US3227215A - Apparatus for preventing well fires - Google Patents

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2 Sheets-Sheet 1 Jan. 4, 1966 J. w. MARX APPARATUS FOR FREVENTING WELL FIRES Filed NOV. 20, 1963 BYZdy Jan. 4, 1966 J. w. MARX 3,227,215

APPARATUS FOR PREVENTING WELL FIRES Filed Nov. 20. 1963 2 Sheets-Sheet 2 SEPARATOR ERBURDEN INVENTOR. J W. M A R X A TTG/PNE YS United States Patent r, t 3,227,215 i. f APPARATUS FOR PREVENTING WELL 'FIRES .lohn W. Marx, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Filed Nov. 20, 1963, Ser. No. 325,121 8 Claims. "(Cl. 16o-63) This `is a continuation-impart lapplication of applications Serial No. 732,730, tiled May 2, 1958, and Serial No. `857,629, filed December 7, 1959, now US. Patent No. 3,135,324. Application Serial No. 732,730 isa continuation-in-part of application Serial No. 526,388, liled August 4, 1955, and now abandoned.

This invention relates to apparatus for preventing borehole iires during in situ combustion of a carbonaceous stratum to recover oil therefrom; a j a In situ combustion in `the Vrecovery of hydrocarbons from underground strata containing carbonaceous material is becoming more prevalent in the petroleum industry. In this technique of production, combustion is initiated in the carbonaceous stratum and the resulting c ombustion zone is caused to move thru the stratum by either inverse or direct air drive, `whereby the heat of combustion of alsubstantial proportion of the hydrocarbon in the stratum drives out and usually upgrades a substantial proportion of the unburned hydrocarbon material.

The ignition of carbonaceous material in a stratum around a borehole therein followed by injection yof air thru the ignition borehole and recovery of product hydrocarbons andcombustion gas thru another borehole in the stratum is a direct 'air -drive process for effecting `in situ combustion and recovery of hydrocarbons from the stratum. In this type of operation the stratum frequently plugs in front of the combustion Zone because a heavy' viscous liquid bank of hydrocarbon collects in the stratum in advance of the combustion zone which prevents movef ment of air to the combustion process. To overcome this diiculty and to permit the continued progress of the combustion zone thru the stratum, inverse air injection has been resorted to. By this technique, a combustion Zone is established around an ignition borehole by any suitable means and air is fed thru the stratum -to the combustion zone from one or more surrounding boreholes. j

In the process of recovering oil by underground cornbustion, it is generally necessary to inject air into the porous, permeable, oil-bearing rock for extended periods. Field test results to date indicate that spontaneous ignition may 4occur during such air injection at high pressures. For example, a petroleum company recently conducted an underground combustion field test in the South Belridge iield, Kern County, California, in which premature spontaneous ignition occurred at the central injection well in a ldirect injection system. Subsequent performance indicated that this ignition was limited to the upper portion of the pay Zone, and that this partial ignition detracted from the r'ield performance Vin that it reduced the volumetric sweep eiciency of the direct drive' front.

Spontaneous ignition at air injection wells in any counteriiow combustion process would have even worse effects as it would force immediate shutdown and possibly result in loss of a whole well pattern since there would be burning at the Wrong places in the pattern.

Infield tests in which hydrocarbons Were recovered by in situl combustion in a tar sand by inverse air injection it was found that a material proportion of theV injected air lay-passed the combustion front and appeared in the production borehole along with produced hydrocarbons. Even in the ignited zones, air is believed to by-pass the rire front because of thermal fracturing which provides some channeling therethru. The by-passed oxygen mixes with the combustible products fom the burning zones a 3,227,215y -letales tgl??? and appears in the production Well which isr generally above the ignition temperature of the hydrocarbonoxygen mixture when this happens, and field tests to date indicate, as a rule rather than'the exception, that the mixture burns in the production borehole and production tubing u nless suitable precautions are taken. Temperatures in excess of 2500 F. have been frequently observed in a produc# tion borehole from this cause. This temperature has been `more than sufficient to melt downhole equipment on several occasions. Furthermore, if the by-passed oxygen quantity is larger, it may consume the entire product, thereby rendering' the process entirely useless. In addition, serious personnel hazards are created.

This invention is concerned with apparatus'aforpreventing undesirable or premature' spontaneous combustion in either a direct or inverse drive in situ combustion process during injection of combustion-supporting, oxygen-containing gas thru an injection Well in the stratum being produced. It is also concerned with apparatus for preventing lire in a production Well in either a direct or a reverse drive process.

Accordingly, it is an object of the invention to provide apparatus for preventing fire in a well associated with an in situ combustion process. Another object is to provide a means for maintaining the temperature of a stratum adjacent an injection borehole, during air injection, below ignition temperature at ambient conditions. It is also an object of the invention to provide apparatus for controllingand regulating borehole temperatures. A further object is to provide apparatus for preventing combustion of produced gases in a production well during either direct or inverse in situ combustion. Other objects of the invention will become apparent upon consideration of the accompanying disclosure. Y

A broad aspect of the invention comprises apparatus for sensing the temperature either in an injection borehole within the stratum to be ,produced .while injecting airor other combustion-supporting gas or ina production well during movement of a combustion front toward same, and, as the temperature approaches the ignition temperature of hydrocarbon material in the borehole or in the wall of the borehole, injecting into the borehole a line `dispersion of water, such as a water aerosol, in suflicient quantity or at a suicient rate to maintain the temperature at a safe margin below the ignition tern'perature. The apparatus comprises, inhcombinatiou with a cased well extending into the stratum being or to be produced, a temperature sensing device' in the well within the stratum, a supply of Water under sufficient pressure for" injection and dispersion, a line leading from the water :supply into the well, a valve in this line, and means responsive to the sensed temperature of said sensing device inoperative control of said valve.

A more `complete understanding of the invention may be hadtbyl reference tothe accompanying schematic drawing of which FIGURE 1 is an elevation thru a section of stratum showing an arrangement of apparatus in accordance with thev invention; FIGURE 2 is an elevation in partial section showing another embodiment of the' water dispersion means; FIGURE 3 is a view similar to FIGURE 2, showing another embodiment of the` water injection means; and FIGURE 4 is a similar elevation showing another arrangement of apparatus in accordance with the invention.

Referring tov FIGURE 1, acarbonaceous stratnr'n 10, Stich as an oil sand, is penetrated by a well orborehole 12 provided with acasing 14 extending to the stratum, and alwellhead 16. In one embodiment atherrnocouple 18 is suspended on acablef 20, including an electrical con! ductor cable 22, thru tubing- 24.Tubing 24 is provided with valve means (not shown) for maintaining au air tight seal around the cable. Movement of the cable up and down in the well is facilitated bypulleys 26 and 28 or by other suitable means.

Anair line 30 connects withcasing 14 below the wellhead as shown or this line may pass thru the wellhead, similarly to tubing 24. Ablower 32, or other suitable means, passes a stream of pressurized air thruline 30 into the well. A source of water under pressure, such as a tank 34, is connected with the well either directly orthru line 30 by means ofline 36 containingmotor valve 38. Water is admitted to tank 34 fromline 40 as needed and pressurizing gas is passed into tank 34thru line 42.

Atemperature controller 44 is connected with cable 22 and withmotor valve 38. This instrument (44) is set to maintain a suitable well temperature as sensed bythermocouple 18, such as not exceeding 300 or 400 F., depending upon the spontaneous ignition temperature of the adjacent stratum.

It is also feasible to utilize a series of vertically spaced spaced apart themocouples such as 18, 46, and 48 in xed or vertically adjustable position withinstratum 10. In this arrangement, the maximum temperature sensed by the Series of thermocouples actuatestemperature controller 44 which operatesvalve 38 to introduce dispersion of water into the injected gas.

The apparatus of FIGURE 1 is used to prevent spontaneous combustion in well 12, particularly, in the adjacent stratum, during pressuring of the stratum prior to establishing in situ combustion in the stratum or during use of this well to inject air to a combustion front moving toward said well.

In FIGURE 2, a high-pressure water line 50 containingflow control valve 52 leads intoair line 30 and is positioned so as to direct water onto a hemisphericalsolid surface 54 ondevice 56. This arrangement of apparatus assures the formation of a very nely divided water mist which is carried by the injected air into the well.

In FIGURE 3, a steam line 58 leads thrucasing 14 into the path of the injected air and is provided with aow control valve 60. This embodiment of the apparatus and process bleeds steam into the injection air to provide water droplets needed to maintain control of the temperature of the stratum in the well.

It is sometimes necessary to utilize an air injection pressure of several hundred to 1000 p.s.i.g. or more and it is, of course, essential to have available water pressure well above the air injection pressure. In such cases the steam pressure in line 58 and the water pressure inlines 50 and 36 must be adequate to effect injection and dispersion of the water against the pressure within the air line or well.

The water aerosol or mist is injected continuously in small quantities or intermittently in larger quantities automatically or by hand operation ofvalve 38 or the corresponding valves in the other embodiments of the apparatus. The quantity of water to be introduced varies from about an ounce to or more pounds 1,000 standard cubic feet of gas, depending on the ainity of the reservoir hydrocarbon for oxygen, the injection pressure, and the nature of the emergency involved. Native petroleum and bitumens vary greatly in their oxygen affinity, i.e., their tendency to ignite spontaneously. Heavy crude from Kern County, California, exhibits an oxygen demand of the order of 1,000 times as much as some typical Missouri bitumens. Such crude definitely tends to ignite spontaneously upon prolonged exposure to high pressure air and, as previously pointed out, spontaneous ignition actually did occur during preliminary air injection operations on a recent underground combustion field test in the South Belridge field. While some crudes and bitumens exhibit far less tendency to ignite spontaneously than the Kern County example, it is good insurance to have available in all underground combustion operations means for injecting finely dispersed water into the injection gas.

It might be well to note that the combustion front can itself tolerate small quantities of well-dispersed water, so that injection well bores can thus be kept cool without extinguishing the countertiow combustion front. The preferred and most advantageous cooling fluid is H2O in liquid form and/or steam form, but other coolants inert in the well bore ambient and readily separable from the production eiiluent may be utilized. Such coolants include N2, CO2, combustion gases, etc. The ensuing decription of the invention will be limited to H2O as the coolant but it is to be understood that other coolants may be utilized, even tho less advantageously.

Referring to FIGURE 4, aborehole 70, spaced from well 12 of FIGURE 1, penetratescarbonaceous stratum 10 and is provided with acasing 72, extending from ground level to the upper level of the stratum, and withproduction tubing 74, extending from adjacent the lower end of the casing through well head 76'to separating means 78.Line 80 carries water fromseparator 78 to waste or to recycle to the process as desired.Line 82 carries recovered hydrocarbons to refining or storage facilities.

Awater line 84 extends to a level incasing 72 adjacent the lower end oftubing 74, or to a lower level withinstratum 10, and is provided with a spray head or nozzle 85.Water line 84 passes throughwell head 76 and connects with a supply source, such as water tank 88. A pump is inserted inline 84 for providing the desired pressure atspray head 86.Motor valve 92 is positioned inline 84 downstream ofpump 90.ThermocoupleI 94, positioned in the well adjacent or below the lower end ofproduction tubing 74 and preferably just above the level ofspray nozzle 86, is connected with a temperaturerecorder-controller 96 which is in operative control ofmotor valve 92.

Instruments 44 and 96 are conventional temperaturerecorder-controller devices which are available from sev eral sources. The Brown Instrument Company, of Philadelphia, Pa., is a supplier of this type of instrument which is illustrated in their Bulletin No. 15-4, copyrightcd in 1942. Similar temperature-recorder-controllers are illustrated in Principles and Methods of Telemetering, by Borden et al., Reinhold lPublishing Corporation, 330 W. 42nd St.,New York 18, New York, copyrighted 1948. Chapter 13 of this publication at page 184 illustrates one type of instrument suitable for the instant application.

At the stage of the process illustrated in the drawing, there front 98 has advanced fromborehole 70 through the stratum a substantial distance toward surrounding air injection boreholes such asborehole 12 of FIGURE l. The product hydrocarbons pass through the burned out areaintermediate lire front 98 andborehole 70 to the borehole and intoproduction tubing 74 in conventional manner.Fire front 98 eventually progresses to the injection boreholes and upon arrival, with continued air injection, the front is reversed in direction and is driven back toborehole 70 by direct air drive, feeding upon the carbonized residue left in the stratum during the inverse air injection phase of the process.

During the inverse air injection -phase of the process, the hydrocarbons produced in and around refront 98 by the heat of the combustion process and the flushing action of the combustion gases, principally in vapor form, pass into the borehole 70 at elevated temperatures around 1000 F. and sometimes as high as 1500 or 1600 F. In this type of in situ combustion, the produced hydrocarbons passing through the hot burned out zone back of the combustion front, together with O2 which by-passes the tire front, appear in admixture in the production borehole and the temperature of the mixture sustains combustion, so that all of the oxygen present inborehole 70 consumes hydrocarbons and to that extent destroys valu-- able products, as well as contributing to excessive tern,- peratures and damage to downhole equipment.

5. During the direct drivey of the combustion front from the injection wells back to the production well, the far-ont travels through the still hot burned out stratum and bypassed oxygen is again present `in production 'i0 in admixture with hot hydrocarbons thereby causing Vborehole fires. The present invention prevents borehole 'fires or, if a .borehole tire develops, the process can be utilized to extinguish the same and prevent the .occurrence .of further borehole combustiori. n

In operation of the invention, Water is sprayed `in to the borehole, preferably, under substantial pressure Such as to 90 p.s.i.g., through a downhole spray, such las 4spray 86, so as to maintain the Atemperature "in the. borehole in the stratum below combustion .supporting temperature at the concentration of oxygen in the borehole. It has been found that borehole fires do not occur when the temperature of the borehole is maintained below about 750 F. and it is Apreferable to controlqthe injection of i water into the borehole so as to maintain the temperature in the range of about 600 to about 700 F., although temperatures as low ,as 500 and as high as 750 F. have been used successfully. At higher temperatures, particularly at higher concentrations of oxygen, fire develops in the borehole and destroys valuable hydrocarbons being produced. As the temperature in the borehole drops below about 500 F., liquid products accumulate in the bottom of the borehole 4and water injected into the borehole forms an emulsion therewith which greatly complicates the separation problem inseparator 78. In addition, at lower borehole temperatures the water-hydrocar bon emulsion in the bottom of the borehole is agitated by the ow of gases intothe borehole and considerable erosion of the borehole wall below casing '72 occurs, with substantial amounts of sand and eroded material from the borehole appearing `in the production effluent, further complicating the separation process. In other 4respects, at temperatures below 500 F., the process is just as effective in preventing borehole fires and preserving valuable hydrocarbons, but operation in this manner introduces other problems and disadvantages to the process which are undesirable.

While it is preferred to inject water in the manner shown in the drawing it has also been found effectiveV `to merely spray or otherwise inject water into the `mouth of the borehole at ground level, whereby the water descends by gravity into the :hot downhole section of the borehole where it effectively cools the p-roduction effluent so as to prevent the combustion of hydrocarbons with bypassed oxygen and thereby avoids well bore res.'

A preferred method of operation comprisessensmg the temperature adjacent the upper level of the stratum being produced by means oftherniocouple 94, or other tem-l temperature in the Well bore adjacent the producing.

stratum has been found satisfactory in a number of well tests. It is not necessary that the injection of Water be continuous, as intermittent injection of water has been successfully tested.

Field tests in inverse air injection insitu combustion in a tar sand of substantialV thickness at a level between 50 and 80 feet below the surface extending over aperiod of several months have been completed utilizing injection of water into the production boreholes at various levels in the well bore both intermittently and continuously. The injection of water in the manner described was found to be completelyetfective in eliminating borehole lires when the the temperature was maintained below the range of 700 to 750 F. It was foundthat when as low a `concentration ,of-oxygen in the production welll bore as 0.5 volume percent occurred, the temperature in the Well bore rose from about 1000 F. to the yrange of 1500 to 1600 F., without injection of water into the borehole, and with an oxygen concentration of only 3.0 percent, the temperature rose to at least 2500 F. Oil production without borehole combustion was sustained in some of these tests in which as much as percent of the injected air by-passed the tire front and where the non-condensible efuent gas contained more than 18 percent oxygen. It was surprising that the critical maximum borehole temperature was as high as the range of 700 to 750 and that operation at borehole temperatures below about 500 F. was so undesirable because of .complicating problems resulting therefrom.

A preferred method of initiating in situ combustion in and around the ignition `or production borehole in an inverse burning process `comprises heating the wall of the borehole within the carbonaceous stratum to ignition temperature and, while at this temperature, passing air thru the stratum into the borehole from one or more sur.- rounding injection boreholes so as to initiate combustion of the carbonaceous material in the stratum. Thereafter, continued passage of air thru `the stratum to the ignition borehole causes the resulting combustion zone or front to move thru the stratum countercurrently to `the injected air. It is advantageous to incorporate a small percent fuel gas, such as :1 ,to v,2% propane, with the injected air while initiating in situ combustion.

While the simplest method of injecting water into the hot production borehole within the stratum is thru a water line leading into the borehole and, preferably, to a level just above the stratum, it is also yfeasible to inject water into the borehole, or its wall, from one or more ,boreholes in the stratum within a short radius, such as one to several feet from the production borehole. Water injected in this manner into the wall of the production borehole has the beneficial cooling and diluting effect but requires drilling extra boreholes and is less desirable for this reason.

While the foregoing description of the invention is limited to fluid coolants, it is feasible to use readily Vaporizable solid coolants such as particulate, solid CO2 (Dry Ice) or ordinary ice, although the problem of introducing these materials to the well bore is a factor to be considered which makes injection of liquid H2O or gaseous CO2 preferable.

It has been found in inverse air injection field tests that the rate of air injection must be at least about 20 standard cubic feet per square foot of combustionl front per hour in order to sustain a combustion front moving inversely to the air flow. When the air injection rate is reduced below this minimum, the combustion front is either reversed in direction, so as to turn back to the production borehole, or the tire goes out. The upper limit of the air injection rate depends upon economic factors such as compressor loss consumption of valuable hydrocarbons in the stratum and the character of the carbonaceous stratum itself; however, air rates of about 50 standard cubic feet per square foot of lire front per hour are marginal and can be economically utilized, while air rates of s.c.f.h. per square foot of fire front are generally uneconomical and are maximum in any type of stratum.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. Apparatus for controlling temperature in a cased injection well used in an in situ combustion process which comprises in combination:

(1) at least one temperature sensing device in said Well adjacent a pay zone therein; ('2) a conduit leading thru the casing of said well for (7) means actuatably connected to said temperature sensing device and responsive thereto for opening said motor valve when the temperature adjacent said temperature sensing device reaches a predetermined value; and 'i (8) means for raising and lowering said temperature sensing device within said well during gas injection. 2. The apparatus of claim 1 wherein a plurality of temperature sensing devices are positioned in vertically spaced-apart arrangement within the portion of well within said pay zone for sensing temperatures at different levels therein, said temperature controller being actuated by the maximum temperature sensed by said devices.

3. Apparatus for preventing well re in a well in use in an in situ combustion process which comprises in com-v bination:

(l) temperature sensing means in said well adjacent an oil-bearing stratum for sensing temperature' therein; (2) means for lowering and raising the means of (1) in said well;

(3) a tubing extending thru the well head into said (4) an injection line for coolant communicating with said well;

(5) ow control means in the line of (4); and v l(i6) means responsive to the temperature sensing means of (l) in operative control of the flow control means of (5) for opening said ow control means when the temperature adjacent said sensing means reaches a predetermined value and controlling flow of coolant to substantially maintain a set temperature in said well adjacent the sensing meansof 1).

4. The apparatus of claim 3 wherein the injection line of (4) extends to the level of said stratum and including a spray head on the lower end thereof.

S. The apparatus of claim 3 wherein said well is a production well in a reverse drive in situ combustion operation, the tubing of (3) is a production tubing, and the injection line of (4) is a Water line.

6. Apparatus for controlling the temperature in a well penetrating a stratum undergoing in situ combustion comprisingin combination:

(1) temperature sensing means in said well for sensing temperature therein; A

(2) means for lowering and raising the means of (l) in said well;

( 3) an air injection line communicating with said Well for injecting air therein;

(4) an injection line for water communicating with the line of "(3,

(5) flow control means in the line of (4); and

(6) means responsive to the temperature sensing means of (1) in operative control of the flow control means of (5) fori? opening said ow control means when the temperature adjacent said sensing means reaches a predetermined value and controlling flow of coolant to substantially maintain a set temperature in said well adjacentthe sensing means of (l).

7. The apparatus of claim 6 including water dispersing means in the line of (3) adjacent the delivery end of the line of (4). f,

S. Apparatus for controlling the temperature in a well penetrating a stratum undergoing in situ combustion comprising in combination:

(l) a plurality of temperature sensing devices positioned in vertically spaced-apart arrangement within the portion of Well within said stratum for sensing vtemperatures at dierent levels therein;

(2) a conduit leading into said well for conduction of gases;

(3) a supply of coolant under pressure;

(4) a coolant line leading from the supply of (3) into said well for.,injecting coolant thereto;

(5). a motor valve in the line of (4); and

(6) means actuatably connected to the temperature sensingY devices of (1) and responsive to the maximum temperature sensed by said devices for opening the motor valve of (5) when the maximum temperature adjacent said stratum sensed by said devices reaches a predetermined value.

References Cited by the Examiner UNITED STATES PATENTS 724,053 3/1903 Schroeder 239-4432 X 1,539,667' 5/1925 Halagarda 137-79 2,041,394 5-/1936 Belcher 166-90 2,630,307 3/1953 Martin 166-4 2,853,136 9/1958 Moore et al. 166-11 2,858,891 y11/1958 Mollet al 166-11 2,930,598 3/1960 `Parker 166-11 X 3,013,609 12/19'61 Ten Brink 166--39 CHARLES E. ocoN-NELL, Primary Examiner. i BENJAMINHERSH, Examiner.

Claims (1)

1. 3. APPARATUS FOR PREVENTING WELL FIRE IN A WELL IN USE IN AN IN SITU COMBUSTION PROCESS WHICH COMPRISES IN COMBINATION: (1) TEMPERATURE SENSING MEANS IN SAID WELL ADJACENT AN OIL-BEARING STRATUM FOR SENSING TEMPERATURE THEREIN; (2) MEANS FOR LOWERING AND RAISING THE MEANS OF (1) IN SAID WELL; (3) A TUBING EXTENDING THRU THE WELL HEAD INTO SAID WELL; (4) AN INJECTION LINE FOR COOLANT COMMUNICATING WITH SAID WELL; (5) FLOW CONTROL MEANS IN THE LINE OF (4); AND (6) MEANS RESPONSIVE TO THE TEMPERATURE SENSING MEANS OF (1) IN OPERATIVE CONTROL OF THE FLOW CONTROL MEANS OF (5) FOR OPENING SAID FLOW CONTROL MEANS WHEN THE TEMPERATURE ADJACENT SAID SENSING MEANS REACHES A PREDETERMINED VALUE AND CONTROLLING FLOW OF COOLANT TO SUBSTANTIALLY MAINTAIN A SET TEMPERATURE IN SAID WELL ADJACENT THE SENSING MEANS OF (1)

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