US2674877A - Well productivity measurement - Google Patents

Description

3 Sheets-Sheet 1 VELOCITY BY W W ATTORNEY D. SILVERMAN ET AL WELL PRODUCTIVITY MEASUREMENT April 13, 1954 Filed July 1, 1950 w m m B w m 2 2 3 O I 4 2 t; //w 13 fl/ M m 4m a 3 M M P: //W/ /w m #5 m w KL 4 RALPH E. HARTLINE FIG. 1

P 13, 1954 D. SILVE'RMAN ET AL WELL PRODUCTIVITY MEASUREMENT 3 Sheets-Sheet 2 Filed July 1, 1950 Eom o IE8 TIME .FIG. 5 FIG. 6

INVENTORS: DANIEL SILVERMAN RALPH E. HARTLINE BY W W FIG. 4

ATTORNEY April 13, 1954 D. SILV'ERMAN ET AL 2,674,877

WELL PRODUCTIVITY MEASUREMENT Filed July 1, 1950 I 5 Sheets-Sheet 5 b l 5 g L I ,44 '6 es I3 67 INVENTORS DANIEL SILVERMAN RALPH E. HARTLINE WPT ATTORNEY Patented Apr. 13, 1954 WELL PRODUCTIVITY MEASUREMENT Ralph E. Hartline, Tulsa, anolind Oil and Gas Com- Daniel. Silvermanv and Okla, assignors tov St pany, Tulsa,

Okla, a corporation of Delaware Application Ju1y':1-, 1950, Serial N 0. 171,699

6 Claims.v (Cl. 73-155) This invention, relates to' fluid: productivity measurements in wells producing gas, oil, or water, or mixturesoi thesefluids and is directed particularly to measuring the fluid productivity profile of such wells. Bythe termrfluid productivity profile it is intended to designate the log of thefluidproduction in the producing zone 0f;a well,v as afunction of depth.

Numerous methodsof measuring the porosity or permeability ofrwellformations producinggas, oil, or water have been proposed; many of which methods depend upon introducing-into the well formations foreign substances, some-of which can producedeleterious efiects. It is well known, for instance, that fluidscontainingwater can cause permanent damage if introduced into. oil-bearing formations containing swellable clays. A further disadvantage: of the porosity and permeablity measurements which involve. injecting fluids intothe well formations is-thatthe true ability of. the formations tolproduce liquids into the well bore may not:be ascertained because no allowance is'made for the actionof the driving forces whiclrinove-the. fluids intoth wellbore.

Other methods ofv testing well formations to determine thefluids produced. have been proposed, some of which involve diflicult operations; as, for example, those which depend, uponthe setting of onevor-morepackers against the-for.-

mationto segregate, the-production; of. one stratum. from that :of. other-formations. Adrawback of: those methods of, productivity testing; involving, setting packers is. that, generally; the-.tests are carried. out with. the well. formations producing at rates far different fromthoseineflectduring normal well production.

It is accordingly a primary object of our in-. vention to provide a-method of well-formation productivity profiling which. gives improvedresults because-it is carried out withthewell in v a condition approximating normal fluidproduce tloni Another object isto provide-a method-of well productivity profiling. which yields a complete profile at a single operation. Still another object. is to provide a well productivitylogging procedure which avoids injecting into the well formations fluids foreign to. those, produced. Still another object is to provide a well. productivity measuring process which takes fully into account the driving iorcesinvolved in producing the Well fluids from the various formations.v Other objects, uses, and advantages of; the inventionwill become; apparent as. the. description proceeds.

In general, the. foregoing and. other objects are accomplished;- by: a method of: well productivity movable, as a plug. or-piston, along. the well borev by the well fluids as theyareproduced andflow along the well bore, for example, to thewell: tubing inlet; then causing the well formations to produce, for example, by pumping through the tubing or. allowing the well to flow, the. pointof removal of the produced fluids. being at a. difierent level from that where they identifiable ma-. terial is inserted; and then determining the-variations inmovement of the.-identifiablematerial as it is carried along the well boreby the. produced well fluids past the variousproducing strata. Aseach stratum contributesto. the. stream flowing along the wellbore, its-presence and. productivity are revealed by the changes in velocity of movementof the material.

This will be betterunderstood by reference to the accompanying drawings forming. a part of this application and illustrating. certain embodiments of the invention In thesedrawings:

Figure 1 shows diagrammaticallyin crosssection. awell and producing formations, with one embodiment of the invention in operation therein;

Figure. 2 shows a typical; recordobtained, correlated in positionwith theformations of. the well in Figure 1;.

Figure 3 is a plot of velocity of. the, objector fluid against depth, obtainable. from the :chart of Figure 2;

Figure 4. shows an alternative embodiment of the invention in operation in the well. of. Figure 1, shown diagrammatically illCI'OSs section;

Figurev 5 isa graph obtained in the operation of the embodiment of Figure 4;

Figure 6 is the velocity-depthgraph obtainable from the graphof Figure 5;

Figure? is a diagrammatic. representation, with parts in cross section, of afurther embodiment of the invention; and

Figure-8 .is a wiringdiagram of: certain parts of the apparatus shown inFigure '7.

Referring now. to these drawings: and, imparticular, to Figure. 1, a well representedgenerall-y by the. numeral. ll penetrates a variety oiproducing formations l2, l3, and [4' separatedby non-producing formations I5, I6, and". Well I l istypically equipped with a casing 20 cemented in the non-producing formation l5; at the level 2| and. extending to theground surf'ace22. Well H is; also provided with. a. production tubing 23 having-an inlet 24- through, which the well fluids are produced to the surface 22 either by natural flow or, for example, by means of a reciprocating pump 25 of any conventional type.

In accordance with our invention, the relative productivity of formations l2, l3, and i4 and their location in the producing zone of well ii are determined by first introducing into the well bore a plastic or deformable mass or body 3!! of material which is identifiable in the presence of, and of about the same specific gravity as, the well fluids 3i normally filling the bore of well i l. Typically, the material 30 may comprise a stable emulsion of oil and water or an oil-base gel formed by a mixture of crude or refined oil with such bodying agents as the alkali metal salts of long-chain fatty acids or mixtures thereof. One example of such agents is the mixture of hydroxy aluminum stearate, palmitate, and oleate sold commercially under the trade name Napalm. Preferably, the body 38 also forms a definite interface 32 with the well fluids 3i, which interface is detectable with a pair of electrodes 33 and 34; but this is not strictly essential, as material 33 may also comprise a quantity of miscible liquid. such as water, differing substantially in salinity or other properties from the well water and miscible therewith. If the length of producing zone to be surveyed is limited, the main body of identifiable fluid can still be followed even though some intermingling occurs with the well fluids.

The amount of material in or volume of the well bore occupied by the body 38 is not critical, but it should ordinarily be sufiicient to fill the well bore for a length at least equal to the well diameter. It can, of course, be and preferably is several times this amount, a length of five or ten feet being entirely practical, particularly if tlgale length of well bore to be explored is considera e.

One manner of introducing the deformable or fluid body 30 close to the bottom of the well bore H is by means of a conventional dump bailer 31 lowered from surface 22 on a wire line 38, preferably containing at least one insulated conductor and being wound on a reel 39 at the surface. The

electrodes 33 and 34 are mounted in an exposed position on the outside of bailer 31. Through the insulated conductor of cable 38, one of the electrodes 33 or 34 is connected in series with an indicator or recording meter M! and a generator or battery 4|, the other termnial of which battery is connected to the ground surface 22 at point 42. The other one of the electrodes 33 or 34 is similarly grounded in the well I l to the body of bailer 31.

Bailer 31 having been lowered through the annular space 43 between tubing 23 and casing 20 and the mass of emulsion or gel 30 having been deposited near the bottom of well H, production of fluid from the well formations is started by operating pump 25 and withdrawing wellv fluids through the tubing 23. It will be noted in Figure 1 that the tubing inlet 24 is located at the op posite end of the producing zone of well i i from the body 30. Accordingly, when pump 25 is operated and the well formations produce into the well bore, the general movement of fluids in the well bore is that indicated by the arrows as. and the body 33 is swept along in the direction of the movement of fluids by production from the stratum l4. Simultaneously, an operator at the surface 22 observing the meter 43 is able to determine when the electrodes 33 and 34 are located at the interface 32 between the body 38 and well fluids 3i, and he is then able to regulate the up which is proportional ward motion of the electrodes and bailer 31 by reeling in the cable 38 in a manner to follow the movement of body 30. Upon recording with conventional means, the depth of electrodes 33 and 34 on a chart moved in accordance with time, a graph is obtained such as that shown in Figure 2.

Knowing the position of the body 33 as a function of time, assuming, of course, that the production rate of the well is constant or is known with suflicient accuracy to make appropriate corrections and that the diameter of the well bore is reasonably uniform, it is a simple matter to obtain or compute the graph of Figure 3 which shows the velocity of movement of body 30 as a function of depth. This is an idealized plot to illustrate the principles of the invention, but it will be observed that the velocity of the body 36 increases over the producing interval M, reaching a constant value of V1 which continues throughout the non-producing stratum 11. Upon reaching the producing stratum 13, a second change in velocity occurs from V1 to V2, and the body 30 then subsequently moves with uniform velocity through the non-producing interval [3. A third increase in velocity occurs as the body 35 passes the producing stratum l2 and levels off to the value V3 opposite the nonproducing stratum I5. From such a plot as Figure 3, it is a simple matter to obtain both the location in depth of the producing strata-those locations being identified by the regions where the velocity of the body 38 is changing-as well as the relative productivities of these strata, to the relative magnitudes of the changes in velocity. As all of this information is obtained with the well producing its normal fluids in normal quantity from the formations, there is no possibility of error due to varying permeability of the formations to fluids foreign to those naturally produced. Consequently, such a plot as Figure 3 is an accurate indication of the true well productivity profile.

If the production rate of the well is not constant, but varies in a known way throughout the period of measurement, then there is superimposed on the velocities shown in Figure 3 a varying velocity which must be accounted for or subtracted off the observed or computed values to arrive at the true velocity-depth profile. Likewise, if the well diameter is not uniform, but is known from previous caliper measurements, for example, its effect in producing apparent changes in velocity must be considered. The apparent interface velocity varies inversely as the crosssectional area of the well bore (and thus inversely as the diameter squared) regardless of whether the interface is opposite a producing or a non-producing formation. Consequently, the effect of known diameter variations should always be evaluated and removed before the resulting interface velocity-depth log is interpreted in terms of formation productivity.

By interpreting the foregoing data in conjunction with surveys to determine the nature of the various fluids produced by the strata outlined in Figure 3, it is possible to determine both the productivity and the identity of the fluids produced by the strata l2, l3, and M.

In Figure 4 is shown an embodiment of the invention capable of being carried out chiefly by operations performed at the ground surface 22. In this embodiment, the material 30 is merely introduced from the ground surface 22 by pouring it into the annular space 43 and allowingsit to fall into the well fluids 31; If desired ornecessary; additional well fiuids-.50 may be poured back" into the annular: space 43 on top of 'the-body-30 to cause ittomovedownwardly, at least until it reaches the top producing' stratum l2- Pump-'25: is operatedv inuthe meantime with the tubing inlet 24 set as close as-possible to the well bottom. Consequently, the arrows 44 indicating the general direction of fluid movement pointdownwardly, and the body 30 with interface 32 simil'arl'y moves" in thed-irecti'on of the pump inlet. As in Figure 1; thisinterface32 'is followed by the electrodes 33 and 34 which may be mounted on-a simpleelec trode carrier 5| instead of-thelargebail'er 31. By moving-them in-synchronism with theint'er face-32, as observed'by the'i'ndi'cations'of meter; 40, the operator reeling'outthe cable 3t from thereel- 39 is able to-obtainthe plotof the depth of-body 30 asa' function cf-"time shown in Figure li:

Figure .5;- it-will be recognized, is analogous-to Figure 2; except that the reversal-of direction of fluid movement has-invertedfrom top' to bottom the graph showing-the" depth of body 38 as a function-of time;

The plot of velocity asa function of" depth, shown' -in Figure 6, is in all waysanalogous to that shown in Figure 3 and explained in con-- nection with that figure. As before, the zones [2 and-|3 are delineated'by the-depth intervals over which velocities change from V1 to V2, and from V2 to V3, and the relative magnitudes of these velocity changes are the indications of the relative formation productivities.

In this particular illustration the velocity change V3 to V4 is an indication ,of only that part offormation l4 producing above the leveljof pump inlet 24, since the position of this inlet determines the bottom limit of investigation possible with this embodiment of the invention. The top of formation l4, however, is clearly marked by the point of the curve where the velocity begins to increase above the constant value V3. The relative magnitudes of the observed velocity changes indicate relative formation productivities, as far as they go.

An obvious advantage of this embodiment over that shown in Figure 1 is that the equipment lowered in annular space 43 is considerably simpler, and the rate of production from the formations of well H can be readily regulated by the rate of introducing an additional fluid 50 into the annular space 43, relative to the pumping rate through tubing 24. That is, after a period of constantly pumping the well I I through tubing 24 at a given rate and constantly introducing liquid 50 at a somewhat lesser rate down annular space 43, a producing condition is reached in which the well formations l2, l3, and I 4 contribute fiuids at a rate just sufficient tomake up the difference between the rate of introduction of fluid 50 and the rate of removal of..;fluids by pump 25. Thereafter, the three rates-introduction, production, and pumpingremain substantially constant, or, in other words, a producing equilibrium exists. For example, by making the rate of introduction of fluid 50 one-half of the rate of removal of fluid by the pump 25, the well formations l2, l3, and I4, when equilibrium conditions are reached, will then produce at onehalf of their normal rates. An additional control on the rate of production of the well formations is thus provided.

A further embodiment of our invention is that shown in Figure 7 in which there is lowered in- 62? tor -the= annular space 3: of well: l.-lcap aratus'=. comprising a plurality of umbrelld-packersxor: b'afflesfillt 6|, and 62. Theseare; rurrvinto; well Pin a closeclpositlon ona: tubular member-63.;

- loosely coupled tov the. bottom. of dump-ballet:

3-T'containing a highly'viscous materiaLsuchi as; an oil-and-water emulsion. oran" oil-base: gel; Upon' reachingthe bottom of well. I I; a: rod 6k: is actuated to release thegel intothe tubularv member.- 63'. and to expand the packers. 6.0;. 6], and '62 into contact with the wellwalls Through. the tube 63. and. suitable ports therein, the gel. 65 then fills the space between and around;- the expanded flexible, packers and thus helps to prevent well'fluids fromby-passing them. Cone shown in Figure 8, resistors 19;.and1l of different;

value respectively in serieswiththe contacts168 andtlserving toidentify by different values-of? current: flow to an operator att.the surfaces; observing meter: 4%; whichv of the. contacts: 6121011- 68.- is closed; with themoving .contactor: 661.. The; operator'is thus able to follow. the upward move. ment of the packers and; gel by. reeling in the; cable 33', on, therreel. 39.: without imposing: any; appreciable force. on the packer: structure;

It will be understoodthatrthisembodimentroff the invention gives-.a'plotgof deformable plugg position asa function of time in passing the pro. ducing formations l2, l3; and. M, which is, inall. respects, similar. to thatof; Figure 2. However;. uncertainties as tothe-possible; relative movement of'the-a fluid column as a. whole and:the.-gel5 body 30 are reduced in this embodiment which, even more than in the previous embodiments, moves along the well bore like a flexible piston.

Although the embodiments described thus far have made use of artificial interfaces established in the well bore and moved therealong by production from the formations, similar results are sometimes obtainable by observing the motion of natural interfaces, such as the natural oilwater interface, in wells where such exist. Also. it is not always necessary to remove well fluids to cause movement of an interface along the well bore. For example, a natural or artificial interface in the embodiment of Figure 4 could be made to move upwardly from near the pump inlet 24 simply by stopping the pump, while the well formations continue producing at a decreasing rate until static equilibrium is reached. Anomalous movements of this interface are observed as it passes the formations l3 and I2 in moving upwardly.

There are, also, conditions under which no movement of an interface is significant. Thus, after a period of steady production of the well II, a condition of producing equilibrium is reached with no further downward movement of the annulus fluid column above the top producing formation I2. Upon then establishing a plurality of successively lower interfaces in this column and noting whether they move or not, the top of formation I2 is accurately delineated at that depth where the established interface can first be observed to move. Following this interface from there on down the well gives the de-' sired productivity profile.

While our invention has been described with reference to certain particular embodiments and explained by idealized diagrams of the results obtained, it is to be understood that these are for purposes of illustration only, and that modifications thereof will occur to those skilled in the art. The scope of our invention, therefore, should not be considered as limited strictly to the described embodiments but is to be ascertained from the scope of the appended claims.

We claim:

1. The method of measuring the productivity profile of a well which comprises establishing in the fluids in the well bore in the vicinity of the producing zone of said well an identifiable liquid barrier body movable as a unit by the well fluids as they flow along said well bore, removing well fluids from said well bore at a different level from that where said body was established to cause production of additional fluids from the well formations into the well bore, and following the movement of said body to determine the variations in said movement as said 'body passes strata producing into the well bore.

2. The method of locating at least one stratum producing fluids into a well bore which comprises establishing in the fluids in the well bore at a depth difierent from said stratum a barrier body of identifiable material movable as a unit by the well fluids as they flow along said well bore and forming two observable interfaces with the well fluids respectively above and below said body, producing fluids from the formations into said well bore to cause movement of said body past said stratum, and following the movement of said body by observing at least one of said interfaces to determine variations in said movement as said body passes said stratum.

3. The method of measuring the productivity profile of a well which comprises inserting into 8. the well-bore fluids near one boundary of the well producing zone a barrier body of identifiable liquid material movable as a unit by the flow of fluids along the well bore and forming two 0bservable interfaces with the well fluids respectively above and below said body, removing fluids from said well bore near the other boundary of said zone to cause fluid flow from the formations into the well bore and movement of said fluids and body along said well bore, and following the movement of said body by observing at least one of said interfaces to determine variations in said movement as said body passes producing strata in said zone.

4. The method of claim 3 in which said body is inserted near the upper boundary of the well producing zone and fluids are removed from near the bottom of said well bore.

5. The method of claim 4 including the further step of introducing from the surface additional liquid into the well annulus on top of the well fluids therein, to cause said body to move downwardly through said zone.

6. The method of claim 3 in whichsaid body is introduced into the well fluids near the bottom of the well bore and fluids are removed from said bore at a point above the top of the producing zone.

References Cited. in the file of this patent UNITED STATES PATENTS Silverman Oct. 10, 1950

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