GB2093091A - Accelerated downhole pressure testing - Google Patents

Abstract

Apparatus for completing a hydrocarbon producing formation 18 while concurrently measuring the shut in bottom hole pressure includes a casing gun 28 which is run downhole on the end of a tubing string 20. A packer 22 is located above the gun, with a vent assembly 38 being located between the gun and the packer. A valve means 30 is located uphole and in close proximity of the packer 22 and far downhole of the wellhead 54. The upper tubing string 42 above the valve 30 can be rotated respective to the lower string 44 below the valve to close or open the valve means 30. The gun is fired, the formation is cleaned, and the valve 30 is thereafter closed to determine the shut-in pressure. A capillary tubing 88 runs down the casing annulus to a location below the valve 30, 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 34 enables the string located immediately above the packer to be removed from the wellbore and a production string substituted therefor. <IMAGE>

Description

SPECIFICATION Accelerated downhole pressure testing The present invention relates to the completing of hydrocarbon wells.

In the art of completing wellbores, it is customary to obtain the initial downhole pressure, the flowing downhole pressure, and the bottom hole shut-in pressure. After a well has been completed, 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 employment of surface measuring means, as contrasted to downhole recorder devices which must be removed from the borehole for examination.Apparatus for completing a borehole and simultaneously measuring the downhole pressure, and for achieving the shut-in pressure within a few hours of perforating the formation is specifically described hereafter.

The present invention provides a method of completing a hydrocarbon containing formation through which a cased borehole extends comprising the steps of: (1) positioning a casing perforating means below a packer means and adjacent to the formation to be completed; (2) placing a valve means in a tool string and connecting the tool string to the packer so that a flow path is formed from the lower annulus into the tool string, through the valve, and to the surface of the earth: (3) actuating the perforating means, and flowing hydrocarbons from the formation, through the perforations into the lower annul us, and into the tool string; (4) closing the valve and measuring the shut-in bottomhole pressure.

Preferably the shut-in pressure of the formation is measured from the surface by the following preferred method, commencing by forming a cased borehole which extends down through a hydrocarbon producing formation and running a casing perforating means into the borehole on the end of a tubing string. The tubing string includes a packer, a vent assembly underlying the packer, and a valve means between the packer and the wellhead.

The valve means is preferably positioned in close proximity to the packer, and the packer is preferably positioned in close proximity to the gun and vent assembly, so that the relative volume below the valve is extremely small as compared to the volume of the tool string above the valve. The sensing means is preferably positioned in communication with the tubing interior and at a location below the valve means, and therefore the sensor may then provide a signal for e.g. an above ground recorder which relates to the downhole pressure.

The valve means may be closed by manipulating the upper tubing string. After closure of the valve, the downhole pressure of the formation in the preferred embodiments rapidly reaches equilibrium due to the relatively small volume contained below the valve means. After the downhole pressure characteristics have been determined, a blanking plug can be placed above the packer, the upper tool string parted at an on/off sub, and the upper string removed from the borehole. A production tubing string can subsequently be substituted for the removed tool string.

A down hole recorder can also be placed below the valve means for verification of the pressure build-up as well as measuring temperature and other down hole perimeters.

The invention will be illustrated by the following description of preferred embodiments with reference to the accompanying drawings, in which: Figure 1 is a part diagrammatical, part schematical, cross-sectional view of a strata of the earth having a borehole formed therewithin in accordance with the present invention; Figure 2 is a broken, cross-sectional view which illustrates part of the borehole of Figure 1 in another operative configuration; Figure 3 is a broken, cross-sectional view which illustrates the borehole of Figure 2 in still another operative configuration; Figure 4 is an enlarged, fragmentary, part cross-sectional view taken along line 4-4 of Figure 1; Figure 5 is a curve which illustrates two downhole variables of the borehole seen in Figures 2 and 3;; Figure 6 is a part diagrammatical, part schematical, broken part cross-sectional view of a strata of the earth having a borehole formed therewithin in accordance with another embodiment of this invention; 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, part cross-sectional, detailed view of part of Figures 6 and 7.

In Figure 1 of the drawings, a borehole 10 has been formed down into the earth by a drilling rig 12. The borehole extends below the surface 14 of the ground. The borehole is cased at 16, and the casing extends through a hydrocarbon containing formation 1 8. 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 immediately above the packer. Vent assembly 38 underlies 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 44. The tubing string 42 can be rotated clockwise or counter-clockwise respective to tubing string 44, thereby opening or closing valve 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 extends upwardly from the wellhead. The capillary is connected by flow conduit 58 to a pressure apparatus 60 and to a flow rate measuring apparatus 62. Flow conduit 64 connects pressure regulator 66 to the illustrated source S of fluid pressure. Recorder apparatus 68 is connected to receive signals 60 and 62, respectively, by means of lines or conduits 70 and 72, respectively.

In Figure 4, a lower pocket 74 underlies the before mentioned pocket 32. The pocket 32 includes a chamber 76 which receives the lower marginal end 78 of the capillary tubing 52 therewithin. The terminal end 80 of the capillary tubing is received within the chamber 76. Port 82 communicates the inside 84 of the tool string or tubing 20 with the chamber 76 so that the lower end 80 of the capillary tubing is subjected to the pressure effected 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 small tubing 90. A recorder device 92 includes a clock and scribe type information storage means for recording of bottom hole temperature and pressure. The recorder is shock mounted at 94 and 96.

In Figure 2, the upper tool string 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 into and contaminating the interior of the lower tool string.

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.

Figure 5 shows a curve which is a plot of 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 shutin pressure obtained in accordance 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 Patent 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 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 Patent Nos. 4,066,282 or 3,966,238. The casing gun can take on several different forms, as for example, as disclosed in Patent Nos. 3,706,344; 3,717,095; 3,717,099; 4,009,757; and 4,140,188.

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 1 800 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.

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 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 82, and into the tubing interior 84.

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 perforations and into the lower annulus 26, into the open vent 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 action 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 data obtained at 68 indicates that a suitable formation has been completed, a blanking plug is run down into sub 46, and the upper end of the tool string removed by utilizing the on/off tool, thereby leaving the well in the configuration of Figure 2. At some subsequent time, a production tubing 98 is next installed at the on/off tool, the blanking plug is removed; 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, although it is sometimes desirable to leave the gun in the illustrated position of Figures 1 and 2 so as to reduce abrasion of the lower end of the borehole casing.

After the upper tool string has been removed, the 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, Caiifornia 90040. The blanking plug wand seating nipple is on pages 433-436 of the 1r974-75 Baker Oil Tool, Inc. catalog.

In the embodiment set forth in Figures 6-8, a pocket 74 is located uphole of the packer, and another pocket 1 74 is located downhole 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 1 74 is therefore substantially acceptable or equivalent as being the pressure at the pay zone.

In Figure 7, a slick line 103 has a fishing tool 104 connected 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 either of the pockets by employment of the fishing tool and slick line.

In operation of the embodiment set forth 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 within one of the pockets 74 and 1 74. The tool 104 is returned 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 annulus into the vent assembly, and up the tubing string to the surface of the earth.

After sufficient flow has occurred to clean up the well, the well is shut-in to determine the bottom hole or formation shut-in pressure. The tool 104 is again run downhole and latched onto a recorder in the indicated manner of Figures 7 and 8. The recorder provides temperature and pressure data which enables the potential 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 bottom hole pressure to be ascertained, without the necessity of removing any of the major completion components from the wellbore.

Hence the present method enables completion 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 therefore, enables a cased wellbore to be permanently completed and tested in a single trip.

In the embodiment of the invention disclosed in Figures 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 1 74. 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 within the pocket.

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

The recorder is placed within and removed from the pocket in a manner similar to that of a gas lift valve, which is often changed with the use of a fishing tool and slick line assembly.

Using the method and apparatus specifically described above, one may monitor downhole pressure following completion and rapidly determine the downhole pressure of a production formation in a very short time interval.

Thus one may complete a wellbore and immediately thereafter determining the potential production of the formation.

Claims (12)

1. A method of completing a hydrocarbon containing formation through which a cased borehole extends comprising the steps of: (1) positioning a casing perforating means below a packer means and adjacent to the formation to be completed; (2) placing a valve means in a tool string and connecting the tool string to the packer so that a flow path is formed from the lower annulus into the tool string, through the valve, and to the surface of the earth; (3) actuating the perforating means, and flowing hydrocarbons from the formation, through the perforations into the lower annulus, and into the tool string; (4) closing the valve and measuring the shut-in bottom hole pressure.

2. A method of completing a cased wellbore which extends through a hydrocarbon formation, comprising the steps of: (1) running a tool string into the borehole, said tool string includes a perforating gun, a packer, and a valve means; (2) setting the packer to form an upper and lower annulus; (3) forming a flow path from the lower annulus, into the tool string, and uphole to the surface of the ground; (4) perforating the casing by actuating the gun; (5) measuring the shut-in pressure of the formation by closing the valve means and sensing the pressure at a location below the valve means.

3. A method as claimed in Claim 1 or Claim 2 wherein the valve is opened and closed by manipulating the upper tubing string.

4. A method as claimed in any preceding claim wherein the pressure is monitored from the surface of the ground by a capillary tube which is run down the upper annulus to a location within the tubing and below the valve.

5. A method as claimed in Claim 4 wherein the bottomhole shut-in pressure is measured by using a fluid flow through the capillary.

6. A method as claimed in Claim 4 or Claim 5 wherein the capillary tube is wound about the interior of the valve.

7. A method as claimed in any preceding claim wherein said packer is located near the formation and the valve means and locating the valve means far from the surface of the ground so that a relatively small volume exists below the valve means respective to the volume which exists above the valve means.

8. A method as claimed in any preceding claim wherein an on/off tool is included between the packer and the valve means so that a production tubing string can be substituted for the tool string.

9. A method as claimed in any preceding claim wherein a recorder is located downhole below the valve means and records the downhole pressure, and means are provided by which the recorded data is retrieved after the shut-in pressure has been measured.

10. A method as claimed in Claim 9 wherein a pocket means is provided for removably storing said recorder; and said recorder is retrieved by running a fishing tool downhole on the end of a slick line, engaging the recorder, and withdrawing the recorder from the borehole.

11. A method of completing a hydrocarbon containing formation substantially as hereinbefore described with reference to Figures 1 to 5 or Figures 6 to 8 of the accompanying drawings.

12. Hydrocarbons obtained from a formation completed by a method as claimed in any preceding claim or refined from such obtained hydrocarbons.