CA1194780A

CA1194780A - Accelerated downhole pressure testing

Info

Publication number: CA1194780A
Application number: CA000395560A
Authority: CA
Inventors: Roy R. Vann
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-02-17
Filing date: 1982-02-04
Publication date: 1985-10-08
Also published as: NO164934C; NO820461L; GB2093091A; NO164934B; GB2093091B

Abstract

ACCELERATED DOWNHOLE PRESSURE TESTING
ABSTRACT OF THE DISCLOSURE
Apparatus for completing a hydrocarbon producing formation while concurrently measuring the tubing pressure which the perfo-rated formation may exert thereon. A casing gun is run downhole on the end of a tubing string. A packer is located above the gun, with a vent assembly being located between the gun and the packer.
A valve means is located uphole and in close proximity of the packer and far downhole of the wellhead. The upper tubing string above the valve can be rotated respective to the lower string below the valve to close or open the valve means. The gun is fired, the formation is cleaned, and the valve is thereafter closed to deter-mine the shut-in pressure. A capillary tubing runs down the casing annulus to a location below the valve, where the capillary tubing is connected to the interior of the tubing string. The volume of the borehole measured from the wellhead to the valve means is much greater than the volume measured between the valve means and the gun. An on/off tool enables the string located immediately above the packer to be removed from the wellbore and a production string substituted therefor.

Description

R. Ro V~NN

BACKGROUND OF THE INVENTION
In the art of comple-ting wellbores, it is customary to obtain the initial downhole pressure, the flowihg downhole pressure, and the bot-tom hole shut-in pressure. After a well has been com-pleted~ and the tubing closed or shut-in at the wellhead, several days are often required in order for the final shut-in pressure to reach a maximum value. This is especially so where the formation pressure is relatively low. It would therefore be desirable to be able to obtain the shut-in pressure within a few hours of completing the well as contrasted to several days or weeks. It would also be desirable to be able to sense the downhole pressure by the employ-ment of surface measuring means, as contrasted to downhole recorder devices which must be removed from the borehole for examina-tion.
Apparatus for completing a borehole and simultaneously measuring the downhole pressure, and for ~chieving the shut-in pressure with-in a few hours of perforating the formation is the subject of -the present invention.

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Summary of the Invention The present invention includes a method and apparatus for measuring downhole pressure and/or temperature of an oil or gBS well and is particularly useful where the well hns been perforated by a perforRtin~ gun suspended on a tubing string. A tubing string having a valve, pressure sensing means, an on/off sub, blanking plug sub, packer vent ~ssembly, release coupling, and perforating gun are lowered and suspe~ded within the well with the gun adjacent to the formation to be test2d or completed. The valve is located above, but relatively near to, the perforating gun, particularly as compsred to the distance between the gun and the surface.
After the perforating gun has been detonated to perforate the formation, and hydrocarbon fluids hsve been permitted to flow into the tubing string ViQ
the vent assembly to clean out the well, the valve is closed to prevent further hydrocarbon flow through the tubing string to the surface. Closing the valve shuts-in the well. The pressure from the formation then builds up in the lower borehole annulus below the valve and packer. The shut--in pressure is then sensed by the pressure sensing means.
The pressure sensing means ma~ take the form of several embodiments. It should be understood that each of the embodiments may function separately and alone to accomplish the objectives of the invsntion and no individual embodiment is preferred ovar another. Esch embodiment of the s~nsing means i~cludes Q small housing disposed on the e~terior of the tubing strinK below the valve. The housing for~s d chamber therewithin. ~ port or aperture through the wall of the tubing string provides fluid communication between the flow bore of the tubing string below the valve and the ch~mber of the housing.
In one embodiment, the sensing means includes a small diameter pressure tubing e~tending from the housing up the tubing/cssing annulus to the surface. The lower end of the pressure tubin~ is in fluid communication with the chamber of the housin~ and the other end is connected to a pressure monitor device. The pressure monitor device includes a constant, regulated flow of fluid through a flowmeter and pressure sensor and into the pressure tubing. The pressure sensor at the surface provides output sign~ls which are communicated to a recording device.
In operation, the shut-in pressure wi`ll vary the pressure at the pressure sensor as the flow rate of the eluid p~ssing through the pressure tubing, chamber, and into the flow bore of the tubing string is held constnnt. The shut-in press~re is thus measured at the surface. It should be understood that the discharge pressure at the surface is held constant the shut-in pressure is determined from the chsnge in flow rate at the surface.
One variation of this embodiment is the disposal of a diRphrsgm on the lower end of the small diameter pressure tubing (within the chamber) to prevent comminglin~ of the fluid in the pressure tubing with the hydrocarbon fluids in the tubing string. In this embodiment, the fluid does not flow thr-ough the pressure tubing but merely transmits the variation in the downhole pressure as the diaphragm flexes in response to the downhole pressure.
Still snother embodiment is a self-contained pressure sensin~ and measuring means which is disposed within the chamber of the housin~. The pressure tubing described for previous embodiments is not present in this embodiment. This e~bodiment requires the retrieval of the pressure sensing and me~surin~ means.
Although the above embodiments have been dsscribed as method and apparatus for measuring the shut-i~ pressure, tbey may also be used to provide a continuous monitorin~ of the downhole pressure. Thus, the present invention i8 not limited to closing the flow bore of the tubing string but can be used to measure downhole pressure of a producing well with hydrocarbon fluids flowing to the surf~ce during pressure measurement.
The present invention overcomes the problems of the prior art by providin~
an efficient technique snd app~ratus by the use of which a well may be perforated with a gun suspended on a tubing string, with its inherent ~dvantages, and subsequently tested and evaluated without defeating the advanta~es of such Q technique, and without introducing additional time into the perforating process. These and other objects and advantages of the present invention will become readily apparent to those skilled iQ the art on reading the following detailed description and claims and by referring to the accompanying drawings.

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R. R. VAl~l~

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a par-t diagrammatical, part schema-tical, cross-sectional view of a strata of the earth having a borehole formed therewi-thin in accordance with the present invent;on;
Figure 2 is a broken, cross-sectional view which illus-trates par-t of the borehole of Figure 1 in another operative con-figuration;
Figure 3 is a broken, cross-sectional view which illus-trates the borehole of Figure 2 in still ano-ther operative configu-ra-tion;
Figure 4 is an enlarged, fragmentary, part cross-sectional view taken along line 4-4 of Figure l;
Figure 5 is a curve which illustrates -two downhole vari-ables of the borehole seen in Figures 2 and 3;
Figure 6 is a part diagramma-tical, part schematical, b~oken part cross-sectional view of a strata of the edrth having a borehole formed therewithin in accordance with another embodiment of this in-ven-tion;

Figure 7 is a broken view of part of the borehole seen in Figure 6, with apparatus associated therewith being disclosed in a different configuration; and;
Figure 8 is an enlarged, par-t cross-sectional, de-tailed view of par-t of Figures 6 and 7.

R. R. VANN 'A

DETAILED DESCRIPTION OF THE PREFERRED EM~ODIMENTS
In ~igure 1 of the drawings~ a borehole 10 has been formed down into the ear-th by a drilling rig 12. The borehole ex-tends below -the surface 14 of the ground. The borehole is cased at 16, and the casing extends throu~h a hydrocarbon containing forma-tion 18. Tubing string 20 is concentrically arranged respective to the casing, and includes a packer device 22 which separates an upper annulus 24 from a lower annulus 26. A jet perforating gun 28 is connected to the lowermost end of the tubing string.
A ball valve 30 is located in close proximity to a pocket 32, the details of which will be more fully discussed later on.
The pocket is located above an on/off sub 34. A blanking plug sub 36 is located imr~ediately abo~e the packer. Vent assembly 38 under-lies the packer and is positioned above a tubing release coupling 40.
The upper tubing string 42 is extremely long as compared to the lower tubing string ~4. The tubing string 42 can be rotated clockwise or coun-ter-clockwise respective to tubing string 44 thereby opening or closing ~alve 30.
Tubing strings 44~ 46, 48, and 50 are relatively short as compared to the length of tubing string 42. Capillary tubing 52 extends from the wellhead 54 and down -the upper casing annulus.
The upper -terminal end 56 of the tubing string e~tends upwardly from the wellhead. The capillary is connected by flow conduit 58 to a pressure apparatus 60 and to a Flow ra-te measuring apparatus 62. Flow conduit 64 connects pressure regulator 66 to the illus~
tra-ted source S of fluid pressure. Recorder appara-tus 68 is con-nected to receive signals 60 and 62, respectively, by means of lines or conduits 70 and 72, respecti~ely, R.R. VANN

In Figure 4, a lower pocket 74 underlies the before men-tioned pocket 32. The pocket 32 includes a chamber 76 which re-ceives the lower marginal end 78 of the capillary tubing 52 there-within. The -terminal end 80 of the capillary tubing is received within the chamber 76. Port 82 communica-tes the inside 84 of -~he -tool string or tubing 20 wi-th -the chamber 76 so -that the lower end 80 of the capillary tubing is subjected to the pressure effec-ted at 84, which is essentially -the downhole pressure~ there being only a few feet further to the very bottom of the hole.
In Figure 1, the flow conductor at 58 is received -through the wellhead, where the tubing continues at 52 down through -the upper annulus -to the valve 30. The tubing 52 describes a loop 86 about the valve 30 and continues at 88 on down -the annulus at 78 -to the pocket 32.
Looking again to Figure 4, the lower pocket 74 forms a chamber which is in communication with the -tubing interior 84 by means of a pup joint of smail tubing 90. A recorder device 92 in-cludes a clock and scribe -type informa-tion storage means for re-cording of botton~ole temperature and pressure. The recorder is shock mounted at 94 and 96.
In Figure 2, the upper tool s-tring has been removed from the lower tubing 46 by means of the on/off tool. A blanking plug is set inside a profile at 46 to isolate the lower tubing string 48, thereby precluding material or debris from being transferred in-to and contaminating the interior of -the lower -tool s-tring.
In Figure 3, a production tubing 98 has been stabbed onto the lower tubing 46 by means of the on/off sub 34. The releasable coupling 40 has been actuated, thereby releasing the lower tubing 50 and permitting the gun to fall into the rathole.

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Figure 5 shows a curve which is a plot o~ downhole pressure versus time. The curve illustrates that the pressure rate of increase declines with time. Numeral 100 indicates the shut-in pressure obtained using conventional techniques, while numeral 101 indicates the shut-in pressure obtained in accord-ance with the present invention.
In operation, the tool string is assembled in the manner of Figure 1 and run into the borehole. As the packer 22 is set, the vent assembly 38 can simultaneously be moved to the open position in accordance with United States Patents Nos.
4,151,880; 4,040,485; 3,931,855; and 3,871,448 to which reference is made for further background of this invention.
The blanking plug and profile of sub 36 can be made by Baker Oil Tool, Inc. as shown in their 1974-75 catalog on page 436;
or as set forth in United States Patent No. 3,812,911.
The valve 30 can be made by Baker Oil Tool, Inc. The releasable coupling 40 preferably is made in accordance with United States Patents Nos. 4,066,282 or 3,966,236. The casing gun can take on several different forms, as for example, as disclosed in United States Patents Nos. 3,706,34~; 3,717,095;
3,717,099; 4,009,757; and 4,1~0,188.
The capillary tubing 52 can be attached to the exterior tubing wall at 300-500 foot intervals. The tubing loop 86 is wound so that the loop is loosened when the upper string 20 is initially rotated respective to the lower string 44, thereby obviating placing -the tubing in undue tension. The valve 30 is opened upon 180 rotation of tubing 20 respective to tubing 44.
The valve, when open, must have an axial passageway of sufficient size to admit proper introduction of tools into the tubing string.

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Flow from the source if controlled by the pressure regulator. The flow rate measuring apparatus 62 relays a signal at 70 to the recorder 68 while pressure measuring apparatus 60 relays a - 8a -7~

R. R. ~ANN -, pressure signal at 72 to the recorder, The recorder integrates the signals 70 and 72 to provide downhole pressure data. The flow from S therefore proceeds along the path 66, 64, 62, 60, 58, 52, 86, 88, 78, and out of end 80 into chamber 76, through port 8~, and in-to the tubing interior 8L~, The gun is fired by dropping a bar down through the entire tubing string, all in accordance with the above recited patents.
This action perforates the formation as indicated by numeral 99 in Figure 2. Flow from the formation 18 proceeds through the perfora-tions and into the lower annulus 26, into the open ~ent assembly 38, and uphole through -the tubing 20 where the produced fluids are flared at the mud pit of the drilling rig.
As soon as the well has been cleaned up, valve 30 is closed by rotating the upper tubing 42 respective to tubing 44.
This ac-tion isolates the relatively small lower end of the borehole from the relatively large upper end; accordingly, the pressure build-up is rapid and is achieved within a few hours, as contrasted to the heretofore required several days or several weeks, depending upon the driving force and size of the reservoir.
As soon as the da-ta obtained at 68 indicates that a suit-able formation has been completed, a blanking plug is run down in-to sub 46, and the upper end of the tool string removed by utilizing the on/of tool, thereby leaving -the well in the configu-ration of Figure 2. At some subsequent time, a production tubing 98 is next installed at the on/off tool, the blanking plug is re-moved; and, if desired, the gun can be dropped to the bottom of the wellbore. The well is produced in the configuration seen in Figure 3, al-though i-t is someti~nes desirable to leave the gun in the illustrated position o Figures 1 and 2 so as -to reduce abr~-sion of the lower end of the borehole casing.

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Af-ter the upper -tool string has been removed, thë recorder 92 is retrieved from lower pocket 74, whereupon temperature and pressure readings are available for further study.
The ball type valve 30 and on/off sub 34 are available from Baker Oil Tool, Inc., 7400 E. Slauson Avenue, Los Angeles, California 90040. The blanking plug and seating nipple is descirbed on pages 433-436 of the 1974-75 Baker Oil Tool~ Inc. catalog.
In the embodiment set for-th in Figures 6-8, a pocket 74 is located uphole of the packer, and another pocket 174 is located down-hole of the packer. A recorder device 92 is removably supported within either of the pockets. The pockets are relatively close -to the packer, the packer is relatively close to the pay zone, and the packer is relatively far from the surface.
The pressure and -temperature measured at 74 and 174 is therefore subs-tantially acceptable or equivalen-t as being the pres-sure at the pay zone.
In Figure ~, a slick line 103 has a fishing tool 104 con-nected -thereto. As seen in Figure 8, the recorder has a fishing neck 105 associated therewith which is engaged by -the fishing tool 104 so -that the recorder 92 can be engaged and removed from the pocket and brought to the surface. Moreover, a recorder can be sent downhole and placed within ei-ther of the pocke~ts by employment of -the fishing tool and slick line.
In operation of the embodimen-t set for-th in Figures 6-8, a slick line 103 is run down through valve 56 and lubricator 56'.
The fishing tool 104 releases the recorder 92 wi-thin one of the pockets 74 and 174. The tool 104 is re-turned uphole, the gun fired, and the well is cleaned up by allowing -the flow from -the pay zone to follow a flow path which extends into the casing, up the lower an-nulus into the vent assembly, and up -the -tubing s-tring to -the sur face of the earth.

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R.R. V~N

After sufficient flow has occurred to clean up the well, the well is shut-in to determine the bottom hole or formaiton shut-in pressure. The tool 104 is again run downholè and latched onto a recorder in the indicated manner of Figures 7 and 8. The recorder provides temperature and pressure data which enables the poten-tial of the well to be calculated using known techniques.
The present method enables a pay zone to be completed and the downhole pressure and temperature to be measured before, during, and after perforation, as well as the shut-in botto~ hole pressure to be ascertained, without the necessity of removing any of the major completion componen-ts from the wellbore.
Hence the present method enables comple-tion of a wellbore and evaluation thereof to be carried out while making only a single trip into the borehole. The method set forth in Figures 6-8 there-fore, enables a cased wellbore to be permanently comple-ted and tested in a single trip.
In the embodiment of the invention disclosed in F'igures 6-8, the gun can be placed downhole below the packer, and a blanking plug left in the seating nipple 36 until it is decided to complete the well. At that time, the plug is removed from the nipple, and a recorder is placed downhole at either 74 or 174. The recorder is run into position with a special fishing -tool supported on the end of a slick line which enables the recorder to be placed wi-thin the pocket.

The details of the recorder, fishing tool, and pocket are known to those skilled in the art of testing boreholes. The re-corder is known as an Amarada bomb, or as a Kuster bomb. The lubri-cator, wireline operation, and detonation of the gun are well known-techniques, and can take on several different forms.

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R. R. VANN

The recorder is placed within and removed from the pocket in a manner similar to that of a gas lif-t valve, which is oEten changed wi-th the use of a fishing tool and slick line assembly.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for completing and/or testing a hydrocarbon formation of a well having a cased borehole, comprising the steps of:
running a string of production tubing into the borehole, said tubing string including a perforating gun on the lower end thereof, a valve above, but relatively near, the perforating gun, a packer apparatus below the valve, and a vent assembly below the packer apparatus;
setting the packer apparatus;
opening the vent assembly;
firing the perforating gun;
shutting-in the well at the valve; and measuring the shut-in pressure within said tubing string below the valve.

2. A method according to claim 1 further comprising the step of placing a pressure measuring sensor means in communication with said tubing string below the valve prior to said firing.

3. A method according to claim 2 further comprising the steps of:
removing a tool string from the borehole; and stabbing a production string in place of the tool string.

4. Apparatus for completing and/or testing a well having a cased borehole, comprising:
a string of production tubing disposed within the cased borehole;
a perforating gun attached to the downhole end of said tubing string;
the perforating gun having an impact responsive firing head;
a weighted object adapted to pass through the tubing to impact and actuate the firing head;
means on said tubing string near said perforating gun for closing the interior of said tubing string to the flow of fluids in a first state of operation and in a second state of operation providing an opening therethrough of sufficient size to permit the weighted object to pass therethrough; and means on said tubing string downhole of said closing means for measuring pressure within said tubing string.

5. Apparatus according to claim 4 wherein said closing means comprises a valve which can be actuated by turning the upper end of said tubing string.

6. Apparatus according to claim 4 wherein said measuring means comprises:
a pressure measuring apparatus;
a housing affixed to said tubing string for supporting at least a portion of said measuring apparatus, and means for communicating fluid pressure within said tubing string to said housing.

7. Apparatus according to claim 6 wherein said measuring apparatus comprises a sensor means disposed within said housing and an indicating means disposed at the surface of the borehole.

8. Apparatus according to claim 6 wherein said measuring apparatus comprises a sensor means and an indicating means both disposed within said housing.

9. Apparatus according to claim 8 further comprising:
a packer apparatus disposed between the borehole casing and said tubing string;
means for removing an upper portion of said tubing string including said measuring means, leaving a lower portion of said tubing string supported by said packer;
means for connecting a second string of production tubing to the lower portion of said tubing string; and means for releasing said perforating gun from the downhole end of said tubing string.

10. Apparatus according to claim 8 further comprising means for retrieving and replacing said measuring apparatus while said tubing string remains disposed within the borehole.

11. Apparatus according to claim 10, wherein said retrieving and replacing means comprises:
means for accessing said housing from the interior of said tubing string;
a wireline; and means on said wireline for gripping said measuring apparatus.

12. Apparatus for completing and/or testing a well having a cased borehole, comprising:
a string of production tubing disposed within the cased borehole;
a perforating gun having an impact responsive firing head affixed to the lower end of said tubing string;
a weighted object adapted to pass through the tubing to impact and actuate the firing head;
a housing protruding from the exterior of said tubing string, said housing being in fluid communication with the interior of said tubing string;
a valve within said tubing string above said housing for closing said tubing string in a first state of operation and, in a second state of operation, providing an opening therethrough of sufficient size to permit the weighted object to pass therethrough, and means for measuring pressure within said tubing string, at least a portion of said measuring means being disposed within said housing.

13. Apparatus according to claim 12 wherein said measuring means comprises a sensor means disposed within said housing and an indicating means disposed at the surface of the borehole.

14. Apparatus according to claim 13 wherein said measuring means comprises:
a source of fluid, said source providing a generally positive flow of fluid at a substantially constant pressure;
means for transporting a continuous flow of fluid from said source into a borehole;
means for measuring the flow rate of fluid through said transporting means and providing an output indicative thereof;

means for measuring pressure in said transporting means near said source and providing an output indicative thereof; and means connected to said pressure measuring means for determining pressure in the borehole.

15. Apparatus according to claim 12 wherein said measuring means comprises a sensor means and an indicating means both disposed within said housing.

16. Apparatus according to claim 15 further comprising means for replacing and retrieving said measuring means from the interior of said tubing string without pulling said tubing string.