US3407831A

US3407831A - Apparatus for preventing corrosion

Info

Publication number: US3407831A
Authority: US
Inventors: Donald R Anthony; Rado G Loncaric; Robert E Fields
Original assignee: Atlantic Richfield Co
Current assignee: Atlantic Richfield Co
Priority date: 1961-02-20
Filing date: 1966-11-02
Publication date: 1968-10-29
Anticipated expiration: 1985-10-29

Description

Oct. 29, 1968 D, R ANTHONY ET A1. 3,407,831

APPARATUS FOR PREVENTING CORROSION Original Filed Feb. 20, 1961 IN VE /V TORS DONALD R. ANTHONY RADO G. LONCARIC ROBERT E. FIELDS United States Patent 3,407,831 APPARATUS FOR PREVENTING CORROSION Donald R. Anthony, Rado G. Loncairic, and Robert E. Fields, Dallas, Tex., assiguors to Atlantic Richfield "Company, Philadelphia," Pa., a corporation of Pennsylvania I Original application Feb. 20, 1961, Ser. No. 90,527, now Patent No. 3,298,438, dated Jan. 17, 1967. Divided and this application Nov. 2, 1966, Ser. No. 591,631

11 Claims. (Cl. 137-209) g j ABSTRACT OF THE DISCLOSURE A truck-mounted injection system for liquefied normally gaseous inhibitors has an inhibitor supply section; a pressurized water-miscible liquid storage section and a metering pump section connected to a back-pressure valve and an injection line. A three-way valve on the side of the truck opposite the injection line allows alternate switching of the inlet of the pump between inhibitor supply and water-miscible liquid storage. The system may include means for heating or cooling the inhibitor prior to entry into the pump, a gas pressurizing system for the Water-miscible liquid, a sight flow indicator, and a vent line with relief valve.

This is a division of copending application Ser. No. 90,527, filed Feb. 20, 1961, now Patent No. 3,298,438.

This invention relates to inhibition of corrosion of metallic surfaces exposed to corrosive vapors. More specifically, this invention covers a portable apparatus for injecting anhydrous ammonia or normally gaseous amines into the annular vapor space of oil, Water and gas wells. Still more specifically, this invention pertains to portable, truck mounted, injection equipment for injecting liquefied normally gaseous inhibitors.

In crude oil and natural gas production, various types of wells are used to either produce the underground fluids or to inject fluids into underground formations. Usually, these Wells have an outer string of pipe called casing and an inner string of pipe called tubing. Since the tubing is smaller than the casing, there is a space between the two strings which is called the annulus or annular space. Normally, the fluids are flowed inside the tubing and a vapor space is formed in the annulus. In many instances, the entire annular space may be a vapor space and the vapor space, therefore, may extend thousands of feet into the ground. Frequently, the fluids flowing in the well contain water and acid gases like hydrogen sulfide, carbon dioxide or both. As the fluids are flowed, water vapors and acid gases collect in the annular vapor space. These gases cause corrosion of the tubing and casing exposed to the corrosive vapors. Various types of corrosion inhibition measures have been proposed to prevent this acid gas corrosion and the use of volatile inhibitors like ammonia has been suggested. But no one has suggested a practical, safe way of introducing liquefied normally gaseous inhibitors like ammonia into this annular space especially when the pressure Within the annular space exceeds the vapor pressure of the liquid inhibitor.

For the most part, moreover, prior art practices utilizing volatile inhibitors are designed for vapor zones where the pressure is below the vapor pressure of the liquid inhibitor and the inhibitor is added in its vaporized state or in some reacted form. These systems are impractical for high pressure equipment. Even in low pressure wells, moreover, it is undesirable to leave containers containing liquefied normally gaseous inhibitors unprotected at the wellhead since many of these inhibitors are highly toxic. In addition, whenever a large number of separate units are used to handle toxic materials and untrained personnel may be involved, the hazards are increased 3,407,831 Patented Oct. 29, 1968 ice many fold. It is, therefore, desirable to have a portable system for introducing the volatile inhibitor into not only high pressure systems but into low pressure systems as well. It is desirable that the injection equipment he portable and designed to protect personnel from the hazards of handling toxic materials. Such equipment, moreover, should be capable of metering the amount of inhibitor used and lend itself to use with commercially available containers. The prior art does not provide equipment of this nature for handling liquefied normally gaseous toxic inhibitors.

Accordingly, it is the object of this invention to provide an apparatus for preventing vapor space corrosion regardless of the pressure encountered utilizing liquefied normally gaseous inhibitors.

A further object of this invention is to provide portable injection equipment for safely handling toxic, liquefied normally gaseous inhibitors.

A still further object of this invention is to provide injection equipment for metering the amount of liquefied normally gaseous inhibitor used.

A more specific object of this invention is to provide such equipment especially adapted to liquid ammonia and volatile amines.

Another object is to provide injection equipment for preventing plugging of lines used in introducing the inhibitor and for purging such lines after use.

Another specific object of this invention is to provide such equipment especially suited to injection of liquefied normally gaseous corrosion inhibitors into the annular space of well bores.

For a better understanding of this invention, reference should be had to the accompanying drawing in which:

FIGURE 1 is a schematic, isometric view of the portable injection equipment.

This invention relates to inhibition of corrosion of metallic surfaces exposed to corrosive vapors. This invention covers apparatus for injecting anhydrous ammonia or normally gaseous amines into the annular vapor space of oil, water and gas wells.

The mobile injection equipment is designed to. provide a safe, compact unit for injecting pure, volatile, toxic, liquefied normally gaseous inhibitors into high or low pressure systems. In general, the injection unit is mounted on a truck bed and comprises an inhibitor reservoir section with pump intake system, a water-miscible liquid storage section with inert gas pressurizing system and a calibrated pump section with high pressure injection and venting equipment. The equipment permits operation from ground level and the high pressure system is located on one side of a truck bed away from the driver and most of the controls used during actual injection of the inhibitor.

While the injection equipment is suitable for all types of liquefied normally gaseous inhibitors, the following description of the injection equipment will be limited to anhydrous liquid ammonia and volatile amines like ethylamine, propylamine, isopropylamine, butylamine and all other volatile water-soluble amines.

Referring now to FIGURE 1, the mobile unit as illustrated has inhibitor supply means or reservoir 11. Covering inhibitor reservoir 11 is cover 13 which permits heating of the liquid inhibitor during cold weather. Inhibitor reservoir 11 is connected by way of flexible hose 15 to manifold valves 17 interconnecting inhibitor reservoir 11 with inhibitor delivery line 19 and venting line 21. The manifold valves are located under the rear end of the truck bed so that the valves are operable from the ground and out of the way of loading and unloading the inhibitor. Moreover, in this position, the manifold valves can be covered and locked to prevent tampering while the unit is not in use.

Venting line 21 connects all the lines of the injection equipment with vent hose 23 on vent hose reel 25. Vent line 21 and vent hose 23 permit venting and draining of the injection lines to a point remote and downwind of the truck. The end of vent hose 23 is equipped with spikes (not shown) which can be driven into the ground to prevent the end of the hose from whipping.

Inhibitor delivery line 19 passes through insulated box 27 which allows cooling of the inhibitor in delivery line 19 during hot weather. On delivery line 19 is pressure guage 29 which is used to measure the vapor pressure of the liquid inhibitor. On delivery line 19 after insulated box 27 is sight flow indicator 31 which has windows on both sides for see-through use to indicate when delivery line 19 is purged and full of liquid inhibitor, when there is flow in the line and when inhibitor reservoir 11 is empty. These features are important since the amount of inhibitor injected is measurable only so long as inhibitor delivery line 19 is full of liquid inhibitor.

Next to flow indicator 31 is two-way plug valve 33. One branch of two-way valve 33 connects with line 35 which in turn is connected to the bottom or outlet of storage tank 37. Storage tank 37 acts as a reservoir for a Water-miscible liquid like glycol or alcohol, which liquid is inert to the inhibitor and acts as a purging fluid as hereinafter described. Between storage tank 37 and two-way valve 33 on line 35 are valve 39 and check valve 41. Check valve 41 acts as a safety valve to prevent liquid inhibitor from backing up into storage tank 37.

Storage tank 37 is equipped with sight gauge glass 43, pressure gauge 45 and pressure relief valve 47. Also connected to the top of storage tank 37 is line 49 which communicates with cylinder 51. Cylinder 51 contains an inert gas like helium or nitrogen of sufiicient pressure to pressurize storage tank 37 to a pressure above the vapor pressure of the liquid inhibitor.

The second branch of two-way plug valve 33 is connected to pump inlet or intake line 53 which in turn leads to inhibitor pump 55 and to vent line 21 by way of valve 57. Two-way plug valve 33, therefore, permits rapid switching from inhibitor to water-miscible fluid or vice versa without stopping inhibitor pump 55. Moreover, since the water-miscible fluid is at a pressure higher than that of the liquid inhibitor, the inhibitor does not vaporize and vapor-lock inhibitor pump 55 when two-way valve 33 is used to switch pump intake line 53 from inhibitor to the water-miscible fluid in line 35.

Inhibitor pump 55 can be any suitable adjustable delivery pump capable of pumping at pressures exceeding the pressure in the equipment to be treated and capable of pumping at a rate sufiicient to overcome vapor-locking tendencies of the liquefied normally gaseous inhibitor. The pump used herein was a duplex, positive displacement single-acting reciprocating plunger-type pump with adjustable capacity. Inhibitor pump 55 can be motivated by a power take-off drive which is engaged from inside the truck. The truck engine rpm. is measured by a tachometer installed inside the truck. This allows adjusting the truck speed to correlate with the desired pump rate.

On the outlet or high pressure side of inhibitor pump 55 is injection line 59 which has three branches. One branch leads to pressure relief valve 61 which upon opening discharges the contents of line 59 to vent line 21. Pressure relief valve 61 operates as a safety valve should unusually high pressures be reached in injection line 59.

A second branch of injection line 59 leads to backpressure regulating valve 63 which holds back pressure on the inhibitor in injection line 59 and prevents vaporlocking of inhibitor pump 55. Back-pressure regulating valve 63 also permits the injection equipment to be used for treating equipment with internal pressures below the vapor pressure of the liquid inhibitor. The valve,

d therefore, is set at a pressure dependent upon the material being pumped, e.g., for ammonia, it is set at 300 p.s;'i.g.

The third branch of injection line 59 leads to valve 65 which is used to open by-pass line 67 around back-pressure valve 63. By-pass line 67 also has a branching line leading to valve 69 which upon being opened discharges the contents of by-pass line 67 to vent line 21.

Connected to back-pressure regulating valve .63 and by-pass line 67 is injection hose 71 which is wound around injection hose reel 73. The real operates with an automatic rewind to facilitate handling of the injection hose. Injection hose 71 is a high pressure hose designed for this particular service.

The outlet end of injection hose 71 is equipped with check valve 75 which prevents high pressure fluids from the equipment being treated from entering the injection equipment. Check valve 75 has a manual by-pass (not shown) used to equalize pressure across the check valve to open the valve should it be closed during operation. The end of injection hose 71 is also equipped with a quick-connect union (not shown) having a double sealing feature. This allows rapid connection to the equipment to be protected and speeds operation while maintaining safety.

In operation, the mobile unit is parked from 40 to 50 feet crosswind from the equipment to be treated. Vent hose 23 is unreeled and staked .down downwind from the mobile unit. Two-way valve 33 is opened to storage tank 37 containing the water-miscible liquid. All other valves are closed. The connections (not shown) on the equipment to be treated are purged of oxygen by venting some of the gas in the equipment to the atmosphere. Thereafter, injection hose 71 is unreeled and connected to these connections. After connecting injection hose 71 to the equipment to be treated, one of manifold valves 17 is opened to let liquid inhibitor from inhibitor reservoir 11 fill inhibitor delivery line 19. The operator checks sight-flow indicator 31 to note when the inhibitor delivery line 19 is full of liquid inhibitor. Inhibitor delivery line 19 must be kept full of liquid inhibitor at all times during an injection period. If the liquid vaporizes, the pump will vapor lock. In order to prevent the formation of vapors, it was discovered that the liquid inhibitor in the inhibitor reservoir 11 must be kept at a higher temperature than the liquid inhibitor in inhibitor delivery line 19. It was found that this temperature differential could be maintained by cooling inhibitor delivery line 19 on hotter days and heating inhibitor reservoir 11 on gooler days. To cool inhibitor delivery line 19, insulated box 27 is filled with ice or other refrigerant. To heat inhibitor reservoir 11, the exhaust from the truck can be piped over the reservoir or an electrical heating unit can be installed under cover 13.

After filling deliver line 19 with liquid inhibitor and insuring that the inhibitor will remain liquid, storage tank 37 is pressurized with inert gas from cylinder 51 to a pressure above the vapor pressure of the liquid inhibitor. This pressure is determinable from pressure gauge 29 in delivery line 19. Valve 39 in line 35 is opened to let water-miscible liquid flow from storage tank 37 through two-way valve 33 to pump intake line 53. The water-miscible liquid is an important feature of the injection process since water collects in the equipment connections and ammonia or volatile amines in the presence of water react with carbon dioxide to form a solid precipitate which may plug the equipment connections. The water-miscible liquid removes water from these connections. The water-miscible liquid is also useful in purging oxygen out of the injection lines. Oxygen accelerates corrosion. The water-miscible liquid is also used to purge the equipment lines of traces of the toxic inhibitor which being hazardous could otherwise cause injury to operating personnel. Another advantage of water-miscible liquid is to insure future free operation of valves. The water-miscible liquid should be inert to the inhibitor and acid gases.

Materials suggested are glycols, alcohols, and ketones.

Thereafter, the truck engine is set at the desired r.p.m. The optimum speed is predetermined to fit the type of inhibitor and pump capacity being used. For example, for ammonia, it was found that a speed of 1000 rpm. was optimum for a pump having a capacity of 0.52 gallon per minute at 51.1 strokes per minute. When a constant speed is used, the amount of inhibitor depends solely upon time, and therefore an accurate means for metering the inhibitor is provided.

The pump power take-off is engaged thereby causing inhibitor pump 55 to pump water-miscible liquid from storage ,tank 37 until two-way valve 33 is switched to open pump intake line 53 to inhibitor delivery line 19. Inhibitor is pumped for the desired period of time depending upon the amount to be injected. Immediately thereafter, two-way valve 33 is reswitched to line 35 and water-miscible liquid is pumped for suflicient time to purge the injection equipment of the inhibitor.

After pumping the water-miscible liquid, inhibitor pump 55 is stopped and the truck engine shut 01f. The valve on the equipment being treated is closed. The bypass around check valve 75 is opened and vent valve 69 is opened to drain the injection hose and lines. Injection hose 71 is disconnected from the equipment just treated and rewound on reel 73. All valves are then closed and the mobile unit taken to the next location. When the last injection is made, all lines are vented to vent line 21 to drain the injection equipment of toxic materials.

The description herein presented has set forth a portable apparatus for injecting liquefied normally gaseous inhibitors into both high pressure and low pressure equipment. It will be understood that many modifications and variations may be made in the details hereinbefore set forth without departing from the scope of this invention which is limited only as defined in the appended claims.

We claim:

1. A portable apparatus for introducing liquefied normally gaseous corrosion inhibitor into operational equipment comprising in combination an inhibitor supply means having an outlet connected to an inhibitor delivery line, a water-miscible liquid storage means having a top and an outlet, a metering pump means having an inlet and having an outlet connected to a high pressure injection line, a valve switching means connected to said inhibitor delivery line, to said outlet of said water-miscible liquid storage means and to said inlet of said pump means thereby allowing said pump means to be alternately connected between said inhibitor supply means and said water-miscible liquid storage means, said inhibitor supply means, water-miscible liquid storage means, valve switching means, pump means and high pressure injection line being mounted on a truck bed with said valve switching means and said high pressure injection line on opposite sides of said truck bed, heating means adapted to heat said inhibitor in said supply means, cooling means adapted to cool said inhibitor in said supply means, pressure supply means adapted to maintain within said water-miscible liquid storage means a pressure above the vapor pressure of said liquefied inhibitor, and a back-pressure regulating valve in said high pressure injection line, said back-pressure regulating valve being set to hold a predetermined back-pressure in said outlet of said pump means, said back-pressure being greater than the vapor pressure of said liquefied inhibitor.

2. The portable apparatus of claim 1 wherein the cooling means is an insulated box and the inhibitor delivery line passes through said insulated box.

3. The portable apparatus of claim 1 wherein the pressure supply means is comprised of a cylinder containing a gas inert to said water-miscible liquid, said gas being at a pressure above the vapor pressure of said inhibitor, and said cylinder being connected to the top of said water-miscible liquid storage means.

4. The portable apparatus of claim 1. wherein the outlet of the pump means is also connected to a venting line, said venting line being in turn connected to a venting hose.

5. The portable apparatus of claim 4 wherein there is a pressure relief valve in the venting line between said pump outlet and the venting hose.

6. The portable apparatus of claim 1 wherein there is a sight flow indicator in the delivery line between th valve switching means and the inhibitor supply means, said sight flow indicator having a window for visual indication of the presence of liquid inhibitor in said delivery line.

7. A portable apparatus for introducing liquefied normally gaseous corrosion inhibitor into operational equipment comprising in combination an inhibitor supply means having an outlet connected to an inhibitor delivery line, a water-miscible liquid storage means having a top and an outlet, a metering pump means having an inlet and having an outlet connected to a high pressure injection line, a valve switching means connected to said inhibitor delivery line, to said outlet of said watermiscible liquid storage means and to said inlet of said pump means thereby allowing said pump means to be alternately connected between said inhibitor supply means and said water-miscible liquid storage means, said inhibitor supply means, water-miscible liquid storage means, valve switching means, pump means and high pressure injection line being mounted on a truck bed with said valve switching means and said high pressure injection line on opposite sides of said truck bed, a pressure supply means adapted to maintain within said watermiscible liquid storage means a pressure above the vapor pressure of said liquefied inhibitor, a venting line connected to a venting hose and to said outlet of the pump means, a pressure relief valve in said venting line between said pump outlet and said venting hose, a backpressure regulating valve in said high pressure injection line, said back-pressure regulating valve being set to hold a predetermined back-pressure in said pump outlet of said pump means, said back-pressure being greater than the vapor pressure of said liquefied inhibitor, and a sight flow indicator in said delivery line between said valve switching means and said inhibitor supply means, said sight flow indicator having a window for visual indication of the presence of liquid inhibitor in said delivery line.

8. The portable apparatus of claim 7 wherein a heating means is adapted to heat the inhibitor in the supply means.

9. The portable apparatus of claim 7 wherein a cooling means is adapted to cool the inhibitor in the supply means.

10. The portable apparatus of claim 9 wherein the cooling means is an insulated box and the inhibitor delivery line passes through said insulated box.

11. The portable apparatus of claim 7 wherein the pressure supply means is comprised of a cylinder containing a gas inert to said water-miscible liquid, said gas being at a pressure above the vapor pressure of said inhibitor, and said cylinder being connected to the top of said water-miscible liquid storage means.

References Cited UNITED STATES PATENTS 2,506,412 5/1950 Chausse 222144.5 X 2,620,106 12/1952 Weeks 137209 X 2,646,817 7/1953 Cox 137267 X 2,792,014 5/1957 Granberg 137--267 2,980,295 4/1961 Sacco 222,144.5 X 2,992,757 7/1961 Richards 137,209 X 3,147,886 9/1964 Sacco 222--144.5 X

ALAN COHAN, Primary Examiner.