Explosive well-fracturing system

• US 4,248,303 A
• Filed: 12/01/1978
• Issued: 02/03/1981
• Est. Priority Date: 12/01/1978
• Status: Expired due to Term

• Current Assignee: XPLO Corporation
• Original Assignee: XPLO Corporation
• Inventors: Charpentier, John J.
• Primary Examiner(s): BROWN, DAVID
• Application Number:
  US05/965,620
• Time in Patent Office: 795 Days
• Field of Search: 166/63, 166/299, 103/20, 103/21, 103/24 HC, 103/21.6, 103/22 R, 103/23
• US Class Current: 166/299
• CPC Class Codes: E21B 43/263 using explosives
• CPC Class Codes: F42D 1/00 Blasting methods or apparatus, e.g. loading or tamping

Abstract

Method of and apparatus for fracturing and creating multiple fissures in hydrocarbon impregnated rock. The invention uses a sequence of explosive charges involving a main, centrally located high velocity, shape charge shot directed out horizontally into the stratum to be fractured, and two supplemental charges of bulk explosives of a lower detonation velocity positioned above and below the main shot and simultaneously detonated following the main charge, the purpose of the sequence and the physical arrangements being to effect greater penetration of the stratum. In the preferred embodiment a metal shaped charge containing a liquid explosive is used for the centrally located main shot comprising a number of longitudinally extended tined spokes directed radially outward from a common center (note FIG. 3). The diameter of the shaped charge can be varied to fit and preferably generally fills up the diameter of the well bore.

Claims

1. The method of fracturing wells comprising the following steps:

(a) positioning in the well holes a first, relatively low velocity, supplemental explosive charge at a position below the area to be fractured;

(b) positioning in the well hole a relatively high velocity, central explosive charge at a position next to the area to be fractured and adjacent said first charge;

(c) positioning in the well hole a second, relatively low velocity supplemental explosive charge at a position above the area to be fractured and adjacent the top of said central charge,

(d) detonating said central charge; and

(e) thereafter detonating said first and second supplemental charges.

2. The method of claim 1 wherein in step "e" the supplemental charges are detonated simultaneously.

3. The method of claim 2 wherein in step "e" the supplemental charges are detonated within a few microseconds of detonating the central charge.

4. The method of claim 1 wherein in steps "a" and "c" said first and second supplemental charges are positioned by placing in the hole explosives in loose bulk form.

5. The method of claim 4 wherein in step "b" said central charge is provided in the form of an elongated body with the explosive located in the central area thereof behind longitudinally extending "V" shaped air stand-off areas and is lowered down in the hole in unitary form.

6. An explosive system for fracturing a well comprising:

a first, lower, relatively low velocity, supplemental explosive charge in bulk form;

a relatively high velocity, central explosive shaped charge comprising a cylindrical metal member containing a liquid explosive in its cental area extending axially at least substantially the full axial length of said cylindrical member and surrounded by longitudinally extending air stand-off areas in said cylindrical member having at least a general "V" shape to each of them with their apexes located to the inside of said cylindrical members; and

a second, upper, relatively low velocity, supplemental explosive charge in bulk form;

said three charges being associated for positioning in the hole with said central charge located adjacent the area to be fractured with said first and second supplemental charges being located below and above it respectively.

7. The system of claim 6 wherein the diameter of said cylindrical member is comparable to the diameter of the hole to thereby fill up the hole with the exterior surface of said cylindrical member being in near face-to-face engagement with the hole.

8. The system of claim 6 wherein there is further included detonation means associated with said three charges for initially detonating said central charge and thereafter detonating said supplemental charges simultaneously with each other.