddenly increase their relative movement enormously. Thus, impact ring 108 on knocker 107 collides violently with the impact surface 202 of spline housing 124. This collision causes the jar or shock to the drill string. At this point, the piston assembly 180 and the piston actuator 116 assume the condition depicted in Figure 3.
[0033] The driller will ordinarily jar the tool several times to free the stuck drill bit or well tool and, therefore, he will now ordinarily lower the drill pipe. Piston assembly 180, under the influence of piston return spring 179, will closely follow in contact with piston actuator 116 until it returns to its rest position against shoulder 147 of hydraulic cylinder 133. Thereafter, the piston actuator will continue to move until it returns to its rest position depicted in Figure 1 before a further jar is initiated.
[0034] Reference is now made to the embodiment of Figure 5 wherein, as earlier described, a metering valve 182 is placed in parallel position with a pressure relief valve 197. In this configuration, the relief valve 197 will allow the hydraulic fluid to release at a certain pressure such that the maximum pull on the jar tool 100 can be limited.
[0035] Reference is made to Figure 6 wherein, as earlier described, a pressure relief valve 198 is placed in parallel with a combination of a pressure relief valve 197 and a metering valve 182. In this configuration, the minimum as well as the maximum pull can be controlled. The low pressure valve 197 will not open until a minimum pressure is reached and, thereafter, pressure relief valve 198 will limit the maximum pressure.
[0036] Reference is made to Figure 7 wherein, as earlier described, a pressure relief valve 197 is placed in series with metering valve 182. In this configuration, the jar will not commence opening until a minimum pressure is reached. The maximum pull on the jar will not, however, be limited.
a mandrell adapted to be connected at one end to an adjacent piece of drill pipe;
a housing surrounding the major portion of said mandrell and defining therein a passageway for drilling fluid and an annular chamber for hydraulic fluid, said annular chamber having first, second and third sections, said first section being of relatively smaller diameter and located adjacent to said second section and said third section being located adjacent said first section;
coupling means between said mandrell and said housing, said coupling means acting to transmit torque between said mandrell and said housing and to allow longitudinal relative movement between said housing and said mandrell between closed and open positions;
respective pairs of abutment faces between said housing and said mandrell to define said closed and open positions of said tool;
a piston assembly mounted within said annular chamber and around said mandrell, said assembly being adapted to move longitudinally relative to said housing and mandrell between said first section and said second section and acting to seal said third section from said first section, said third section being located adjacent said first section on the end of said piston assembly opposed from said second section, said first section being adapted to closely receive said piston assembly;
shoulder means in said annular chamber between said first and third sections defining a rest position for said piston assembly, said piston assembly further defining a metering passageway for hydraulic fluid;
piston actuation means mounted on said mandrell in said third section and acting to actuate and move said piston assembly from said first section to said second section as said tool moves from said closed to open positions;
spring means within said housing acting on said piston assembly to retain said assembly on said shoulder means;
whereby, as said tool moves from said closed to said open position, said piston actuation means moves said piston assembly from said first section to said second section as said fluid flows through said metering passageway wherein in said second section, said fluid freely flows past said piston allowing said abutment faces on said mandrell and housing to collide and impart shock to said drill string; and wherein said spring means acts to return said piston assembly to said shoulder position when said tool moves from said open to said closed position.
a mandrell adapted to be connected at one end to an adjacent piece of drill pipe;
a housing surrounding the major portion of said mandrell and defining therein a passageway for drilling fluid and an annular chamber for hydraulic fluid, said annular chamber having first, second and third sections, said first section being of relatively smaller diameter and located adjacent to said second section and said third section being located adjacent said first section;
coupling means between said mandrell and said housing, said coupling means acting to transmit tongue between said mandrell and said housing and to allow longitudinal relative movement between said housing and said mandrell between closed and open positions;
respective pairs of abutment faces between said housing and said mandrell to define said closed and open positions of said tool;
a piston assembly mounted within said annular chamber and around said mandrell, said assembly being adapted to move longitudinally relative to said housing and mandrell between said first section and said second section and acting to seal said third section from said first section, said third section being located adjacent said first section on the end of said piston assembly opposed from said second section, said first section being adapted to closely receive said piston assembly; shoulder means in said annular chamber between said first and third sections defining a rest position for said piston assembly, said piston assembly further defining a metering passageway for hydraulic fluid;
piston actuation means mounted on said mandrell in said third section and acting to actuate and move said piston assembly from said first section to said second section as said tool moves from said closed to open positions;
spring means within said housing acting on said piston assembly to retain said assembly on said shoulder means;
whereby, as said tool moves from said closed to said open position, said piston actuation means moves said piston assembly from said first section wherein said fluid flows through said metering passageway to said second section wherein said fluid freely flows past said piston allowing said abutment faces on said mandrell and housing to collide and impart shock to said drill string; and wherein said spring means acts to return said piston assembly to said shoulder position when said tool moves from said open to said closed position.
a mandrell adapted to be connected at one end to an adjacent piece of drill pipe;
a housing surrounding the major portion of said mandrell and defining therein a passageway for drilling fluid and an annular chamber for hydraulic fluid, said annular chamber having first, second and third sections, said first section being of relatively smaller diameter and located adjacent to said second section and said third section being located adjacent said first section;
coupling means between said mandrell and said housing, said coupling means acting to transmit torque between said mandrell and said housing and to allow longitudinal relative movement between said housing and said mandrell between closed and open positions;
respective pairs of abutment faces between said housing and said mandrell to define said closed and open positions of said tool;
a piston assembly mounted within said annular chamber and around said mandrell, said assembly being adapted to move longitudinally relative to said housing and mandrell between said first section and said second section and acting to seal said third section from said first section, said third section being located adjacent said first section on the end of said piston assembly opposed from said second section, said first section being adapted to closely receive said piston assembly;
shoulder means in said annular chamber between said first and third sections defining a rest position for said piston assembly, said piston assembly further defining a metering passageway for hydraulic fluid;
a metering valve and a pressure relief valve in said metering passageway whereby said hydraulic fluid will flow through said metering passageway until a predetermined pressure is reached;
piston actuation means mounted on said mandrell in said third section and acting to actuate and move said piston assembly from said first section to said second section as said tool moves from said closed to open positions;
whereby, as said tool moves from said closed to said open position, said piston actuation means moves said piston. assembly from said first section to said second section as said fluid flows through said metering passageway wherein in said second section, said fluid freely flows past said piston assembly allowing said abutment faces on said mandrell and housing to collide and impart shock to said drill string.