US 2985240 A
Description (OCR text may contain errors)
May 23, 1961 L. w. EMERY BOTTOM HOLE BURNER Filed May 21. 1959 INVENTOR. LEONARD W EMERY A TTORNE Y5 United rates Patent BOTTOM HOLE BURNER Leonard W. Emery, Humboldt, Kans., assignor to Sinclair Oil & Gas Company Filed May 21, 1959, Ser. No. 814,696
2 Claims. (Cl. 166--59) This invention is a novel bottom hole burner for use in oil wells or other wells which require heat to be applied to the mineral in order to reco'ver it. Although simple in construction, this invention has proven effective in actual use.
Recently, attention has been given to recovering oil from underground formations such as shale and oil sands which previously have been considered unproductive because the hydrocarbon contained in these formations is in a nonflowable state. Experimentation has shown that some of these formations may be subjected to a heat treatment whereby the hydrocarbon materials, due to liquefaction, vaporization or chemical breakdown under the influence of heat, are made recoverable. Frequently, this heat is generated by burning hydrocarbons contained in the formation or by burning extraneous fuels-usually hydrocarbon gases-in proximity to the oil-bearing sub terranean stratum, or by using the second of these methods to initiate the first. As shown for example, in US. Patent 2,877,847, in order to ignite and maintain combustion of a gas-air mixture in a temperature range which will not damage the well casing and the cement behind it, a downhole burner using a primary and secondary system is advantageous. In such a system, a combustible gas is conducted to the site of the burning, usually in or nearthe bot-tom hole of the well. A combustion supporting gas-the primarygas-is also conducted to this site. A secondary gas, which may be the same chemical composition as the primary gas, is conducted to the area around the burning to control the temperature and to help convey the hot gaseous products of combustion to the petroliferous formation.
In the past, workers have used multiple strings of pipe of provide control of primary air, secondary air, and fuel gas separately. This is an elaborate and'expensive installation and becomes complicated when multiple strings have to be put in a slim hole completion such as 2" or 2 /2" casing. This invention provides a burner design which has been quite successful in both 2" and larger cased wells. It is unique in that it functions as a primarysecondary burner by splitting total air flow into two streams just before the burning zone while its simple construction allows it to be run on a single string of macaroni tubing inside either tubing or casing completions. Thus, the burner is merely lowered into the well bore on the bottom of a fuel gas injection string and in essence may be a larger, perforated pipe section surrounding the gas injection tubing. The upper open end of the burner separates the air and other gases passed down the annulus between the gas tubing and the enclosing well tubing or easing, into primary and secondary streams according to the relative cross-sectional areas of the open upper burner end and the free tubing space surrounding the burner.
The invention will be better understood by reference to the accompanying drawings in which Figure l is a cross-sectional representation of a well Patented May 23, 1961 ice bore containing the novel burner arrangement of the invention;
Figure 2 is a plan view of the bore at the line 2-2 a of Figure 1;
Figure 3 is a plan view along the line 33 of Figure 1; and
Figure 4 is a plan view for the same position as Figure 3 showing a modification of the burner support means.
:In these figures, 10 represents a well bore which pierces a non-oil bearing stratum 12 and a petroliferous stratum 14. The wall or casing 16 of the bore is frequently a ferrous metal pipe backed with concrete. A conduit 18 for air or other combustion supporting gas connects with the extension of the casing 20, above the earths surface at 22. A tube 24 extends from above the surface of the earth into the bore 10 to the vicinity of the top 26, of theoil bearing stratum 14. Attached to tube 24 is a supply line 28, for fuel, usually a hydrocarbon or other combustible gas. The lower end of this tube supports the burner shell 30, which is made preferably of stainless one, preferably a plurality of vents 33 and 34, for the escape of combustion gases and is advantageously positioned in the well bore in such a way that the uppermost of the vents 33 is aligned with the top 26, of the pe'froliferous stratum- In this embodiment the supporting flange 32 is provided with-perforations 36, for entry of combustion supporting gas from the bore 10 into the burner combustion zone 38. Other ways may be found to provide the opening for the primary gas stream, for example the burner shell 30 may be supported on the tube 24 by three or four straps, 40, as shown in Figure 4, or several perforations may be joined to form slots.
The open end 31, and the uppermost vents 33, are arranged in such a way that secondary gas contacts exhaust gas before the cool secondary gas contacts the formation 14. The alignment should be such that at least enough exhaust gas passes through the vent 33 to give the sec ondary gas a temperature which will prevent cooling of or adjacent formation will be damaged. The exact positioning of the vent 33, therefore, will vary from one installation to another, depending in each case on the combustion temperature of the fuel, the initial velocities of the primary and secondary gases and the vectors taken by the flue gas and the flue gas-secondary gas mixture.
The tube 24 and burner 30, are preferably positioned in approximately the vertical mid-line of the bore 10, concentric with the casing 16. Preferably also the burner shell 3%) is arranged concentrically with the tube and casing or bore hole. This arrangement defines a passage 42 for the combustion supporting gas from the opening 22 to the top edge of the burner. The burner separates the passage into inner annular path 46 and outer annular chamber 48. The radial dimension of the annular path 46 is designated X; the radial dimension of the outer annular chamber 48 is designated Y. Y
The ratio of cross-sectional area between the tubing string 24, and the burner shell to the cross-sectional area between the shell and the casing will be approximately the same as the ratio of primary air to secondary air. This ratio may be in a ratio of about .3 volumes primary air/1 volume of secondary air to about 1/1 and can be varied to fit specific needs by changing pipe size, when the embodiment of Figure 4 of the drawings is used, otherwise. it may be changed, controlled or adjusted by changing' the number or size of the perforations 36 with .or without changing the cross-section diameter of the burner 30' and thus changing the dimensions X and Y. This simple. arrangement allows entry of enough gas into the shell to support combustion to the extent desired.
In using the apparatus a combustion supporting gas, usually air, is pumped through the conduit 18' and enters the well bore10 at 22. It'flows through the passage 42 until it reaches the top edge of the burner. There the flow is divided into a primary gas stream which flows through the inner annular path 46 and a secondary gas stream which flows through the outer annular chamber 48. The primary gas stream meets the stream of fuel gas from tube '241in the combustion compartment 38. The initial mixture of fuel and air may be ignited by use of the processes of the aforementioned patent. Once lit, the fire is kept going by supplying the proper quantities of'fuel and combustion supporting gas.
The primary air entering the shell 30 mixes with the fuel gas and burns inside the shell. The hot combustion gases are exhausted through vents 33 and 34 in the lower part of the shell, are mixed with and cooled by the secondary air in the chamber 48 and are carried into contact with the oil-bearing stratum. The shell serves as a shield for the flame and becomes hot enough to insure reignition in case of momentary interruptions in the fuel supply.
With a burner such as shown in a 2" completion, it has been possible to burn mixtures containing as little as 10 B.t.u. per cu. ft. calorific value. As pointed out above,
installation of the burner preferably positions it so that no cold air will enter the formation. This requires that the top opening in the burner shell be generally aligned hori zontally at or above the top 26 of the oil bearing formation, so that the secondary gas will be warmed before it contacts the stratum.
For example, a burner having an outer shell of 1%" standard weight stainless steel pipe 48" long is attached to a string of A" pipe. The lower 18" of the shell is perforated with A holes in a density of 2 holes per linear inch. The shell is attached so that the end of coincides with the top of the perforations when the shell is vertical in the well. The pipe string with shell attached is installed in a well employing as casing 2" pipe (2.067 I.D.) which has been cemented in a permanent type completion. The burner is positioned so that the top perforations in the shell coincide with the top of the oilbearing stratum, in this case, oil sand.
Natural gas having a calorific value of 1000 B.t.u. per cu. ft. is injected down the A" at the rate of 200 s.c.f. per hour. Air is injected down the annulus between the A and the 2" at the rate of 9800 cu. ft. per hr. Of this 9800 cu. ft. per hour of air, approximately 4400 cu. ft. is passed inside the shell mixing with the fuel gas, giving a ratio of primary/secondary air of about .8/ 1. The remaining air is mixed with the gas-flue gas mixture being exhausted through the vents forming a total mixture which is not readily ignitable. After ignition, flame temperatures inside the burner may be as high as about 2000 F. However, temperatures at the well bore wall will not exceed about 1200 F. and temperatures at the casing shoe, which is cooled by the flowing air, do not exceed about 800 F.
After ignition is obtained the fuel gas rate may be reduced to as low as 100 s.c.f.h. yielding a temperature inside the burner of approximately 1200 F. and a temperature of approximately 600 F. at thewell bore wall. These conditions may be maintained for a suflicient'period of time to heat the formation to ignition temperatures,
1. In a well bore which penetrates a non-oil-bearing stratum and a lower oil-bearing stratum, a burning device in said bore which comprises a tube extending from the surface of the earth to approximately the top of the oil-bearing stratum and a burner shell positioned on the tube and surrounding and extending below the lower open end of the tube, said shell being spaced away from the bore hole wall and provided with an opening at its upper endin said bore for the admission of a combustion sup: porting gas from the bore and with vent means for the release of flue gases from the shell, the size of the upper end of the burner shell and its opening being selected so that gas flow downward in the well bore is divided into a primary stream sufficient to support combustion of the fuel and a secondary stream sufficient to carry off hot flue gases from the vent.
2. The device of claim 1 in which the shell is so aligned with the top of the oil-bearing stratum the secondary gas contacts exhaust 'gas from the said vent means before said secondary gas contacts said oil-bearing stratum.
References Cited in the file of this patent UNITED STATES PATENTS 1,678,592 Garner et al. July 24, 1928 2,225,775 Garrett Dec. 24, 1940 2,506,853 Berg et al May 9, 1950 2,668,592 Biros et a1 Feb. 9, 1954 2,877,847 Pelzer et a1 Mar..17, 1959 2,902,270 Salomonsson et a1. Sept. 1, 1959