US2244684A - Means for and method of flowing oil and gas wells - Google Patents

Description

June l0, 1941. E, v, FORAN MEANS FOR AND METHOD OF FLOWING OIL AND GAS WELLS Filed July 5, 1939 Edwin 1/. Fora/7 Patented June 10, 194i s' PATENT oFFlcE MEANs'roR AND METHOD F FLOWING OIL AND GAS WELLS Edwin V. Foren,- San Antonio, Tex., assign'or to i Eureka Process-Corporation, Tulsa, Okla.,.a corporation of Delaware 'p Applicaun July 51,1989, serial No. 282,888 y claims.. (ci. 18e-1) This invention relates to.v new and useful im- Drovements'in means for and methods ofi-lowing oil and gas wells. o

In the conducting'of deeper oil and gas well exploratory operations in the more recent years, the oil and gas industry has observed, on` many occasions, the occurrence of distillate gas and petroleum crude oil in the same common porous voir producing stratum maybe occupied by the distillate gas and only a relatively small portion l of the producing stratum occupied bythe liquid pertroleum crude oil. Any water which may be present in the same producingA stratum will, of course, underlie the liquid crude oil. When a well is completed ina stratum or `formation under these conditions it often becomes extremely diliicult or even impossible to produce, for example, the crude oil without at the same timel producing undesirable and large quantities of distillate gas.

combinationewells or ,distillate wells., In

thosecases where there is no readily available or useful disposition ofthe excessive volumes of gas, after separation at the surface, it becomes,

necessary, in order to conform with the conserva-` tion. laws of most oll and gas producing states,

now lixfforce, to return the gas to the sand, after having separated the gas from the oil at the surface.

Wells of this type or character are often referred to as "high gas-oil ratio wells,"`

order to avoid the otherwise excessive daily gas waste, which is prohibited by the conservation laws" of the principal oil producing states. In some cases, it has been the practice to produce the liquidi crude oil together with a more or less restricted amount ofgas through a small string of tubing and at the same time conduct the excess distillate gas upwardlyA through the casing of the well.

In the high pressure, deeper reservoirs, havingl a high gas-oil ratio, the gas overlying the oil is in contact with the oil and the gas and oil are in a state of equilibrium, under which condition the gas is, 'of course, saturated with condensable vapors. These condensable vapors, which are, carried by the gas, are stable in the gas phase only so long as the reservoir pressure and temperature are maintained and any lowering of either pressure or temperature, or both, will resuit in condensation of portions of said vapor.

It is well known thata natural drop in pressure and temperature takes place in transit between the point of entry from the formation at the bottom oi' 'the hole, and the point of discharge at the casing heady on the surface. Gas, in its travel upwardly through the casing will, of necessity, have avery low velocity as compared to its velocity when travelling through the' smaller tubing with theu crude oil. This is true because of the larger crossselctional area of the casing," as

compared to the smaller cross-sectional area of the tubing. A oonsiderableamount of distillate condensation will occur during the -upward travel of the gas in the casing, due to the pressure and temperature drop, `with the resultv that precipi-l tation due to gravity will take place and the liq` uids derived from condensation, which are usual- .If both the oil and gas are conductedl from' the y bottom of the well to thesurfacethrough a common iconductor or singlestring of tubing, in the conventional manner, it is obvious lthat the pressure at which the gas and oil are Kdelivered at pressure at which the oil and gas are delivered i to the point oi' separation at the surface, the cost of recompressing the separated or residue gas sumciently to return it to'the same reservoir from which it camemay, and often does, prove to be prohibitive. Under these circumstances,

the well would either have to be shut in until n acceptable disposition of the gas was obtained or the operator would be required to greatly reduce the daily amount of oil taken from it in ly water-white in color, will gravitate downward to the bottom of the hole and become diluted or contaminated with the crudeoil. Such precipitation occurs because the velocity of the'gas" flowing upwardly through the casing isinsuflicient to overcome the forces of gravity.` There-l fore, when the conventional single liquid" conductor within the casing is employed, especially at moderate or low rates of flow, the condensates which precipitate from the gas flowing upwardly through the casing, dilute or contaminate the crude oil at the bottom of the well bore and are yproduced therewith through the single conductotal separation of unstable reservoir distillate gas and crude oil takes place at the bottom. of the well, in the immediate locality of the producing formation, thus segregating the unstable distillate gas from the oil at temperatures and pressures which do not permit appreciable condensation of the distillate gas, whereby the dilution of the crude oil by distillate condensate is minimized and at the same time, approximately the full initial condensate content of. the unstable distillate gas entering the Well bore remains preserved in the upward flowing gas stream.

A further object of the invention is to provide an improved method wherein the major portion of the distillate gas is separated from the crude oil in the immediate vicinity of the producing formation, or at the bottom of the well, and conv ducted to the top of the well and discharged therefrom with only such'pressure dropor loss as is incidental to its travel up the well, whereby such gas may be delivered for processing. or

. ably below the liquid level in the reservoir or well other handling, on the surface, at ,such high pressures as to make for economic recompression of the residual gas for returning it to the subsurface or otherwise; at the same time utilizing a relativelyA small quantity of the gas for iowing the crude oil to the top of the Well.

Another object of the invention is to cause such condensates as may be condensed from the gas during its travel up the well, due to natural coollng and pressure drops, to remain entrained with the gas and to be discharged from the well head therewith, thus preventing gravitation of such condensates to the bottom ofI the well and their admixture and production with the crude oil.

A particular object of the invention is to provide an improved method of 'owin'g wells of the high gas-oil ratio type, wherein the distillate gas is conducted from the producing stratum or zone to the surface approximately without segregation, diversion o r appreciable loss of any of the condensate vapors, wherebyvsaid gas, is delivered to the surface with approximately the same total components which said gas contained at the point of Entry into the well bore from the stratum.

Still another object of the invention is to provide an improved apparatus for carrying out the foregoing method including a dual conductor having an outer gas conducting pipe with gas inlet openings at its lower end and an inner oil conducting pipe extending through and below the gas.conductor and having an oil inlet which is spaced a sufficient distance from the gas inlet to provide an adequate separating 'zone below said inlet.

A further object of the invention is to provid an improved apparatus which is so constructed that the distillate gas is conducted upwardly to the surface at a velocity which is sucient, even at restricted rates of production, to prevent gravity precipitation of the condensates downwardly to the bottom of the well and other ultimate admixtures with the oil thereat; and also whereby condensates which might gravitate -in the conductor are preventedfrom flowing therefrom into the separation zone and are thus trapped in the line of flow and ultimately discharged with gas streams.

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

which an example of the invention is shown, and wherein:

Figure l is a transverse, vertical, sectional view of an apparatus for carrying out the method, and Figure 2 is a horizontal, crosssectional vie taken on the line 2`2 of Figure l.

In carrying out the, method, there may be installed in the well, a dual conductor string Ill, preferably in concentric forni,` as shown in the drawing. The string includes an inner smaller or lesser diameter pipe ll which extends prefere bore, and as near to the bottom of the well as possible, as indicated in the drawing. The

larger or outer diameter pipe I2 of the dual conductor serves to surround or jacket concentrically the smaller pipe but extends into the well at I bore from the formation, but such distance is same time confined within the larger of the two subject to considerable variation. When 'installed ready for operation; the larger diameter or outer pipe of the dual conductor string is supported from lthe casing head I3 of the well, and the smaller or inner pipe is, in turn, supported by the tubing headM which may be a continuation of the outer conductor pipe" of the dual conductor. The inner pipe II will be referredY to hereinafter as the oil pipe or tubing, while the outer pipe I2 will be designated as the gas pipe or conductor.

. At the lower end of the gas pipe I2, a seat I5 is provided which receivesa collar I6A fastened on the oil pipe II, for partially supporting the oil pipe so that the entire weight of the smaller liquidconductor pipe shall not at all times be in tension from its Asurface support, as is conventional, but will be given partial tension relief due to thesupporting ability of the gas conductor pipe. ,Oftentimeawhen inner oil tubing is swung in tension, in great lengths, it may part at some point Within the well and create a diicult mechanical recovery problem; whereas if it may be partly supported near Ithe bottom, and at the pipes of the dual conductor string, it would,

- therefore, be very easy to recover if for any The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawing, in

reason it should part. Shortly above the seat I5, the outer gas pipe I2 is provided with inlet openings or ports I 8 for admitting gas from the casing.

When the dual conductor is installed in the well and the well subsequently placed on production at relatively low rates of flow, as for example, one to two million cubic feet of gas daily, accompanied by some forty to fty barrels of crude oil, it will be observed that under the existing high 'bottom hole pressures, a gas volume of say -one to two million cubic feet daily, may travel upwardly within the well bore and the normal size well casing I1 at a low velocity; however, such flow will not have the ability to carry upwardly the crude oil liquid which entered the well bore with the gas from the formation. The

gas, on rising upwardly through the well bore and through the extreme lower portion of the well casing to the point of entry near the base of the outer or larger pipe (I2 of the dual conductor, will undergo littleor no change in either temperature or pressure since it is still in the immediate locality of the formation from which it came. Since the well casing Il is stopcocked or shut in at the surface, the upwardly flowing gas is trapped or stored in the well casing and dual conductor.

can only enter the outer or larger member of the In passing from the casing chamber into that of the gas conductor pipe I2, the gas must pass through the restricted openings I8 near the base of the gas conductor pipe and then continue to flow upwardly in this larger member of the dual conductor. While in upward transit in the gas pipe I2, condensation from the vapor phase will take place due to a drop in temperature and pressure, as all high pressure distillate gases do when subjected to lowering of pressure and temperature. However, since the cross-sectional area of the pipe I2 is less than the cross-sectional area of the casing, velocities within the gas conductor pipe are much higher than velocities would be for the same volume of 'gas moving through the casing. Therefore, the liquids condensed from the gas within the pipe I2 are` entrained and carried upwardly with the flowing gas stream, because of the ability of the higher velocity to overcome the effect of gravity i separation or precipitation of the condensates. Even though at; Ytimes the velocity in this conf, e

ductor; tubing may Y, fall below that necessary to produce continuous lifting l of lthe liquids upward- 1y as Athey condense, in which;,case-,somev liquids would, therefore, precipitate by. gravity, .and y,falldownward toward the base of thezgasuconductor pipe, .they could ,not `reenter ,thetwell .casing 1 chamber,` since,` theI relatively -high velocityl through theopenings` L8, atthe base of the gas I pipe would prohibit any reversepassage. Only a limited amount :of gravity lprecipitation can occur within the gas pipe sincethe sustained presl sure of the upwardly flowing gas will, in `a short time, liftV the precipitated condensates in, the.

formof a head ,or other temporary, .irregularflow. Although the restricted ports I8 are pref-L erably used, any means of preventing backflow into the casing maybe employed.`

On arriving at the1 surface the gasand companying liquid particles, which .latter were produced by condensation, would arrive under a very high pressure and could be processedfor their products, and thenresidue gas cheaply recompressed and/returned to the same formation very economically. At relatively restricted rates of oil and distillate gas production, with the type of installation shown `in the drawing, the liquids entering the well bore from the formation, practically all of which would be the crude oil, can only enter `the small conductor tubing II at its base. ,This crude oil will be accompanied by a limited amount of reservoir gas, either the gas naturally in solution in the oil and possibly its 'ac-r.

as the larger of the pipes of the dual conductor. Oftentimes, the situation arises wherein in reservoirs of this type, one party may own distillate gas rights in place, while another party owns the oil rights in place in the reservoir, and it becomes necessary to produce both products simultaneously through the same well. With the apparatus and method disclosed herein, this is readily and efficiently accomplished.

It will be noted that approximately all of the gas confined to that -portion of the casing lying above the point of entry near the base of the gas conductor string, is substantially in a static condition, when the surface casing controls are closed. The casing gas could be packed off aroundthe gas conductor and the gas in the lower portion of the hole confined below such l to the fact that a large volume ofhigh pressure gas is presentata all tirnes within thejcasingand is immediately available and having ready access at the point of entry into thegas conductor"1 string, 'this gas would, vof necessityycor'npensate i any yabnormal flow, and in that way preventl the rise, or tendency to riseof the oil ,with the gas] and increase of its flow from the bottom of theA n hole. v

The casing head I3 may be provided with the usual outletbranchesl havingvalves`2l0 therein, y

which are `closed whenl the well isI 4in operation.y

Branches 2| equipped with valves 22' extend'fromthe tubing head H. The oil tube I I extends through `the head l Il and connects with a lateral pipe 23 which includes a valve 24.

It is obvious that by separating the major por- "tion of the gas at the bottom of the well and small amounts of the free gas, and this limited volume of gas, together with its accompanied crude oil, will be conducted upwardly to the sur-V face within the smaller oil pipe II of the dual conductor. It is pointed out that the size -or area of each liquid inlet port of the small pipe II, is subject to variation so as to restrict the volume of free gas which may also enter the pipe I I with the oil. The liquid flowing upwardly through the pipe II will arrive at the surface at a relatively low pressure, due to the relatively small amount of gas which, latter, because of its relatively small volume, with respect to the oil may be disposed of in any legal manner, such as burning in flares or for lease gas operations, or otherwise. When operated in the manner described, the device shown in vthe drawing convertsthe lower portion of the well bore into a gravity type separating zone or chamber wherein flowing the gas up the well, with only the impedance offered by the flow conductor, such gas is delivered with a minimum loss in pressure. Also such liquefiable fractions which are present in the gas, "and particularly those which will condense intransit up the well, are delivered with the gas from the well head. A gas or gaseous streamso acquired has many advantages. Such a stream is particularly advantageous when utilized in methods such as are set forth in Patent No. 2,080,351 of which I am co-patentee, andan applica-tion filed by Jay P.' Walker and myself March 23, 1939, Serial No. 263,658, as well as various other methods wherein advantages is taken of retrograde condensation and cooling.

The base of the gas tube I2 is sufllciently above the formation to create a separating chamber of such volume as to give the liquidsfull opportunity to separate from the gas and gravitate to the bottom of the well bore.

From the foregoing, it will be manifest that a separating zone is formed between the inlets Il of the gas conductor and the inlets-of the oil tubing. This zone is located in the immediate vicinity of the producing stratum or reservoir and therefore, separation of the gas and oil takes condensable vapors in the gas occurs, with the result that said vapors remain in the gas and enter the gas conductor I2 with said gas. This reduces to the practical minimum, condensation of the condensable vapors prior to their entry into the gas conductor l2 and thus; dilution or contamination 'of the crude oil by such condensates is likewise reduced to the practical minimum, and assures delivery of the maximum of such vapors and condensates with the gas. The cross-sectional area of the gas conductor l2 is such that the upwardly flowing gas stream will have suiicient velocity to maintain the condensates entrained therein, and thus ultimately deliver the said condensates to the surface wit the gas. l

It is pointed out that under some Well condi tions, a surging or lheading of Ithe flow of crude oil in the oil tubing Il might occur and, if desired, a stabilizer port 25 may be provided in the oil tubing below the gas conductor i2. This port is preferably located immediately below the base of the gas conductor, as illustrated, but it may be at any point in the tubing between said gas conductor and the oil inlet at the lower end of said tubing Il. 'I'he port is relatively small and permits only a restricted amount of gas to flow from the separation zone into the oil tubing, such restricted flow being continuous at all times. This continuous admittance of a small volume of gas serves to steady the ow of oil through the tubing Il and reduces 'heading or surging thereof. The port 25 is not essential to the invention and may be omitted Without effecting the operation of the apparatus or the practice of the method, as herein disclosed.

' Ihe valves 22 and 24 may be of any type suitable for use in this method, as for instance, they may be regulating or choke valves for controlling or regulating the ilow from. the two conductors or one of them, or for reducing the pressure of the ow. It is to be understood that any water or other liquids entering the well bore will be separated and produced in the same manner as the crude oil.

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

1. The method of owing high pressure oil and gas wells from subsurface reservoirs wherein the gas which is under pressures and at temperatures within the range of retrograde condensation overlies the oil and is inI contact therewith which includes, separating the oil from the major portion of the gas at the bottom of the well with substantially no precipitation from the gas of condensible components, whereby the'oil is Segre gated from the gas and its condensible content, conducting the oil up the well in a. segregated path, and conducting the separated gas up the well in a path separate from the oil while maintaining the condensible content entrained therewith.

2. The method of owing high pressure oil and gas wells from subsurface reservoirs wherein the gas which is under pressures and at temperatures within the range of retrograde condensation overlies the oil and is in contact therewith which includes, separating the oil from the major portion of the gas at the bottom of the well with substantially no precipitation from the gas of condensible components, whereby the oil is segregated from the gas and its condensible content, conducting the oil up the well in a segregated path, and conducting the separated gas up the Well in a path separate from the oil and under such velocity as to maintain the condensate in suspension in the gas stream, whereby the gas is delivered to the surface with substantially all of its condensates entrained therein and the oil is delivered to the surface substantially free from such condensates.

3. 'I'he method of flowing high pressure oil and gas wells from subsurface reservoirs wherein the gas which is under pressures and at temperatures within the range of retrograde condensation overlies the oil and is in contact therewith which includes, separating the oil from the major portion of the gas at the bottom ofthe well with substantially no precipitation from the gas of condensible components, whereby the oil is segregated from the gas and its condensible content, storing gas above the point of oil and gas separation for providing a static body of gasfor compensating abnormal flows of gas from the formation, conducting'the oil up the Wellin a segregated path, and conducting the separated gas up the well in a path separate fromthe oil While maintaining the condensible content entralned therewith.

4. In an apparatus for flowing high pressure oil and gas wells wherein distillate gas at pressures and temperatures within the range of retrograde condensation overlies crude oil, the combination of, means for shutting in fthe well to trap gas, an oil string extending up the well from the lower portion' of the formation through said means, and a gas string surrounding the oil string and having its upper end extending through said means, the lower end of the gas string terminating a substantial distance above the top of the formation, whereby a gas and oil separation zone between the lower end of said Vgas string and the top of the oil formation is

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