US3323361A

US3323361A - Methods and apparatus for analyzing well production

Info

Publication number: US3323361A
Application number: US301753A
Authority: US
Inventors: Maurice P Lebourg
Original assignee: Schlumberger Technology Corp
Current assignee: Schlumberger Technology Corp
Priority date: 1963-08-13
Filing date: 1963-08-13
Publication date: 1967-06-06
Anticipated expiration: 1984-06-06

Description

June 6," 1967 M. P. LEBOURG METHODS AND APPARATUS FOR ANALYZING WELL PRODUCTION 2 Sheets-Sheet 1 Filed Aug. 15, 1965 ATTORNEY June 6, 1967 M. P. LEBOURG 3,323,361

I METHODS AND APPARATUS FOR ANALYZING WELL PRODUCTION 2 Sheets-Sheet 2 Filed Aug. 13, 1963 Ma u/vce f. 1 eou/y United States Patent "ice 3,323,361 METHODS AND APPARATUS FOR ANALYZING WELL PRGDUCTION Maurice P. Lebourg, Houston, Tex, assignor, by mesne assignments, to Schlumberger Technology Corporation, Houston, Tenn, a corporation of Texas Filed Aug. 13, 1963, Ser. No. 301,753

12 Claims. (Cl. 73-155) This invention relates to methods and apparatus for analyzing production from an oil well. More particularly, the methods and apparatus of the present invention are useful in wells which are incapable of flowing in production quantities without the use of in-place pumps or other artificial fluid-lifting equipment.

Usually it is necessary to extend a casing through a well bore to prevent the cave-in of unconsolidated earth formations. The casing is normally cemented to the wall of the borehole to prevent undesired fluids, such as water, in other formations from leaking into the production zones. After being cemented in place, the casing is then perforated along those portions adjacent to producing formations so that the production fluids may enter the casing and be recovered. Occasionally, earth formation will be consolidated and it is not necessary to case the entire well. In this event, production fluids enter the well bore directly from the earth formations.

Although only oil and gas are desired, it is common experience that produced fluids will include quantities of water which reduce theetfective oil and gas output of a well. Water may enter the well either from formations within the production zone or from remote formations if the cementing happens to be defective. Most of these problems can be cured, however, by common remedial procedures but the nature of the problems must first be determined or defined.

Where the formation fluids do not flow in any appreciable quantities and require production by secondary recovery techniques, it will be readily grasped that determination of problems in the production zone is not easy.

The present invention concerns apparatus and methods for profiling the fluid flow characteristics of a well requiring artificial fluid lifting wherein the well is capable of producing through the wall surfaces into a well bore over a given interval. The method includes the steps of: lowering a tubing string to a zone for testing, packing off the tubing string in the well bore above the test zone, artificially producing flow from the isolated zone into the tubing string, isolating the flow from the wall surfaces of the well bore into at least two parts, sequentially trapping individual fluid flow parts, and recovering the trapped fluid flow parts for analysis. In a further application of the present method, pressure measurements are taken to analyze the other conditions of the well.

Apparatus in accordance with the present invention includes a device for isolating at least two producing sections of a well bore from one another. The device has means for diverting the entire 'fiuid flow into the interior of a string of pipe. A retrievable sampling apparatus is arranged for positioning in the device and obtains a fluid sample of fluid flowing from one isolated part of the producing section while fluid flowing from the other isolated section is directed into the string of pipe. Means are also provided for obtaining pressure measurements of both parts of the fluid flow.

Accordingly, it is an object of the present invention to provide new and improved methods and apparatus for determining fluid flow characteristics of a well requiring artificial fluid lifting.

Still another object of the present invention is to provide new and improved methods and apparatus for test- Patented June 6, 1967 ing the production of a well requiring artificial fluid lifting.

Another object of the present invention is to provide new and improved methods and apparatus for sampling a part of a fluid flow from a well which requires artificial fluid lifting.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view in cross-section illustrating apparatus for the present invention using a first type of wireline sampler;

FIG. 2 is a view similar to FIG. 1 by illustrating a second type of wireline sampler;

FIG. 3 is a view in cross-section of another type of apparatus of the present invention;

FIGURES 4A and 4B are views in cross-section of another type of sampling tool;

FIGURE 4C is a view in cross-section of a sampling tool having a slide valve; and

FIGURE 4D is a view in cross-section of a sampling tool having a fluid cushion.

Referring now to FIG. 1, an apparatus or tool 10 is disclosed positioned within a casing 11 by means of a tubing string (not shown). The casing 11 has groups of

perforations

12a, 12b, 12c and 12d along its length coextensive with production zones of the earth formations. A borehole 14 traverses the earth formations and the casing 11 is cemented to the borehole 14 by a column of cement. A typical perforation 12d, such as those produced by a conventional perforating device, is shown extending between the earth formations and the interior of the casing.

The apparatus 10 is generally tubular and coupled to the lower end of a tubing string, the central bore 16 of the apparatus being generally the same size as the bore of the tubing string. At the terminal end of the tool, bore 16 is interrupted by a bore section 17 of reduced diameter, a bore 13 of the same diameter as bore 16, followed by a bore section 18 of reduced diameter. On the exterior of tool 10, and disposed above and below bore section 17, are spaced packers 19, 219 which

straddle flow ports

21, 21a extending between bore section 17 and the exterior of the tool. A bypass passageway 22 extends longitudinally of the tool and connects bore 16 to bore 13 for fluid flow in the event bore section 17 is blocked off.

The tool is provided with one or more communicating ports 23, 23a disposed intermediate of its length and the upper portion of the tool has a packing element 25. A sampling tool 27 is shown disposed in bore 16 of the tool. It will be appreciated from the description thus far that when packing

elements

25, 19, 2t) sealingly engage with the casing and, in the absence of sampling tool 27 fluid flow to the upper end of bore 16 (which is connected to a tubing string) is permitted in the following manner:

(a) From below tool 10 via

bores

13, 13, 17 and 16 or bore 18, bore 13, bypass 22 and bore 16,

(b) From between the

sealing elements

19, 20 via

ports

21, 21a, bore 17, bore 16,

(c) From between sealing

elements

19 and 25, ports 23,

23a and bore 16.

It is also important to note that packer 25, when expanded, closes the annulus between tool 10 and casing 11 so that all of the flow paths described above are directed into the bore 16 of the tool. It will also be appreciated that the flow is from the entire interval of perforations below the packer 25.

In FIG. 1, the

packers

25, 19, 21) are shown in an expanded position and a retrievable sampling tool 27, which may be lowered by means of a releasable wireline (not shown), is positioned within tool 10. Sampling tool 27 has an elongated cylindrical chamber 29 which is ported at its upper end 30 and open at its lower end by a bore 31 extending lengthwise to the lower extremity of sampling tool 27. A one-way check valve 32 is disposed in chamber 29 for closing the upper end of bore 31. A floating piston 33 is provided in chamber 29, the piston initially being disposed at the lower end of the chamber adjacent to check valve 32 and the upper end of bore 31. Sampling tool 27 has a shoulder portion 34 intermediate of its length which engages a corresponding shoulder 35 immediately above bore section 17 in tool 10. Below the shoulder portion 34 of sampling tool 27 is a section 36 reduced in diameter to form an annular space within bore section 17 when the sampling tool is inserted into tool 10. The lower end of section 36 is sized for reception into the terminal bore section 18 of tool 14 and O-ring sealing means are provided thereon to seal section 36 within bore 18. A port 37 is provided in the lower end of section 36 for communicating the exterior of the section with bore 31.

In the position shown, sampling tool 27 has bore 31 opening to the casing below packer 2% where a fluid from below packer 20 can enter bore 31. Fluid entering bore 31 is collected in the lower portion of sampling chamber 29 formed between movable piston 33 and check valve 32. The portion of chamber 29 above piston 33 can contain a fluid, for example a light-weight fluid such as kerosene, which is exhausted out the port in upper end 30 when the piston is moved in response to fluid filling the lower portion of sampling chamber 29.

During the time a fluid sample is being taken, formation fluids between

packers

19, 20 can flow through

ports

21, 21a, bore 17, bore 13, bypass 22 and the annulus between the exterior of sampling tool 27 and bore 16. Formation fluids between

packer elements

19 and 25 can flow through ports 23, 23a to the bore 16. It will be appreciated that formation fluids can flow from along the entire interval beneath packer 25, and that these fluids are separated into at least two parts with one of the parts being trapped for recovery. After a sample has been trapmd between piston 33 and valve 32, the sampling tool 27 is retrieved for analysis of the flow sample.

Before proceeding further, a brief discussion of the usual nature of fluid flow from formations in to a well is in order. In a well requiring artificial production, if the artificial motivating means is stopped, there generally is suflicient formation or reservoir pressure to build up a fluid column within the well and above the production zone to a static level where hydrostatic pressure from the fluid column equals the pressure in the earth formations. The fluid flow to build up a static fluid column may be either (a) Slow, so that a considerable period of time is required for the fluid column to rise to its static level; or

(b) Rather rapid so that the fluid column rises to its static level in a short period of time.

Considering first the case (a) above: the tool 10 is positioned in the well adjacent the production zone and the packer elements actuated to seal with the casing at spaced locations. Next, a swab unit (not shown) is lowered into the tubing and fluid is bailed from above tool 10 to reduce the fluid column well below the level of tool 10. Immediately following this, sampling tool 27 is lowered into place within the tool 10. Because of the reduced level of the fluid column, the fluid will naturally flow to build up the fluid column and it is during this fluid build-up that the trapped fluid sample is obtained. If an increased flow rate is desired, the tubing string may be swabbed while obtaining the fluid sample.

In case (b), as in case (a), tool 10 is positioned in the casing and the packer elements set. However, sami pling tool 27 is first positioned in the tool 10 and wireline is disconnected from the sampling tool and removed. A swabbing unit is then inserted into the tubing to pump the fluids upward while the sampling tool is in position with the resultant trapping of a fluid sample therein.

Following a first sampling operation of formation fluids flowing from below packer 20, the first sampling tool 27 is removed and a second sampling tool 27' is utilized in a similar manner. Sampling tool 27, as illustrated in FIG. 2, is similar to tool 27 but has a modified nose piece 36 below the shoulder portion 34 which has seal

\ ing elements

39, 40 straddling a port 41 which leads to a blind bore 31 in the nose piece 36. Thus, with sampling tool 27', formation fluids from below the packer element 20 enter bore 18 of tool 10 and travel via bore 13 and bypass 22 to bore 16 and on into the tubing string above tool 111. Formation fluids intermediate of

packers

19 and 20 enter

ports

21, 21a of too-l 10, port 41 of sampling tool 27 and pass via bore 31 into the lower portion of sample chamber 29 of the sampling tool between piston 33 and valve 32. Fluids intermediate of

packer elements

19, 25 enter tool 10 via ports 23, 23a and pass on into bore 16. Hence, it will be appreciated that with sampling tool 27', fluids from a different interval of frmations are recovered for analysis.

Following the recovery of the sample in tool 27', the packers can be unseated and tool moved to another interval of the casing for flow testing of this second interval in the same manner as described above. The operation is continued in this manner for the entire interval of formations being tested thus permitting recovery of discrete flow samples for individual sections along the entire interval of interest.

Tool 10, as seen in FIG. 1, includes a longitudinallyextending tubular mandrel body 45 with

bore sections

13, 16, 17 and 18 arranged therein as described heretofore. The upper end of the mandrel is threaded for coupling the tool to a string of tubing.

The packer at the lower end of the mandrel is attached between an upwardly-facing shoulder 48 on the mandrel body 45 and a lower spacer housing 49 slidably mounted around mandrel body 45. Lower spacer housing 49 has the port 21a which communicates with the port 21 of the mandrel. Packer 19 is attached to mandrel body 45 between lower spacer housing 49 and slidable upper housing 50 which has the ports 23a. Packer is attached between the upper housing 50 and a slidable expander element 51. Above expander element'51 is a cage assembly 52 which has wall-engaging friction members 53 and slips 54. Cage 52 is releasably connected to the mandrel body in the usual manner with a I-slot and pin. The packer 25 may be of the type disclosed in Patent No. 3,074,484. To set the packers, cage 52 is unlocked relative to the mandrel body so that the mandrel body can be picked up relative to the cage. Expander element 51 brings slips 54- into looking engagement with the casing 11 and packer 25 is then set or expanded. Continued upward pull on the string sets

packers

19 and 20 in order. It will be appreciated that the hardness of the rubber used to make the packers is adjusted in a well-known manner to obtain the sequential setting of the packers.

To perform operations in accord with the present invention, packer 25 is first set above the uppermost perforation and

packers

19 and 20 are then set as described above.

Next, the sampling tool 27 is lowered into the mandrel body 45 and flange 34 of tool 27 engages shoulder of mandrel 45.

At this time, if the well column has been previously bailed out, the part of the fluid returning to the well bore below packer 2%) will enter bore 31 of tool 11 thereby displacing piston 33 upwardly. The fluid returning to the well bore between

packers

20, 19 and

packers

19, 25 is bypassed to bore 16 and on into the tubing string.

If the well has a relatively fast fill-up, sampling tool 27 is positioned in mandrel body 45, before tool 11) is set in place. After positioning tool 27, the wireline is disconnected from the sampling tool 27 and removed. Flow can then be induced by a swabbing operation which pumps the formation fluids upwardly. Alternatively to a swabbing operation, a fluid-drive or gas-lift operation can be used to move the fluid.

After retrieving sampling tool 27, its contents can be analyzed to provide a determination of the nature of the fluids flowing from formations beneath packer 20. Following retrieval of sampling tool 27, sampling tool 27' is placed in mandrel 45 and a sample obtained of fluids flowing from formations intermediate the locations of

packers

19 and 20 in a manner similar to that described with respect to sampling tool 27.

To test the next section of the perforated interval of the well bore, the packers are unseated and tool is picked up and repositioned for testing of the next formation interval. ()nce again the packers 19, 2t) and 25 are seated in the casing.

Sampling tools

27 and 27 are used to recover a fluid sample as described heretofore.

Each interval is successively tested in a like manner and, ultimately, the tool is retrieved from the well bore.

A further refinement of the present invention is illustrated in FIGS. 1 and 2 wherein the

sampling tools

27, 27 are provided with conventional pressure recorders 60, 61. One of the pressure recorders 60 is disposed in the sampling chamber between piston 33 and bore 31, while the other recorder 61 is connected to the lower end of the tubular extension.

The pressure recorders 60, 61 are used to measure and record pressures of the fluid at their location during test operations. From these independent pressure measurements, the potential of the isolated zone can be subsequently determined and also the existence of leakage of fluids either between the casing and the formation or within the formation itself (through a fracture or the like) can be determined.

To the foregoing description, it will be appreciated that once packer 25 is set, well fluids within the annulus between the casing and tubing and above packer 25 are isolated from the testing zone for the entire operation. Thus, the testing operations may be accomplished quickly without requiring that the well bore be emptied of fluid each time that tool 10 is moved.

Referring now to FIG. 3, another apparatus on tool 10 of the resent invention is illustrated. In FIG. 3, the mandrel body includes three

sections

63, 64, 65 which are telescoped to provide a continuous sealed bore 16. On lower mandrel section 65, a cage assembly 52 is mounted above a slidable expander element 51 and packer 20', the packer 20 being attached between a shoulder 48' on the mandrel and the expander element 51.

The upper end of mandrel section 65, which receives the lower end of mandrel section 64, has a flange 66. Packer element 19 is attached between flange 66 and a flange on a tubular sleeve 67. Sleeve 67 is pin-connected through slots in mandrel section 65 to the lower end of mandrel section 64 and a spring 68 is provided between sleeve 67 and an abutment on mandrel section 65 tending to maintain the packer 19' in a retracted position.

The upper end of mandrel section 64, which receives the lower end of mandrel section 63, has a flange 69. Packer element 25 is attached between flange 69 and a flange on a tubular sleeve 70. Sleeve 70 is pin-connected through slots in mandrel section 64 to the lower end of mandrel section 63 and a spring 71 is provided between sleeve 70 and an abutment on mandrel section 64 tending to maintain the packer 25 in a retracted position.

The rubber used to make packer 25' has a greater strength, i.e., about 80 durometers Shore hardness as compared to that used in

packers

19, 20 which may be about 50 durometers Shore hardness. Spring 71 is also stronger than spring 68. It should be appreciated that if the rubber used in packer 20' is about 70 durometers Shore hardness, the spring 68 could be eliminated.

The tool 10' otherwise is similar to the tool 10 described in relation to FIGS. 1 and 2 and sampling tools 27 and 27' are used in the tool.

To operate the packers, cage assembly 52 is unlocked to bring the slips into wedging engagement with the casing and to set packer 20'. Further upward pull causes the force of spring 68 to be overcome and packer 19 is set. Still further pull overcomes the force of spring 71 and packer 25 is set. The method of sampling is performed as previously described.

The foregoing described embodiments of the present invention permit recovery of a fluid sample which can be analyzed for the quality of contribution relative to flow from other sections. In FIGS. 4A, 4B, the samplers 27a, 27b illustrated can retrieve a fluid sample which can be analyzed for quantity or potential of flow relative to other sections. Samplers 27a, 27b are generally constructed as samplers 27, 27', respectively, and therefore are only illustrated as to modified portions; however samplers 27a, 27b do include internal and external pressure recorders 60, 61.

Samplers 27a, 27b are closed at their upper ends 30' and the interior space 33a between the piston 33 and closed end 30' is at atmospheric or a low pressure. It is noted that should ball valves 32 leak before positioning of a sampler, other valves such as slide valve 31a (FIG. 4C) can be provided for controlling flow to bore 31. Further, as shown in FIG. 4D, the interior space 33a can be modified to have a fluid cushion 33b and an orifice place .330 as well as an air or low-pressure chamber 33d. In

any event, the closed samplers 27a, 27b recover a fluid sample over a given period of time to provide a rate of flow and pressure build-up measurements for the particular section tested. Hence, the potential of the tested zone can be determined. The external and internal pressure measurements indicate the reliability of the test and indicate if there is communication between the tested zone and other zones.

The advantages of the present invention are manifold. For example, the testing produces results which are both qualitative and quantitative. The qualitative results are obtained from the retrieved fluid sample which can be analyzed for its precise fluid content. Quantitative results are obtained by retrieving a sample before the sample chamber is completely filled while measuring the time required to obtain the sample. This gives an indication of the rate of fluid flow from the formation interval being tested. If desired, a timing device can be attached to the sampling tool to indicate the time of fill-up for the sample chamber.

From the pressure measurements it can be determined if the cement column has channelled. For example, if there is no pressure build-up of the fluid within the sample chamber, it is easily deduced that fluids are bypassing the formation interval at that point. The pressure measurements may also be used to indicate a leakage or channelling between fluid levels within the formations which will result in a higher-pressure production zone being thiefed by a lower-pressure production zone.

While particular embodiments of the present inven-v tion have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A method of determining the fluid flow characteristics throughout an interval of earth formations incapable of naturally flowing fluids into a well bore comprising the steps of: packing off the interval of earth formations at a point above the uppermost portion thereof to isolate the entire interval from well fluids thereabove; packing off a relatively short section of the entire interval below said point; artificially producing a flow of formation fluids into the well bore along the entire interval including said short section; lowering fluid samplers into the Well bore and collecting samples of formation fluids flowing into said interval including a sample of fluids flowing into said short section; retrieving said fluid sampler-s to the earths surface for analysis of the fluids contained therein; then sequentially packing off other short sections along said interval and performing the recited producing, lowering, collecting and retrieving steps for each pack off; and, during each of said sequential pack offs, packing off the interval above the uppermost portion thereof so that the entire interval of earth formations can produce in a normal fashion as said flow samples are being collected.

2. The method recited in claim 1 further including the steps of measuring the pressure of fluids being collected and recording the pressure measurements as a function of time.

3. The method recited in claim 2 further including the steps of simultaneously measuring the pressure of fluids flowing into said interval other than those being collected, and recording said measurements as a function of time.

4. The method recited in claim 1 further including the step of measuring the time required to collect a flow sample to give an indication of flow rate.

5. Apparatus for testing a well comprising: at least three longitudinally-spaced packer means for packing off a well bore; a longitudinally-extending flow pipe means interconnecting said packer means and adapted for connection at its upper end to a string of pipe, said flow pipe means having flow ports disposed intermediate of said packer means; a retrievable flow sampling tool adapted to be lowered through a string of pipe into said flow pipe means; means on said flow pipe means and said retievable flow sampling tool cooperative for positioning said tool relative to said flow pipe means; said sampling tool having a ported sampling chamber and sealing means cooperative with a flow port in said flow pipe means intermediate of adjacent packer means for receiving a fluid sample.

6. The apparatus of claim 5 and further including fluid bypass means in said flow pipe means for bypassing fluid about said sealing means.

7. Apparatus for testing a well comprising: at least three longitudinally-spaced packer means for packing off a well bore; a longitudinally-extending flow pipe means interconnecting said packer means and adapted for connection at its upper end to a string of pipe, said flow pipe means having flow ports disposed intermediate of said packer means; a retrievable flow sampling tool adapted to be lowered through a string of pipe into said flow pipe means; means on said flow pipe means and said retrievable flow sampling tool cooperative for positioning said tool relative to said flow pipe means; said sampling tool having a ported sampling chamber, a slidable piston therein, and sealing means cooperative with a flow port in said flow pipe intermediate of adjacent packer means for receiving a fluid sample.

8. Apparatus for testing a well comprising: at least three longitudinally-spaced packer means for packing off a well bore; a longitudinally-extending flow pipe means interconnecting said packer means and adapted for connection at its upper end to a string of pipe, said flow pipe means having flow ports disposed intermediate of said packer means and being open at its lower end; a retrievable flow sampling tool adapted to be lowered through a string of pipe into said flow pipe means; means on said flow pipe means and said retrievable flow sampling tool cooperative for positioning said tool relative to said flow pipe means; said sampling tool having a sampling chamber ported at opposite ends, a slidable piston in said chamber, valve means between said chamber and one of said ported ends, and sealing means cooperative to place said one ported end in fluid communication with a flow port in said flow pipe intermediate of adjacent packer means for receiving a fluid sample, said flow pipe means including bypass means for fluid communication extending between the open end of said flow pipe means and the upper end of said flow pipe means operative for passing fluid therethrough when said sampling tool is positioned in said flow pipe means.

9. The apparatus of claim 8 and further including first pressure-sensing means in said sampling tool in fluid communication with the portion of the chamber between said piston and valve means.

10. The apparatus of claim 9 and further including sec- 0nd pressure-sensing means attached to said sampling tool and responsive to pressures outside of said sampling tool.

11. In apparatus for testing a well, the subcombination comprising a retrievable fluid sampling tool including a housing having a sample receiving chamber therein and upper and lower ports at opposite ends of said chamber, a floating piston in said chamber normally disposed at the lower end of said chamber, said upper port being open to the well bore, valve means between said lower port and said piston means for retaining a fluid sample between said piston and valve means, seal means on the exterior surface of said housing and located above and below said lower port and shoulder means on said housing for cooperably positioning said housing within a testing apparatus.

12. The apparatus of claim 11 and further including a first pressure-sensing means in communication with the said housing portion of the chamber between said piston and valve means, and a second pressure-sensing means attached to said housing for measuring Well pressures other than pressure between said seal means.

References Cited UNITED STATES PATENTS 2,441,894 5/1948 Mennecier 166-147 X 2,781,663 2/1957 Maly et al. 166-3 X 2,959,226 11/1960 Blood 166147 X 3,103,813' 9/1963 Bourne et al. 73-155 3,115,187 12/1963 Brown 166224 RICHARD C. QUEISSER, Primary Examiner.

I. W. MYRACLE, Assistant Examiner.

Claims

1. A METHOD OF DETERMINING THE FLUID FLOW CHARACTERISTICS THROUGHOUT AN INTERVAL OF EARTH FORMATIONS INCAPABLE OF NATURALLY FLOWING FLUIDS INTO A WELL BORE COMPRISING THE STEPS OF: PACKING OFF THE INTERVAL OF EARTH FORMATIONS AT A POINT ABOVE THE UPPERMOST PORTION THEREOF TO ISOLATE THE ENTIRE INTERVAL FROM WELL FLUIDS THEREABOVE; PACKING OFF A RELATIVELY SHORT SECTION OF THE ENTIRE INTERVAL BELOW SAID POINT; ARTIFICIALLY PRODUCING A FLOW OF FORMATION FLUIDS INTO THE WELL BORE ALONG THE ENTIRE INTERVAL INCLUDING SAID SHORT SECTION; LOWERING FLUID SAMPLERS INTO THE WELL BORE AND COLLECTING SAMPLES OF FORMATION FLUIDS FLOWING INTO SAID INTERVAL INCLUDING A SAMPLE OF FLUIDS FLOWING INTO SAID SHORT SECTION; RETRIEVING SAID FLUID SAMPLERS TO THE EARTH''S SURFACE FOR ANALYSIS OF THE FLUIDS CONTAINED THEREIN; THEN SEQUENTIALLY PACKING OFF OTHER SHORT SECTIONS ALONG SAID INTERVAL AND PERFORMING THE RECITED PRODUCING, LOWERING, COLLECTING AND RETRIEVING STEPS FOR EACH PACK OFF; AND, DURING EACH OF SAID SEQUENTIAL PACK OFFS, PACKING OFF THE INTERVAL ABOVE THE UPPERMOST PORTION THEREOF SO THAT THE ENTIRE INTERVAL OF EARTH FORMATIONS CAN PRODUCE IN A NORMAL FASHION AS SAID FLOW SAMPLES ARE BEING COLLECTED.