US1740102A - Of los angeles - Google Patents

Description

Dec. 17, 192.9. F. w. LAKE v DISPLACING DEAD CASING OIL FOR INITIATING GASl LIFT INl O IL WELLS Filed July 18, 1927 l\\\\\ \\fn Francis ATTORNEY Patented lec. 17, i929 P AT1;

FRANCIS W. LAKE, 0F WHITTIER, CALIFORNIA, SSIGNOR T0 UNIDN OIL CMPANY 0F CALIFORNIA, OF LOS AN GELES,.CALIFORNIA, A CORPORATIDN 0]? CALIFORNIA DISPLACING DEAD CASING OIL FOR INITIATING GAS LIFT IN OIL WELLS Application led July 18, 1927. Serial No. 206,678.

rThis invention relates to'the so-called gas lift method of iowing deep wells, particularly oil wells, and has been designed to overcome the excess hydrostatic head of oil which ordi- 5 narily accumulates in such wells prior to starting gas lift and which ordinarily cannot be removed by direct application of a reasonable gas pressure in attempting to initiate gas lift.

Gas lift, as'now commonly practiced, consist-s in passing gas under pressure into a Well containing a flow tube, so that the gas passes around the lower 'end of the flow tube in a stream and in its passage atomizes the oil as 'fast as it is forced up to said tube end by the natural rock pressure in the well, the atomized oil being carried to the surface in the gas stream. The gas may be introduced either through the iiow tube or through thel casing, the atomi'zed oil being discharged from the other of the two; however, it is preferred vusually to introduce the gas into this) casing and discharge the oil from the flow tue.

But, as above indicated, the initiation of .y gas lift usually `offers difficulties, due to the heightmay be vas much as.

fact that during a preceding period of idleness a relatively great hydrostatic head of oil has accumulated in the well hole, which head usually cannot be overcome by steady application of a moderate pressure to one side of the flow tube. This condition arises for the reason that, as pressure is applied to one side of the tube to depress the oil level therein,ithe

hydrostatic head increases in the other side.

While someof the oil is forced back into the' formation (depending upon the viscosity of the oil, the friction ofthe formation, and the like) the effective rock pressure in the vicinity of the well increases until itis sufficient to balance the increased hydrostatic head. Thus, upon any attempt to start gas lift by straight application of pressure to one side in order to force over the entire excess load ofaccnmulated oil and uncover the lower end ofthe tube for passage of gas thereunder, thehydrostatic head will increase until it reaches themaximum, that is; until it is equal to the entire height of thel tube, which eral thou/Sand feet. Moreover, the pressure which would be high enough to start gas lift by such steady application, that is, a normal starting pressure, under these conditions, would be excessive for all other purposes, since which the oil level is lowered and gas lift started7 normal continuation of gas lift may be and should be carried on with a much lower pressure, this being made possible by a much lower density of the gas-and-oilA column in the `flow tube during normal gas lift as compared with the oil before gas lift. Thus, itis clear that it is not convenient or desirable to maintain said excessive pressure merely for the purpose of overcoming said hydrostatic head.

Another important consideration is the fact that the oil body found in some Vwells is so heavy and so free from absorbed gas and other light constituents, that the hydrostatic pressure of a given column is materially A greater than that of a less heavy oil. Thus, this reavy gas-free oil, which is commonly termed dead oil, oifers additional diiiiculties, especially when very dead, that is, when'containing no material quantities of light' elements. c o,

The object of this invention, is to overcome the diticulties described and provide a method whereby the head of accumulated oil, particularly where the oil is very dead, may be removed with comparative ease so that the available relatively low gas pressure may be employed to initiate and maintain normal gaslift.; f v. l v

:Thismethod comprises essentially the in' troduction ofa quantity' of relatively light oil into a well Casing'to raise the level of the oil and decrease the hydrostatic head which would otherwise develop in the `flow tube upon application of pressure to the casing. The dead oil is discharged through the flow tube and introduction of lightoil intoV the top of the casing is continued whereby the dead oil iseventually displaced by 'he light oil. The light oil may be obtained oy introducing gas (preferably natural gas) into the casing with a heavyoilwhereby the heavy oil is livened up or rejuvenated, the proportion of the gas sointroduced being gradually increased so that said light oil successivelybecomes very light., eventually isl atomized, and finally is u gradually displacing the light oil with gas.

entirely-displaced with gas. Meanwhile, discharge through the'ilow tube is continued so l that the light oil which displaces the dead oil is itself displaced by a much lighter 011, and

then bythe atomized oil and finally by gas,

,whereupon normal gas lift commences and continues; vMore briefly stated, the invention may be considered, generically, to bea method v.

for initiating gas liftin a well 'containing a considerable head of dead oil, by gradually' displacing the dead oil'with a lighter oil and In the accompanymg drawings wherein the various steps of this method are represented diagrammatically, l

Fig. -1 indicates a well in which a considerable head of heavy oil has accumulated prior oil beingfintroduced has been almost entirely' replaced with gas; and

' F ig. 6 represents the final stage wherein the atomized oil has been 'displaced and gas is passing into the lower end of the flow tube to 'atomize lthe deadoil asflows into the' In the drawings the well casing 10 is shown as containing a'lar e quantity of very dead oil intowhich the ow tube l2 depends, the level of the said oil being indicated at 15 as lying sufficiently high above the lower end of the How tube as to materially hinder the ini.-

tiation of gas lift. A casing inlet 16 lfor oil oil supply line 20, whereby light oil may be and gas is connected with a Compressor or pump 18 having a gas supply line 19 and an introduced inte .the casing above the dead oil. 0f^course, as the light oil is introduced into the casing and the total hydrostatic head is therebyincreased some of the dead oil is thereby forced back into the formation, but since this return of the dead oil to the formation is vrelatively slow., the casing can be readily filled with thelight oil thus causing the head of dead oil to rise in the tube. When the casing has become Vfilled with light oil, thepressure of the pumplS will then be suflicient to overcome the excess head of the dead oil over the light oil, and discharge of dead oil from the flow tube will commence with consequent lowering ofthe dead oil in the casing (Fig.

2).' The introduction of light'oil through inlentirely displaced as indicated in Fig. 3.-

Then, in order to displacev thellight oil, gas

let 16 is continued until the dead oil has-been in large quantities is introduced into the casing therewith', and the proportion of gas so Aintroduced is gradually increased. Meanwhile, discharge through the flow tube continues so that the light oilis gradually removed. and displaced by the oil and gas rmxture. This removal of light oil and increase in. quantity of gas introduced with thelight oil,l is continued until all ofthe head of oil above the lower end of the ilow tube is removed and only gas is introduced intol the casing as indicated in Fig. 6, gas lift thus being accomplished.

- It will be seen that since the circulation from the top `of the casing is' downward to the lower end of the flow tube andthence upward through the tube to the surface, the head of -heavier oil will be graduallydisplaced by the light oil and. the static head in the tube Will be gradua-llyreduced correspondingly due to thedifl'erence in specific gravity and to the elevating'effect of the dissolved gas. Thus, lthe pressurel appliedto the'casing will always be sufficient to overcome the excess static head of the fluid contained in the flow tube, sov that this gradual displacement of a heavier fluid by a lighter' fluid is accomplished very read-jf ily. Therefore, this method comprises, pri- Q marily, two merging steps, namely, gradual displacement of the very heavy., dead oil with light 'oil and the gradual displacement ofthe 4light oil with gas untilgas lift is finally established. Moreover, gas lift may in this 7 'manner be accomplished with a much lower pressure than would be required by othermethods.` For example, where a pressure as` 4 high as 800 pounds would be insufficientto v overcome the hydrostatic head and initiate gas lift by direct application in the usual manner, a pressure of 300 pounds to 400. pounds applied bythe oil pump will be sufiicient'to initiate gas lift by the present method, this pressure being lowered as the amount of introduced gas isincr`eased, untilnormal gas lift is effected when it may be continued with about 120 pounds.

The above disclosures are to be considered merely as illustrative of the generic inven- -tionand not as limiting, since many variations obvious to those skilled in the art ma be made within the scope of the following claims.

' I claim:

'1. A method for removing a head of dead oil from an oil well comprising introducing live oil into the well andl simultaneously effecting removal of oil from the` well until thle dead oil vhead has been replaced by live o1 oil from a Well comprising introducing a light oil into the well to displace the-head of 2. A method for removing a head of dead dead oil by effecting removal of said dead oili from the well until such displacement occurs and introducing gas into thevlight oil and iso " gas displaces the live oil and gas lift upward` and displacing the light oil with prising ldisplacing adually increasing the guantity of gas untilthe light oil has been isplaced by gas.

v3. A method for establishing gas lift in, an f y oilwell in which a head of dead oil exists and 5 Y i introducing a relatively light oil intothe well' into which 4avilow tube depends, comprising to raise ',the'head, and' simultaneously removing' oil through the flow tube, introducin'g gas into-the well with said light oil in gradually increasing quantities while continuing to remove v'oil throu h the flow tube, until the through the low tubeis established. f 4.' A` method for establishing gas lift in an oil wellcomprising a casing and low tube elements containing a head of dead oil, comthe head of-dead oil in at 'elements with lighter oil gas until least one of said normal gas lift commences v n -5. A Finethod for removing a quantity of dead oil in an oil. well in which a -flow tube vdepends into the oil, comprising introducing lighter oil into the well above the dead oil tol displace the dead oil and toreduce the hydrostatic head in the ow tube, removal of the dead oil being eli'ected through said tube while introducing the light'oil above said dead oil, removing the light oil, and then flowing thewell by'gas lift.

6.' A method for establishing gas lift in an oil well containing a head of dead'oil comprising introducing a lighter oil to displace l the dead oil head, the dead oil head being removedruntil displaced by light oil, then introducing as into the well with the light oil and gra ually increasing the as while effecting removal of light oil an gas until the l 40 light oil is displaced by gas.

7. A-method for establishing gas lift in an oil well containing a head of dead oil comprising displacing said head'of dead oil with a lighter oil, then displacing the light oil by the introduction of gas, and continuing-the introduction of gas to produce gas lift of oil which then flows into'thewell. v

8. A-method for removing a head of dead oil from an oil well which comprises introducing' light oilinto the well and thereby displacingthe dead oil head, continuing the the gas to cause gas litt.

11. A method of establishing gas lift which comprises displacing an'oil in a well by a gas charged oil and then introducing gas into thewell to cause gaslift."

'12. A method for removing a quantity or deadv oil from a well containing a casing into which'a flow tube depends and in which .casv

ing and tube a head of Vdead yoil stands, comprising introducing a quantity of lighter oil on top of the deadoil on one sideof the tube to reduce the hydrostatic head on the other Y side of the tube, removal of the dead oil from said other side being eected while introducs i ing said lighter oil on theoneside, thereby displacing the dead oil with said'lighter oil. 13. A method according to claim 12 wherein displacement of dead oil is followed by removal of light oil, and the well i's then ilowed by gas lift'. v i

f 14. A method for removing a quantity of relatively heavy oil'from a well containing a 'casing into which a flow tube depends and in which casing and tube a head 'of the heavy .oil stands, comprising introducing a quantity of relatively light oil on one side of the tubeto" reduce'the hydrostatic head on-the other side of the tube, effecting removal of heavy oil head while introducing light oil until the heavy oil head is displaced, then introducing gascwi'th the light oil to displace the light oil head with a still lighter oil.l i '15. A method for establishing gas lift according to the method of claim 14 wherein the displacement of the light oil head is followed by .successively increasing the gas propor-v tions until the lighter oil head is entirely dis'- placed by gas, and the introduction of s is i then continued to flowY the well by gasli Signed at Los Angeles, in the county of Los Angeles, and State of California, this 12th day of July A. D. 1927. k FRANCIS Wg'LAKE.

' introduction of light oil and then introducing gas vwith the light oil in gradually in- .j

creasing quantities whereby the light oil head is graduallydisplacedby the gas.

9. A method for establishing gas oil well containing a head of dead oil comprisin `'introducing a lighter oil into the Well 1in `in an in su .cient quantity to displace the dead oil head, cgntinuing the introduction of light oil 1 and introducin gas4 with `the li ht oil so ,l

introduced,"gra ually increasing t e quantities of gas introduced with the light oil until then continuing the introduction of the gas the light oil head is displaced 'the gas, and A

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