US 3804182 A
Seismic energy for geophysical prospecting is provided by drilling a shot-hole to a selected depth using a cutting tool such as a hydraulic jet nozzle or a downhole drill motor attached to a non-rotating, continuous flexible spooled conduit; pumping a liquid explosive and detonating means actuatable from the earth surface down the conduit, through the cutting tool and into the shot-hole; withdrawing the conduit and cutting tool from the shot-hole; and detonating the explosive.
Description (OCR text may contain errors)
United States Patent [191 Adair et al. I
[ Apr. 16, 1974 METHOD OF PLACING EXPLOSIVE CHARGES  Inventors: James C. Adair, Bellaire; Robert R.
Luke, Houston, both of Tex.
 Assignee: Shell Oil Company, Houston, Tex.
 Filed: July 27, 1972  App]. No.: 275,857
 US. Cl 175/1, 175/67, 175/237 [51'] Int. Cl E21b 7/18  Field of Search 102/20, 21, 21.8; 181/.5 XC; 175/1, 57, 67, 122, 162, 220, 237, 317
.  References Cited UNITED STATES PATENTS 2,880,966 4/1959 Blount 1 75/1 2,883,154 4/1959 Daniel 3,075,463 l/l963 Eilers et al 102/21 X 3,100,542 8/1963 Stark 175/1 3,590,738 7/1971 Holzman.... 102/21 3,702,635 11/1972 Farr ,175/1 X Primary Examiner-David H. Brown Attorney, Agent, or Firm-Tom M. Moran; Harold L. Denkler  ABSTRACT Seismic energy for geophysical prospecting is provided by drilling ashot-hole to a selected depth using a cutting tool such as a hydraulic jet nozzle or a downhole drill motor attachedto a non-rotating, continuous flexible spooled conduit; pumping a liquid explosive and detonating means actuatable from the earth surface down the conduit,,through the cutting tool and into the shot-hole; withdrawing the conduit and cutting tool from the shot-hole; and detonating the explosive.
5 Claims, 4 Drawing Figures METHOD PLACING EXPLOSIVE CHARGES BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates generally to the art of forming and loading shot-holes; and, more particularly, to a method of forming a shot-hole and loading it with an explosive charge to be used as a source of seismic energy for geophysical prospecting.
2. Description of the Prior Art In acquiring seismic data for geophysical prospecting, it is a common practice to detonate an explosive charge at a subsurface location in a shot-hole. The explosion creates shock waves which travel downwardly through the earth. Portions of the shock waves are reflected back towards the earths surface as the waves intersect planes of contact between various earth formations. These reflected waves are detected by sensing apparatus atthe surface. The recorded waves may subsequently be analyzed to provide information as to the subsurface geological structure of the area tested.
A significant part of the cost of acquiring such seise mic data is expended in drilling shot-holes and loading these holes with explosive. For example, the cost of a typical seismic crew may be on the order of $100,000 per month. It is common for such a crew to spend as much as 45 percent of their time in the field drilling and loading shot-holes. Therefore, it can be seen that any substantial savings in the time required to provide loaded shot-holes can result in a significant decrease in the cost of acquiring seismic information.
To this end, a number .of methods have been sug gested for loading shot-holes through in-place drill pipe. This has the advantage of reducing loading time by eliminating the need for pulling the shot-hole dril ling equipment from the hole before loading the hole with an explosive charge. It also has the advantage of substantially eliminating the chances of shot-hole cavein prior to loading. Such cave-ins are often encountered when placing the charge through loose, unconsolidated soils such as sandy or muddy soils.
For example, US. Pat. No. 3,590,738 .teaches sealing the lower end of a rigid drill pipe with a removable cover; driving the pipe toa desired depth in an earth formation, preferably with sonic means; and lowering an explosive charge into the hole on a detonation wire which is attached at a point just above the top of the pipe to support means that is just large enough to pass through the pipe with enough frictional engagement to retain the end of the wire above the surface of the ground as the pipe is pulled up over the wire and support means. The pipe is then pulled away from the removable bottom cover and extracted from the hole. A somewhat similar system is disclosed by US. Pat. No. 3,434,549 which teaches using a mechanical cutting element with a releasable latch means through which an explosive may be lowered into the borehole.
Both of these prior art methods have the disadvantage of requiring a number of time consuming manipulative steps at the earth surface as each step of the respective processes is carried out. That is, workmen at the surface are required to prepare the shot-hole drilling equipment for drilling the hole, drill the hole, disassemble the drilling equipment from the pipe string at the surface, lower the charge into the pipe, and then raise the pipe from the hole. If the hole is drilled deeper than the lift height of whatever lifting mechanism is used at the surface, it is necessary to uncouple and rack one or more joints of drill pipe as the pipe is extracted from the hole.
SUMMARY OF THE INVENTION We have now discovered a method for drilling and loading shot-holes which comprises the steps of attaching an earth boring means to a spooled flexible conduit at least as long as the desired depth of the shot-hole; ad-
vancing the earth boring means and the attached flexible conduit into the earth to form the shot-hole; pump- The earth boring means may be any boring means A suitable for drilling a hole using a non-rotating string of pipe. For example, it may be a mechanically cutting bit rotated by a down-hole motor, such as a down-hole mud turbine driven by fluid pumped from the surface through the drill pipe. Or the hole may be drilled by reverse circulation where loose material, such as mud or sand, is sucked from the'hole through the drill pipe by forcing liquid or air down a separate conduit to a point above a rotating bit and then up the drill pipe to carry debris from the hole. In a preferred embodiment, the shot-hole is drilled using a hydraulic jet bit of a type which bores the shot-hole through the action of high pressure fluid impinging upon the earth formation to be cut. The bit may cut solely by hydraulic jet means or may be combined with mechanical cutting elements suitable for cutting formations which are highly resistant to the jet action of the bit,
Detonator means for igniting the liquid explosive can be pumped into the well through the flexible drill pipe. Preferably the pump means which delivers fluid to the bit or other cutting element is operatively connected to a manifold means through which both the'liquid explosive and the detonator may be inserted into the stream of flowing fluid by appropriately adjusting one or more valves in the manifold means.
In a preferred embodiment, a hydraulic jet bit is provided with a frangible plug which is blown from the bit to provide a passage sufficiently large for the detonator means to be emitted from the bit upon the application of sufficient pressure drop across the frangible plug. This pressure drop may be achieved by temporarily plugging the nozzles of the hydraulic jet bit as by inserting a plugging means into the drill pipe through the flow manifold and pumping the plug means down the drill pipe into contact with thenozzles. In one embodiment the plug means comprise fracture sealing balls which seal off the nozzles of the bit thereby increasing the pressure drop across the plug means.
The detonator can be one which is remotely actuatable, e.g., one which is actuated via detonation wires which couple it to .a detonation controller at the surface. The detonator is preferably pumpedinto the well through the spooled drill pipe. The upper end of the detonator wire is preferably attached to a means of relatively small surfacearea for frictionally engaging the interior of the pipe string to retain the upper end of the wire above the earth surface as the pipe is withdrawn from the shot-hole in a manner similar to that taught by US. Pat. No. 3,590,738.
It is advantageous in some cases to enlarge the lower end of the shot-hole prior to inserting the liquid explosive into the shot-hole in order to provide a less linear and more point-shaped shot. In many formationsthis may be achieved by circulating fluid through the hydraulic jet bit while maintaining the bit at a constant depth at the bottom of the shot-hole to wash out an enlarged hole. In other formations it may be' necessary to provide remotely actuatable reaming means for enlarging the hole. One method for doing this is to direct the hole sealed by the frangible plug means of the hydraulic jet bit at an angle such that when the plug is removed a jet of fluid'will emerge from the bit at such an angle that it contacts the sidewall of the shot-hole. In this way, the shot-hole may be enlarged prior to placement of the explosive charge.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view', partially in cross-section, of a preferred apparatus for use in practicing the method of this invention.
FIG. 2is a .vertical cross-section of a hydraulic jet nozzle of a type which may be effectively used in the DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, we see a shot-hole drilling apparatus which may be mounted on a truck 11. The apparatus comprises a spooled, continuous flexible conduit 12 such as ,a hose or a flexible metallic drill pipe. An earth boring means such as hydraulic jet nozzles 13 is attached to the conduit 12. .The conduit 12 is spooled on a drum 14 which is coupled to suitable means (not shown) for spooling and unspooling the conduit 12 by turning the drum. Guide means such as pulley 15 and conduit guide 16 arepreferably provided for controlling the direction of movement of the conduit as it is unspooled.
In the embodiment of FIG. 1, energy is applied to the face of a formation 17 to be cut by pumping a fluid from a fluid source (not shown) through pump 18 and into the flexible conduit 12. This fluid passes down the conduit 12 and is emitted through one or more nozzles 19 in the hydraulic jet nozzle 13. Preferably, at least one of these nozzles is canted so as to create a rotational thrust on the hydraulic jet nozzle 13. A swivel joint 20 or other rotatable connection couples the hydraulic jet nozzle 13 to the flexible conduit 12. Therefore, as fluid is emitted through canted nozzle 19, the nozzle head 13 turns causing the jet emitted from the nozzles 19 to traverse the face of the formation 17.
In a preferred embodiment, the guide 16 comprises a large diameter conduit 21 slideably mounted on the base of the truck 11. The conduit 21 is preferably provided with a fluid return outlet 22 for carrying retuming drilling fluid away from a shot-hole 23. The guide 16 is advantageously connected to a lowering means such as hydraulic means 24 which may be used to seat 4 the guide 16 firmly in the hole drilling is commenced. The guide 16 comprises a bowl portion 26 of diameter sufficient to accommodate passage of the hydraulic jet nozzle 13. The bow 26 is advantageously tapered to hold a set of guide slips 27. The slips 27 preferably have a tapered outer face for seatingly engaging the tapered bowl 26 and have a curved inner surface 28 which defines an opening of decreasing cross-section passing from the top to the bottom of the slips. The curved face 28 of the slips 27 is sized to slidingly engage conduit 12 and hold it vertical as it enters shot-hole 23. To further ensure the initial straightness of the shot-hole 23, it is preferred to use a short segment of rigid pipe 29 immediately above the hydraulic jet nozzle 13. This section is preferably on the order of 5 to 10 feet long. As pipe segment 29 passes through guide slips 27, it is held in the vertical position by the slips 27.
FIG. 2 shows a hydraulic jet nozzle head 13 of a type which may be advantageously used in the practice of this invention. The bottom of the nozzle 13 comprises a port or opening 30 of diameter sufficient to allow passage of an explosive detonating means. This opening 30 is closed with a frangible plug 31 which may be expelled from the opening 30 upon application of a sufficient pressure drop across the face of the hydraulic jet nozzle 13. Such a pressure drop may be achieved by rapidly increasing the rate of flow through the pumps 18 and nozzle head 13. Alternatively, pressure drop may be increased by sealing the ports 32 of the nozzles 19 of the nozzle head 13. This may be accomplished by pumping a nozzle shut-off means down the conduit 12 and into contact with nozzle ports 32. For example, a number of fracture sealing balls 33 may be injected into the flowing fluid stream down stream of the pump 18. When these balls reach the nozzle head 13' they will lodge in the ports 32 and plug these ports. This will cause an increase in pressure in the interior of the nozzle head 13 which will result in the expulsion of plug3l from opening 30.
Liquid explosive and detonating means may be pumped into the shot-hole 23'through the opening 30 in the nozzle head 13. FIG. 3 illustrates a preferred means for delivering a detonating means 35 attached to a detonating wire 36 to the bottom of the shot-hole. A pulling member, such as a brush 37, is attached to the lower end of wire 36 to pull the wire 36 through the conduit 12 as fluid is pumped down the conduit 12. The bristles of the brush 37 are preferably longer than the radius of the conduit 12 and should be sufficiently flexible to allow the brushes to pass through the reduced diameter opening 30in the bottom of nozzle head 13.
The upper end of the wire 36 is preferably attached to a support means 38 which engages the conduit 12 with enough friction to retain the end of the wire above the surface of the ground as the pipe is pulled up over the wire and the support means, but with insufiicient friction to cause the wire to be withdrawn from the shot-hole 23 as the flexible conduit 12 is removed from the hole. The support means should allow fluid to pass so that brushes 37 can be pumped downconduit 12. For example, the support means may be a scratcher which comprises a plurality of scratcher arms such as stiff wires 39 that engage the interior of conduit 12 while still allowing fluid to pass. The support means 38 is advantageously sized to pass through the opening 30 in the nozzle 13 upon upward flexing of the wires 39.
earth surface 25 before shot- FIG. 4 schematically shows a manifold means 40 of a type which may be used to sequentially insert sealing balls 33, detonating means 35 and liquid explosive into the shot-hole 23. The respective materials are held in chambers 41-43. By appropriately opening the valves of the manifold 40 any one of the chambers 41 through 43 may be emptied into the conduit 12. The detonating wire 36 may be wound on a spool 44 rotatably mounted inside housing 45 of chamber 42. As the brushes 37 pull the wire 36 into the conduit 12, the wire is drawn off the spool 14. The supportmeans 38 can be releaseably attached to spool 44 with means such as a thin wire or string (not shown) which breaks under tension when the wire 36 is fully unwound from the spool 44.
To form and load a shot-hole 23 according to the method of this invention using the apparatus of the Figures, guide means 16 and hydraulic jet nozzle 13 are lowered into contact with earth surface 25. Fluid is then pumped through the conduit 12 and nozzle head 13 to form shot-hole 23. As the nozzle head 13 progresses into earth formation 17 the drum 14 is turned to unspool conduit 12.
When the desired depth of shot-hole is reached, the valves of manifold 40 are appropriately adjusted to pump sealing balls 33 from chamber 41 down conduit 12 to seal ports 32 in nozzle 13. This increases the pressure in nozzle 13 causing plug 31 to be blown therefrom. A suitable liquid explosive, such as a nitromethane based liquid explosive of the type described in US. Pat. Nos. 3,659,652 and 3,633,324, is then pumped from chamber 43 of manifold 40 down conduit 12 through nozzle 13 and into' the shot-hole 23. A remotely actuatable detonator 35 is pumped from chamber 42 of manifold 40 through the conduit 12 and nozzle 13 into the shot-hole adjacent the liquid explosive. Conduit 12 is then withdrawn from the shot-hole 23 by respooling the conduit on the drum 14. This leaves a loaded shot-hole ready for detonation upon receipt of an appropriate signal. According to one preferred embodiment, prior to pumping-liquid explosive into the shot-hole, after the desired depth has been obtained, fluid is circulated through the hydraulic jet nozzle while maintaining the conduit 12 stationary in the shot-hole 23. This will enlarge the bottom portion of the shothole and thereby provide a shot cavity shaped more like a point source than a line source.
We claim as our invention:
1. A method of forming and loading a shot-hole comprising the steps of:
attaching an earth boring means to a spooled flexible conduit at least as long as the desired depth of the shot-hole; advancing the earth boring means and attached flexible conduit into the earth to form the shot-hole; pumping a liquid explosive into the shot-hole through the flexible conduit to load the shot-hole; and withdrawing the flexible conduit and attached earth boring means from the loaded shot-hole.
2. The method of claim 1 including the steps of:
pumping into the shothole a detonator wire longer than the shot-hole is deep attached at its lower end to a detonating means and at its upper end to a support means for frictionally slideably supporting the upper end of the wire within the flexible conduit above the earth surface as the flexible conduit is withdrawn from the shot-hole.
3. The method of claim 2 including the step of opening a port in the earth boring means of diameter sufficient to allow the detonating means to pass through the port and into the shot-hole means before pumping the detonator wire into the shot-hole.
4. The method of claim 3 wherein the step of opening a port in the earth boring means comprises increasing the pressurewithin the earth boring means to blow a plug from the wall thereof.
5. The method of claim 4 wherein the step of increasing the pressure in the earth boring means comprises pumping one or more fracture sealing balls down the flexible conduit and into the earth boring-means.