US2324172A

US2324172A - Processing well fluids

Info

Publication number: US2324172A
Application number: US363737A
Authority: US
Inventors: George L Parkhurst
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1940-10-31
Filing date: 1940-10-31
Publication date: 1943-07-13
Anticipated expiration: 1960-07-13

Description

July-13, 1943. G. L. PARKHURST 2,324,172

PROCESSING WELL FLUIDS Filed oct. s1, 1940 s sheets-sheet 1 5 Sheets-Sheet 2 G. l.. PARKHURST PROCESSING WELL FLUIDS Filed oct. :51, 1940 July 13, 1943.

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July 13, 1943. G. L.. PARKHURST 2,324,172

PROCESSING WELL FLUIDS Filed 0012. 5l, 1940 3 Sheets-Sheet 5 Patented July 13, 1943 PnocnssrNG WELL FLUms George L. Parkhurst, Chicago, Ill., assignor to Standard Cil Company, Chicago, Ill., a corporation of Indiana j Application october 31, 1940, serial No. 363,737

3 Claims. (Cl. lii-50) This invention relates to methods of hydrocarbon conversion and recycle which are particularly applicable for usein connection with wells of the so-called distillate or condensate type. The method is applicable also in connection with production from other types of wells when it is desired to cycle gas to repressure an underground formation. More particularly this invention relates to a combination of distillate recovery and the Fischer or Fischer-Tropsch process.

Production from certain deep hydrocarbon reservoirs of the so'-cal1ed distillate type is wholly or largely in the vapor phase although these vapors contain substantial amounts of normally liquid hydrocarbons commonly including gasoline hydrocarbons and hydrocarbons boiling somewhat above the gasoline range. The existence of these hydrocarbons in the vapor phase in the subsurface reservoir is due to the high pressure existing in the formation which brings into play the so-called retrograde phenomena, whereby a hydrocarbon system which would exist as a liquid phase plus a vapor phase at moderate pressures exists as a single dense vapor or supercritical phase.

If gases coming from these extremely high pressure wells, e. g. at pressures of the order of 2000'to 4000 pounds per square inch, are reduced in pressure to pressures of the order of 700 to 1200 pounds per square inch, a distillate or condensate is formed. In handling' the production from such reservoirs the well uids are reduced in pressure and sometimes cooled to bring about the phenomenon of retrograde condensation, whereby a large part of the normally liquid hydrocarbons and also a substantial part of three and four carbon atom hydrocarbons are thrown out in the liquid phase and separated. This liquid phase can then be stabilized or flashed to atmospheric pressure. The gases originally separated, and sometimes those resulting 'from the stabilization or flashing operation are recycled to the underground formation from which they were pro. duced, thereby maintaining the pressure in such formation and preventing retrograde condensation therein, thus greatly improving the ultimate recovery from the reservoir. In some instances, these gases are used for the maintenance of the pressure in or the repressuring of an underground formation 'other than that from which they originated. ,e

It has been proposed to recover the liquid components of high pressure well fluids of the type described by a high pressure absorption or high pressure adsorption process followed by recycling of the gases to the same or another sub-surface reservoir for pressure maintenance or repressuring purposes.

Although the present invention is particularly applicable to production from high pressure weils of the distillate type, it is also applicable to ordinary gas wells, particularly where natural gasoline is present in the gas and to wells producing a liquid phase as well as a gas phase at the well head.

It is an object of my invention to increase the quantity of motor fuel produced from well uids of the distillate type. Further, it is an object of f this invention to provide repressuring gases having an increased ability to promote retrograde vaporization or prevent retrograde condensation in the reservoir. It is also an object to provide a process in which increased quantities of motor fuel are obtained from well liuids of the distillate type and in which the quantity and quality of the repressuring gases are increased. A more particular object is to provide a process in which at least a part of the gases remaining after a distillate recovery operation are so treated as to produce a synthetic crude oil which can be further processed to motor fuel. Other objects will appear hereinafter.

The production from distillate wells normally includes a large amount of methane and lesser amounts of higher paralnic hydrocarbons. Ordinarily this includes a substantial amount of Cz, C3 and C4 hydrocarbons, witha substantial amount of hydrocarbons within the gasoline boiling range, i. e. up to about 400 F., and usually some still heavier hydrocarbons in varying amounts. In distillate recovery, whether by retrograde condensation vor high pressure absorption, it is customary to recycle practically all of the C1, Cz andv C3 hydrocarbons and often a large part of the C4 hydrocarbons to the underground formation. The desirable normally liquid hydrocarbons are recovered and are not available for The above and other objects are accomplished by subjecting to catalytic oxidation certain of the light hydrocarbons present in the dry gas resulting from a distillate recovery operation to produce a synthesis gas comprising carbon monoxide and hydrogen. This synthesis gas is subjected to a Fischer or Fischer-Tropsch process,v and high pressure nitrogen and/or hydrogen is cycled to the input well.

Briefly, this method is followed by ilrst separating the distillate from gases by retrograde condensation or by high pressure absorption at pressures of about 1000 pounds per square inch or more. These gases are processed as outlined below. The distillate is separated into a predominantly Cs and C4 fraction, a light naphtha in the gasoline boiling range and a heavy naphtha. 'I'he normally gaseous Ca and C4 hydrocarbons may be subjected at high temperatures and preferably at high pressures to a thermal polymerization Aprocess which produces not only a large amount of gasoline range hydrocarbons but also an amount of gas of even greater volume than the gaseous volume of the hydrocarbons going to the polymerization operation. I'hese gases are available for recycling. The thermal polymerization process involves, among other reactions, the dehydrogenation oi' Ca and C4 hydrocarbons and of ethane to some extent, and the polymerization of the olefinic hydrocarbons thus produced to form normally liquid hydrocarbons ordinarily boiling largely in the gasoline range but including a heavy polymer fraction, which is very useful in connection with a high pressure absorption operation. The overhead from the initial Fischer product separation comprising mainly C3 and C4 olefins can be subjected to catalytic polymerization and the polymer combined with the product from the distillate C3-C4 thermal polymerizer. This combined stream is further fractionated and cycled as described in detail in connection with the drawings.

In a preferred process the normally gaseous hydrocarbons remaining after recovery of -the liquid hydrocarbons from the high pressure well fluids and comprising predominantly methanev are desulfurized and subjected to cracking in the presence of oxygen to produce a synthesis gas comprising carbon monoxide and hydrogen.

The methane or gas fraction can be cracked to produce the synthesis gas mixture consisting largely of carbon monoxide and hydrogen by any of a variety of processes. Thus it can be reacted with steam or with oxygen. Preferably the dry gas is cracked in the presence of oxygen produced either by electrolysis of water or by a low temperature distillation process from air. For example, the oxygen necessary for this gas-cracking step canbe produced by the Linde or Linde- Frnkl process. This results in a volume of high pressure nitrogen which theoretically will be equal to twice the volume of 'methane cracked, since one-half mol of oxygen will theoretically be usedy for each mol of methane and about two mols of nitrogen will be produced for each half mol of oxygen. This nitrogen is available at an elevated pressure and can be used directly' for reinto an underground reservoir to increase or maintain its pressure and displace the hydrocarbons in that reservoir towards the outlet wel! or wells. Thus electrolysis yields hydrogen and the oxygen concentration yields nitrogen under high pressure. v

Alternatively or additionally the tail gases from the Fischer or Fischer-,Tropisch process can be compressed and recycled through the formation or sent to another formation to displace the hy-4 drocarbon fluids en masse towards the output well or wells and to prevent the precipitation of liquids within the reservoir which would result from a pressure drop. These tail gases not only contain hydrogen as the principal component but also contain nitrogen, carbon monoxide and light hydrocarbons and enhance the operation of the retrograde phenomena.

Ii the gas cracking is carried out with steam rather than oxygen, an excess of hydrogen will exist in the synthesis gas and in the tail gas from the Fischer process. 'Ihese tail gases particularly high in hydrogen are highly beneficial for cycling to a sub-mirface reservoir to increase or maintain the pressure in the reservoir thus increasing the ultimate recovery of valuable hydrocarbons from the reservoir.

The normally gaseous hydrocarbons heavier than methane, i. e. Cz and/or C: and/or C4 hydrocarbons, can be separated wholly or in part in one or more fractions from the products of the Fischer synthesis oven, which can be operated in one or two or more stages with or without an intermediate product recovery step. All or part of the normally gaseous products can be recycled to the gas-cracking step or can be compressed and cycled to the input well. Likewise, someof the gaseous hydrocarbons from the Fischer process can be cycled to fuel. It will be apparent to those skilled in the art that the ultimate disposition of the gases remaining after the various separations will vary depending not only upon the composition of the well fluid undergoing recovery but also upon the manner in which the various steps are operated. Various economic considerations will enter to determine further what is to be done with the various gas fractions otherthan the methane fraction from the distillate recovery. Ordinarily the methane fraction iscracked to synthesis gas and the hydrogen, nitrogen and 'Fischer tail gases ordinarily are sent to an underground formation under pressure, the hydrogen and nitrogen being under considerable pressure.

In a preferred process,` the gases comprising the methane fraction remaining after recovery of liquid hydrocarbons from the well fluids are cracked to produce a synthesisgas mixture made up largely of carbon monoxide and hydrogen. Any of a variety of processes can be used, for example, the gases can be reacted with steam or with oxygen. Some hydrocarbons oi' higherA molecular weight thanmethane canbefincluded in the methane fraction separated vfr Qm the well fluid,l particularly where their presence fserves to produce a better balanced vsynthesis,gasmixf` ture and the synthesis gas can,v.if desired-bc made entirely from C2 and Cs. Q1f`Cz, Cs.,and,C4'-

bons heavier thanmethane, i. e., the C: and/or Ca and/or C4 hydrocarbons, can be separated wholly or in part in one or more fractions from the liquid products of the Fischer synthesis. The recovered gases can be recycled in whole or in part to the sas-cracking step or the synthesis gas step or they can be thermally or catalytically polymerized. An intermediate fraction of the Fischer synthesis product can be thermally or catalytically polymerized to liquid hydrocarbons either separately or along with the distillate hydrocarbons. Hydrogen produced by either the thermal or catalytic treatment o; the hydrocarbons can, of course, be forced down a well to repressure an underground formation. y

In order that the invention may be better understood, reference is made to the accompanying drawings which show in Figures 1, 2 and 3 flow diagrams illustrating my invention and forming a part of this specification. 4 Referring first to Figure l, a producing well I0 furnishes well iluids from a sub-surface reservoir which is normally a deep high pressure well of the distillate type. The well fluids pass through valve II and line I2 to one or the other of drlers 28. These driers may contain any desired drying material, for example, calcium chloride. The particular drier used at any particular time is controlled by the operation of valves 00. Normally one drier is onstreaxn and the other is being regenerated by passing hot gases therethrough by means of valves 21. The purpose of the drying operation is to remove water which would otherwise form natural gas hydrates on reduction of the temperature and pressure, thereby interfering with the operation of the subsequent apparatus. and pressure of the separation step are such that hydrate formation is not objectionable. the drying step can be omitted.

'I'he well iiuids pass through cooler I3 and pressure reduction valve I4 to separator I5. The cooler and pressure reduction valve are controlled to give a temperature and pressure in the separator I 5 which may be varied within considerable limits depending on the desired operation and the particular character of the well fluids. However, they are such as to give a substantial recov- However, if the temperature ery of liquid hydrocarbons by virtue of the retrograde condensation phenomenon.

'I'he gas phase from separator I5 is predominantly methane but also includes ethane and minor amounts of heavier hydrocarbons. 'I'his gas vphase passes through line I8 -to methane cracker or synthesis gas generator |40, where it undergoes an exothermic catalytic oxidation. (If

necessary the gasesfrom separator |5 may be reduced in pressure prior to introduction to the methane cracker |40.) The liquid phase formed in separator I5 and withdrawn through line 23 by valve 22 controlled by float 2|, includes a major part of normally'liquid hydrocarbons present in the well fluids and normally gaseous hydrocarbons, particularly C3 and C4 paraillnic hydrocarbons. 'I'hese gases may be recovered by known means and the fraction in the gasoline boiling range passed from s'urge drum 23 by line |13 to Fischer Process gasoline stora'ge tank 83.

The synthesis gas generator |40 is supplied with oxygen produced by electrolysis of water with by-product hydrogen under high pressure, for example, about 4000 pounds per square inch, or by the Linde-Frnkl process with nitrogen under high pressure as a by-product. The hydrogen or nitrogen is cycled via line |5| to input well |52 and oxygen passes to methane cracker |40 by line |42. The synthesis gas comprising largely hydrogen and carbon monoxide is withdrawn from methane cracker |40 by line |55 and Introduced in synthesis over IAQ. .In oven |48 the carbon monoxide and hydrogen are reacted to produce higher molecular weight hydrocarbons largely of the gasoline boiling range. This step is well known in the art and it is contemplated that it may be carried out under any one of the variety of conditions under which it is known to operate. Thus it may be carried out at pressures ranging from about atmospheric up to about 150 pounds per square inch or somewhat higher, and within the temperature range of between above 300 F. and 400 F., although somewhat higher and somewhat lower temperatures may be selected.

Considerable quantities of water are produced in the hydrocarbon synthesis from carbon monoxide and hydrogen and this water ordinarily is removed from the hydrocarbons and discarded from the system by valved line 202 in response to float control |59. When the process is operated to produce a predominantly synthesis gasoline, it is drawn off by valved line |62 and passed to stabilizer 32, the bottoms from stabilizer 32 being drawn ofi' byline 59 through cooler 6I and thence to product tank 83.

Returning to the fractionator |80, the gas phase Withdrawn overhead by line |92 may be introduced to stabilizer 32 by either of valved lines 35. Reilux in addition to that resulting by the use of the cold material from the product sepacan be recycled to methane cracker |40 or used as fuel.

Although the simple flow diagram and arrangement of apparatus shown in FigureA l is advantageous in many respects, it is also desir- Alternatively, the gas phase able in some instances to use more extensive processingV and equipment. This is particularly true where large production is Vavailable and where the characteristics of the formation in well fluids are such that the production of the well or wells declines only very slowly, justifying a high capital investment in obtaining increased eiiiciency. Figures 2 and 3 taken together illustrate some of these possibilities.

Referring to Figures 2 and 3 in more detail, the production from one or more producing wells I0, which are preferably of the distillate type, passes through valve II and line I2 into cooler I3 and pressure reduction valve I4 tov a separator absorber I5 whichl if valves I8 and I8 are closed and no absorber il is introduced by lines 20 and I1, operates as a retrograde condensation separator similar to that shown in Figure 1. One diierence, however, is that Figure 2 shows the use of an antifreeze system as one method of preventing natural gas hydrate trouble. A fluid antifreeze material, for example, calcium chloride brine, can be circulated with the `ivell fluids through pressure reduction valve I4 and this serves to prevent the formation of natural gas hydrates.. In the case of liquid antifreeze material, the antifreeze separates at the bottom of the separator absorber I5 and is withdrawn by valved line 25 under control of iioat 24 which floats at the interface between the antifreeze and the hydrocarbons. The antifreeze is withdrawn to a regeneration, storage and recycling system from which it goes back into the line either preceding or following cooler I3. In Figure 2 the regenerated antifreeze is returned by valved line 21 between the cooler I3 and pressure reduction valve I4.

It`will be understood, however, that some of these apparatus arrangements may be omitted depending upon the character of the well fluids and the character of the subsequent operations. Thus, for example if the well fluids are available at moderate pressures, for instance 1500 to 3000 pounds per square inch, a pressure reduction ordinarily will not be needed and is not desirable when the distillate recovery is eiected by absorption. If the product is very low in water content or if the separator-absorber I5 is operated at a temperature above that at which hydrates form under the particular conditions involved, the antifreeze step can be omitted. An alternative method of avoiding the natural gas hydrates is shown in Figure l, wherein the well fluids are dried by passing-them through a drier containing a solid contact mass such as calcium chloride for example.

The well iuids enter the high pressure separator-absorber I5 and the gases, chiefly methane, are withdrawn from separator I5 by line I6. The liquid hydrocarbons in separator I5 are withdrawn through valve 22 under the control of float valve 2| and passed by means of line 23 to surge drum 28. This surge drum can be operated at about the same pressure as separator I 5 in which case it serves only as the surge drum. Or it may be operated at a pressure intermediate that of separator I5 and that of stabilizer 32, in which case it serves not only as a surge drum but also as a separator. Thus, for example, the distillate recovery vessel I5 can be operated at 1200 pounds per square inch, the surge drum 28 at 600 pounds per square inch, and stabilizer 32 at 300 pounds per square inch. Valved line 3| leading from surge drum 28 to fuel gas system 88 is provided.

Thus whensurge drum 28 is operated as a separator, some of the gases can be removed to fuel. The liquid present in surge drum 2l passes through line 28 and pressure reduction valve 30' into stabilizer 32. Before entering the stabilizer 32 all or part of the liquid can be used to cool the stabilized product by wholly or partially closing valve 34 and opening valves 33, thereby passing this cooled stream from the surge drum 2l through heat exchanger 60. On the other handv it is often desirable to utilize the low temperature of this material from the surge drum not al4 indirect heat-exchange material in heat exchanger 60 but rather as reiluxing material in stabilizer 32. When the stream from the surge drum is not routed through the heat exchanger 60 prior to introduction into the stabilizer, the

point of introduction preferably is the one corresponding to the upper of the three alternative valved lines 35.

' In stabilizer 32 hydrocarbons lighter than butane are removed and the stabilizer is pret' erably`operated at such pressure, reflux ratio, and top temperature as to eliminate a portion of the C4 hydrocarbons not desired in the nished motor fuel. Reflux in addition to that resulting by the use of the cold material from the surge drum 28 can, if desired, be furnished by passing the off-gases from the stabilizer 32 via line 33 through partial condenser 31 to separator Il from which a part of the liquid phase can be pumped by means of pump 40 through valve 4I and line 42 back into the top of stabilizer 32. I! the hot material from polymerizer 41 is introduced into stabilizer 32 through line 53, as will -be discussed hereinafter, little or no reboiling is necessary. However, if this is not the case, i. e if a separate fractionator apparatus is used for the polymerization products, reboiling can be furnished by means of trapout plate 64 and heater 65. Some heating at this point may be desirable, even if the hot polymerization products are discharged into the stabilizer.

Stabilized material from stabilizer 32 can be cooled by heat exchanger 60 and/or cooler Il and then passed to intermediate products storage tank 63. Since the material in this intermediate porducts storage tank normally contains a considerable amount of hydrocarbons boiling above the gasoline range, it can be rerun. Therefore, it is withdrawn by means of pump 66 and passed through line 61 to rerun tower 68. When desired. the liquid product from the Fischer process may be rerun with the bottoms from stabilizer 32 which may include gasoline, polymers and distillate hydrocarbons.

Rerun tower 68 can be operated at low pressure and is a conventional piece of equipment. If cooler 6I has been used, the material from intermediate product storage tank 63 can be used to cool the hot bottoms from rerun tower 38 by closing valve 68 and opening valves 10, thus passing this relatively cold stream through heat exchanger 1I. In any event the material to be rerun enters the rerun tower 68 by line 61. The tower is provided with dephlegmating coil 12 and reboiling equipment 13. Stabilized gasoline of the desired endpoint is taken off through line 14, passed through condenser 15 and then passed via line 16 to storage tank 11 which with proper control may contain the final gasoline produced directly from the distillate. If the liquid product from the Fischer process has not been rerun .with the intermediate product from stabilizer 32, this gasoline can be withdrawn through valved line 18 for shipment or for further treatment. Alternatively, it mayl be withdrawn through valved line 18 and blended in line 8| with the gasoline produced in the polymerization operation, and this is in general desirable since Vthe polymer gasoline has a relatively high knock rating and the distillate gasoline has a relativelyv distillate tank 88 can be omitted and all the heavy distillate can be passed along with the heavy polymers in tank 84. 'Ihe heavy polymers separately accumulated in tank 84 is the best absorber oil-for use in distillate separator l5. Therefore, when the separator i is operated as a high pressure absorber, the heavy distillate can be collected in storage tank via valved line 85- and removed by valved line 81.

Returning now to separator 38 in connection p with stabilizer 32, the liquids from this separator alternately are passed by pump 40 through valve 48, line 4.4, line 45, heat exchangers 48 and line 48 into the coils of the polymerization furnace 41.

The gases from separator 38 on the other hand can be utilized in a variety of ways which will depend for themost part upon their composition. Their composition in turn depends on the pressures chosen for various parts of the apparatus and on the composition of the original well fluids. If gases from the surge drum 28 are not usedas fuel, gases from separator 38 can be used as part or all of the fuel for polymerlzer 41. Fuel gas storage tank 88 normally floats on the line. 40

gases from separator 38 do not contain large f amounts of polymerizable hydrocarbons, is to pass all or a part of these gases through valve v88, compressors 80, valve 82, compressors 83,

line 84, line |80, compressors 203, and line 204 to input well |52. polymerizer 41 discharges into stabilizer 32, to cycle the greater part of the gas from separator 38 to the'input well or wells |52. Gases from downstream points can be picked up and recycled ,to a point in the Fischer proc'ess. For example,

valved line 201 can be provided for that purpose.

Referring now in more detail to polymerizer 41, the hydrocarbons entering it are preheated by means of heat exchangers 48, or by one of them if sodesired, by control `of ow of product by valves 50, and then pass with any desired routing through the coils of the polymerization furnace 41. This polymerizer is preferably operated at a temperature of between about 950 and 1150 F., for instance about l025 F., and at a pressure of 1000 to 3000 pounds per square inch, for example 1500 pounds per square inch.

Other types of polymerizers may be used, preferably high temperature thermal polymerization I prefer, particularly when systems, but also including thermal and catalytic systems in which the gases are rst dehydrogenated and then polymerized in a separate operation. Such a polymerization can be applied to the synthetic crude produced by the Fischer process as will be described below. Although the operation of polymerization involves dehydrogenation as well as polymerization. in the strict sense of the latter term, I refer to the comblned reactions. whether occurring together or in separate steps, as polymerization. This is i accordance with the usage in the art.

The reaction products from the polymerizer 41 pass out through line 48 and heat exchangers 48 and thence through valved lines 5|, 54, or 85. If desired, the hot polymerization products from polymerizer 41 can enter separator 55 by valved line 54 in which case valve 5I is closed. 'Ihe heavy polymer may be withdrawn by valved line 58 in response to float control 51. The remaining vapors then pass by valved line 58 and one of valved lines 53 to stabilizer 32. This has the advantage of using a single column for two purposes and utilizing the hot stream from the polymerizer and the relatively cold stream from the distillate recovery operation to good advanltage in eliminating or cutting down the amount of reflux and reboiling necessary in connection with this tower. When this operation is carried out in this fashion,

tanks

83, 11 and 88 will, of course, contain `the polymer product as well as the distillate product, and stabilizer 81, fractionator 88, bubble tower 88 and

tanks

84 and 88, together with the associated equipment, can be eliminated.

On the other hand, it is sometimes advantageous to keep the polymerization products entirely separate from those of the distillate recovery operation, and when this is desired valves 5| and 54 can be closed and valve 85 opened, thus sending the products from the polymerizer 41 to a separate fractionation system. Another possibility is to utilize a vseparate fractionation system only for such part of the polymer products as it is desired to keep separate and to retain the advantages lof single tower operation insofar as the bulk of the polymer products is concerned. This can, of course, be accomplished vby proper control of valves 5|, 54 and 85.

The material, if any, passing through valved line can be used, if so desired, to heat reboiler |00, whereuponit enters fractionating column 88 which is operated under such conditions that the f fractionator 88 passes into stabilizer 81 through line |03 and one of the three alternative valved lines |04. The bottoms from the stabilizer is withdrawn through valve |05 and passed through cooler |08 to, storage tank 88 as part of the stabilized polymer gasoline product. The overhead from stabilizer 81 passes through line |01 and partial condenser |08 to separator |08. A portion of the liquid phase from this separator can be passed by pump H0 through valved line III to serve as reux in stabilizer 81. Likewise all or a portion can be recycled by valved line H2, line 45, heat exchangers 48 and line 48 to the coils of the polymerization furnace 41 to produce higher ultimate yields of polymer gasoline. Alternatively, all or a portion of the liquid phase from separator |88 may be routed by valved line |35 and line |1| to furnace |15 and subsequently subjected to `catalytic polymerization together with the-synthetic crude produced by the gascracking \and hydrocarbon synthesis steps.

The gas phase from separator |09 may be handled in any one or more of the three alternative Ways discussed in connection with the gas phase from separator 38. Thus it may be passed through valve H3, compressors ||4, valve |I5, line 45, etc. to the coils of the polymeriaer 41; or through valve ||6 and line ||1 to burner ||8 or fuel gas storage 88; and/or it may be passed by valved line H3, compressors H4, valve H9, compressors 93, line 94, line |90, compressors 203, and line 204 to one or more input wells |52. This latter is ahighly desirable operation, since it is important to keep up the amount of gas available for recycling to the formation and this gas being rich in hydrogen is a particularly desirable material for recycling. In many instances, it will be possible to eliminate part of the compressors referred to, since it will not be desired to utilize al1 of these possible alternative arrangements shown.

Reverting now to the bottoms from the fractionator 96, these can be used, if desired, to cool the bottoms from bubble tower 98 by closing valve |20 and opening valves |2|, whereby the hot, stream passes through heat exchanger |22 and thence through line |23 into the bubble tower 98. This bubble tower is conventionally equipped with dephlegmating means |24 and reboiling means |25; It is so operated as to eliminate a heavier than gasoline bottoms and a gasoline overhead. The latter is passed through condenser |26 and line |21 to polymer product tank 99 while the bottoms pass through heat exchangers |22 and/or cooler |28 to heavy polymer tank 84.

The heavy polymer can be withdrawn from tank 84 for any desired purpose through valved line |29 and the heavy distillate from tank 96 similarly can be withdrawn through valved line 81. However, it is advantageous to use one or both of these materials as an absorber oil and to operate vessel I as a high pressure absorber rather than merely as a retrograde condensation separator, since the recovery of distillate can ordinarily be increased quite substantially by so doing.

The polymer product of gasoline boiling range can be withdrawn from tank 99 through valved line |30 for storage, further treatment or use, or can be, and preferably is, withdrawn through valve 3| for admixture with the distillate gasoline in line 8|.

As has been pointed out above. the preferred absorber oil is the heavy' polymer separately accumulated in tank 84 and this is one of the principal reasons for' using a separate fractionating system on at least a part of the polymer products. In connection with small installations, it will be apparent that this fractionating system can be simplified considerably. In the preferred operation using heavy polymers as absorber oil, the heavy distillate is withdrawn from the system through valved line 81, valves 83 and |32 being closed, while such part of the heavy polymer as is by line |39. Ordinarily, the methane or gal fraction is passed concurrent to the flow through the unit as a cooling medium around the tubes. The methane fraction is then circulated by line |43 to the top of the methane cracker |40 and re-enters the unit with the oxygen in line |40. These combined gases enterthe catalyst bed at about 900 F. and the product gases are removed from the bottom of the methane cracker |40 at about 1600 F. Heat exchangers |4| are provided on the product gas line to preheat the oxygen flowing via lines |42 or |44 and |45 to the stream entering the `methane cracker. In passing through the methane cracker the methane is subjected to catalytic oxidation at a temperature of about 1600 F. and at a pressure of about i 140 pounds per square inch. The methane fracbefore the synthesis gas reaches the synthesis needed for absorber oil passes through valve |33,

oven |48. A portion of vthis heat is removed by heat exchanger |4| in preheating the oxygen and the heat above about 700 F. is recovered in waste heat boiler |41. The remainder of the heat may be discarded in a water cooler (not shown).

The oxygen for the catalytic oxidation of the methane fraction may be obtained by the electrolysis of water or by the Linde or the Linde# Frnkl process from air. In the electrolysis of water, electrode pressure of the order of 1000 atmospheres of hydrogen may be obtained for cycling to the input well |52.

The electrolysis of the water as a source of oxygen produces a quantity of by-product hydrogen under very high pressure and this hydrogen may be cycled to the underground reservoir dispensing with the recompression of the gases. In Figure 2 the water enters the system by line |40, the oxygen being led to line |42 by valved line 49;` the hydrogen passing via. valved line |50and line |5| to input well |52. When the oxygen necessary for the gas-cracking step is produced by the Linde or Linde-Frnki process, there results a volume of by-product nitrogen which is available at an elevated pressure. The air is passed through heat exchanger |31 and the recovered oxygen is led to line |42 by valved line |53, the recovered high pressure by-product nitrogen passing via line |54 to line |5| and ultimately to input well |52. Thus by my'process there is no deficiency of recycled gas and an increased quantity of motor fuel is produced from the well fluids.

According to the preferred procedure, the methane fraction which may includeselected higher hydrocarbons is subjected to catalytic oxidation at high temperature and under moderate pressure according to the known process. Suitable temperatures are of the range of 1450 F. to

1700 F. andpressures may range from atmospheric up to about pounds per square inch.

A suitable catalyst for use in the synthesis oven are metals of the eighth group, i. e. iron, cobalt and nickel, with cobalt being particularly useful. The catalyst may be supported on kieselguhr, for example, and is rendered more active by the presence of small amounts of diftlcultly pressing the discard gases cycled to the input well.

Alternatively, the synthesis gas may be produced by reacting the methane with steam. This latter reaction is less desirable since it is not exothermic, as is the reaction between methane and oxygen, and further since it produces an excess of hydrogen, the mol ratio of hydrogen t0 carbon monoxide being about 3:1. This can be compensated by including some hydrocarbons higher than methane with the methane fraction or by introducing carbon monoxide from another source. 'I'he gaseous reaction products of the catalytic oxidation are, of course, carbon monoxide and hydrogen. From this carbon monoxide and hydrogen, hydrocarbons are synthesized by the Fischer process, A mol ratio of hydrogen to carbon monoxide of about 2:1 ordinarily is used to produce hydrocarbons predominating in `paralllns. Decreasing the hydrogen content of the synthesis gas gives a more olenic product. Thus a hydrogen to carbon monoxide ratio of about 1.5 to 1 yields more olens.

The synthesis gas comprising largely hydrogen and carbon monoxide is withdrawn from methane cracker |40 Aby line |55 by which it passes to the synthesis oven |46. In oven |46 the carbon monoxide and hydrogen are reacted with each other and with any hydrocarbons present to produce higher molecular weight hydrocarbons largely of the gasoline boiling range. This step is well known in the art and it is contemplated that it may be carried out under any one of the variety of conditions under which it is known to operate. Thus it may be carried out at pressures ranging from atmospheric up to about 150 pounds per square inch, or somewhat higher,

and within the temperature range of between about 300 F. and 400 F., for example 383 F., although somewhat higher and somewhat lower temperatures may be used if desired.

It is well recognized that the Fischer synthesis is highly exothermic and if uncontrolled the heat effect raises the temperature of the reaction to a point where methane and carbon are produced. At the same time it is necessary to keep the reaction temperature between narrow. limits. The dissipation of the heat of reaction may be effected by circulation of water around the catalyst containers, thereby generating steam suitable for process use.

Considerable quantities of water are produced in the Fischer process and this water ordinarily is removed from the hydrocarbons and dis- The 'heavy liquid fraction from a Fischer synthesis frequently has a very low octane number and therefore'it may be desirable to send the product to a reforming step by valved line |64. However, where a nished motor fuel is produced in the Fischer synthesis `it may be pumped by pump |66, line |65 and line 61 to rerun tower 68.

The elevated temperature maintained in the polymerization zone is ordinarily in the range of 300 to 500 F. and the pressure usually is about 150 to 1500 pounds per square inch. The above conditions are for catalysts of the phosphoric acid-kieselguhr or metal pyrophosphate types. Sulfuric acid and aluminum halide may be used at lower temperatures. Valves |91 and |99 are provided whereby one catalyst chamber is onstream, while the other is being regenerated.

The reaction products' are removed from the catalyst chamber by line |99, and can be. passed by valved line 200 and valved line 95 to fractionator 96. Alternatively, the reaction products may be introduced by valved line 20| to valved lines 5| or 54 and blended with the reaction products from polymerizer 41.

Vessel I5 when operated as an absorber can usually be operated at a somewhat higher pressure and, if desired, at a slightly higher temperature than when operated as a retrograde condensation separator. More specifically as an absorber its pressure may range from 1000 to 4000 pounds per square inch, usually from 1200 to 3000 pounds per square inch, for instance 2000 pounds per square inch. The absorber oil in any desired ratio, for example two to six gallons per thousand cubic feet of gas, can be introduced above bailles |34or part of it or even all of it can be passed through cooler Il into the absorber along with the well fluids. 'The absorber oil, of course, is 'removed from vessel i5 along with the distillate hydrocarbons and finds its wayV through surge drum 28 and stabilizerV the'unewly produced heavy polymer is continu-v ously sent to the absorber as an absorption medium, since its aromatic character and its high critical temperature make it possible to operate lseparator-absorber l5 at a higher pressure than would otherwise be the case. If desired, the material to be used as absorber oil may be fractionated.. Thus for'instance the heavy polymers in tank lcould be fractionated and the desired fraction could be sent to the absorber I6. For economic reasons the operation at a higher pressure is more desirable. i

It is to be understood, of course, -that the var-- ious ilow diagrams presentedv are merely illustrative of some oi' the possibilities and other alternative routings will occur to those skilled in the art in view of this description.- Therefore my invention is not restricted to the details shown. Likewise, it will be understood that these flow diagrams are simplified for purposes of convenience and that various items of pumping and compressing equipment,A insulation control devices, safety equipment, and various other 'details are not indicated.

Having described my invention what I claim is:

l. A method of effecting maximum recovery from a high pressure petroleum reservoir and of preparing liquid hydrocarbons from high pressure well fluids recovered therefrom comprising the steps of simultaneously generating oxygen and a by-product gas of the oxygen generation at about the pressure of the high pressure reservoir, injecting said high pressure by-product gas into a high pressure petroleum reservoir to eiect maximum recovery of high pressure well fluids, separating said well fluids at a high pressure into at least one fraction rich in normally gaseous hydrocarbons and at least one fraction rich in distillate motor fuel hydrocarbons, generating a synthesis gas comprising carbon monoxide and hydrogen by treating said normally gaseous hydrocarbons at an elevated temperature in the presence of said generated oxygen, subjecting the said synthesis gas to an'exothermic hydrocarbon synthesis step, fractionating the product from said hydrocarbon synthesis into at least one gas fraction and at assura f least one liquid fraction, said liquid fraction being rich in motor fuel hydrocarbons.

2. A method of effecting maximum recovery y from a high pressure petroleum reservoir and of preparing liquid hydrocarbons from high pressure well fluids recovered therefrom comprising the steps of simultaneously generating oxygen and a by-product gas of the oxygen generation at about the pressure of the high pressure reservoir, in- Jecting said high pressure by-product g in to a high pressure petroleum reservoir to eifect maximum recovery of high pressure well fluids, separating said well fluids at a high pressure into at least one fraction rich in normally gaseous hydrocarbons and at least one fraction rich in distillate motor fuell hydrocarbons, cycling at least a portion ofthe high pressure normally gaseous hydrocarbons along with the high pressure byproduct gas to the high pressure petroleum reservoir to enhance the retrograde vaporization effeet of the pressuring gases, generating a synthesis gas comprising carbon monoxide and hydrogen by treating said normally gaseous hydrocarbons at an elevated temperature in the presence of said generated oxygen, subjecting the said synthesis gas to an exothermic hydrocarbon synthesis step, fractionating the product from said hydrocarbon synthesis into at least one gas fraction and a .least one liquid fraction, said liquid fraction be ng rich in motor fuel hydrocarbons.

3. A me' od of eil'ecting maximum recovery from a highpressure petroleum reservoir and of preparing liquid hydrocarbons from high pressure well fluids recovered therefrom the steps comprising simultaneously generating oxygen and a by-product gas of thev oxygen generation at a high pressure of the magnitude of the pressure existing in a petroleum reservoir, injecting said high pressure by-product gas into the high pressure petroleum reservoir to effect maximum recovery of high pressure well fluids, separating said well fluids at high pressure into at least one fraction rich-in methane and at least one fraction rich in distillate motor fuel hydrocarbons, generating a synthesis gas comprising carbon monoxide and hydrogen by cracking said fraction rich in methane in the presence of said oxygen, subjeeting said synthesis gas to an exothermic hydrocarbon synthesis step, recovering from the product of said hydrocarbon synthesis .step at least one synthesis fraction rich in motor fuel hydrocarbons, and blending said distillate motor fuel hydrocarbons and said synthesis fraction.

GEORGE L. PARIU-IURST.