Heating device for passage through subterranean asphalt and method of use
A lowermost casing segment in a tubular casing string, capped with a cast iron end cap, has an ignitable thermite mixture within the interior of such casing segment which, when ignited, superheats the end cap and the casing segment, to allow the casing segment and the end cap to be lowered completely through a subterranean asphalt formation without allowing the asphalt to enter the interior of the casing segment. The cast iron end cap is then drilled out to allow further drilling through the casing segment into oil and gas formations beneath the asphalt formation. In a first embodiment, the casing segment has a top cap to constrain the thermite mixture. In a second embodiment, the thermite mixture is located within a metal capsule which can be lowered into the casing segment to rest against the bottom end cap, and then be removed by a wireline.
The present invention relates generally to systems and methods used for creating passages through subterranean asphalt.
BACKGROUND OF THE INVENTIONThe use of drilling equipment to discovery and recover oil has been in place for centuries. Recent drilling improvement have lead to drilling for hydrocarbons in a variety of areas that were previously not thought possible. It has been recently discovered that deposits of hydrocarbons may exist under certain patches of naturally occurring subterranean asphalt. One of the problems associated with drilling through asphalt is the gummy, tarry nature of asphalt gumming up drill casing and closing boreholes. In several embodiments the present inventive device addresses the issue of removing asphaltic borehole clogs and laying casing through the asphaltic layers without gumming up the casing with asphalt.
Several other unique attributes of the inventive device will be illustrated in the detailed description sections.
The above mentioned and other objects and advantages of the present apparatus, and a better understanding of the principles and details of the present apparatus, will be evident from the following description taken in conjunction with the appended drawings.
The drawings constitute a part of this specification and include exemplary embodiments of the present apparatus, which may be embodied in various forms. It is to be understood that in some instances, various aspects of the apparatus may be shown exaggerated, reduced or enlarged, or otherwise distorted to facilitate an understanding of the present apparatus.
For a further understanding of the nature and objects of the present apparatus, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers.
DETAILED DESCRIPTION OF DRAWINGS AND PREFERRED MODES FOR CARRYING OUT THE INVENTIONFor a further understanding of the nature, function, and objects of the present apparatus, reference should now be made to the following detailed description taken in conjunction with the accompanying drawings. Detailed descriptions of the embodiments are provided herein, as well as, a mode of carrying out and employing embodiments of the present apparatus. It is to be understood, however, that the present apparatus may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present apparatus in virtually any appropriately detailed system, structure, or manner. The practice of the present apparatus is illustrated by the following examples which are deemed illustrative of both the process taught by the present apparatus and of the product and article of manufacture made in accordance with the present apparatus. It should be noted that throughout this application the term “asphalt” is meant to include a dark brown to black cementitious material in which the predominant constituents are bitumens that occur in nature or are obtained in petroleum processing. “Asphalt” may also include bitumens, which is a generic term for natural or manufactured black or dark-colored solid, semisolid, or viscous cementitious materials that are composed mainly of high molecular weight hydrocarbons. The term “asphalt” as used in this application also includes any tars and pitches derived from coal.
In drilling for oil and gas, the drill string is typically made up with a plurality of tubular drill pipe joints threaded together and having a drill bit at its lower end. As is well known, as the upper end of the drill string is rotated at the earth's surface, usually with a rotary table, the rotating drill string causes the drill bit to rotate and to thus drill deeper and deeper.
If the drill pipe and drill bit encounter an asphalt formation, the drill bit drills right through the formation, allowing the drill bit and tubular drill string to pass right on through the asphalt formation. However, when the drill bit and drill string are removed, for whatever the reason, such as for example, to replace a dulled or damaged drill bit, or to run in a series of steel casing joints to line the borehole, the borehole remains substantially intact in the rock and/or sand formation above the asphalt, and in the sand and/or rock formation below the asphalt, but the plastic asphalt formation “closes” the borehole. When one attempts to run the steel casing into that section of the borehole, the casing string is impeded by the plastic asphalt, typically warmed up and at least partially liquified because of the depth of the asphalt formation surrounding the borehole. When the asphalt is not warmed up enough to liquify, the casing merely stops because of the capped lower end being unable to penetrate the still solid asphalt. If the lower end is open, i.e., uncapped, the presence of the asphalt within the interior of the casing is highly undesirable.
Such asphalt formations are oftentimes not encountered above oil and gas formations, but in many cases, when existing, are found at depths of some 3,000 to 5,000 feet below the mud or ground line. At other times, asphalt is found at more shallow depths, for example, when drilling in river beds, such as the settled tar pits existing beneath the silt formations underneath the river beds. However, in all such cases, regardless of the depths at which the asphalt formation is encountered, it is highly desirable to prevent the asphalt from entering into the interior of the steel casing liner or impeding the interior of the casing and thus adversely effecting the drilling and completion operations involved in producing oil and gas from underneath said asphalt formations.
Referring now to the drawings in more detail,
The grind of the aluminum determines the speed of burning of the thermite mixture. When ground very finely, such as with flour, the thermite mixture burns very fast. The thermite mixture burns more slowly as the grind creates larger size particles. Thus, with a given grind of the aluminum, the time of the burn is dependent upon the length of the column of thermite. In a typical job, the thermite may burn at the rate of one foot per five minutes of burn. If the asphalt layer is 100′ thick, a column of thermite 20′ long will take approximately 100 minutes to burn the entire column, such as the column 13 illustrated in
Lower casing segment 8 is lowered into the borehole 5 such that the bottom end of the lower casing segment (joint) 8 is preferably in contact with the uppermost portion of the asphalt formation layer 3. The contact portion of the lower casing segment 8 is preferably a lower dome 9 composed of preferably, but not limited to, a drillable cast iron. The cast iron dome or cap 9 is preferably engaged with the lower casing segment 8 such that there is a substantially tight seal between the two so that no solids, liquids or gases can escape into or out of the lower casing segment 8 through the cast iron dome or cap 9. The dome or cap 9 is also preferably constructed to withstand extremely high temperatures without cracking, corroding or becoming otherwise compromised. Located substantially opposite of the dome or cap 9, but still connected within the lower casing assembly 8 is another dome or cap 10. The dome or cap 9 and the dome or cap 10 are substantially aligned so as to create a hollow, interior chamber 12 within the lower casing assembly 8 which is substantially defined by the interior walls of lower casing assembly 8, the dome or cap 9 and the dome or cap 10. The dome or cap 10 is also preferably constructed of drillable cast iron to withstand extremely high temperatures without cracking, corroding or becoming otherwise compromised. The cast iron dome or cap 10 is preferably engaged with the lower casing segment 8 such that there is substantially tight seal between the two; however dome or cap 10 is preferably constructed so that there is an exhaust valve 11 running from the exterior of dome or cap 10 through dome or cap 10 and into the interior chamber 12. The exhaust valve 11 is constructed to allow for any gases existing or generated in the interior chamber 12 to escape from the interior chamber 12. The interior chamber 12 is preferably filled with a thermite mixture 13 which is preferably dormant until ignited or triggered. The thermite mixture 13 is preferably created to heat to a temperature which, when ignited, heats the lower casing assembly 8 and the cast iron dome or cap 9 sufficiently to heat and lower the viscosity of the asphalt 3 and/or boil the asphalt blocking the borehole 5 without compromising the lower casing assembly 8 or the iron dome or cap 9. The firing head 14 is located on the top of the dome or cap 10, and in one embodiment is preferably constructed so as to be activated when an actuation drop bar or ball 17 strikes the firing head 14 surface. An ignitable drop bar 15 is located inside the interior chamber 12. When the firing head 14 is activated the drop bar 15 ignites and drops into the thermite mixture 13 igniting the thermite mixture 13 as it proceeds (
The preferred embodiment of the invention contemplates that the column of thermite can be burned from the top of the column down to the bottom of the column, or the most preferred, from the bottom of the column upwardly to the top of the column. This variation can be achieved, for example, by varying the length of the ignition cord, or alternatively, by causing the ignitable drop bar to drop 15 to the bottom of the thermite column 13 before igniting the thermite mixture.
It may be seen from the preceding description that a new and improved system and method for heating a device for passage through subterranean asphalt has been provided. Although very specific examples have been described and disclosed, the embodiment of one form of the apparatus of the instant application is considered to comprise and is intended to comprise any equivalent structure and may be constructed in many different ways to function and operate in the general manner as explained hereinbefore. Accordingly, it is noted that the embodiment of the new and improved system and method described herein in detail for exemplary purposes is of course subject to many different variations in structure, design, application, form, embodiment and methodology. Because many varying and different embodiments may be made within the scope of the inventive concept(s) herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.
Claims
1. A system for allowing a casing string to be lowered through a subterranean asphalt formation, comprising:
- a tubular joint of casing at the lowermost end of said casing string, said tubular joint of casing having a first end and a second end, said first end having a first cap sealing said first end against entry of asphalt through said first end into the interior of said joint of casing;
- a second cap within the interior of said tubular joint of casing, and located between said first and second ends of said tubular joint of casing; and
- a thermite mixture within the interior of said tubular joint of casing, between said first and second caps, for heating the first cap and at least a portion of said tubular joint to allow said tubular joint of casing to be lowered through said asphalt formation.
2. The system according to claim 1, including in addition thereto, a firing head for igniting the thermite mixture.
3. The system according to claim 2, wherein said first cap comprises cast iron.
4. The system according to claim 3, wherein said second cap comprises cast iron.
5. The system according to claim 1, wherein said thermite resides within an envelope which can be lowered into and removed from the interior of said joint of casing by a wireline running from the earth's surface down to the envelope.
6. An apparatus for melting through a subterranean asphalt formation comprising;
- a lower casing assembly with side walls, a top end, and a bottom end capable of being lowered into said asphalt formation;
- said bottom end being covered by a bottom cap;
- a top cap between said top end and said bottom end, therein creating a substantially hollow chamber within the lower casing assembly as defined by the side walls, the top cap and said bottom cap, said hollow chamber housing a thermite mixture capable of producing heat significant to reduce asphalt to a soft, viscous, flowing material upon ignition; and
- a firing head in contact with said top cap and with said thermite mixture, and being capable of igniting said thermite mixture, wherein when said firing head is actuated the thermite mixture ignites and produces heat which heats the bottom cap and the lower casing assembly significantly to reduce asphalt to a soft, viscous, flowing material, thereby allowing the lower casing assembly and bottom cap to be lowered through the asphalt layer.
7. The apparatus of claim 6 further comprising:
- a first drop bar located in the hollow chamber and attached to the top cap, and said first drop bar being capable of igniting said thermite mixture, said firing head being in communication with the first drop bar, wherein upon actuating said firing head the first drop bar is dropped in the thermite mixture, thereby igniting the thermite mixture.
8. The apparatus of claim 6, further comprising:
- a second drop bar located at the earth's surface, above the firing head, wherein when said second drop bar contacts the firing head the firing head is activated.
9. The apparatus of claim 6, further comprising:
- an exhaust port for releasing gases from the hollow chamber, wherein said exhaust port runs through the top cap and into the hollow chamber.
10. The apparatus of claim 6, further comprising:
- an ignition cord capable of igniting a thermite mixture, wherein said firing cap is connected to the ignition cord and said ignition cord is in contact with the thermite mixture.
11. The apparatus of claim 10, further comprising:
- said ignition cord being capable of igniting said thermite mixture from the top of the thermite mixture downwardly.
12. The apparatus of claim 10, further comprising:
- said ignition cord being capable of igniting said thermite mixture from the bottom of the thermite mixture upwardly.
13. A method for lowering the bottom end of a tubular casing string through a subterranean asphalt formation, comprising the steps of:
- capping the said bottom end of said casing string;
- heating the capped bottom end and at least an additional portion of the lowermost joint of casing in said casing string, by igniting a thermite mixture located with said lowermost joint of casing; and
- lowering said tubular casing string through said asphalt formation during said heating step.
14. The method according to claim 15, including in addition thereto, the step of drilling through the said capped bottom end, and then drilling further into the formations beneath the said asphalt formation.
Type: Application
Filed: Mar 5, 2007
Publication Date: Sep 11, 2008
Inventor: Louis Wardlaw (Maracaibo)
Application Number: 11/715,086
International Classification: E21B 7/14 (20060101); E21B 36/00 (20060101); E21C 37/16 (20060101); E21B 43/24 (20060101);