Fluid Powered drilling jar

A hydraulic drill string jar is powered and actuated by drilling fluid pressure controlled from the earth surface. By selective manipulation of drilling fluid flow, the jar can be conditioned to operate in drilling mode to avoid activation of the jars while normal drilling and fluid flow activities take place. By different fluid flow manipulations, the jar is conditioned to operate in the jarring mode. In the jarring mode, the jars will axially shock the drill string each time the flow rate is reduced below a preselected amount and then increased to a higher preselected amount.

DETAILED DESCRIPTION OF DRAWINGS 
FIG. 1A is a side view of the preferred embodiment of this invention. Body 
1 serves as a length of drill string. Upper terminal 1a has a tool joint 
connection 1g for fluid tight attachment to an upwardly continuing drill 
string. The drilling fluid flowing down the drill string continues down 
bore 1e into the body. The upper terminal is threadedly connected to the 
outer body tube 1b. The outer body tube is, in turn, threadedly connected 
to lower body terminal 1h. The lower terminal has bore 1f to conduct 
drilling fluid from the body to a downwardly continuing drill string. The 
lower terminal has tool joint 1d to connect the body with fluid tightness 
to the drill string. A wash pipe 1c is threadedly connected for fluid 
tightness to the upper terminal and is a continuation of bore 1e. The wash 
pipe is threadedly connected, fluid tight, to valve locator 3. Valve 
locator 3 continues downward to the upper end of the lower body terminal 
1h. Locator 3 has opening 3a to accomodate and position remote control 
selector valve 4 and permit fluid flow around the valve. Orifice 4a is 
secured in the lower end of opening 3a and fluid flowing through the 
washpipe goes through the orifice when poppet 4b is above the orifice. 
Poppet 4b, part of the control selector valve, 
In the annular opening 1p between the body tube bore and the washpipe, mass 
piston 2 is situated for limited axial movement therein. The mass piston 
is heavy and gravity biased toward the first, or lower, end of opening 1p. 
If added biase is needed, a spring such as spring 8 of FIG. 2 can be added 
around washpipe 1c between abutting element 1m and mass piston 2. In FIG. 
2 the mass piston is shown to have an annular opening to protect and allow 
spring length clearance. 
Pilot valve 5 has annular poppet 5b situated to occlude the annular orifice 
3b. The annular orifice controls fluid communication from ports 3f, which 
open into opening 3a, to the mass piston face 2b through channels 3c. 
Channels 3c are distributed about, and extend generally parallel the body 
centerline. 
Pilot valve 5 includes bias spring 5c which is situated to urge the annular 
valve piston 5a upward to occlude orifice 3b, with poppet 5b. 
The pilot valve piston 5a has a pilot by-pass clearance 5e down which fluid 
can flow. When pressure at ports 3f exceed a preselected amount, the 
pressure acting on the piston face 5f will urge the pilot valve downward, 
overcoming spring 5c to open orifice 3b. The area of poppet 5b, once the 
poppet moves, becomes an added piston area and the pilot valve then moves 
rapidly downward. When the pilot valve moves near the lower stroke limit, 
piston face 5f uncovers by-pass channel 3d and fluid can flow from ports 
3f through channel 3d and to the central bore 3g and downward to the 
continuing drill string. Considerable fluid pressure energy builds up in 
the upwardly continuing drill string before the pilot valve moves. When 
the pilot valve starts motion, then opens rapidly, fluid is admitted to 
the mass piston face 2b and the mass moves rapidly upward. During upward 
movement of the mass, fluid is displaced from the upper end of the opening 
through vent channels 1k to the well annulus. 
Abutting element 1m is removably attached to the top terminal by cap screws 
(not shown) and has holes forming a continuation of vent channels 1k. Mass 
piston 2 has removable abutting element 2a fastened by cap screws 2c. When 
the abutting elements contact, the mass is suddenly stopped, delivering a 
shock blow to the body and hence the drill string. 
When the abutting elements are in contact the vent holes and channels are 
closed. Fluid under pressure can by-pass the cylindrical surfaces of the 
mass and stopping vent flow avoids consequent erosion. 
FIG. 1A shows the drill string before the jarring activity is initiated. 
The normal drilling activity may be carried out with full drilling fluid 
flow. The remote control selector valve is open and drilling fluid flows 
from the upwardly continuing drill string through bore 1e, through the 
bore of the washpipe 1c, through opening 3a, through orifice 4a, down bore 
1f and into the downwardly continuing drill string. This fluid route 
comprises a first communication means. 
A second fluid communication means includes inlet 1e, the bore of washpipe 
1c, opening 3a, ports 3f, channels 3c, and the lower, or first, end of the 
annular opening between the bore of body tube 1b and washpipe 1c. 
A third communication means includes inlet 1e, the bore of washpipe 1c, 
opening 3a, ports 3f, pilot by-pass clearance 5e, port 3d, bore 3g and 
outlet 1f. 
Ideally, mass piston 2 will have completed an impact excursion before 
by-pass channel 3d opens. Pilot valve vent ports 3e are sized to delay the 
rate of movement of the pilot valve 5. This delay means is adjustable by 
selection of the sizes of holes 3e in replaceable transition block 1n. 
The remote control selector valve has retained the poppet 4b above orifice 
4a, has disabled the jar, for normal drilling, and selector valve 4 has 
functioned as a disabler means. The pilot valve annular piston will not 
move downward under the influence of normal drilling fluid flow with the 
poppet 4b open. 
FIG. 1B shows the apparatus of FIG. 1A after drilling fluid pressure 
manipulations have placed the remote control selector valve 4 in the 
jarring mode. Poppet 4b has moved down to occlude the orifice 4a. Before 
pilot valve 5 moved down to the position shown, the downward movement was 
slowed by restriction of vent 3e so that mass piston 2 reached the upper 
limit of movement, and delivered a jarring action before the pilot piston 
surface 5f opened channel 3d. 
When channel 3d opened, fluid could flow through the jar and to the 
downwardly continuing drill string. To re-activate the jarring action 
repeatedly, fluid flow can be reduced enough to allow the pilot valve to 
move up to close orifice 3b. Some fluid flow will be maintained so that 
poppet 4b will not move up to reset the remote control selector valve from 
jarring mode when fluid flow is again increased. With the system still in 
the jarring mode, but the orifice 3b closed, the mass piston will move 
down by gravity force while fluid in opening 1p by-passes the piston by 
way of radial clearances. 
When the mass piston is at the upper, or second, end of opening 1p, element 
2a closes the channels to vent ports 1k. 
The remote control selector valve preferred for control of apparatus of 
this invention is responsive to fluid flow. When used in a drill string 
assembly, fluid flow is produced by pressure applied at the earth surface. 
The jarring mechanism is actuated by fluid pressure and powered by fluid 
volume under pressure. When viewed at the earth surface where fluid flow 
manipulations are controlled, fluid flow is proportional to pressure, and 
flow resistance inherent in the down hole apparatus of this invention will 
also appear as added pressure. From the earth surface, fluid flow and 
fluid pressure can be expressed interchangably and no ambiguity exists. 
Apparatus of this invention is classified as a drilling jar in deference to 
oil field practice but drilling jars are commonly used on pipe strings for 
other purposes, such as fishing and workover. The drilling jar definition 
should not be viewed in a limiting sense. 
FIG. 2 represents an apparatus functionally identical to the apparatus of 
FIG. 1A, but oriented to deliver a jarring impact downward instead of 
upward. 
The principal change is the addition of spring 8 to bias the mass piston 
upward to overcome the force of gravity. To accomodate the spring in 
minimum structure, bore 2d has been added to the mass piston. 
Valve locator 7 differs in configuration to allow channel 7g to fluidly 
communicate the low pressure end of the pilot valve 5, by way of ports 7e, 
to bore 3g, downstream of the orifice 4a. When the pilot valve 5 opens, 
by-pass port 7d is similarly in communication with bore 3g. 
The first fluid communication means includes inlet 1e, opening 7a, bore 3g, 
the bore of washpipe 1c and outlet 1f. The second fluid communication 
means now includes inlet 1e, opening 7a, port 7f, channels 7c and the 
first end of the mass piston opening. The third fluid communication means 
now includes inlet 1e,. opening 7a, port 7f, pilot by-pass clearance 5e, 
by-pass channel 7d, channel 7g, bore 38, the bore of wash 
pipe 1c and outlet 1f. 
The positions of the various elements, once actuated, have been described 
in detail relative to FIG. 1B and are not repeated for FIG. 2. 
In FIG. 2, the mass piston 2 has to be lifted back to the starting position 
after a hammer blow and spring 8 is provided to drive the piston upward. 
By manipulation of the drilling fluid flow controls, at the earth surface, 
the remote control selector valve 4 can be actuated to put the jar into 
action The preferred characteristics of fluid flow manipulation to 
activate the jar involves effectively stopping drilling fluid flow and 
restarting fluid flow. By preference, the remote control selector valve 
will change from one mode to the other each time the drilling fluid flow 
is effectively stopped and restarted. By selection of closing bias force, 
the pilot valve can be caused to function at a fluid flow rate higher than 
the low flow rate required to activate the control valve. To repeatedly 
jar the drill string, then drilling fluid flow can be decreased, while the 
selector valve is in the jarring mode, until the pilot valve allows the 
mass to return to the first end of the opening, then increasing fluid flow 
until the pilot valve opens to drive the mass against the abutting 
surfaces to jar the string. The axial strain can be held on the drill 
string as jarring repeatedly takes place. 
If drilling fluid flow drops low enough to cause the selector valve to 
change mode, the pressure visible on surface pressure indicators will 
reveal the change. A decrease, followed by an increase, in fluid flow rate 
will cause the selector valve to again change mode back to the preferred 
status. The fluid flow can again be increased to exercise the preferred 
mode. 
The mass piston may be regarded as a hammer and limited movement in the 
opening implies means to stop the movement of the mass, or hammer. The 
hammer stopping means can be defined as an anvil and attached, as is the 
opening, to the body. 
It is practical to use a plurality of jars of this invention, in series, in 
one drill string assembly. Each jar can be assembled to actuate at a 
drilling fluid pressure independently of other jars. As drilling fluid 
pressure is increased, they will actuate, or trigger, in succession while 
in the mode for jarring. All jars in one drill string assembly will have 
to be in the same mode, drilling or jarring, when sent downhole. All jars 
will then change mode at the same time and retain synchronization. 
In addition to serial assembly of jars in the drill string, jars can be 
mixed in terms of upward and downward jarring direction. Additionally, 
jars of this invention can be actuated below stuck points not subject to 
axial manipulation of the drill string. A series of jarring actions both 
above and below the stuck point, if above the bit, applied in both up and 
down directions can be expected to yield the best possible combination to 
loosen stuck strings. 
From the foregoing,.it will be seen that this invention is one well adapted 
to attain all of the ends and objects hereinabove set forth, together with 
other advantages which are obvious and which are inherent to the method 
and apparatus 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
As many possible embodiments may be made of the apparatus and method of 
this invention without departing from the scope thereof, it is to be 
understood that all matter herein set forth or shown in the accompanying 
drawings is to be interpreted as illustrative and not in a limiting sense.