US 3823773 A
Methods and apparatus for testing offshore wells with testing equipment operated in response to changes in the pressure of fluids in the well annulus, wherein the test valve is opened and closed in response to such pressure changes to alternately flow and shut-in the formations, and a reversing valve is automatically opened after a predetermined minimum number of pressure changes have occurred to enable fluids received in the pipe string to be removed before withdrawing the test tools from the well.
Claims available in
Description (OCR text may contain errors)
t mi United States Patent [191 Nutter .n 3,823,773 July 16, 1974 Inventor:
PRESSURE CONTROLLED DRILL STEM TESTER WITH REVERSING VALVE Benjamin P. Nutter, Bellville, Tex.
Schlumberger Technology Corporation, New York, NY.
Oct. 30, 1972 U.S. Cl l66/.5,- 166/250, 166/152 Int. Cl E2lb 47/00 Field of Search 166/.5, .6, 152, 250
References Cited UNlTED STATES PATENTS 3,741,305 6/1973 Young et a1. l66/.5 X
Primary Examiner l-lenry C. Sutherland Assistant Examiner-Richard E. Favreau Attorney, Agent, or Firm-David L. Moseley; William R. Sherman; Stewart F. Moore a [57 ABSTRACT 18 Claims, 8 Drawing Figures .PRESSURE CONTROLLED DRILL STEM TESTE WITH REVERSING VALVE This invention relates generally to drill stern testing apparatus and methods, and more particularly to new and improved apparatus and methods for conducting a drill stem test of an offshore well from a floating drilling vessel.
It has heretofore been recognized that it is preferable to avoid, where possible, the use of drill stem or pipe motion as a means of actuating downhole formation testing tools during a test that is being conducted in an offshore well from a floating drilling vessel. This is because the vessel, of course, will oscillate vertically under the thrust of waves and tides, and yet it is highly desirable to keep the rams of the usual sub-sea blowout preventers closed against the pipe during the test to ensure absolute control of the well. Moreover, there is a certain amount of danger inherent in rotating a pipe that contains fluid under high pressure. Accordingly, avoidance of pipe motion is made in the interests of safety to personnel and equipment, and preferably the tools that are designed for this particular type of formation testing are operated in response to pump pressure applied to the well annulus between the drill pipe and the casing as disclosed in my copending application Ser. No. 199,554, filed Nov. 17, 1971 and assigned to the assignee of this invention.
It is further desirable from the standpoint 'of safety to be able to purge the pipe string of the formation fluids recovered during a drill stem test to avoid spillage and consequent fire hazards at the rig floor as the drill pipe and tools are being withdrawn from-the well at the completion of a test. Although reversing valves are quite well known that enable the displacement of "fluid recovery in the pipe string for conventional land based or fixed platform tests, such equipment is for the most part operated bydrill pipe rotation, and thus is not considered to be suitable in concept, or compatible in operation, with annulus pressure operated testing tools of the type discussed above. i
It is accordingly the principal object of this invention to provide new-and improved drill stern testing techniques and equipment for safely conducting drill stem tests of offshore wells. froma floating drill ship or other vessel.
This and other objects are attained in accordance with the concepts of the present invention through the provision of a string of testing tools that includes a test valve and a sampler for obtaining flow and shut-in pressure measurements and for trapping a flowing sample of formation fluids, together with a reversing valve that enables the fluid recovery to be displaced from the pipe prior to removal of the tools,'all of the equipment being operated by the application and release of pump pressure in the well annulus between the drill pipe and the casing. More specifically, the reversing valve includes a sliding sleeve within a valve body that normally closes off a set of lateral ports in the valve body and prevents communication to the well annulus during at leasta predetermined number of annulus pressure variations that result in operation of the test valve and the sampler, but will uncover and open the ports when the said number of. pressure variations is exceeded. Opening of the ports enables the annulus pressure to be used to displace the fluids recovery within the pipe string upa safe and convenient manner, whereupon the drill pipe and testing tools can be withdrawn from the well with a representative sample of formation fluids trapped within the'sampler chamber. Since no manipulation is required to operate the tester or the reversing valve, the test can be conductedwith utmost safety to rig personnel and equipment.
The present invention has other objects, features and advantages that will becomemore clearly apparent in connection with the following detailed description of a preferred embodiment, taken in conjunction with the appended drawings in which:
FIG. Us a somewhat schematic view of a drill stem test being conducted in an offshore well from a floating drilling vessel;
FIGS. 2A 2C are detailed cross-sectional views, with portions in side elevation, of a pressure controlled tester apparatus including a test valve, sample chamber and reversing valve;
FIG. 3 is a plan view of a mechanical indexing system that controls the longitudinal position of the test valve and opening of the reversing valve; and
FIGS. 4-6. are schematic views to illustrate the operation of tools, during the shut-in, flowing, and shutin/reverse circulating portions of a test, respectively.
Referring initially to FIG. 1,.there is illustrated an offshore well which is normally lined by casing 10 and into which extends a pipe string 11 that extends upwardly to a floating drilling vessel 12'having.a derrick 13 for handling the pipe string. A riser 14 will usuallyextend from a subsea well head assemblyls upward to the vessel 12 which is anchored or otherwise held on station above the well, and the pipe string 11 can include a control valve assembly 16 of typical design that provides a landing shoulder 17 that-seats in the well head assembly 15 so that the pipe string is suspended from a fixed point not subject to vertical motion that the vessel 12 experiences due to the action of waves and tides. Preferably, the pipe string 11 comprises a major section 18, such as a length of drill pipe, and a minor section 19, such as predetermined length of drill collars having a known weight, connected together by a slip joint and safety. valve combination tool 20 of the type disclosed in U.S. Pat. No. 3,653,439, Kisling, assigned to the assignee of this invention..The lower end of the minor pipe section 19 may be .connected to the upper end of a pressure controlled testing tool 21 constructed in accordance-with the principles of this invention, which is in turn connected to a flow control valve'assembly 22 of the type shown in my U.S. Pat. No. 3,308,887,'which valve assembly is actuated in response to only vertical motion of the pipe string 11. For purposes of isolating the well interval ,to'be tested from the hydrostatic head of fluid in the casing 10 thereabove, a well packer 23 is provided and includes packing elements 24 to seal off the well bore," and slips 25 to anchor at the proper level above the well interval. to beitested. The packer 23 can be of the type shown in U.S. Pat; No. 3,399,727, McGill, assigned to the instant assignee, and includes an internal fluid bypass arrangement that enables well fluid to bypass through the packing elements 24 during running, but is closed off when the packer is set.Of course at the end of the test'the bypass is opened to equalize pressures and enable release of the packer 23 and retrieval of the tools to the surface. Suspended below the packer 23 is a perforated nipple 26 to enable fluid entry during the test, and suitable pressure recorders 27 are provided to make a record of the pressures of the fluids versus time as the test proceeds. Other typically used equipment such as a safety joint 28 and a jar 29 can be connected between the control valve 22 and the packer 23 but are shown only schematically to simplify this disclosure.
Turning now to FIGS. 2A and 2B, an embodiment of a pressure controlled testing valve assembly 21 that is constructed in accordance with the principles of this invention will be described in detail. The assembly includes a tubular mandrel 32 that is fixed concentrically within a tubular housing 33 with their respective outer and inner walls 34 and 35 laterally spaced to provide an elongated annular cavity 36 therebetween. The upper portion of the mandrel 32 has a central flow path 37 with side ports 38 and 39 extending to the cavity 36, whereas the lower portion of the mandrel has a central flow path 40 whose upper end terminates in a side port 41. The upper port 38 constitutes a reversing port that is normally closed by a vertically movable reversing valve sleeve 42 having seals 43 and 44 spanning the port, the sleeve being movable between a lower position as shown to an upper position where the port 38 is placed in communication with one or more lateral ports 45 extending through the wall of the housing 33 for placing the upper end of the cavity 36 in communication with the well annulus.
An annular sampling and valve member 48 is also disposed for vertical movement within the cavity 36 and surrounds an intermediate portion 49 of the mandrel 32. The member 48 has an elongated internal recess that provides a sample chamber 50, the chamber being located below an upper piston section 51 of the member and a lower valve head portion 52 thereof. The piston section 51 has an upwardly facing transverse surface 53 that is exposed to the pressure of fluids in the well annulus via the housing ports 45, and fluid leakage is prohibited by internal and external seal rings 54 and 55 that are slidable against the walls 34 and. 35 of the mandrel and housing, respectively. The member 48 is urged upwardly within the cavity 36 by the action of a coil spring 56 that presses between the lower end surface 57 of the member and an outwardly directed shoulder 58 on the mandrel.
The cavity 36 extends for a substantial distance below the member 48 and is arranged to contain a compressible medium such as nitrogen gas. As disclosed in further detail in my copending application Ser. No. 199,554, a floating piston 59 having seal rings 60 and 61 is positioned near the lower end of the cavity 36 and is movably arranged to transmit the hydrostatic pressure of the well fluids externally of the housing 33 to the gas, the fluids entering the cavity below the piston 59 via a port 62. The outer portion of the port 62 extends laterally to the outside of a reduced diameter valve head section 63 of the housing 33, the section 63 being sized to be received within an annular valve seat 64 on the upper end of the control valve assembly 22. Seals 65 and 66 are disposed respectively above and below the outer portion of the port so that the port can be closed off by the valve seat 64 by longitudinal movement just prior to initiation of a test. Thus the pressure of the nitrogen gas is equalized to, and corresponds with, the hydrostatic pressure at test depth, whatever that value may be. Of course the pressure will act upwardly on the lower end face 57 of the sampler and valve members 48, which is also being acted upon by the upward thrust of the coil spring 56.
The structural details of the flow control valve assem bly 22 will not be set forth at length here since reference may be had to my aforementioned US. Pat. No. 3,308,887. In general, however, the assembly as shown in FIG. 2C includes an index section 70, a hydraulic delay section 71 and a test valve section 72. The index section has a sleeve 73 that is mounted for rotation relative to both the housing 74 and the mandrel 75, and
carries an index pin 76 that engages in an external channel configuration 77 on the mandrel. The hydraulic delay section 7l is constituted by a metering sleeve 78 that works within a fluid filled, stepped diameter chamber 79 and functions to retard downward movement of the mandrel within the housing 74, but on the other hand enables free upward movement. The valve section 72 comprises a valve head 80 on the mandrel 75 that normally engages an annular valve seat 81 to close off fluid flow past a transverse barrier 82. When the mandrel 75 moves downwardly, however, a flow path including ports 83 and 84 and the space 85 externally of the mandrel is placed in communication with the bore 86 of the mandrel above the barrier 82.
Referring still to FIGS. 2A and 2B, the sampling and valve member 48 is movable longitudinally within the cavity 36 between three longitudinally spaced positions. In the intermediate position as shown, spaced apart seals 90 and 91 span the laterally extending port 39 that terminates the lower end of the upper portion 37 of the flow path, and spaced apart seals 92 and 93 span the port 41 that terminates the upper end of the lower flow path portion 40. Thus fluid flow through the assembly is blocked and the valve is closed. However in the lower position of the sampler and valve member 48, the sample chamber 50, together with a flow course 94 extending from the chamber to a point above the upper seal ring 90, places the upper and lower portions 37 and 40 of the flow path in communication so that production fluids can flow through the assembly via the sample chamber 50. In the uppermost position of the member 48 within the cavity 36,'the upper surface 53 can engage the sleeve valve 42 to shift it upwardly and communicate the flow path 37 and thus the'bore of the pipe string 11 thereabove with the well annulus via the ports 38 and 45.
The longitudinal relative position of the sampler and valve member 48 is controlled by the provision of an index control system coacting between the member and the mandrel 32. The control system 100 is constituted by a rotatable sleeve 101 that is carried within an internal annular recess 102 in the member 48 with suitable thrust bearing rings 103 and 104 above and below. The sleeve 101 has a stop lug 105 that projects inwardly into a channel or slot configuration 106 formed in the external surface of the mandrel 32 and shown in plan view in FIG. 3. The channel system 106 has a series of upper pockets A, C, E and G and a series of lower pockets B, D, F and H each series being located at the same ICVCL'TI'IC lower series of pockets are circumferentially offset with respect to the upper series of pockets, with alternating pockets being connected by inclined channels 107-l10 and 11l1l4. The pocket H is connected by the channel 114 to a considerably elongated pocket I which extends well above the pockets A, C, E and G and by a distance that substantially corresponds to the extent of vertical travel of the reversing valve sleeve 42. Due to the inclined configuration of the various channels, the stop lug 105 is automatically guided into a predetermined sequence of pockets as the sampling and valve member 48 reciprocates vertically. It will be recognized that when the lug is in any one of the upper pockets A, C, E or G the member 48 is in the intermediate or closed position, whereas when the lug is in any one of the lower pockets B, D, F or H the member is in the lower or open position. However when the lug goes into the pocket I, the member 48 can function to move the reversing valve sleeve 42 to the open position. When the member 48 has moved completely upwardly, any suitable means such as an expanded, split snap ring 120 on the housing 33 can be provided and arranged to resile inwardly into a locking recess 121 on the lower end of the member in order to lock the member against subsequent downward movements in response to a pressure differential.
In operation, the parts are assembled as shown in the drawings and prepared for use by injecting a charge of nitrogen gas into the cavity 36 below the sampler and valve member 48 through suitable closable ports (not shown), the charge pressure, for example, being in the neighborhood of 2,500 psi for most tests but is not critical. A guide that can be used is to have a charge pressure about 500 psi less than the estimated hydrostatic pressure at test depth. The sampler and valve member 48 is in the intermediate or closed position, and of course the control valve assembly 22 is closed also, as is the reversing valve sleeve 42. The string of tools is then lowered from the vessel 12 into the well casing until the packer 23 is located at a proper point above the formation interval to be tested. At an elevation in the well considerably above the setting point, the hydrostatic head of fluids will have become in excess of the precharge pressure of the gas within the cavity 36, and of course the'floating piston 59 will move upwardly somewhat as it transmits the hydrostatic head pressure to the compressible gas. In any event, the sampler and valve member 48 remains stationary because essentially the same pressure is acting on the opposite end faces 57 and 53'thereof, and the stop lug 105 is shouldered against the top of the pocket A. Due to the compressibility of the gas however, the member 48 can move readily downwardly against'the bias of the coil spring 56 when a pressure difference of a sufficient magnitude is imposed in a downward direction thereacross.
The length of the minor pipe string 19 is selected to provide the proper amount of weight to set the packer 23, and the landing shoulder 17 is located in the major string 18 at the proper spacing such that when the packer is anchored at setting depth and the pipe 11 is suspended in the sub-sea well head 15, the slip joint 20 is in its closed or contracted condition to enable the weight of the drill collars 19 to be applied via the test' tools to the packer. The packer 23 is conditioned for setting by appropriate manipulation of the pipe string moved downwardly to cause the control valve 22 to open, admitting fluids into the interior of the lower portion 40 of the flow passage. Downward movement of the housing 33 with respect to the control valve hous-* ing 74 positions the'valve head 63 within the seat 64 to close off the port 62 from communication with the well annulus. The result is to trap or memorize the hydrostatic head pressure of the fluids within the cavity 36 below the sampler and valve member 48 as described in my copending application Ser. No. 199,544 so that a substantially constant pressure acts upon the lower face 57 of the sampler and valve member.
With the blowout preventers atthe well head assembly 15 closed in a typical manner so that the well is completely under control, a formation test can be conducted without resort to manipulation of the pipe strings 18 and 19 in the following manner. Fluid pressure is applied by surface pumps and control lines (not shown) to the well annulus 30 between the pipe string 11 and the well casing 10, and the pressure feeds through the housing ports 45 to the upper surface 53 of the sampler and valve member 48. A greater pres sure, that is to say a pressure sufficiently in excess of the hydrostatic head pressure that is entrapped in the cavity 36 below'the member 48, will force the member downwardly against the bias of the coil spring 56 to the positionshown in FIG. 5 where the seal 92 is below the port 41, and the ports 39 and 94 are in' registry. In this position, formation fluids can flow from the lower flow passage 40 to the upper flow passage 37 via the sample chamber 50 and on upwardly into the bore of the pipe string 11. The valve is left open for a period of time sufficient to draw down the pressure in the isolated well bore interval below the packer 23 to enable connate fluids within the formation to be produced into the well bore. During downward movement of the valve member 48 toopen position, the stop lug will have moved, relatively speaking, from the pocket A into the .pocket B, theinclined channel 107 automatically guiding the lug intothe correct, position as the sleeve 101 undergoes an angular rotation as will be apparent to those skilled in the art. After a sufficient time lapse, the
applied pump pressure is bled, off at the surface to enable the coil spring56to move the valve member 48 upwa'rdlyto its closed or shut-in position as shown in FIG. 4. During this reciprocation the lug 105 moves from the pocket B automatically into the pocket C due to thev inclined channel 111 with the sleeve 101 indexing as noted above. The valve member 48 is left in the closed position for a shut-in period of'time during which the pressure recorders '27 make a record of the pressure build-up data. Annulus pressure can be repeatedly'applied and released to obtain additional flow and shut-in pressure data.
In response to at least a predetermined number of discrete annulus pressure changes, in the case shown herein a total of foursuch changes, the stop lug 105 will arrive at the pocket B, so that the next time the pressure is relieved the lug is guided by the inclined channel 114 into the elongated vertical slot or pocket I. In this position the sampler and valve member 48 can move completely upwardly under the force of the spring 56 to the condition shown in FIG. 6 where the reversing valve sleeve 42 is driven upwardly to open the reversing port, 38 for communication with the housing port 45. The lock ring will resile inwardly to lock the member 48 in the upper position where the test ports 41 and 39 remain closed to trap a sample of formation fluids within the chamber 50. The sample of formation fluids that has been collected in the bore of the pipe string 11 can be removed for collection or disposal at the surface by once again applying annulus pump pressure to cause annulus fluids to circulate through the open ports 45 and 38 to drive the formation fluids upwardly through the pipe string 11 to the surface.
To terminate the test, it is only necessary to lift straight upwardly on the pipe string 11 from the surface, thereby extending the slip joint and lifting the drill collars 19 and the tester housing 33, causing the control valve 22 to close as the mandrel 75 moves upwardly. The bypass associated with the packer 23 is opened to equalize pressures across the packing elements 24 so that they can be retracted, which is then accomplished by further lifting of the packer mandrel. As the housing 33 is elevated with respect to the control valve housing 74, the ports 62 is exposed to the well annulus, so that the pressure of the nitrogen gas can experience a gradual decrease to the original precharge pressure as the hydrostatic head is reduced during withdrawal of the tools from the well. A sample of the last portion of the flowing formation fluidls will have been trapped within the chamber 50 upon simultaneous closure of the test ports and can be removed for inspection and analysis at the surface.
It will now be recognized that a newand improved pressure actuated formation testing tool and procedure have been disclosed that enable an offshore well to be tested, safely through avoidance of pipe motion altogether during the test. Of course certain changes or modifications may be made in the structural detail thereof without departing from the inventive concepts. For example, although the movement control sleeve 101 has been disclosed as coacting between the member 48 and the mandrel 32, it could coact between the member 48 and the housing 33 since the housing and mandrel are fixed relative to one another. Moreover, the locking ring 120 could take many other structural forms and locations so long as it functions to lock the member 48 in the upper or reversing position against subsequent downward movement in response to an increase in annulus fluid pressure. Thus it is the aim of the appended claims to cover all such changes and modifications fallingwithin the true spirit and scope of the present invention.
1. In a well testing apparatus having a flow passage and valve means for opening and closing said passage in response to changes in the pressure of fluids in the well annulus surrounding said apparatus, normally closed reversing valve means adapted to communicate a portion of said flow passage above said valve means with the well annulus, and means responsive to at least a predetermined minimum number of said pressure changes for opening said reversing valve means to enable formation fluids to be removed from a well by reverse circulation of well bore fluids.
2. The well testing apparatus of claim 1 wherein said flow passage has a normally closed port in communication therewith, said valve means including a slidable sleeve arranged to span said port in one position and being movable to another position opening said port.
3. The well tester apparatus of claim 2 wherein said opening means includes piston means within said apparatus having a transverse surface area subject to the pressure of fluids in the well bore surrounding said apparatus so that fluid pressure can act to shift said piston means in one longitudinal direction, and means for urging said piston means in the other longitudinal direction. v
4. The well tester apparatus of claim 3 wherein said opening means further comprises means to control the relative longitudinal position of said piston means in such a manner that said piston means does not function to movesaid sleeve in response to a number of said pressure changes less than said predetermined minimum number, but can function to move said sleeve to open position when said minimum number of pressure changes is exceeded.
5. The well tester apparatus of claim 4 wherein said control means comprises stop means including an index pinthat works within a grooved channel means, said channel means defining a series of vertically spaced stop shoulders, some of which are located at the same level and at least one of which is vertically spaced by a distance sufficient to enable said piston means to move said sleeve to open position.
6. A well testing apparatus comprising: an inner member defining a flow passage and being disposed concentrically within an outer member, said members being laterally spaced to provide an'elongated cavity therebetween; first and second port means for respectively communicating said flow passage with said cavity and said cavity with the well annulus surrounding said members; normally closed reversing valve means for closing said first port means to prevent fluid communication between said flow passage and said well annulus, said valve means being shiftable to open position; piston means sealingly slidable within said cavity and having a transverse surface area exposed to the pressure of fluids in said well annulus via said second port means so that said pressure can be utilized to force said piston means in one direction within said cavity; means for continuously urging said piston means in the opposite direction; control means for preventing movement of said piston means in said one direction by a distance sufficient to shift said valve means to said open position; and means responsive to at least a predetermined minimum number of pressure changes in said well annulus for disabling said control means to enable said piston means to shift said reversing valve means from closed to open position.
7. The well tester apparatus of claim 6 wherein said control means comprises cam slot and follower means, said slot means includes upper and lower spaced apart series of pockets joined by inclined channels in such a manner that said follower means is automatically guided through a sequence of said pockets, one of said series of pockets providing stop limits to movement of said piston means in said one direction.
8. The well tester apparatus of claim 7 wherein said disabling means includes a vertically extending channel adapted to receive said follower and extending vertically beyond said one series of pockets by a distance sufficient to enable said piston means to shift said reversing valve means from closed to open position.
9. The well tester apparatus of claim 8 wherein said reversing valve means includes a sleeve member sealingly slidable on said inner member from a lower position spanning said first port means to an upper position where said first and second port means are in direct communication.
10. A well tester apparatus comprising: an inner memberdefining a flow passage and being concentrically disposed with an outer member, said members being laterally spaced to provide an elongated annular cavity therebetween; a first port means in said inner member and a second port means in said outer member; reversing valve means movable between said members and adapted for normally closing first port means; test valve means in said cavity and movable between longitudinally spaced positions therein for opening and closing said flow passage to the flow of formation fluids, said test valve means including piston means sealed with respect to said inner member and said outer member to provide a transverse surface area subject to the pressure of fluids in the annulus surrounding said members via said second port means; means for continuously urging said test valve means toward a position closing said flow passage, said test valve means being shifted to a position opening said flow passage in response to an increase in the pressure of fluids in said well annulus, and being returned by said urging means to a position closing said flow passage in the absence of said increase in pressure; means for limiting movement of said test valve means in said spaced positions during a predetermined minimum number ofincreases of fluid pressure; and means for enabling movement of said test valve means beyond a limit position thereof and to a position actuating said reversing valve means'to open position where said first and second port means are in direct communication.
11. The well tester apparatus of claim 10 wherein said flow passage is comprised in part by vertically flow-through communication of said openings when i said test valve means is in the open position.
12. The well tester apparatus of claim 11 wherein said annular member includes valve heads at each end of said recess adapted to simultaneously close said side openings to trap a sample of formation fluids in said recess in the closed position.
13. The well tester apparatus of claim 12 wherein said urging means includes a coil spring surrounding said inner member and pressing between an outwardly directed shoulder thereon and a lower end surface of said test valve means.
14. The well tester apparatus of claim 13 wherein said cavity below said test valve means is enclosed and adapted to contain a compressible fluid medium; means for equalizing the pressure of said fluid medium with the hydrostatic head of the well fluids externally of said members; and selectively operable means for closing said equalizing means to enable an increase in the pressure of well fluids surrounding said members to shift said test valve means between said spaced positions.
15. A method for testing an offshore well formation with a tester valve connected to a pipe string extending upwardly to the surface, said tester valve having a flow passage with portions extending above and below a normally closed, pressure responsive valve means adapted for opening and closing said flow passage in response to changes in the pressure of fluids in the well annulus adjacent said tester valve, comprising the steps of: changing the pressure of fluids in the well annulus adjacent said tester valve to alternately open and close said valve means to control the flow of fluids from said formation into the pipe string; and subsequent to at least a predetermined minimum number of such pressure changes, communicating the portion of the flow passage extending above the valve means with the well annulus to enable a subsequent increase in annulus pressure to be utilized to reverse circulate a fluid recovery through said pipe string to the surface.
16. A method for testing an offshore well formation with a tester valve connected to a pipe string extending upwardly to the surface, said tester valve having a flow passage extending from below a pressure actuated valve means to a locationthereabove in communication with said pipe string, said valve means being arranged for alternately opening and closing said flow passage in response to changes in the pressure of fluids in the well annulus adjacent said tester valve, comprising the steps of: opening said valve means in response to an increase in the pressure of fluids in the well annulus adjacent said tester valve to enable fluids to flow from said formation into said pipe string; closing said .valve means in response to a decrease in the pressure of fluids in the well annulus adjacent said tester valve to shut-in said formation; communicating said flow passage above said valve means with the well annulus; and then increasing the pressure of said fluids in the well annulus to reverse circulate a fluid recovery through said pipe string to the surface.
17. The method of claim 16 including the further step of trapping a flowing sample of formation fluids within said tester valve upon closing of said valve means.
18. The method of claim 16 including the further step of locking said valve means in the closed position prior to implementation of the communicating step.