US2380639A - Production of oil - Google Patents

Description

July 31, 1945. W VG; 5R15 PRODUCTION OF OIL Filed Sept.v 16, 1943 Mfo/v 6. f/f.

5% ATTORNE s Patented July 31,'1945 vUNITED STATES PATENT Vorifice y l y :ascesa PRODUCTION F Olli..

Wilson G. Bris, Napoleonville, La., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application 'september 16, 1943,' segni No. tosses 7 Claims. (Cl. 1034-232) pumping crude oil tending to deposit paraflln wherebyproduction ofv the oil is accomplished cillciently and the deposition of paraiiln is re; duced or prevented. i

When the vnatural ilow of crude oil from a well has ceased or become too slow for economical production, articial production methods are employed, and in many cases, it is advantageous,

, at least during the ilrst part of the artiilciai pro duction period, to employ gas lift. NumerousV types of equipment for producingoil by gas lift are available, but they all rely upon the same general principles of operation. In the usual case, dry Gas consisting essentially of methane and ethane is forced down the annulus between the tubingand thecasing and into the oil in the tubing. As the oil in the tubing becomes aerated with gas, the density of the oil decreases, and veventually the weight of the column of aerated oil in the tubing becomes less than the pressure exerted on the body of oil in the well. and ilow of oil occurs at the surface. While in some cases the dry gas may be introduced through the tubing so as to cause production through the annulus, this is not preferred unless special conditions are Present.

It has been recognized that gas-lift methods for producing crude oil are of questionable value when un ou tends to deposit params. 'rms is because it has been found that vparaiiln deposition in a gas-lift well is particularly heavy. Accordingly, it has been frequently been decided not to use gas-lift methods because the expense of controllingparamn deposition would more than. offset' any advantages obtained through the use of these methods.

An important problem encountered in producing a well by gas lift arises in starting the ilow of oil. The gas-lift systems available on the market generally comprise an arrangement of valves in the tubing whereby the gas may be introduced nrst into the'upper part of the column of oil in the tubing and then at lower points so that it is not necessary to raise the entire column of oil in the tubing a substantial distance prior to the mixture oi the gas with the oil. `'I'hese systems of gas lift satisfactorily accomplish the object of lessening the problem of starting production. When the crude oil being produced tends ao deposit paramn, however, the presence of the, valves makes the Job of cleaning parailln from the tubing more dlilicult.

With the foregoing problems'in mind. it is a principal object of the present invention to provide a method of producing crude oil tending to dapositfparaillncby gas lift, whereby the oil may be produced etiiciently, while. at the same time,

the deposition of parailln is reduced or prevented.

Other objects of the invention will in part be obvious and will in part appear hereinafter. I have discovered in accordance with the invention that crude oil tending to deposit par can be produced by gas lift while avoiding troubles due to paralln deposition, provided a gas is uti lized which contains .light hydrocarbons dispersed therein in the liquid phase. As pointed out above, the dry gas which is conventionally used is composed essentislly ol' methane and ethane, and any small amount lofothcr hydrocarbons that may be present inthe gas are in the vapor phase under the conditions at which' the dry sas is employed for gas lift. In the method of the invention, l employ a mixed uld which comprises an amount of liqueflable hydrocarbons such that an important proportion of these hydrocarbons are present in the liquid form under the pressure and temperature conditions existing at the time of gas lift; the particular amount required for the desired reduction or prevention of parailln deposition being dependent upon the specic conditions of production in the oil well and the characteristics of the liqueilable hydrocarbons.-

, The liqueable hydrocarbons'may vary in composition; for example, hydrocarbon mixtures such as a petroleum ether or light naphtha fraction of petroleum, natural gasoline, and hydrocarbons otherl than methane and ethane present in a fluid owed from a distillate or condensate well may be employed as the liquid phase material in the gas. Thus, the hydrocarbons in the gas, other than methane and ethane, preferably comprise hydrocarbons containing not more than 8. parv tlcularly from 4 to 8, and especially from 3 to 8 carbon atoms. The dispersed liquid hydrocarbons may and usually will also include heavier hydrocarbons. Hydrocarbons containing 3 or more carbon atoms are conventionally referred to as liquefiable hydrocarbons, because, although thee` lighter members such as the C: and C4 hydrocarbons may be gases imder atmospheric conditions. they can be obtained in liquid form from a wet 'gas suchv as a distillate iluid by conventional recovery methods. f

The method of the invention may be practiced in various ways. The liquid hydrocarbons which it is desired to have present in the ses may be injected intotheusualdrygastobeusedingas lift, preferably in such manner as to eilect dis-- persion of the liquid hydrocarbons throughout the gas. This may .be accomplished by any conventional means. For example. the liquid hydrocarbons 'may be injected through an aspirator nozzle into the gas at the pressure required in the sas-lift operation. The dry gas may be gas viroxn a natural gasoline plant which has been compressed to the desired pressure. gas from a high-pressure gas well, or residue gas from a distillate recovery plant. Gases of the latter types ordinarily will be at a sufliciently high pressure to permit their being used without compression.

When practicing the method in this way, the

liquid hydrocarbon mixture employed may be any a of the classes of mixtures referred to above. Itis preferred to use a mixture of` this type which contains a substantial proportion of propane and butanes in additionto the other hydrocarbons normally includedin suchl mixtures. Thus, if natural gasoline or distillate is used as the liquid hydrocarbon mixture, it is preferred that it not be subjected to weathering, which would permit evolution of propane and butanes.

I have found that the method or the invention can be carried out in a particularly effective manner in areas where suitable wells are available by ing the pressure and temperature of a distillate fluid, substantial condensation of liquelable hydrocarbons occurs due .to the phenomenon of retrograde condensation and also the normal temperature effect. The pressures required for gas lift operations are such that substantial condensation. of liqueable hydrocarbons occurs on reducing the pressure on a distillate fluid to the pressure of gas lift, and these condensed liqueable hydrocarbons will include propane and butanes as well as higher boilinghydrocarbons. A distillate fluid is usually employed in accordance with the invention by flowing the fluid from a distillate iormation, reducing the pressure on the fluid by means of a pressure-reducing valve located either at the surface or in the distillate well to the pressure of gas lift, and then passing the resulting iiuid containing dispersed liquid hydrocarbons into the well or wells to be produced by gas lift. Y

The manner in which the invention may be practiced utilizing a distillate .fluid is illustrated in the accompanying drawing in which the single gure is a moreor less diagrammatic view, partly in section, showing an oil well, surface equipment, and a distillate well utilized in causing fiow of the oil well.

Referring to the drawing, the weil A is an oil well producing crude oil tending to deposit parafn, and the well B is a distillate well which produces a duid at a high pressure within the retrograde condensation range of the constituents of the casing, a standing valve Il. a bull p1ug'20.`

and three valves 22, 24, and 28. which furnish communication between the annular space above the packer and interior of the flow tubing. These valves are controlled by a cylindrical bar (not showni'disposed inthe tubing-which may be raised and 4lowered from .the surface by means of awire 2l which is operated by any suitable assenso means not shown.' The bar, on being placed opposite a valve, opens that valve. In the arrangement shown, valves 22 and 24 are starting valves, and the valve 2B is a now valve.

When the system disclosed'is in regular operation, the distillate fluid is flowed from .the well sulting mixed fluid is flowed into the annular space between the casing and the tubing andperiodically Vis permitted to pass vinto the flow tubing through-valve 26, this valve being opened and closed at regular intervals to permit the alternate lling of the tubing with oil and the flow of oil to the surface by means of the gas lift. By the arrangement shown, the distillate fluid containing the dispersed liquefied hydrocar-` bons enters the crude oil and functions to lift the oil to the surface, while, at the same time, reducing or lpreventing the deposition of paraiiin.

The useof a distillate uid in practicing the present process has other advantages. The liquefiable hydrocarbons present in the distillate fluid are absorbed in the crude oil so that the liquid product from the distillate well and the crude oil `from the oil well may be handled emciently in one stream. There is. no loss of light components since after the crude oil has been passed through a conventional separator. the gases obtained may be treated in a natural gasoline plant for recovery of liqueilable constituents.

Distillate nuids vary in composition, but they are all characterized in that they contain a substantial proportion of hydrocarbons containing 3 to 8 carbon atoms and in that an important proportion of these hydrocarbons are in the liquid phase at the pressure and temperature conditions of gas lift. In starting gas-lift operations it is sometimes necessary initially to employ pressures as high as 1500 pounds per square inch, but after contain more liquid phase material at higher pressures, at pressures of the order of 500 pounds per square inch and at atmospheric temperatures, they still contain important amounts of liquid phase material. A representative distillate fluid was found to have the following composition:

Component Mol. fraction Methane 0. 95173 Ethane 0. 01219 Propane.-. 0.046 Isobutane.. 0. 00274 n-Butane. 0. 00352 Iso-pantano. 0. 00171 n-Pentane 0. 00109 Hexanes. 0.001112 Eeptanes. 0. 00241 Gctanes and heavle 0.00016 Carbon dioxide 0. (D491 In the well frm which this fluid was flowed.

the bottom hole pressure was about 5000 pounds atmospheric temperature and pressure, whereby but that at soo4 pounds per square meh the num at 40 F. had a liquidvolume of 0.00198 cubic foot per pound and at 100 F. a liquid volume of l 0.00154 cubic foot per pound.

A The method of theinvention has been practiced three dollars per month. A conventional gas-lift system was installed when the flow ceased. The gas for gas lift was obtained from a distillate well in the vicinity, and the entire distillate fluid was introduced into the oil well. The pressure on the distillate fluid was reduced to about 500 pounds per square inch by means of a valve in the distillate well. This reduction in pressure and concomitant reduction in temperature caused substantial condensation of liquid hydrocarbons, tests showing that at the rate the well was flowed about 2.40 barrels of liquid hydrocarbons were beingintroduced into the oil well during each 24 propane through octanes and heavier.

The oil Well was produced at a rate of about 45 barrels per day for an extended period and no difliculties due to parain deposition were experienced. Inasmuch as i1; would normally be expected that when placing a well on gas lift, paraffin troubles would increase rather than decrease, this result indicates that the present method represents an important step forward in the production of crude oils tendingto deposit paraii'ln by gas-lift procedures.

It will be understood that the amount bf liquid hydrocarbons required to be used will vary in each case/depending upon `the type of crude oil, equipment in the well, depth of the well and other factors. Accordingly, this amount should be determin'ed by tests in each case. Information obtained in developing the present invention has indicated that when an ordinary distillate fluid is used, an excess of liquid hydrocarbons will be present, This, of course, is not a disadvantage because the excess is recovered along with the crude oil. For example, tests have indicated that in the above Well a uid containing an amount of liquid phase material corresponding to 5 to 10 gallons per 24 hour period would be satisfactory. Although when the production from a distillate well is used in the process, there will usually be present more than enough liquid phase materiaLto accomplish the objects of the invention, it will be understood that in a case in which this liquid phase material is insuflicient additional liquid hydrocarbons may be added. l

Obviously many modications and variation of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim: v

1. lIn the process of producing from asubsurface reservoir by gas lift a crude oil tending, to deposit paraili'nl the improvement which comprises introducing from the surface into an oil well tap-v Ping the crude oil reservoir, under the pressure required for gas lift, a mixed fluid comprising a gas and liqueable hydrocarbons in the liquid phase dispersed in said gas, said liqueable hydrocarbons comprising a substantial proportion of hydrocarbons which are in the liquid phase at the crude oil is aerated and is caused to iiow to the surface while avoiding substantial deposition of paraffin.

2. In the process of producing from a subsurface reservoir by gas ylift a crude oil tending t0 deposit paratlin, the improvement which comprises introducing from the surface into an oil well tapping the crude oil reservoir, under the pressure required for gas lift, a mixed iiuid` comprising a gas and liquefiable hydrocarbons in the liquid phase dispersed in said gas, said liquefiable hydrocarbons comprising hyrocarbons containing not more than 8 carbon atoms and a substantial proportion ofhydrocarbons which are in the liquid phase at atmospheric temperature and pressure, and being present in amounts suicient to prevent substantial deposition of paraffin in the well, whereby the crude oilv in the well is aerated and caused to flow to the surface while avoiding substantial deposition of parain.

3. In the process of producing from a subsurface reservoir by gas lift a crude oil tendingto depositv parafiin, the improvement which comprises introducing from the surface into an oil well tapping the crude oil reservoir, under the pressure required for gas lift, a mixed fluid comprising a gas and liqueable hydrocarbons in the liquid phase dispersed in said gas, said liqueable hydrocarbons comprising hydrocarbons containing 3 to 8 carbon atoms and a substantial proportion of hydrocarbons which are in the liquid phase at atmospheric temperature and pressure, and being present in amounts suiiicient to prevent substantial deposition of parain in the well, whereby the crude oil inthe Well is aerated and caused to w to the surface while avoiding substantial deposition of parafn.

4. In the process of producing from a subsurface reservoir by gas lift a crude oil tending to deposit paraffin, the improvement which comprises introducing from the surface into an oil well tapping the crude oil reservoir, under the pressure required for gas lift, a mixed iluid comprising a gasl and liqueable hydrocarbons in bon atoms, whereby the crude oil in the well is aerated and caused to flow to the surface while avoiding substantial deposition of paraiiin.

5. In the process `of producing from a subsurface reservoir by gas lift a crude oil tending to deposit paraiiin, the improvement which comprises introducing from the surface into an oil well tapping the crude oil reservoir, under the pressure required for gas lift, a mixed uid comprising a gas and liqueable hydrocarbons in the liquid phase dispersed in said gas, said liquefiable hydrocarbons comprising hydrocarbons containing not more than 8 carbon atomsand a substantial proportion of hydrocarbons which are in the liquid phase at atmospheric temperatureA and pressure, and being present in amounts suilcient to prevent substantial deposition of paraffin in the well, said mixed fluid being obtained by mixing with a gas comprising normally gaseous hydrocarbons a hydrocarbon mixture in liquid phase recovered from a uid owed from a well tapping a distillate formation, whereby the crude oil in the well is aerated and caused to ow to the surface while avoiding substantial deposition of parailln 6. In the process of producing from a subsurface reservoir by gas lift a crude oil tending to deposit parain, the improvement which comprises`introducing from the surface into an oil` well tapping the crude oil reservoir, under the pressure required for gas lift, a uid which com prises the production from a well tapping a distillate formation and consists of a mixed fluid comprising normally gaseous hydrocarbons in the vapor phase 'and liqueiiable hydrocarbons in the liquid phase dispersed in said gas, said liquelable hydrocarbons comprising a substantial proportion of hydrocarbons which are in th liquid phase at atmospheric temperature and pressure, whereby the crude oil in the Well is aerated and caused to flow to the surface while avoiding substantial deposition of paramn.

'7. In the process of producing from a subsurface reservoir by gas lift a crude oil tending to deposit paraflin, the improvement which comprises reducing the pressure on a iiuid owed from a. well tapping a distillate formation from the pressure of the distillate formation to the pressure of gas lift, whereby the distillate iiuid is converted to a mixed fluid comprising normally gaseous hydrocarbons in vapor phase and liqueable hydrocarbons in liquid phase dispersed in said vapor phase, said liqueable hydrocarbons comprising a substantial proportion of hydrocarbons which are in the liquid phase at atmospheric temperature and pressure, introducing said mixed iiuid into an oil well tapping the crude oil reservoir, under said pressure of gas liftI whereby said crude oil is aerated and caused to ow to the surface While avoiding substantial deposition of paraffin, said crude oil containing dissolved therein liquefiable hydrocarbons of said mixed uid, and recovering said crude oil containing said liqueiiablel hydrocarbons of said mixed fiuid.

WILSON G. ERIS.

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