US2873814A

US2873814A - Methods and means for low temperature separation of liquid hydrocarbons from naturalgas

Info

Publication number: US2873814A
Application number: US654422A
Authority: US
Inventors: Joseph L Maher
Original assignee: National Tank Co
Current assignee: Cameron Solutions Inc
Priority date: 1957-04-22
Filing date: 1957-04-22
Publication date: 1959-02-17
Anticipated expiration: 1976-02-17

Description

Feb. 17, 1959 J. L. MAHER 2,373,814

METHODS AND MEANS FOR LOW TEMPERATURE SEPARATION OF LIQUID HYDROCARBONS FROM NATURAL GAS Filed April 22, 1957 4: ll 9 2/ 4o... /.2 1 v I? 20 v lo -;EATER H. P. 3SEF'ARATOR V EXCHANGE H M LL 27 Z5 as.

v SEPARATOR 5i" V v 49 .50 .67

0'7 55 I A; 5.9 2P" 5;" a 54 LOW TEMPERATURE SEPARATOR v V LOW PRESSURE SEPARATOR V v V LL ll 53 52 34 V w a 4 Fig./

I Fig. 2

Q 7 r 36 3y z f INVENTOR Joseph L. Maker as Fig.3

2? ATTORNEYS United States Patent METHODS AND MEANS FOR LOW TEMPERATURE SEPARATION OF LIQUID HYDROCARBONS FROM NATURAL GAS Joseph L. Maher, Tulsa, Okla, assignor to National Tank Company, Tulsa, Okla., a corporation of Nevada Application April 22, 1957, Serial No. 654,422

16' Claims. (Cl. 183-25) lowed by separation of the chilled stream into liquid and gaseous phases and the subsequent recompression of the gaseous phase by compressor means driven by the turbine unit.

The low temperature separation of hydrocarbon liquids from natural gas present in petroleum well fluids has become an accepted practice, and often results inincreased recoveries of marketable hydrocarbon liquids, or in the recovery of such liquids of increased value, as well as recoveries of gas in merchantable condition. There are, however, many wells which do not produce at a pressure level sufficient to permit the economic use of low temperature separation, and there are other wells, originally producing at a relatively high pressure but which are undergoing pressure depletion and approaching the point at which low temperature separation is not'usable.

In general, low temperatureseparatio'n depends upon the ability to permit the well stream to undergo a quite considerable pressure drop, resulting in cooling due to the Joule-Thompson effect, with the gas separated from the hydrocarbon liquids being conducted into a gas pipe line or transmission means. Since pipe lines currently are operating at pressures of 600 to 1,200 pounds per square inch, it is quite obvious that a well producing at 1,500 pounds per square inch can only be permitted to go a 300 pound per square inch expansion or pressure drop if the residual gas is to be disposed of into a 1,200 pound per square inch transmission pipe line. A pressure drop of this magnitude is not adequate to achieve the full benefits of low temperature separation, and usually will not result in an increased liquid hydrocarbon recovery of suflicient magnitude as to Warrant the cost and expense of a low temperature separation unit. Nor will such a pressure drop always produce merchantable gas.

To be merchantable in present oilfield practice and under present contracts for the purchase of oil field gas, the gas must be at least at pipe line pressure,-and must contain not more than a maximum stated quantity of water and hydrocarbons which may normally be expected to liquefy under pipe line conditions. These requirements are usually stated by providing that the gas shall not contain more than seven pounds of Water per one million cubic feet, or more than two hundred gallons of hydrocarbon, as determined by the standard test for charcoal hydrocarbon content, per one million cubic feet, all under standard or agreed conditions of temperature and pressure. Thus, as used herein, merchantable gas means gas meeting present day pipe line conditions as set forth above, and under a pressure of 600 to 1200 pounds per square inch. I

It has also been the practice to produce wells at relatively high pressures of several thousand. pounds per square inch, and to flow this high pressure fluid considerab-le distances to a low temperature separation unit for expansion at that point. Manifestly, this requires a gathering pipe network of heavy duty pipe which is capable of withstanding these high pressures and which is quite expensive. In instances, it is desirable to reduce the pressure of the well stream at the well head, and then to flow the production fluids through relatively inexpensive low pressurepipe to a low temperature separation unit for further processing. k

In view of the foregoing factors, it becomes apparent that the separated gas must be produced at certain minimum pressures and of certain qualities'to be merchantable, thatminimizing of the upstream or inlet pressure to the low temperature separator is often desirable, and that the pressure and temperature within the separator should desirably be kept at certainlevels. The latter follows from the fact that excessive pressures within the separator result in the dissolving and ultimate lossof increased quantities of gas'within the separated liquids, while excessively low temperatures within the separator cause the same undesirable result.

The present invention achieves these desirable objectives by causing the well stream to undergo expansion through a turbine unit'wherein not only cooling due to the Joule-Thompson effect is realized, but also wherein cooling is effected because work is taken from the well stream, or, the well stream is forced to do work in undergoing expansion. The stream is permitted to expand to a pressure 'somwhat below that of the gas pipe line into which the residual gas is to be introduced, and then, followingseparation of liquid hydrocarbons from the well stream at low temperature, the residual gas is taken at the low pressure and raised to pipe linepressure by a compressor driven by the turbine unit. The whole may befj'contained in a single vessel wherein the well stream is temporarily placed in a transient state or condition of very low temperature and low pressure at which optimum recoveries may be had of liquid hydrocarbons. The residual gaseous phase,'which must be conserved, is then compressedlto a higher pressure level and passed readily into the gas transmission pipe line. The turbine-compressor. unit is a free-running, self-governingunit, accommodating itself automatically to varying rates of flow and providing additional compression facilities automatically, with increased extraction of work from the incoming well stream, in accordance with an increase in volume ofsaid incoming stream. The speed of revolution of the turbine compressor unit may vary with the volume of flow therethrough, but since the work extracted from the incoming well stream is not necessarily proportional to turbine speed, no harmful impairment ofthe. units operation is caused.

Utilizing this invention, the required pressure and water and hydrocarbon-contents of the outlet gas are known i l-advance by existing pipe line conditions, and the' temperature and pressure required to achieve those-conditions within the low temperature separator may be determined. Following this, the required inlet pressure for the turbine unit may be determined as that necessary to provide the required temperature drop and to furnish suflicient energy for recompression of the expanded gas to pipe line levels. Preferably, the inlet pressure is kept to that level just sufiicient for this purpose, and according 1y an appreciable pressure drop of the well stream may be carried out at the well head.

In this type of low temperature separation, it is de sirable that a gas hydrate inhibitor, such as one of the glycols, beemployed, both to permit any desired degree of regenerative cooling of the well stream in advance of expansion, as well as to prevent the formation of excessive quantities of hydrate particles within the turbine unit. l-Ience, 1t is an object of the; invention to make provision in this type of low temperature separation for the addition of an inhibitor at any suitable or desirable point to control the formation of gas hydrates selectively within the course of flow of the Well fluids through the unit. A further object of the invention is to make provision for greater cooling of a well stream because of the greater pressure drop immediately prior to separation of liquid hydrocarbons from the well stream, and yet, to maintain a lesser overall pressure drop..

Yet another object of the invention is to provide a method and means of the character described wherein the lower pressure at which separation of liquid. hydro carbons is effected provides for greater liquid recovery due to the proximity of such lower pressure level to the optimum point for condensation for liquid recovery by retrograde condensation at the temperature of separation, an increase of recovery not obtainable at the higher pressure levels of the gas pipe line into which the residual gas must flow.

A still further object of the invention is to provide a method and means of the character described for achieving low temperature separation on relatively low pressure wells by means of a well stream header, for long-continued low temperature separation on the fiow streams of one or more wells by pressure reduction at the Well head and passage of the well stream through low pressure flow lines which may continue until the well reservoir pressures 'drop almost to the operating pressure of the gas transmission pipe line into which the residue gas is exhausted, or to permit the choking of the well streams of a group of wells at the well heads and the immediate passage of the flow streams from each well into a common flow line, high pressure separator, heater, and other necessary or desirable equipment whereby the duplication for such equipment for each well is eliminated and the producing of several wells of different pressures into a single system is rendered practicable.

Yet another object of the invention is to provide a method and means of the character described wherein the expansion step is carried out to an extent sufficient to produce merchantable gas and from the pressure of which the energy available from the expansion is capable of recompressing the gas to pipe line levels, the inlet pressure being only of sufficient magnitude as to 'satisfy such cooling and recompression requirements.

A construction designed to carry out the invention will be hereinafter described together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawing, wherein an example of the invention is shown, and wherein:

Fig. 1 is a diagrammatic view of a low temperature separation system constructed in accordance with this invention and adapted to carry out the methods thereof,

Fig. 2 is a longitudinal, vertical, cross-sectional view of a low temperature separator as employed in the system of Fig. 1, and t Fig. 3 is an enlarged schematic view of the turbine compressor unit.

This application is a continuation-in-part of my copfending application, Serial No. 451,195, filed August 20, 1954.

In the drawings, the numeral designates a producing well or series of wells flowing by a manifold or other suitable connection through a flow line 11. The present invention is applicable primarily to distillate type wells having high gas-oil ratios and producing relatively high gravity distillate or hydrocarbon liquids. The well stream may be produced andpassed into. the flow line 11 at well head pressure, or it may be reduced in pressure, as by the valve 12 so as to enter the flow linell. ata

4 pressure considerably lower than the well head pressure. Thus, the well stream may pass into the line 11 at a pressure of several thousand pounds per square inch, or at pressures as low as 1200 to 2000 pounds per square inch, depending upon the Operating pressure of the gas transmission pipe line into which the separated gas must ultimately discharge.

Depending upon whether subsequent pressure reductions in the system, or pressure reductions at the well head, require heating of the well stream to prevent the formation of gas hydrates or other freezing problems, the well stream may first be passed through a conventional heater 13 which normally is controlled automatically and which is selectively fired to bring the well stream automatically to a constant temperature level. NeXt, the well stream is passed by a conductor 14 from the heater 13 into a Water knockout or high pressure separator 15 wherein there is removed from the well stream such aqueous and hydrocarbon material as may be present in the liquid phase at that point. Liquids are drained from the separator 15 as they accumulate therein and pass through a pipe 16 for further use as will be described hereinafter. The gaseous stream from Which substantially all liquid particles have been removed, leaves the high pressure separator 15 through a flow pipe 17 into which a branch conductor 18 is connected through a valve 19. Since it is now desired to chill or cool the gas stream and gas hydrate or freezing problems may be encountered, it is sometimes desirable to add to the gas stream an inhibitor such as a brine solution or a glycol such as diethylene glycol or triethylene glycol, and such inhibitor may be injected into the flow line 17 through the branch conductor 18. Being thoroughly commingled with the gas stream, the inhibitor will preferentially remove water vapor from the gas stream and reduce the Water vapor dew point of the gas stream to the desired level.

The gas stream then passes through a valve 20 in the flow line 17 and into a regenerative heat exchanger 21 in indirect heat exchange relationship with a cold gas stream supplied from a later step in the process. The chilled gas leaves the heat exchanger 21 through a flow pipe 22 having a branch conductor 23 connected thereinto through a valve 24 and through which the inhibitor may also be injected in the gas stream following chilling.

The cooled gas passes from the pipe 22 to an inlet pipe 25 connected to the high pressure inlet of a turbine cornpressor unit 26. If desired, the valve 20 may be closed, and the gas leaving the high pressure separator 15 may be by-passed around the heat exchanger 21' through a conductor 27 leading through a valve 28 to the inlet conductor 25.

Within the turbine compressor unit 26, the gas stream is expanded and caused to undergo a pressure reduction while driving the turbine wheel 27' of the unit.

The unit 26 is mounted in the wall of a low temperature separator 27" into the interior of. which the expanded gas stream passes in free and unrestricted flow. The gas stream leaving the turbine wheel 27" may have a considerable circumferential velocity, and hence a spinner drum 28 terminating in a. heating coil 29 may be disposed upon the inner Wall of the vessel 27 in registry with the turbine unit 26 in order to confine and control the high entrant velocity of the gas stream as Well as to provide a surface upon which particlesmay be scrubbed from the expanded stream. The heating coil 29 may be supplied with any suitable heating fluid, such as a portion or all of the gas stream flowing through the conductor 14 in order to Warm the spinner structure and prevent the adherence of frozen particles thereto.

In undergoing expansion in the turbine unit, and in doing work in driving the turbine wheel 27, the temperature of the incoming gas stream is greatly reduced, resulting. in the liquefaction of hydrocarbon. and aqueous materials present in the gas stream. Within the separator vessel 27', these liquefied or congealed particles are per mitted to separate from the gas stream and stratify into layers in the lower portion of the vessel 27" to which heat issupplied through a suitable coil 30heated in any suitable manner, preferably the same as utilized for the heater 29. The liquid hydrocarbons are skimmed off into a sump 31 for removal through an outlet conductor 32, and the. aqueous materials are passed into a second sump 33 for removal through an aqueous outlet conductor 34.

It is pointed out that the turbine need not be mounted in the wall of the vessel 27" but may be housed in a considerable pressure drop, as well as in expending energy or work in driving the turbine wheel 27', the gas stream .will be chilled to temperatures of 0 to 20 degrees Fahrenheit or lower, and hence, substantially all liquefiable hydrocarbons and aqueous components will be condensed or congealedfrom the gas stream. The low pressure gas which has been denuded of liquefiable components is taken from the interior of the vessel 27" through the lower pressure gas conductor 35 to the inlet 36 of a centrifugal compressor rotor 37. It will be noted that the turbine wheel 27 and the compressor rotor 37 are mounted upon a common shaft 38, are free of any external regulation or control, and that all of the energy for driving the compressor rotoris derived from the turbine Wheel 27'.

. The lowpressu-re gas taken from the interior of the low temperature separator 27" is compressed by the trolvalve 42. If desired, a portion of the gas leaving the.

low temperature separator unit 27" may be by-passed around the compressor section of the unit 26 and conducted through a pipe 42' and valve 43 directly to the conductor 41. p I

The three-way valve 42 is employed for regulating the quantity of the cold gas that will flow from the conductor 41 through the heat exchanger 21. The valve 42 has connected thereto a pipe 44 leading to the heat exchanger 21 and a pipe 45 by-passing the heat exchanger and connected directly into the outlet conductor 46 by means of which the gas is conveyed to the gas transmission pipe line or other point of use. In accordance with established practice, a temperature sensing element inthe heat exchanger 21 or in the outletconductor 22 leading therefrom, may be employed to control the operation of the valve 42 and to selectively by-passgas around the heat exchanger or pass all or a portion of the cold gas through the heat exchanger in order to maintain the desired degree of chilling or pre-cooling of the gas stream passing through the heat exchanger from the conductor 17 to the conductor 22.

The liquids removed from the gas stream in the high pressure separator 15 may be taken from the drain conductor 16 through a valve 47 into a small separator 48 wherein stratification of the aqueous and hydrocarbon liquids is carried out and the water separately discharged througha valved drain pipe 49. The hydrocarbon liquids are drawnofi from the separator 48 through a valved conductor 50 into an inlet pipe 51 leading into the low temperature separator 27", preferably near that end of ther separator into which the turbine compressor unit 26 discharges the gas stream. If desired,the liquids flowing from the separator 15 may be by-passed around the separator 48 and conducted directly through the pipe 52 to the inlet conductor 51.

Within the low temperature separator, all of the liquids introduced thereinto, or removed from the gas stream passing therethrough, are resolved into aqueous and hydrocarbon fractions, the aqueous fractions being drawn off through the outlet 34, and being suitably processed as necessary or desirable for recovery therefrom of any inhibitor material which may have been introduced into the gas stream. Of course, the inhibitor material, after reconcentration, may be recirculated and again injected into gas stream.

The hydrocarbon liquids are drawn off through the outlet conductor 32, and may be passed through a valved pipe 53 into a low pressure or flash separator 54, or alternatively, may be passed through the valved conductor 55 to the inlet of a stabilizing or desorbing tower or column 56. Liquid passed into the low pressure separator 54 is resolved into a gas fraction which is drawn oif through the gas outlet 57, and a separated liquid fraction which will have been stabilized to a considerable degree by its passage through the low pressure separator and the removal of quantities of gas therefrom, and which may be discharged through the conductor 58 to storage, or may be directed through the valved pipe 59 into the conductor 55 for admission to the stabilizer 56. Within the stabilizer 56, the liquids are properly rectified and stabilized for storage, gas and extremely light hydrocarbon fractions being removedthrough the gas outlet 59, and-a stabilized hydrocarbon liquid being discharged at 60 to storage.

From the foregoing, it will be seen that the system is quite flexible and is adaptable to utilization with many types of well stream production as well as many varieties of operating conditions. Whether or not inhibitor is to be injected, whether the liquid separated in the high pressure separator 15 is to be subjected to an additional separation step before delivery to the low temperature separator, and whether the hydrocarbon liquids from the low temperature separator are to pass through the low pressure separator 54, the stabilizer 56, or both of these vessels, are matters dependent entirely upon the nature of the well stream, the conditions under which it is produced and the degree to which liquefiable hydrocarbons are to be separated therefrom and stabilized for storage. The heater 13 may be employed if there is any likelihood of freezing or congealing occurring at any point in the system prior to theentrance of the flow stream into the turbine unit 26. Thus, depending upon the pressure at which the lean gas stream must enter the conductor 46 for passage into the gas pipe line, and the pressure drop required to achieve the desired temperature in the low temperature separator 27 the well stream pressure may be reduced at the well head to a point just sufiicient to provide the desired pressure drop. Since chilling of the well stream at the well head would occur under these conditions, the heater 13 may be utilized for the prevention of freezing or congealing due to this pressure drop, as Well as to impart to thewell stream suflicient heat for proper operation of the

coils

29 and 30. conventionally, well stream heaters such as the heater 13, may include a pressure reducing choke 61 into which the well stream flows for pressure reduction immediately prior to itspassage through the heating coils 62 of the heater 13, and it is preferable that-the pressure reduction of the Well stream be achieved through utilization of the choke 61 rather than through employment of the valve 12. In this manner, all likelihood of solidification taking place in the flowing well stream with resultant blocking or partia'l clogging of the flow lines is avoided, and the gathering lines or pipes 14, through the well stream flows from one or more wells to the low temperature separation system, may be of relatively lightweight since they are not subjected to high pressure. In many instances, the pipe or pipes '14 may be of quite considerable length, and the possibility of using. light-weight pipe for this.

purpose efiects a quite considerable saving in material costs.

The utilization of this heater system also permits the' simpl e adjustment of the choke 61 to provide for varying or gradually decreasing well head pressures. The choke 61 may be automatic in operation, such as a diaphragm operated choke, and as the well pressures decline, the choke may be opened further in order to maintain a substantially constant pressure in the pipe 14 and throughout the balance of the system. Similarly, a group of wells producing at different well head pressures may be pressure regulated in order to-fiow into a common flow line 14.

The low temperature separation system herein described also permits optimum hydrocarbon recoveries from well streams since the separation of hydrocarbon liquids from the'fiowing stream takes place at a pressure levelbelow that at which the denuded gas is discharged from the system. The maximum liquid point in a liquidgas hydrocarbon system, known as the base of the retrograde range, is not found at a fixed pressure, but

varies with temperature. The lower the temperature at which the system exists, the lower will be the base of the retrograde range or the point at which maximum liquefaction occurs. In low temperature systems wherein separating temperatures of to degrees Fahrenheit are achieved, the maximum liquid point occurs at a pressure well below normal pipe line pressures, and hence, maximum liquid recovery is not made in a system in which the flow stream never reaches pressures below the pipe line or discharge pressure.

In the present system, the flow stream is caused to drop to a pressure well below the ultimate discharge pressure and hence, a pressure much nearer the base of the retrograde range. For this reason, additional liquid recoveries are obtained without any sacrifice in the ultimate discharge pressure of the system.

It is to be noted that the turbine unit is a free-running unit loaded only by the compressor rotor 37 Thus, the flow stream is caused to expand directly into the interior of the separating vessel 27", and to do Work while so expanding. All of the benefits of expansion cooling are achieved, and in addition, work is extracted from the flow stream for further cooling at the point of discharge of the flow stream into the interior of the separator vessel 27". Enhanced cooling results precisely at the zone of discharge of the flow stream into the vessel 27" which is constructed to handle any liquefaction or congealing that may take place. Thus, the problems of turbine blockage and the clogging of flow lines due to liquefaction and/ or congealing of flow stream components is eliminated while, at the same time, isentropic expansion is obtained.

It is again, pointed out that a number of objectives should desirably be obtained in a low temperature separation, but which have not previously been available without very large investments in processing equipment. First, the separated gas must be merchantable and should be produced in as large quantities as possible consistent with optimum distillate recovery. Second, a maximum of retainable and saleable distillate should be obtained in condition suitable for storage and sale. Third, the inlet well stream pressure should be kept at a minimum. The present invention achieves these objectives by setting the inlet pressure at a comparatively low level and. by expanding the incoming well stream to the lowest pres sure from which the energy available is capable of recompressing the low pressure gas to pipe line levels while producing merchantable gas. This, of course, necessarily entails desirably and/or preferentially setting the inlet pressure at such levels as to create within the low temperature separator those temperature and pressure conditions required to produce merchantable gas.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

l. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streams including the steps of, flowing the well stream from the well at a predetermined pressure, expanding the well stream from the predetermined pressure to a lower pressure while causing the well stream to do work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing oif the aqueous and liquid hydrocarbon portions, compressing the gaseous portion to an intermediate pressure sufiicient for introduction of the gaseous portion into a gas transmission pipe line, said intermediate pressure being higher than the pressure of the separation step and lower than said predetermined pressure, compressing the gaseous portion solely by the work done by the well stream in expanding, and drawing otf the compressed gaseous portion, the well stream being expanded in the expansion step to a lower pressure sufficient to produce a pressure and temperature drop adequateto liquefy sufiicient liquid hydrocarbon and aqueous portions from the Well stream as to produce merchantable gas and from which the work available from the expansion step is capable of compressing the gaseous portion to the intermediate pressure, and said predetermined pressure being of sufficient magnitude as to afford adequate temperature reduction in the expansion step suflicient to precipitate the aqueous portion from thewell stream in the production of merchantable gas. V

2. Themethod of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streams including the steps of, flowing the well stream from the well at a predetermined pressure, expanding the well stream from the predetermined pressure to a lower pressure while causing the well stream to do Work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing off the liquid hydrocarbon and aqueous portions, compressing the gaseous portion to' an" intermediate pressure sufficient for introduction of the gaseous portion into a gas transmission pipe line, said intermediate pressure'being higher than the pressure of the separation step and lower than said predetermined pressure, compressing the gaseous portion solely by the work done by the well stream in expanding, and drawing off the com pressed gaeous portion the well stream being expanded in the expansion step to a lower pressure suflicient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in suflicient quantities as to produce merchantable gas and from which the work available from the expansion step is capable of compressing the gaseous portion to the intermediate pressure, and said predetermined pressure being only of sumcient magnitude as to afford adequate temperature reduction in the expansion step sufiicient to precipitate the aqueous portion from the well stream in the production of merchantable gas.

3. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well' streams including the steps of, flowing the well stream from the well at a predetermined pressure, expanding the well stream from the predetermined pressure to a lower pressure while causing the well. stream to do' work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing ofi the liquid hydrocarbon and aqueous portions, compressing the gaseous portion to an'intermediate pressure of 600 to 1200 pounds per square inch solely by thework done by the well stream in expanding, and drawing off the compressed gaseous portion, the well stream being expanded in the expansion step toa lower 9 pressure s'ufficierlt to, produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in suflicient quantities as to produce merchantable gas.

4. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streamsincluding the steps of, flowing the well stream from the well at a predetermined pressure, expanding the well stream from the predetermined pressure to a lower pressure while causing the ,well stream to do work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing oil the liquid hydrocarbon and aqueous portions, compressing the gaseous portion to an intermediate pressure of 600 to 1200 pounds per square inch solely by the work done by the well stream in expanding, and drawing ofi the compressed gaseous portion, the well stream being expanded in the expansion step to a lower pressure sufficient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in suflicient quantities as to produce merchantable gas and from which the work available from the expansion step is capable of compressing the gaseous portion to the intermediate pressure. p

5. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streams including the steps of, flowing the well stream from the well at a predetermined pressure, expanding the well stream from the predetermined pressure to a lower pressure while causing the well stream to do work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing oil the liquid hydrocarbon and aqueous portions, compressing the gaseous portion to an intermediate pressure of 600 to 1200 pounds per square inch solely by the work done by the well stream in expanding, and drawing d the compressed gaseous portion, the well stream being expanded in the expansion step to a lower pressure sufficient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in sufiicient quantities as to produce merchant: able gas and from which the work available from the expansion step is capable only of compressing the gaseous portion to the intermediate pressure.

6. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streams including the steps of, flowing the well stream from the well at a predetermined pressure, expanding the well stream from the predetermined pressure to a lower pressure while causing the well stream to do work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing off the liquid hydrocarbon and aqueous portions, compressing the gaseous portion to an intermediate pressure of 600 to 1200 pounds persquare inch-solely by the work done by the well stream in expanding, and drawing oil the compressed gaseous portion, the well stream being expanded in the expansion step to thejlowest pressure from which the work available from the expansion step is capable of compressing the gaseous portion to the intermediate pressure and being expanded to a lower pressure suflicient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and :aqueous portions'in suflicient quantities as to produce merchantable gas.

7. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streams including the steps of, flowing the well stream from the well at a predetermined pressure of the magnitude of 1500 pounds per square inch, expanding the well stream from the predetermined pressure to a lower pressure while causing the well stream to do work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing off the liquid hydrocarbon and aqueous portions, compressing. the gaseous portion to an intermediate pressure of 600 to 1 200 pounds per square inch solely by the work done by the well stream in expanding, and drawing off the compressed gaseous portion, thewell stream being expanded in the expansionstep to a lower pressure suflicient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in sufficient quantities as to produce merchantable gas.

8. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streams including the steps of, reducing the pressure of the well stream from well head flowing pressure to a predetermined pressure, flowing the well stream from the well at a predetermined pressure, expanding the wellstream from the predetermined pressure to a lower pressure while causing the well stream to do work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing ofl the liquid hydrocarbon and aqueous portions, compressing the gaseous portion to an intermediate pressure suificient for introduction of the gaseousportion into a gas transmission pipe line, said intermediate pressure being higher than the pressure of the separation step and lower than said predetermined pressure, compressing the gaseous portion solely by the work done by the well stream in expanding, and drawing oif the compressed gaseous portion, the well stream being expanded in the expansion step to a lower pressure suificient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in sufl'icient quantities as to produce merchantable gas and from which the work available from the expansion step is capable of compressing the gaseous portion to the intermediate pressure, and

said predetermined pressure being of suflicient magnitude as to afford adequate temperature reduction in the expansion step sufficient to precipitate the aqueous portion from the well stream in the production of merchantable gas.

9. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure petroleum well streams. including the steps of, flowing the well stream from the well at a predetermined pressure, adding a hydrate inhibitor to the well stream, expanding the well stream and the hydrate inhibitor from the predetermined pressure to a lower pressure While causing the well stream to do work, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing off the liquid hydrocarbon and aqueous portions, compressing the gaseous portion to an intermediate pressure suflicient for introduction of the gaseous portion into a gas transmission pipe line, said intermediate pressure being higher than the pressure of the separation step and lower than said predetermined pressure, compressing the gaseous portion solely by the work done by the well stream in expanding, and drawing off the compressed gaseous portion, the well stream being expanded in the expansion step to a lower pressure .suflicient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in suflicient quantities as to produce merchantable gas and from which the work available from the expansion step is capable of compressing the gaseous portion to the intermediate pressure, and said predetermined pressure being of sufficient magnitude as to afiord adequate temperature reduction in the expansion step sufiicient to precipitate the aqueous portion from the well stream'in the production of merchantable gas.

10. The method of separating liquefiable hydrocarbons and an aqueous portion from gaseous high pressure pe- I troleum well streams including the steps of, flowing the well stream from the well at a predetermined pressure, adding a hydrate inhibitor to the well stream, expanding the well stream and the hydrate inhibitor from the predetermined pressure to a lower pressure while causing the well stream to do work by passing the well stream and the hydrate inhibitor commingled therewith through an expansion turbine, separating the well stream into a residual gaseous portion and liquid hydrocarbon and aqueous portions, drawing off the Iiquidhydrocarbon and aqueous portions, compressing the gaseous portion to an intermediate pressure sufficient for introduction of the gaseous portion into a gas transmission pipe line, said intermediate pressure being higher than the pressure of the separation step and lower than said predetermined pressure, compressing the gaseous portion solely by the work done by the well stream in expandinng, and drawing E the compressed gaseous portion, the well stream being expanded in the expansion step to a lower pressure suificient to produce a pressure and temperature drop adequate to liquefy liquid hydrocarbon and aqueous portions in sufficient quantities as to produce merchantable gas and from which the work available from the expansion step is capable of compressing the gaseous portion to the intermediate pressure, and said predetermined pressure being of sufiicient magnitude as to afiord adequate temperature reduction in the expansion step sufficient to precipitate the aqueous portion from the well stream in the production of merchantable gas.

11. The method of producing rnerchantable gas from a gaseous high pressure petroleum well stream and removing an aqueous portion from the well stream including the steps of flowing the well stream at high pressure to a separator enclosure and expanding the stream to a lower pressure into said enclosure while causing the well stream to do work whereby the stream separates into gaseous and liquid hydrocarbon and aqueous portions, drawing 0E said portions, and compressing the gaseous portion to an intermediate pressure of 600 to 1200 pounds per square inch solely by the work done by said well stream in expanding, the intermediate pressure being lower than the pressure from which the well stream is expanded and higher than the lower pressure.

12. The method as set forth in claim 11, wherein the high pressure is only of suflicient magnitude to compress the gaseous portion to the intermediate pressure and to provide a pressure and temperature drop to the lower pressure sufiicient to precipitate the aqueous portion from the well stream in the production of merchantable gas.

13. A low temperature separator structure for a gaseous high pressure petroleum well stream and for removing an aqueous portion from the well stream including, a separator vessel, means in the vessel for maintaining a gaseous layer in the upper portion of the vessel, heating means in the lower portion of the vessel, an expansion turbine in the wall of the vessel having a. well stream inlet and a well stream discharge opening directly into the interior of the vessel, the point of expansion of the well stream in the expansion turbine being disposed within the gaseous layer, means for causing the turbine to do work, and gas and liquid outlets from the vessel.

14. A low temperature separator structure for a gaseous high pressure petroleum well stream and for removing an aqueous portion from the well stream including,

a separator vessel, means in the vessel for maintaining a liquid layer in the lower portion of the vessel and a gaseous layer in the upper portion of the vessel, heating means in the lower portion of the vessel, an expansion turbine in the wall of the vessel having a well stream inlet and a wellstream discharge opening directly into the interior of the vessel, the point of expansion of the well stream in the expansion turbine being disposed within the gaseous layer, compressor means driven by the turbine, a gas outlet from the compressor, gas conducting means extending from the separator vessel to the compressor means, and a liquid outlet from the separator vessel.

15. A low temperature separator structure for a gaseous high pressure petroleum well stream and for removing an aqueous portion from the well stream including; a separator vessel; means in the vessel for maintaining a liquid layer in the lower portion of the vessel and a gaseous layer in the upper portion of the vessel; a turbinecompressor unit in a wall of the vessel comprising, an expansion turbine having a turbine wheel, the turbine wheel being positioned in the vessel at the point at which separation of gas and liquid is initiated, a compressor having a compressor rotor, and a single shaft carrying the turbine wheel and compressor rotor; the turbine having a well stream inlet and a well stream discharge opening directly into the interior of the separatorvessel; the

compressor having a gas inlet from the interior of the separator enclosure and a gas outlet; and a liquid outlet from the vessel.

16. A low temperature separator structure for a gaseous high pressure petroleum well stream and for removing an aqueous portion from the well stream including; a separator vessel; means in the vessel for maintaining a liquid layer in the lower portion of the vessel and a gaseous layer in the upper portion of the vessel; a turbinecompressor unit in a wall of the vessel comprising an expansion turbine having a turbine wheel, the turbine wheel being positioned in the gaseous layer in the vessel at the point at which separation of gas and liquid is initiated, a compressor having a compressor rotor, and

a single shaft extending through the wall of the separator References Cited in the file of this patent UNITED STATES PATENTS 2,355,167 Keith Aug, 8, 1944 2,671,322 Barry Mar. 9, 1954 2,679,145 Hagen May 25, 1954 2,690,814 1954 Reid Oct. 5,

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Claims

1. THE METHOD OF SEPARATING LIQUEFIABLE HYDROCARBONS AND AN AQUEONS PORTION FROM GASEOUS HIGH PRESSURE PETROLEUM WELL STREAMS INCLUDING THE STEPS OF, FLOWING THE WELL STREAM FROM THE WELL AT A PREDETERMINED PRESSURE, EXPANDING THE WELL STREAM FROM THE PREDERMINED PRESSURE TO A LOWER PRESSURE WHILE CAUSING THE WELL STREAM TO DO WORK, SEPARATING THE WELL STREAM INTO A RESIDUAL GASEOUS PORTION AND LIQUID HYDROCARBON AND AQUEOUS PORTIONS, DRAWING OFF THE ACQUEOUS AND LIQUID HYDROCARBON PORTIONS, COMPRESSING THE GASEOUS PORTION TO AN INTERMEDIATE PRESSURE SUFFICIENT FOR INTRODUCTION OF THE GASEOUS PORTION INTO A GAS TRANSMISSION PIPE LINE, SAID INTERMEDIATE PRESSURE BEING HIGHER THAN THE PRESSURE OF SEPARATION STEP AND LOWER THAN SAID PREDETERMINED PRESSURE, COMPRESSURING THE GASEOUS PORTION SOLELY BY THE WORK DONE BY THE WELL STREAM IN EXPANDING AND DRAWING OFF THE COMPRESSED GASEOUS PORTION THE WELL STREAM BEING EXPANDED IN THE EXPANSION STEP TO A LOWER PRESSURE SUFFICIENT TO PRODUCE A PRESSURE AND TEMPERATURE DROP ADEQUATE TO LIQUEFY SUFFICENT LIQUID HYDROCARBON AND AQUEOUS PORTIONS FROM THE WELL STREAM AS TO PROVIDE MERCHANTABLE GAS AND FROM WHICH THE WORK AVAILABLE FROM THE EXPANSION STEP IS CAPABLE OF COMPRESSING THE GASEOUS PORTION TO THE INTERMEDIATE PRESSURE AND SAID PREDETERMINE PRESSURE BEING OF SUFFICENT MAGNITUDE AS TO AFFORD ADEQUATE TEMPERATURE REDUCTION IN THE EXPANSION STEP SUFFICIENT OT PRECIPITATE THE AQUEOUS PORTION FROM THE WELL STREAM IN THE PRODUCTION OF MERCHANTABLE GAS.