US 3107729 A
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Description (OCR text may contain errors)
SEARCH RUOM S'Sheets-Sheet 1 A; BARRY ETAL APPARATUS FOR DRILL STEM TESTING FIG. IA'
Oct. 22, 1963I Filed May 9, 1960 FIG.
38 FIG. s.
MAGNET I9 Oct. 22, 1963 A. BARRY ETAL APPARATUS FOR pRILL STEM TESTING Filed May 9, 1960 Oct. 22, 1963 A. BARRY ETAL.
i APPARATUS FOR DRILL STEM TESTING O 6 9 l 3 a 5 6 7 O 9 8 M m 8 w w 9 V. I O I l m v m Ra 8 l E3 S l H.. E 6 F R FRoM PAcKER lNmvroRs. ADELBERT BARRY,
BY WHITMAN D. MOUNCE,
CSICPPER ATTORNEYI CTRIGGERING CIRCUIT 92 DC- SOURCE F'IG. 9.
United States Patent O M 3,107,729 APPARATUS FOR DRILL STEM TESTING Adelbert Barry and Whitman D. Mounce, Houston, Tex.,
assignors, by mesne assignments, to Jersey Production Research Company, Tulsa, Okla., a corporation of Delaware Filed May 9, 1960, Ser. No. 27,730 3 Claims. (Cl. 16666) This invention relates to apparatus for determining the nature of subsurface geological strata, and more particularly to apparatus for use in connection with the sampling of earth formation fluids.
In connection with the drilling of boreholes in the earth for the purpose of exploiting petroleum deposits therein, often it is desirable to obtain samples of fluids existing in particular formations of the earth through which drilling operations are progressing. In the interest of economy, it tis particularly desirable to achieve this without withdrawing the drill stem `from the well for the attachment of testing tools as is the present practice. To this end it is necessary to seal off the lower part of the borehole by means of a well packer. While formation fluids often will flow to the earths surface through the drill pipe, f
more often it is necessary to pump drilling mud out of the lower portion of the borehole until a relatively pure sample of the formation fluid can be obtained. Various devices for this purpose have been devised in the past. Particularly satisfactory drill stem testing apparatus is described in U.S. Patent No. 2,813,587, W. D. Mounce, and in U.S. patent application Serial No. 656,341 for Drill Stem Testing Device, tiled May 1, 1957, by Adelbert Barry and W. D. Mounce.
In the construction of drill stern testing apparatus, it is particularly desirable to isolate the component parts thereof from drill fluids to be pumped down the bore of the drill stem, insofar as such is practicable. The reasons for this is that drilling fluids are extremely abrasive, and component parts of the drill stem testing apparatus that are in the flow stream of the drilling fluid can be eroded away. Furthermore, it has been found that sand and -other constituents of the drilling fluid have a tendency to pack under moving parts of the apparatus so as to impede their operation.
Another desirable attribute of a drill stem testing apparatus is that it should not require an electrical cable traversing the bore of the drill pipe during testing operations for lthe purpose of actuating the component parts of the drill stem testing apparatus or for conveying information to the earths surface. Manifestly, the electrical leads are subject to damage. Necessary electrical components of the drill stem testing apparatus should be entirely selfcontained insofar as such is possible. It is desirable that such apparatus be suspended in the well bore by the conventional swab line on the well.
A still further desirable attribute of drill stem testing apparatus is that the well packer associa-ted therewith should be held tightly against the drill stem during drilling operations to allow unimpeded passage of drilling uids by the packer, and should be adapted to be readily pressed against the sides of the borehole when drilling operations have ceased preparatory to a testing operation. This is necessary in order to minimize damage to the relatively soft borehole sealing parts of the packer.
Patented Oct. 22, 1963 ICC The objects and features of the invention will become more apparent upon consideration of the following description thereof when taken in connection with the accompanying drawings, wherein:
FIGS. l and l-A taken together show a vertical crosssectional view partially in elevation of a portion of a drilling string incorporating drill stern testing apparatus in accordance with the teachings of the present invention. The apparatus is shown in its nonactuated, `or while-drilling, position;
FIGS. 2 and 2-A taken together show a vertical crosssectional view partially in elevation of the apparatus shown in FIGS. 1 and l-A showing the apparatus in its actuated position for taking a sample with actuating and swabbing apparatus in position in the drilling string;
FIG. 3 is an enlarged Vertical sectional view partially in elevation of a portion of the go-devil actuating apparatus shown in FIG. 2;
FIGS. 4, 4-A, 4-B, and 4-C are vertical sectional views partially in elevation of the drill stem swabbing and sample retrieving apparatus illustrated in FIGS. 2 and Z-A;
FIG. 5 is a fragmentary vertical cross-sectional view partially in elevation of portions of the sample retrieving and go-devil apparatuses shown in FIGS. 2 and 2-A in the sample-taking position;
FIG. 6 is an enlarged vertical cross-sectional view partially in elevation of the well packer actuating apparatus of FIGS. 1 and 2. The apparatus is shown in its nonactuated position;
FIG. 7 is an enlarged vertical cross-sectional view partially in elevation similar to FIG. 6 showing the apparatus in its actuated position;
FIG. 8 is a horizontal cross-sectional view taken along section 8 8 of FIG. 6; and
FIG. 9 is a schematic elec-trical diagram of the electrical portion of the triggering apparatus of FIG. 4A.
With reference now to the drawings, and in particular to FIGS. l, l-A, 2, and 2-A, there is shown a borehole 1 which lhas been drilled into subsurface formations. The drill stem 2, in addition to pipe sections not shown, includes the pipe sections designated by the reference numerals 3, 4, 5, 10, 61, 65, and 74. A drill bit 76 is connected to the lower end of the drill stem. Drill stem sections 4 and 10 are relatively thin walled. Drill stem section 4 is the outer member and elastic pipe 6 is the inner member of a section defining a portion of space or recess 3a that acts as a reservoir for hydraulic actuating lluid for the drill stem testing apparatus to be described. Elastic pipe 6 is fastened to collar 8 by annular clamps 6a. Drill stem section 10 is the outer member and nonmagnetic pipe section 16 is the inner member defining the remainder ofthe recess or space that acts as the reservoir, and additionally within which is housed certain of the drill stem testing apparatus along with the actuating lluid. The two recesses are interconnected by passageways 14 in the coupling collar 8 interconnecting the two sections. Elastic pipe 6 may be formed of neoprene or other rubber-like deformable material. The elastic pipe is secured at one end to coupling collar 8 by annular clamp 6a and at the other end to coupling collar 5 by conventional locking means such as a retainer sleeve 5a.
Packer 66 is affixed to drill stem section 65 by means of a lixed collar member 64. The packer may be similar in construction to the packer described in Patent No.
2,828,823 and may include a multiplicity of cables, or a braid, securely anchored at one end -in mem-ber 64, and at the other end to a slidable sleeve member 70. The pzitckemay be formed of rubber or rubber-like material a xe to the reinforcing braid Qrmcaples 68 b suitable heat treating means lnxmvlttheuprifra'lflieffunctisnfwhesrfeaeieesieev member 7o win @described below. "H
The packer actuating fluid contained within the recess enclosed within drill pipe sections 4 and 10 may flow to the packer 66 by passageway 67, passageway 56, check valves 50 and 52, and a control or slide valve 42. A port 53 in passageway 56 is in uid communication with check valve 52. 'Ihe function of slide valve 42 and check valves 50 and 52 is to permit fluid flow from the reservoir to the packer in one position of the slide valve, and to permit fluid ow from the packer to the reservoir in the other position of the slide valve. The construction of the slide valve and the check valves and the interrelation therebetween will be described below.
The function of go-devil 63 shown in FIG. 3 is to prevent the downward flow of drilling fluid through the bore of the drill pipe while permitting upward How of drilling fluid through the bore. The go-devil also functions to actuate a member in the sample retrieving apparatus to be described below. The go-devil is provided with an elongated spacer 71, a tubular body member or mandrel 38, a valve section 29, and an actuating member generally designated 25. A pair of packer cups 41 are afixed to body member 38 for the purpose of preventing downward lflow of drilling fluid around the outside of the go-devil. The length of the spacer rod 71 is suflicient to place the packer cups 41 between elastic pipe section 6 and elastic pipe section 60. The spacer rod bears on the bottom of the chamber usually found in drilling bits t allow access of drilling fluid to the jets 78. The body portion 38 of the go-devil has a longitudinally drilled bore 179, which is shown most perspicuously in FIG. 3. A ported section 59 is provided on the lower end of body member 38 for the purpose of permitting tluid entry into the drilled bore 179 of the Igo-devil. The member 25 having a retrieving bead 170 functions also as a valve stem and has a generally hemispherical valve member 17 4 at the lower end thereof that normally lits into the upper opening of the bore 179. Thus, iluids passing upwardly through the bore 179 will lift the hemispherical member and will pass out of the go-devil through ports 37 into the bore of the drill stem. The pressure of drilling fluid above the packer cups 41 will tend to force the hemispherical valve member 174 downwardly to effectively seal the well bore against fluid ow downwardly therethrough.
A permanent magnet 39 is aixed to body member 38 for a purpose that will become apparent below.
The general arrangement of the component parts of the swabbing and sample retrieving unit or housing 81 is shown in FIGS. 2 and 2-A. The unit is suspended from a swab line 82 by means of a coupling head 83. Below the coupling head are a latch section 84, a solenoid section 86, a pressure switch 88, a battery housing section 90, a trigger-ing circuit section 92 including a pair of spaced-apart electrodes 94, a swab cup section 9'6, and a sample tube 98 along with the actuating apparatus therefor, and an overshot 7 for the punpose of latching onto the retrieving head 170 of member 25 of go-devil 63.
The details of construction of the swabbing and sample retrieving unit 81 are best shown in FIGS. 4, 4-A, 4-B, and 4-C. As is shown, the coupling head 83 is connected to an elongated mandrel 100 which terminates in a latching head 102 adapted to receive the opposed members 104 and 106 of pivoted latch 108. A cavity is provided in the housing in latch section 84 to accommodate the latch mechanism and mandrel 101. A locking dog 83a is provided for the purpose of locking to the lower reduced section 101 of mandrel 100 after the mandrel is released from the grip of latch 108. The opposed latching members 106 and 104 of latch 108 are held in position against the force exerted by a cross spring 112 when the latch trip is in the position shown in FIG. 4 by stop member 118a on connecting bar 118. The cross spring lits into slots 114 cut in the opposed latching members 104 and 106. The lower ends of members 104 and 106 are lrespectively pivotally connected to the ends of linkage members 104a and 106:1. The upper end of connecting bar 118 .is connected to the other ends of linkage members 10451 and 106a. Suicient clearance exists between members 104 and 106 and lthe latching head 102 so that the upper ends of opposed latch members 104 and 106 can swing toward each other when the lower ends are forced apart by connecting bar 118 as it moves upwardly. When the connecting bar 118` is moved upwardly by plunger 124 responsive to energization of coil 126, the cross spring 112 opens the latching members 106 and 104 to release the mandrel 100. Mandrel is telescopically arranged with respect to the housing section 99 and is shown in its most telescoped position (i.e., the position at which mandrel 100 extends as far as possible into housing section 99'. When released by the latch, the entire housing will drop. Locking dog 83a will pop inwardly under the impetus of spring 85 to hold the mandrel 100 Iin its least telescoped position.
The pressure switch 88, battery 90, triggering circuit section 92, and electrodes 94 function to energize solenoid 126 to t-ripthe latch 108 and release mandrel 100 when the mud in the borehole surrounding the apparatus is of a predetermined resistivity. The schematic electrical diagram of FIG. 9 illustrates the electrical interconnection of the apparatus. 'Ihe D.C. source 200, which may be a battery, is housed in the battery section 90. The output terminals 204 and 206 of the source are connected to a chopper or inverter 202 and also are connected to an amplier 228 by means of leads 208 and 210l to provide operating bias for the amplifier. Chopper or inverter 202 may be a transistorized device such as is illustrated in Patent No. 2,849,614, G. H. Royer et al. Mechanical inverting devices also may be used. The alternating output signal of chopper 202 is applied to input terminals 220 and 222 of a bridge circuit including resistors 212, 214, and 216, and the resistance across electrodes 94. The resistance of resistors 212, 214, and 216 is adjusted so that a signal of predetermined amplitude will appear across output terminals 224 and 226 when the resistivity of the mud or lluid between electrodes 94 is of a predetermined value. The alternating output signal appearing across terminals 224 and .226 is amplified by amplifier 228 and applied to solenoid 126 by means of leads 230. The solenoid 126 is adapted to exert a pull on plunger 124 so as to trip the latch circuit when the fluid resistivity between electrodes 94 is of a predetermined value. The iluid appearing between electrodes 94 enters the charnber within which the electrodes are housed by means of elongated ports 93 in the housing. Pressure switch 88 may be connected between D.C. source 200 and terminal 204. The pressure switch closes when the apparatus has reached a `desired depth in the borehole to positively prevent premature energization of solenoid 126.
The sampling tube section of the apparatus is illustrated in detail in FIGS. 4-B and 4-C.
The swab cups 96 are aixed to a reduced section of the housing. The diameter of the swab cups is such as to contact the sides of the drill stem so that uid above the swab cups will be pulled upwardly as the swab line is lifted. When the apparatus is dropped, fluid will flow through ports 136, through the drilled passageway 134 within the reduced section to which ythe swaby cups are connected, will lift the ball check traveling valve 132, and will pass outwardly through ports 133; thus, uid will be pumped up the valve stem by reciprocating the apparatus in the drill stem. The sample chamber is provided within housing section 98 of the apparatus. A
check valve 142 is provided at the inlet port 144 to the sample chamber 140 for the purpose of permitting fluid entry into and preventing fluid exit from the sample chamber. A screw plug 140a and check valve 140b in passageway 140e at the upper end of chamber 140 are for the purpose of providing access to chamber 140 to remove fluid therein. After sample tube 98 is unscrewed from the other portions of unit 81, screw plug 140:1 is removed and check valve 140b (which opposes fluid egress from the chamber 140) is stabbed open so that fluid will lflow from chamebr 140.
Fluid entry tinto passageway y144 is controlled by a valve including a piston member 150I Slidable within chamber 146. Port 148 provides fluid entry into the chamber 146. A spring 154 in the enlarged oil lled chamber 156 functions to hold the valve piston 150 away from the position whereat drilled passageway 152 therein will provide fluid communication between port 148 and passageway 144. A threaded annular fitting 159 interconnects the lower end of piston 150 'with an actuating shaft 168 therefor. The clearance between fitting 159 and the sides of chamber 156 is only enough to permit slow movement thereof in an upward direction. Passageway 158 and 164 are drilled in the .piston and a check valve arrangement including ball 162 and spring 160I is provided to permit the piston to move quickly downward under the impetus of spring 154. An overshot arrangement 166 is provided at the lower end of the housing to latch onto the retrieving head of go-devil 63 when the retrieving head 170 shoves the actuating shaft 168 a suicient distance upward. In FIG. the overshot is shown latched to the retrieving head 170'. In this position the valve stem will be as shown in FIG. 5 so that fluid ow will be permitted through port 148, passageways -2 and 144, through check valve 142, into the sample chamber 140.
'Ihe valving arrangement for controlling the ow of actuating fluid from reservoir 3a to the packer, and from the packer to the reservoir, is shown in FIGS. 6, 7, and 8.
In FIG. 7 the apparatus is shown in the position which it will assume when the drill stem is making hole and when it is desired to ilow lluid from the packer to the reservoir. In FIG. 6 the apparatus is shown in the position Whereat fluid under pressure will flow from the reservoir to the packer.
The control valve apparatus 42 comprises a valve housing 42a having a passageway 183 drilled therein adapted to receive a valve stem 180. 'I'he valve housing is provided with a port 186 opening into the reservoir 3a, a port 188 connected to a check valve 50 by connection 188a and line 188b for permitting fluid flow from the reservoir to the packer, and another port 184 connected to a check valve 52 by connection 184a and line 184b for permitting fluid ow from the packer to the reservoir. The valve stem 180 has a multiplicity of longitudinal slots 182 cut therein substantially equal in length to the longitudinal distance along the valve housing between ports 184 and 186 and between ports 186 and 188. Annular slots 185 and 187 are respectively hydraulically connected to ports 184 and 188 so that when the valve stem 180 is in the position shown in FIG. 6, port 186 is hydraulically connected to port 188, and so that when the valve stem is in the position shown in FIG. 7, port 186 will be hydraulically interconnected with port 184.
A coil spring 190 is provided in a well within a fitting 191 at the bottom of the valve housing. Spring 190' bears against the bottom of valve stem 180 so as to urge the valve stem in an upward direction. A second spring 28 connected -to a shoulder 40 at the top of the valve stem housing 42a bears against actuating shaft 26 for substantially the same purpose. Shoulder 40 is ported and drilled so that .the upper end of chamber 183` is in hydraulic communication with the fluid reservoir around the valve housing through ports 40a.
A port 194 is provided in fitting 191 so that the lower end of the chamber 183 is in hydraulic communication with a passageway 58, which in turn is hydraulically connected to a recess 62 in valve stem section 61 (see FIGS. l and 2). The recess 62 surrounds elastic pipe section 60 so that when the piston 180l is in the position shown in FIG. 7, the elastic sleeve will bulge slightly into the recess 62 as shown in FIG. 2.
Returning to FIGS. 6 and 7, itis seen that at the upper end of the actuating shaft 26 there is provided a pivoted member including a pivoted arm 23 pivotally aixed to a slotted ball member 27. A slot 27a is cut in the ball member so that the actuating shaft 26 will assume the position shown in FIG. 7 when the arm 23 is rotated from the position shown in FIG. 6 to the position shown in FIG. 7. Spring 22 is provided for urging the arm to the position shown in FIG. 6. The arm is pivotallly supported within the drill stem by a suitable support means 20. A clevis member 24 is connected to one end of the pivoted arm 23 and partially surrounds the nonmagnetic pipe member 16. A clevis actuating member 19a is affixed to the inner pipe member 16 so as to drive the clevis 24 from the position shown in FIG. 6 to the position shown in FIG. 7 when a magnet 19 slidably mounted on the pipe member 16 strikes the lower end of the clevis actuating member 19a. The magnet 19 is supported by an annular stop member 21 and is free to slide between the clevis actuating member 19a and the annular stop member 21.
Turning again to FIGS. l and 2, it is seen that the sliding sleeve member 70 for the flexible packer 66 comprises a tubular outer section 201 having inwardly projecting annular flanges 203 and 205 at the upper and lower ends thereof respectively. The tubular outer section 201 slidingly engages an annular flange 207 on drill stem section 65. Thus there is formed between the drill stem section 65 and the member 201 iirst and second cavities 209 and 211, the volume of which increases and decreases as the member 201 slides up and down on flange 207. Cavity 209 is in fluid communication with the borehole annulus through at least one port 72 which at all times is above ange 207. Cavity 211 is in fluid communication with the drill stem bore through at least one port 213 below flange 207. The braid or cables of the packer are anchored to the upper end of member 70.
When hydraulic pressure is applied to the drill stem and there is no obstruction therein so that fluid circulation is possible, the pressure drop across the bit forces member 70 down since the pressure drop is exerted across member 70 through port 213. However, when the go-devil 63 prevents fluid circulation, or when there is no hydraulic pressure applied to the drill stern, the member 70 is free to move up when hydraulic pressure is exerted on the interior of packer member 66 through passageway 67.
During drilling operations the apparatus will assume the position shown in FIG. l. The packer will be held against the drill stem by virtue of the differential pressure across the drill bit exerted on the sliding sleeve member 70. When it is desired to conduct a drill stem test, godevil 63 is dropped into the bore of the drill stem. Spacer bar 71 will space the packer cups 41 between the elastic pipe sections 6 and 60. Heavy hydraulic pressure is then exerted down the bore of the drill stem. By virtue of the action of the elastic pipe 6, the hydraulic force within the drill stem will be exerted on the Valve stem to force the valve stem into the position shown in FIG. 6. Pivoted arm 23 will rotate due to the pull exerted by spring 22 so that the spherical member 27 will hold the valve stern 180 in the position shown in FIG. 6. Fluid may then flow through port 186, through slots 182, through port 188, check valve 50, passageways 56 and 67 and will be exerted against the inner side of the packer. Slidable sleeve member 70 will be permitted to slide upwardly inasmuch as there is now no differential pressure existing across the drill bit. Hydraulic pressure may now be released. By virtue of the latching action of the spherical member 27 and the check valve 50, the
packer will stay in its inflated position shown in FIG. 2.
The swabbing and sample retrieving member 81 may now be lowered into the bore of the drill stem until the swab cups are adjacent drill stem section 3. This may be done by lowering member 81 until retrieving head 170 engages member 168. The dashpot action of fitting 159 will prevent the stem 150 from moving up rapidly to prematurely open the sampling chamber. Member 81 may be lifted a short distance in drill stem section 3 and spring 154 will quickly force member 168 back to its original position (ball 162 will unseat to permit lluid ilow through passageway 164). The swabbing unit may then be reciprocated in drill stem section 3 without contacting retrieving head 170 to pump iluid out of the earth formation, through ports 59, through passageway 179, through ports 37, up the drill stem bore between the godevil and the swabbing unit, and through the swabbing unit into the portion of the drill stem bore immediately above cups 96. As the iluid around the electrodes 94 i changes from drilling fluid to earth formation lluid, the
resistivity thereof will change. When the resistivity has reached a predetermined value, the electrical triggering circuit will energize solenoid 126 to trip the latch 108 and release mandrel 100. The entire swabbing and sampling apparatus will suddenly drop, which will produce a sudden jerk on the swab line.
Additionally, during the swabbing operations, the swabbing member 81 is periodically lowered to rest on top of the go-devil 63. This gives a depth reference which may be marked on the swab line at the wellhead. The swab line weight is indicated at the wellhead. (When the swabbing member 81 comes to rest on the go-devil 63, a weight indicator falls off.) Bottom reference may be made as often as desired. Short movements of valve stem 150 are not additive due to the return feature of the check valve arrangement (ball 162 and spring 160). Therefore, in addition to a jerk on the swab line (which may be missed by the operating personnel), a positive indication that the mandrel 100 has been released by a detected change in the resistivity of the well fluid is observable at the wellhead by an apparent increase in the length of the swab line upon a bottom reference check. This increase in length of the swab line will be equal to the length of the mandrel 100. Upon this indication at the surface, a sample may then be obtained by allowing the swab unit 81 to rest upon the go-devil 63 for a long enough period to ascertain movement of the valve stem 150 for its full stroke which will open the sample chamber and allow latching onto the go-devil 63. When the retrieving head 170 is engaged by the overshot 166 (see FIG. 5), the valve stem 150 is moved to the position as shown, and formation fluid will flow into the sample chamber which is at atmospheric pressure until the pressure between the sample chamber and the well bore therearound drops to a value sulllcient to close check valve 142 and retain the formation lluid sample. Both the swabbing and sample retrieving unit 81 and the go-devil 63 may then be retrieved from the well bore. As the magnet 39 passes by the magnet 19, the mutual attraction therebetween will cause magnet 19 to be lifted until clevis 24 is stricken by member 19a and pivoted arm 23 will be rotated, releasing the valve stem 180 so that it is free to assume the position shown in FIG. 7. When the go-devil 63 has been removed from the well bore, drilling fluid pressure will force slidable sleeve member 70 down to the position shown in FIG. l, thereby forcing fluid up the passageways 67 and 56 through check valve 52, port 184, slots 182, and port 186 into the lluid reservoir. After a sufficient time to allow the packer to be deflated, drilling operations may recommence.
The invent-ion is not to be restricted to the specific structural details, arrangement of parts, or circuit connections herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of this invention.
What is claimed is:
1. Apparatus for use in drill stem testing an isolated earth formation in lfluid -communication with the interior of a drill stem through the lower end thereof for indieating the presence of earth lluids in the drill stem, comprising: an elongated housing; swab cup means on said housing having a diameter sullicient so that said swab cup means sealingly contact the bore wall of the drill stem; a fluid passageway means including a check valve in said housing, in lluid communication with the exterior of said housing above and below the swab cup means, adapted to permit one-way fluid flow up the drill stem past said swab cup means; an elongated mandrel adapted to be connected to a wireline, and telescopically extending into said housing through one end of said housing; a latching head allixed to one end of said mandrel; stop means on the housing engageable by said latching head to hold said mandrel within said housing at its least telescoped position; a trippable latch in said housing initially latched on to said latching head to hold said mandrel in its most telescoped position; latch Itripping means, including electromagnet means in said housing operatively associated with said trippable latch to trip said latch when said electromagnet means is electrically energized; electrical resistivity detecting means on said housing adapted to measure the resistivity of fluids around said housing and to produce an electrical output signal indicative of the measurement; and means electrically connecting said electrical resistivity measuring means to said electromagnet means operable to energize said electromagnet means when the output signal of the resistivity measuring means is indicative of fluids of given resistivity around said housing.
2. Apparatus for use in drill stem testing an isolated earth formation .in fluid communication with the interior of a drill stem through the lower end thereof for indieating the presence of earth `fluids in the drill stern, comprising: an elongated housing; swab cup means on said housing having a diameter sufficient so lthat said swab cup means sealingly contact the bore wall of the drill stem; means including a check valve in said housing in iluid 'communication with the exterior of said housing above and below said swab cup means, adapted to permit one-way lluid flow up the drill stem past said swab cup means; an elongated mandrel adapted to be connected to a wireline, and telescopically extending into said housing through one end o-f said housing; a latching head atlixed to one end of said mandrel; stop means on the housing engageable by said latching head to hold said mandrel within said housing at its least telescoped position; a trippable latch in said housing initially latched on to said latching head to hold said mandrel in its most telescoped position; and means operatively associated with said trippable latch adapted to measure the electrical resistivity of iluids around said housing and -to ltrip said latch when the measured resistivity is of predetermined magnitude whereby said latching head will be released to permit said housing and said mandrel to assume their least telescoped position.
3. Apparatus for use in drill stem testing an isolated earth formation in fluid communication with the interior of a drill stem through the lower end thereof for indicating the presence of earth fluids in the drill stem, comprising: an elongated housing; swab cup means on said housing having a diameter sufficient to contact the sides of the drill stem; means including a check valve in said housing in fluid communication with the exterior of said housing above and below the swab cup means, adapted to permit one-way fluid llow up the drill stem past said swab cup means; an elongated mandrel adapted to be connected to a wireline, and telescopically extending into one end of said housing so that one end of said mandrel is movable within said housing between a least tele- SCOped POSirtQn of said mandrel and said housing and 9 10 a most telescoped position of said housing and said manrelease Asaid mandrel when the detected electrical resistivity drel; detect-ing lmeans rin said housing for detecting re- 1S 0f Pfedeel'mmed maglmldesistivity of fluids around said housing; and electromagnetic means in said housing electrically connected to said References Clted m the me of this patent detecting means, and normally operatively arranged with 5 UNITED STATES PATENTS respect to said one end of said mandrel in position ini- 2,347,615 Shelley Apr. 25, 1944 tially latching it on to said one endof said mandrel 2,454,740 Lehnhard Nov. 23, 1948 for holding said mandrel in the most telescoped position 2,942,667 Blood et al June 28, 1960 thereof with respect to said housing, and actuatable to 2,945,541 Maly et al July 19, `1960