US 3112233 A
Description (OCR text may contain errors)
DRILLING FLUID CONTAINING EXPLOSIVE COMPOSITION Original Filed May 26. 1960 FIG.
SWIVEL I9 ENCAPSULATED EXPLOSIVE ROTARY I7 KELLY E T D .n V N E Mw ,R .d E T E N J O G A V O A L A LS T MN 1 P U D0 S X G so ESD N P L V l N R E l. P T A X N R l A D A C F B E .l W v w. N O D A N "E HR E L U A m H H N C EN K A BOC R OEA G 2 R L J v.. u B 4 G 4 H 4 P4 D2 U M s n 2 B c a m I 3 J v. ....V /l/ mm 1.7.1. f M G 2 m 3 w R T. S 3 L I R D lead picnate and gnhr dynamite.
United States Patent On ice il Patented Nov. 26, 1963 'Ilhe present invention is directed to the drilling of wells, More particularly, the invention is concerned with a method for increasing the drilling rate in the drilling of oil and gas wells land the like. In its more specific aspects, the invention is concerned with an improved drilling method in which drilling rates are increased by generation of gas adjacent the drill bit.
This application is a tdivision of Serial No. 31,865, tiled May 26, 1960, for Robert H. Friedman, Leon H. Robinson, Jr., and Jack H. Edwards, entitled Rotary Drilling of Wells Using Explosives.
The present invention may be briey described as a method for drilling a well with a drill bit in which a hollow drill string, having a drill bit attached to its lower end, is rotated and in which an aqueous drilling uid is circulated through a path of iiow detined by the hollow drill string and the annulus between the drill string and the |wall of the rwell. The specific feature of the present invention involves introducing into the circulating drilling iiuid a sufiicient amount of water soluble capsules containing an explosive which is rendered harmless by extended contact with water. The capsules have a size within the range from about 0.01 Ito about 0.25 inch and the explosive has a sensitivity as measured by the dropsensitiv-ity test within the range from about 2 to about l0 cm. The capsules are exploded by weight imposed on the capsules by the drill bit such that increased drilling rates are obtained.
The explosive employed in the practice of the present invention should be an explosive which is moderately sensitive in the range from about 2 to about 10' cm. as measured by the standard drop-sensitivity test. This test measures the height in centimeters; a 2 kilogram weight must be dropped to cause explosion. A description or" this test will be found in Meyer, Martin, Explosives, Thomas Y. Crowell, Co., New York, 1943, p. 28, The preferred range of sensitivity is in the range from about `2 to about 5 centimeters.
While the exact composition of the explosive is not critical, the explosive must have the sensitivity set out hereinbefore. As examples of the explosives which are useful in fthe present invention, there may be mentioned These explosives are within the preferred range of sensitivity. Explosives that are in themselevs yabove the range of sensitivity may be brought to the desired sensitivity by admixture with more sensitive materials which function as igniters. Afdmixture serves to decrease the sensitivity of the more sensitive material and increase that of the less sensitive material. Thus, by admixing such explosives las mencury fulminate, for example 80 percent mercury fulminate with 20 percent potassium perchlorate; or antimony trisulfide, lead triazide, or nitrogen triiodide with standard explosives like dynamite, trinitrotoluene, and PETN (pentaerythritol tetranitrate), the sensitivity may be adjusted to a sensitivity within the desired range. A desirable characteristic of the explosive -is that it is rendered harmless by contact with water. `Contact with water prevents dangerous accumulation of the explosives in the drilling fluid.
The encapsulating agent for the explosive may be any 5 Claims.
water impervious, slow-dissolving material. Typical of such materials are the natural gums, such as gelatine, gum arabic, gum tragacanth, or guar seed gum. Other satisfactory materials are the synthetic materials commonly used to encapsulate medicines, polyvinyl alcohols, carboxylated methyl celluloses, or organic compounds slowly soluble in water such las benzoin, camphor or diphenylurea. The granulated, encapsulated explosive should have a particle size in the range from about 0.01 -to about 0.25 inch and preferably in the range from about 0.05 to about 0.15 inch.
'Ilhe amount of the explosive capsules added to lthe drill- .ing fluid is in the nange from about 0.1 to about l0 lbs. per barrel of drilling liuid. A preferred concentration is from about l to about 5 lbs. per barrel of drilling fluid. The explosive capsules are preferably added to the drilling mud intermittently but may be added continuously so long as the desired -concentration is maintained in the drilling mud and there is suflicient explosive concentrated in the region of the drill bit or in the lilter cake on the bottom of the well.
`inasmuch as it is necessary for the capsules to dissolve slowly in water to prevent dangerous accumulation thereof, it is necessary to use an aqueous drilling fluid. In other words, the drilling uid must contain water to contact the encapsulated explosive such that in case any of the capsules are not exploded by setting down weight thereon by the drill bit, the explosive will be rendered harmless by dissolution of the capsules `and contact of the explosive with water.
it will be desirable to provide materials as encapsulating agents which will dissolve in a period of time such that the encapsulating material will slowly dissolve. Thus, the capsules will dissolve at a time within the range from l0 minutes to l0 days such that the explosive is rendered harmless. Little, if any, of the explosive will be in the mud returned to the earths surface in that most, if not all, of that which is not exploded will be dispersed in the filter cake lining the wall of the well bore. Additionally, the concentration of 0.1 to l0 lbs. of small grain encapsulated explosive is such that it will be widely dispersed in the drilling fluid.
The present invention will be further illustrated by reference to fthe drawing in which:
FIG. l is a flow diagram of a preferred mode; and
FiG. 2 illustrates a mode for encapsulating the explosive.
Referring now to the drawing, numeral 1l designates the earths surface from which a well bore l2 has been drilled by rotating a hollow `drill string 13 carrying on its lower end a rock bit 14, suitably a toothed bit, but other well-known rock bits may be used. The hollow drill string extends to the tioor 15 of a derrick 16 wherein it is rotated by a rotary table i7 driven by a suitable power means, not shown. Connected into the upper end of the Idrill string 13 is a kelly joint 18 which connects by means of a swivel 19 to a flexible conduit 20 which, in turn, connects by pipe 2l to a mud pump 22.. Mud pump 22 takes suction by pipe 2.3 'with the mud pit 24'.
Connected into pipe Z1 by a conduit 27 controlled by a valve 28 is a tank 29 which contains a supply of encapsulated explosives. As the mud is drawn into the pump 212 through line 23 and pumped by line 2l a sufficient amount of the encapsulated explosive is discharged by line 27 into line 2,1 to maintain in the dri-lling mud the desired concentration of explosive and the mud containing the explosive is then pumped down the hollow drill string 13 then out through the drill bit liti. The explosive then concentrates in the til-ter cake at the bottom of the well bore and the concentrated encapsulated explosive is then crushed by the weight of the drill string and thus exploded.
n.9 By virtue of the explosion of the explosive by the drill oit M', the `drilling rate is enhanced to a considerable degree lby microscopic fissures or cracks created under the drill bit by the plurality of explosions occurring. This allows the drill bit to fracture the roclf` formation easily and results in increased drilling rates. Not only is the present invention useful in increased drilling rate but explosions in the region of drill :bit ld cause microscopic fissures in the rock which allows the rock to be fractured easily by the drill bit and rernoved as chips. With generation of gas in the immediate vicinity of the roch bit teeth, the pressure dferential :across the rock chips is reduced and the rock chips are efiiciently dislodged and microscopic lissures that are formed are widened rather than healed as encountered in conventional drilling operations.
The exploding capsules El) thus create a plurality ol miniature explosions 3l in the region of the roel; bit ill speedingy the drilling rate and allowing improved drilling operations.
Any of the capsules y.vhich emerge from under the drill bit ltd-without exploding are carried into the annulus 32 and deposited in the filter calce lining the Well bore 'wall and by virtue of the time elapsing, the capsules are slowly dissolved and the explosives are eventually rendered harinless by Contact with the aqueous drilling llt id.
The present invention is quite advantageous and useful in increasing the speed or" drilling through earth formations.
Referring novv to FlG. 2, a mode is described of encapsulating the granulated explosive. ln FlG. 2, numeral 40 designates a hopper containing granulated explosive 4l of suliciently small size to form capsules of a size within the range given. The hopper is controlled by valve 42 which allows a stream i3 of the granulated explosive 41 to be discharged into a tank i4 containing a volume 4S of encapsulating agent such as has been described. The stream 43 of the granulated explosive l? "alls downwardly within the encapsulating agent i5 and is coated thereby and by gravity ilows into the boot d for removal of the encapsulating agent 'by way of line 47 controlled by valve 48. The encapsulated explosive may then be dried as desired and then placed in the tanl; 29 for introduction into line 2l as has been described. While one method has been described of encapsulating the granulated explosive, other methods may be used, For example, the explosive may be encapsulated by a spray-drying technique.
The practice of the present invention has been illus- /l trated by conventional circulation down the drill string7 and up the annulus. lt is to be-understood, however, that reverse circulation may be employed such that the mud is flowed down the annulus 32 and up the drill string 113. In such instances, of course, it would be necessary to change the flow system to prov-ide for returns of the -mud to the mud pit.
The nature and objects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and secure by Letters Patent is:
1. An aqueous dri ing fluid comprising drilling mud containing particles of explosive selected from the group consisting oi lead picrat guln dynamite, mixtures of iercury ulrninate with `potassium perchlorate, and niixtures of antimony trisullde, lead triazide, and nitrogen trilodide i Li dynamite, trinitrotoluene, and pentaerythritol tetrani rate, having a drop sensitivity as measured by the drop sensitivity test within the range *from about 2 to about ll) ein. and having a dry encapsulating coating selected from the `group consisting of gelatine, gum arabic, gum tragacanth, guar seed gui-n, polyvinyl alcohol, carboxylated methyl cellulose, benzoin, ca'niphor, and diphenyl urea, said particles being of a size within the range from about 0.91 to about 0.25 inch, the coating on said particles being water soluble, said explosive being rendered harmless by contact with water for a time within the range from l0 minutes to 10 days.
2. A drilling fluid in accordance with claim 1 in which the explosive is lead picrate.
3. A drilling iluid in accordance with claim 1 in which the explosive is guhr dynamite.
4. A drilling iluid in accordance with claim 1 in which the explosive is a mixture of mercury uilminate and potassium perchlorate.
5. A drilling luid in accordance with claim 1 which contains from about @.1 to about 10 pounds of said particles per barrel of drilling fluid.
References Cited in the le of this patent UNITED STATES PATENTS