US1740039A

US1740039A - Op los angeles

Info

Publication number: US1740039A
Authority: US
Publication date: 1929-12-17
Anticipated expiration: 1946-12-17

Description

Der; 1.7, 1929. A, Q RUBEL 1,740,039?? SOAKING METHOD FOR INITIATING GAS LIFT IN OIL WELLS Filed Juiy 18, 1927 A TTU/e NE Y Patented Dec. 17, 1929 7 -uNlri-:D` STATES ALBERT c, nennt, ormone Jemen, camroma, Assieuoa To UNION orL comm PATENT 'ori-ICE F GALIFOBNIA, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF CALIFORNIA SOAKING' HETHOD FOR INITIATINGAGAS LIIIT IN OIL WELLS appueauen mea my 1s, i927. serial No. zoaese.

This invention relates to the so-called gas lift method of Aflowing deep` Wells-,particularly oil wells, and has been designed to 0vercome the excess hydrostatic head of oil which ordinarily accumulates in such wells prior to starting gas lift and which ordinarily cannot be -removed by'.direct vapplication of a reasonable gas pressure in attempting to initiate gas lift. Gas lift, as now commonly practiced, consistsin passing gas under pressure into a well containing a iiow tube, so that the gas passes around the lower end of the ow tube in astream 'and in its passage atomizes the oil' as fast as it is forced up to said tube end -by the natural roclpressure ily the well, the

atomized oil being carried -to thesurface in the gas stream. The gas may be introduced i either through the flow tube or through the has accumulated in the well hole, which head the flow tube head. Thus, upon any attempt to .startgas 'usuallyzcannot be overcome by steady application of a moderate pressureto one side of rea-son that, as pressure is applied to one side of the tube to depress the oil levelv therein, the

Ahydrostatic head increases inthe other side.

laVhil some of the oil is forced back into the formation (depending upon the viscosity of the oil, the frictiouof the formation, andthe like) the effective rock pressure in the vicinity of the well increases unt-il it is suic-ient to balance the increased hydrostatic lift by straight application of pressure to one side in order to force over the entire eX- cess load of accumulated oil and uncover the lower end of the tube for passage of gas thereunder, the hydrostatic head will increase until it reaches the maximum, that is,

until it is equal to the entire height of the iow tube, vwhich height may be as much as seV- This condition arises for the eral thousand feet. Moreover, the pressurek l which would be high enough to start gas` lift by suchsteady application, that is, a normal starting pressure, under these conditions, wouldbe excessive for vall other purposes,

.since when the oil level is lowered and gas lift started, normal continuation of gas lift mayl be and should be carried on with a much lower pressure, this being made possible by the much lower density 4of the'gas-andfoil Volume in. the flowl tube during normal as lift as compared with the oil before gas lift.

Thus, it is clear that it is not convenient or desirable to maintainsaidexcessive pressure merelyf'for the purpose of overcoming said hydrostatic head.

The term hydrostatic head except where otherwise defined, is used throughout this case to mean the pressure of that'portion of the oil body accumulated in the well hole, which stands as a' column in the' tube and casing above the lower end of theflow tube.

(a fewhours or a'few days according to the well), the head will have reached Vsubstntially its maximum height and will be in substantial equilibrium with the rock pres-` vWhen a well has `stood/idle for a short time Obviously, then, in a non-flowing well under these conditions the said rock pressure or hydrostatic head is less than the static head representedby the length o`f the flow tube between its points of intake'and discharge.

IfV gas under pressure be applied to the casing for example, of awell containing an `accumulated head lofv oil, oil will be forced up into the tube, thereby increasing thestatic head therein, as 'above indicated.' Of course,

if 'the oil level stands suflic-ientlyhigh in, the

well, the available gas pressuremay elevate the oil in the tubing suliciently to discharge some oil fromthe tubing without uncovering 'the lower end thereof, but discharge will cease as soon as the oil levelbecomes depressed to such `a point that the head in'the If a tubing above the oil level balances the gas .pressure being applied. i

In order to initiate gas lift by straight application of pressure, a starting pressure must be employed suiiicient to depress the oil level low enough to, allow the pas! developed in 'the' iow tube. This increased head of oil inthe tubing is here termed the normal starting liead,'and its magnitude is dependent upon .the relative size of the tubing and casing, the amount and density and viscosity of the oil in vthe well, the rock pressure, the friction of the formation, etc.v The normal starting head as the term is herein employed is defined as the hydrostatic head of oil in the flow tube above the point of admission to said liow tube at the time gas would break into the flow tube. In like manner, the normal starting pressure isv defined as the gas pressurevnecessary to depress the oil level in the gas admission tube to the point of gas admission tothe How tube and sufficient to ,start gas lift in the flow tube .whensaid' that they definition applies whether dis! charge flow is from the tube and gas application is through the casing, or vice-versa. as tube is employed and is connected by a Jet to theflow tube in a manner common to air or gas lift, the starting head or pressure may be equal to thehydrostatic head of the oil in the-flow tube above the jet when gas is rst forced into the gas tube, and it may be equal to or slightly greater than the hydrostatic head of oil above the jet when first applied.

The general object of the present invention, is to overcome the hydrostatic head 1 and depress the oil level approximately to the lower end ofthe flow tube by the application of gas under a pressure less than that required to initiate gas lift by steady application to either the tube or the casing in the usual manner, and less than the hydrostatic head naturally existing in the well prior to gas lift initiation.

The obJect is attained by promoting the absorption of a large amountof gas (natural gas preferred) by the oil body, coupled with a depression of the oil level'to as lowA a point as possible with the available pressure, whereby the absorbed gas materially reduces the specific gravity of at least the upper portion of the oil body and whereby the available pressure then becomes suiiicient to elevate and discharge the column of the so-lightened oil in conjunction with the expansive and lifting properties of the absorbed gas.

g In many cases where the available pressure is not sufcient to overcome the hydrostatic head and establishgas lift by employing .other measures in the ordinary fashion, I have found that by continuing theapplication of the maximum available prebsure for aprolonged period of time, it eften possible to produce a considerable depression of the oil level together with such a high absorption ofgas that gas lift will commence immediately upon the release of pressure in the ow tube. For convenience, this method is termed the soak' ing method, and, briefly stated, the novelty therein resides primarily in applying to /the surface of abody of oil collected in the well a soluble gas under a pressure'less than .rock pressure and less than the normal starting pressure, maintaining said pressure for a relatively great length-of time to cause absorption of large amounts of gas, and thenv releasing the pressure on one side of the flow tube while continuing it on the other to initiate gas lift. Thus, a large quantity of gas is caused tobe gradually absorbed bythe oil, this absorption being desired both for the'purpose of lightening the oil body (that is, reducing its specific gravity) and for the expansive and lifting properties Vof the absorbed gas at higher levels as the oil approaches the top of the Well during expulsion, the expansive eEects increasing due to static'pressure decrease as the topis approached. This step also results in gradually forcing a considerable quantity of the accumulated oil body back into the formation. sure is applied both to the tubing Aand the casing, and becomesapproximately if ,not entirely equaliZed therein. After this soaking, or maintained application of gas under pressure, has been continued forwhat is deemed to be a sucient length of time, the pressure on the tube (or the casing, if desired) is suddenly released while pressureI to a natural lsurge of oil into thewell un' der pressure naturally occurring in the formation may be employed to augment the gas pressure, the pressure on the tube being relieved at a time when a head develops Preferably, the presas determined by watching the pressure y gauge. Many variations of the invention are possible as will be apparent to thoseskilled in the art, a preferred embodiment being that generically described above.

In the accompanying drawings the various steps are diagrammatiCaIly represented for the purpose -of illustration, and in these,

Fig. 1 indicates the original condition of the well at the time gas'lift is-to be initiated;

4: fapplied .both to the .casingl and to the flow containing .Fig. 2. indicates the first stepwhereingas under the maximum available pressure/ 1s upon the application .of said7 l 41,740,1 iag1I F1gLv-3represeuts theeonditions attendingl will suilicient to force over theyheadof oil e tube, and `to cause such absorption jij.

'f' for' a' relativelylong lperiod of time. if gas pre's'slire to initiate gas would be maintained for' per-v haps an liour, it wouldfbe necessary ac tehiclr causes/portions of tl" .oil=body ,/,co/rding' to the present method to main- .f.orc,ed back into/the forma/fion; 1/U ,v 'tin such pressure for perhaps six, -to 105,Fgfr-4, inicatesA the die ist ofgppesswr"tiuglitf hours, and where lsuch pressure body is forced 1u'p'on establishinento-Iiorriial gas'lifta. .'fljf these drawings'the usuallxvell. casing i 'i :.410 is sloivn'as receiving aflow tube/l2 which depends into the-oil body, the upper end of the `casi-ng being provided with a connection '13 and the tube witha connection 1li-.into which `gas under 'pressure may be introduced by a compressor C, or from :another Well 1 lovving gas v'under sufficiently high pressure. Tl-1ellevel of oil Vwhich has .accumulated in Y Q/ehamiefirasf/ ,'/tirely to establish new, the maintenance ot pressurefor six'- or. eight hours aintenancejfor. one hour would fail enstancesthirty hours and more, \vill so thoroughlysaturate the oil'tvith gas that -in a great many difficult-cases', flow will commence immediately upon vrelease of the pressure in .the iiow. tube, and the excess headot oil will cessary that-the gas pressure'be mainbe readily expelledfby the pressure main# tained in thecasing. When theloillevel drops tothe lower'end ofthe tube as indicated at 20, Fig. 5, nor'mal gas lift commences, v atl Vwhich time the pressure required to eontinueoper'ation oft-lie We-ll maybe dropped the eo l down below that femployed. instarting "ly 1g; thefmaximum available pressure,

:fw-which'. however, is less than'thel static head .'35V of oilditofboth the Acasing andthe flow tube.,-

lower end of the Vtube and normalgas lift 'velv longperiod of time, "it having been 44.found that by suchmaintenance ofpressure, :fthe body ot oil Will vgradually be forced back -'i into the sands aroundthe Well hole, as indifcatedabythe arrows in'Figs. :Zand 3, Where- 'b v the loil level is eventuallyfbrought down vvtothepoint indica-ted fit-18 in Eig. 3.. It has -thecasing and gas littby this.

'inthe oilW-hen the oil column rises toward the top o ftheflow'tube,

the absorbed lgas 65 the-devel 1G, this-ievehreprealanced in the-tube and cas.-v

Aof the present-.invention'redes 1n maintaining this pressure-'for a rela-.

- =also `:been found thatunder -.t he'se Iconditions, 4

y a relativelygreat amount of gas is absorbed {'methodgitis necessary that 'g'as'absorption be,`

A gavailablefgas E .pressure combined with the lifting effects produced by ftheexpansion of begirsbut does not'coritinue after release'of pressure on the oneside, `the 'entireoperation 1n aybe repeated .'vherebyfthe"resulting Surging et'ect as tlhe oilcolurinns"inthey tubel and casing rise and -fall, further;v increases" gas absorption.v Absorption 'v 'vill 4reach 'a polnt where a portion'of oilvill be"forced over on release,V and ifnecess'arygfurthe rep etition will eventually reduce-the oilI level to the COI'llllleIlCeS;

are apparent'fromthe following: In previous 'attempts to start-certain Wells, ai' pressure of; 900 pounds had Abeen required, but upon continuously 'maintaining a pounds for eight hours, and then releasing the tubing,` 'the Well carne over Without difficulty# Gas lift Wasthereafter'continued at a pressure of 175 poundson' the casing. l

It has been found that in` Wells which The advantages of this methodiof operation i iol .'lpressure of 500 ,headf (which, however,' i'sj truefof most Wells) gas pressure may-be materially aug# niented b'ywatching-the pressure gauge and relea ingv theiiow tube 12 at a time when the maximum eect of-a'headoccurs. 'In fact, by

taking advantage of this 'efect,` itf' i`s frequently possible. to start Well which could not be Started if the p 'rfes'surefvvere released between heads. Toindicatethis condition, arrows directed toward the'wellhole are employed in lVhen normalgaslift has once been initiated by.deprssfi on"ofthe'o`il levelitothe p oint the lovver'end o f the flowtube 12,' Will be'suicient to elevate the incoming' oil 'asapidly as supplied by the natural wellpressure. Obviously, in the' operation of this method, it will 20, indicated ini Figb, the floWjof-lgas under l bep'ossible to'releas'e pressure upon the casing .maintain the pressure on the `flow tube whereby the oil 'will be flowedA out through a connection 13',- and it is intended that thi-sva-v riation `shall be considered 'throughout to be the same invention vas owing out through' the tube. '.Also, it mightbepossible in some in' stances to close thetlowtube and apply gas toA the casing-only, or vice versa, when the well is lg'be'ingallowed'to soak, although the advantages of this modicationfwill' not beso marked as when pressure is applied both'to the casing'andto'the tube.

` From the foregoing, it will-be seen that this 15 process appears to depend upon three factors,

each of which-varies according to the conditions of the individualwell. These factors are: (a) orcin'ga part `of the oil back intoAthe sands.

(b).' l`he absorption of vrelatively large p A quantities o gas under pressure to lighten the` oil and reduce the effective head.

. (c) Heading eifects in the'well.

2 5 4 It can be seen that thefunction of the absorbed gas is considerable-when it is cpnsidered that approximately 160 cubic feet of nat. ural gas will .be absorbed pervbarrel of oil when 4the gas is under pressure of five hundred 'p'o unds. The 'expansionof this amount; of

gas and oil as thewell approaches -the upper' portion of ,the tubing has a lifting effect of' approximatelythirty atmospheres, which constitutes an enormous aid to the pressure of the' ason the casing.` 'lso, it should be noted tha the successful accomplishment under this process', is due largely' to the factor of time.'

The above disclosures are to be considered merely-.as illustrative of the generic inven- 1 40 tion and ynot as limiting, s ince many variations may be' 'made withinfthe scope of the following claims. I clai m:. .l 1. 1. a method for initiating gas lift in oil wells comprising a easing element and a tubingelement dependent therein wherein the hydrostatic head of an oil bodycollected in the well is greater than the available gas pressure, the steps comprising applying said vgas pressure' to the `oil surfaceto force as much as possible of the oil back into the for- .mation and maintaining the pressure of the gas onthe oil to increase absorption of the gas by the oil, said pressure being maintained for a. vconsiderable time, land. then. releasing c5 of relatively large amounts. of gas by the oil said pressure-for a rela` and then releasing the pressure upon one side other side.

3. In a method according to clai'm 2 where in the relea'se 'of pressureiis timed to take 76 place when a heading effect occurs inthe well. 4. In a method for establishing"'gas'lift'jop` erations oil wells, wherein a flow tube dependslinto a body of oil. within a well cas ing, the steps comprising pplying a soluble gas to the oil in the tube and. in the casing simultaneously under a pressure less than the hydrostatic head-in.' the tube until thepressure' is balanced on both sides of the tube, re-l leasing the pressure on one side while mainso taining it onthe other, and repeating thev operation to' cause the oil to surge for further charging the same with gas until a portion of oil is carried over on theireleased side and until the oil level 'in the well has been lowered 85 to the lower end of the tube to bare the same and normal fiow by gas lift is established.

5. Ina method forinitiating gas liftin anv oil well containing a casino' into .which a flow -tube depends and in which yoil has accumii-oo lated, the 4steps comprising applying asolul" blegas under pressure lessthan sufHcient toi overcome the hydrostitic head,"said..pressure 1 being applied-tout least one sideof'said tube, g

maintaining 'saidpressure for a relatively -`o5 long-period of time to-depress the oil level', releasing-the pressure on. said one.s1de and.

applying it on the'other side.

6. In'amethod for initiating Agas lift i an oil well. containing a'body of oil the Steps 100' which comprise applying a soluble gas to the surface of said oil un er a pressure insufficient for normally initiating gas lift of oil to the.

surfaceof. the well, and continuing said ap-v if `plication for a prolonged period of time until:

conditions suitable for gas lift are developed.

- 7. In a method for initiating gas lift in any oil well containing a body of oil into which. allow tube depends the steps which comprise applying a soluble gas to the surface of the -oil under a 'pressure insufficient to start gas lift ofoil up and out through said tube, continuing said application for a prolonged period of time until conditions suitable for. gas i lift have been developed,`and then releasing pressure on one side of said tube. 8. In a method of initiating gas lift in an oilwell containing a body ofoil into which a flow tube depends, the steps which comprise applying a soluble gas to one side of the tube under a pressure insufficient to cause gas liftl ,up and out from the other side of said tube, maintaining said pressure fora' prolonged period of time until gas lift of oil tothe surface is' accomplishe 125 9. In'a method 'ofinitiating gas lift in an oil well containing a body of oil into which alflow tube depends, the steps which comprise applying a soluble gas to one side ofthe tube under a pressure insuicient to cause gas lift -130 up and out from the other side ot said tube, maintaining said pressure. fork a prolonged period of time While maintaining an approximately balanced pressure on the other side of the flow tube, and' releasing the pressure' on one side ofthe flow tube pressure on the other side Signed at Los Angeles,

0s Angeles and State of 10 11th day of July,

While maintaining to obtain gas litt.v in the county of California, this DQ 1927. LBERT C. RUBEL.