Claims
- 1. A method of rubblization of underground oil shale deposits to produce a uniform porosity of at least 20% for in-situ heat extraction of oil comprising the steps of:
- a. excavating two rooms, one above and one below an oil shale deposit to be processed, said excavation producing rooms of a predetermined cross-sectional configuration, each of said rooms occupying at least 10% of said oil shale deposit;
- b. drilling vertical holes of predetermined diameter between said rooms in a uniform, periodically repeated parallel pattern throughout said oil shale deposit;
- c. charging each of said holes with a detonatable explosive, said explosive being disposed in each hole is centered symmetrically therein, and said explosive disposed in adjacent ones of said holes are positioned at different levels therein;
- d. detonating explosives in holes at each of said different levels simultaneously, with time delays between the detonations of explosives at one level with respect to a successive detonation at a different level, in a sequence where said explosives in the two levels nearest to said two excavated rooms are detonated first followed by the detonation of said explosives in said levels adjacent to said levels nearest to said two excavated rooms, said detonations proceeding progressively toward the inner levels of the oil shale deposit sequentially and symmetrically to the horizontal central plane of the oil shale deposit;
- e. detonating said explosives with single electric pulse initiated blasting caps connected electrically in parallel, by lead wires which can initiate all the caps some instantaneously and some after a time delay depending upon their location in the rooms, and exceeding the duration of the successive blasts;
- f. the resulting in situ rubblization of the oil shale for retorting being created to a height of at least one hundred feet with a height to width ratio of 2.0 to 3.5.
- 2. The method defined in claim 1, including the following additional steps:
- a. dividing the explosive loadings into three levels;
- b. disposing the hole location pattern and explosives loading therein to follow a two-dimensional, square lattice configuration and distribution;
- c. using two types of hole loadings, each type of hole being surrounded by four holes of an alternate type located at the four corners of said square lattice configuration;
- d. loading explosives in each of the top and bottom sections of holes of one type to approximately one-third of the hole length, leaving an unloaded central section;
- e. loading explosives in the central section of holes of the other type, to approximately one-third of the hole length, leaving unloaded sections at the top and bottom ends of each of said other type holes;
- f. detonating the explosives in said one type of holes simultaneously, followed by a delayed second detonation of explosives in said other type holes simultaneously;
- g. providing a distance between adjacent holes of the same type of at least 10 times the diameter of the hole; and
- h. providing the diameter of said other type holes to be larger than said one type holes so that more explosives per length can be loaded into said other type of holes.
- 3. The method defined in claim 1, including the following steps:
- a. dividing the loadings into five levels;
- b. disposing hole locations to following a two-dimensional, square lattice configuration and distribution;
- c. providing three types of hole loadings, wherein each of two types of holes is surrounded by four of a third type of hole located at the corners of a square lattice configuration, wherein each of said third type hole is surrounded by two of each of said two types of holes symmetrically;
- d. loading explosives in the top and bottom sections of one of said two types of holes to approximately one-fifth of the hole length, leaving an unloaded central section;
- e. loading explosives in the central section of the others of said two types of holes to approximately one-fifth of the hole length, leaving unloaded portions at the top and bottom sections of the hole;
- f. loading explosives in the two-fifth and four-fifth sections of said holes of said third type to approximately one-fifth of the hole length, leaving unloaded sections at the top, bottom and central sections of the hole;
- g. detonating explosives in said first of said two types of holes first, followed by a delayed second detonation of explosives in said third type of holes, followed by a delayed third detonation of explosives in the second of said two types of holes, each of the delayed detonations of explosives occurring simultaneously for the respective types of holes involved;
- h. providing a distance between adjacent holes of the same type of at least 10 times the diameter of the hole; and
- i. providing hole diameters for each of the three types of holes so that some may be larger than others to permit greater quantities of explosives to be loaded in the larger holes than in the smaller holes.
- 4. A method for rubblization of oil shale deposits comprising the steps of:
- a. excavating rooms above and below the oil shale deposit to be rubblized;
- b. drilling a series of holes vertically through the oil shale deposit, the room, above said deposit and the room below said deposit, said holes being parallel to one another and arrayed in a predetermined pattern;
- c. loading portions of said holes with explosives disposed therein so that said explosives in adjacent holes in the array are at different levels; and
- d. detonating said explosives in a time delayed sequence such that explosives at any one level are exploded simultaneously followed by detonation of the explosives at another level, the sequence being designed to detonate the charges nearest the excavated rooms first, followed by the detonation of charges located in the central portions of the shape deposit, the sequence of explosions progressing from the upper and lower portions towards the central portion of the shale deposit between said excavated rooms, thereby to more completely rubblize the oil shale so that the oil in the shale may more easily be extracted by retorting.
- 5. In the method defined in claim 4, the array pattern of the holes for receiving explosive charges being such that a central hole has a centrally located portion with an explosive charge therein and the surrounding holes, forming a predetermined pattern about the central hole having charges in their respective upper and lower portions, the pattern of central holes and surrounding holes being repeated over the area selected for rubblization.
ORIGIN OF THE INVENTION
The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 USC 2457).
US Referenced Citations (5)