US3212574A

US3212574A - Well formation tester

Info

Publication number: US3212574A
Application number: US134409A
Authority: US
Inventors: Fred K Fox
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-08-28
Filing date: 1961-08-28
Publication date: 1965-10-19
Anticipated expiration: 1982-10-19

Description

Oct.- 19, 1965 F. K. FOX

WELL FORMATION TESTER 7 Sheets-Sheet 1 Filed Aug. 28, 1961 Fred Fox IN V EN TOR.

ATTORA/[YJ Oct. 19, 1965 F. K.'FOX

WELL FORMATION TESTER 7 Sheets-Sheet 2 Filed Aug. 28, 1961 INVENTOR.

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A7'7'0P/VEYJ A w A I Tr, Pl 7/ )I )I Fred Fox 1 m a "W W m Oct. 19, 1965 F. K. FOX

WELL FORMATION TESTER I ffy4a 7 Sheets-Sheet 4 Filed Aug. 28, 1961 &

INVENTOR. 4152 AffO/P/VEVJ 7 Sheets-Sheet 5 Filed Aug. 28, 1961 Fred /K. Fax

IN VEN TOR.

Oct. 19, 1965 F. K. FOX

WELL FORMATION TESTER 7 Sheets-Sheet 6 Filed Aug. 28, 1961 F/ec/ K ox INVENTOR.

ATTORNEYS Oct. 19, 1965 F. K. Fox 3,212,574

WELL FORMATION TESTER Filed Aug. 28, 1961 '7 Sheets-Sheet 7 yffi V A "40 A n, 0O A 3 A 1 A r/\ i 5 A r. A

A A l, \2

IN VEN TOR.

United States Patent 3,212,574 WELL FORMATION TESTER Fred K. Fox, 242 Stoney Creek Drive, Houston 36, Tex. Filed Aug. 28, 1961, Ser. No. 134,409 35 Claims. (Cl. 166-3) This invention relates generally to the testing of well formations by means of drill stem testers. In one aspect, it relates to an improved drill stem tester of the type in which a pad carried on the housing connected to the stem is adapted to sealably engage a formation on the side of a well bore to receive fluid therefrom for flowing upwardly through the stern. In another aspect, it relates to an improved method of obtaining fluid from such a formation with a tester of this latter type.

In another type of drill stem tester, one or two annular packers are carried on a tester body connected to the drill stem for expansion against the well bore to isolate the formation to be tested. Ports in the tester body are then opened to permit the formation fluid to flow into the stem. This type of tester is subject to many shortcomings, not the least of which is the large pressure differential across the top annular packer, which may cause it to fail. For this reason, there has been considerable effort to develop a suitable drill stem tester of the type previously mentioned wherein the pad is sealably engaged against the side of the borehole. However, to my knowledge, none of these side wall drill stem testers have met with substantial commercial success.

It is possible that these previous failures have been due, at least in part, to a concern over the danger of having the stem become stuck in the bore, as by differential pressure sticking. For example, prior testers of this lat ter type have been designed to obtain fluid from the formation as quickly as possible so that the sample is rarely representative. Also, this type of testing procedure makes it impossible to locate the pad acurately relative to the zone to be tested by lowering electrical or radioactive logging tools into the stern. Consequently, the industry has turned to still another type of tester in which the tester housing is run into the well and located adjacent the formation by means of a wire line. This wire line tester not only permits the use of the more accurate logging tools, but also decreases the dangers of pressure differential sticking. However, similarly to prior side wall drill stem testers, it is also limited in the amount of fluid and other data which it may obtain from the formation. Furthermore, since torque cannot be transmitted through the wire line, this last type of tester generally requires an electric motor to expand and contract parts for engaging and then disengaging the pad on the housing with respect to the formation.

An object of this invention is to provide a drill stem tester and a method of using same which overcome the above-mentioned as Well as other shortcomings of prior testers and testing methods.

, Another object is to provide such a tester and method which enables the operator to take a practically unlimited amount of the formation fluid, and thus to effectively produce such fluid through the drill stem, without regard to time, thereby obtaining a measurement of the reservoirs ability to produce and production data from which reserves may be estimated.

A further object is to provide such a tester for producing the formation fluid without the danger of having the pad pulled loose from the formation, as might otherwise occur in prior testers of this type as the upward forces on the tester housing change due to the decreased density of the fluid therein.

Still another object is to provide such a tester having a pad which may be located adjacent and then urged against the formation with considerable accuracy and without the 3,212,574 Patented Oct. 19, 1965 ice necessity of reciprocating the tester housing and pad relative to one another, as is the case of the wedge or slip type pad setting devices of the prior art.

A further object is to provide such a tester which is capable of transmitting torque to the pad and other parts at the lower end of the tester housing, while at the same time being manipulatable to lessen the likelihood of wall sticking.

Yet another object is to provide a tester of this type which is so constructed as to enable the stem to be manipulated, particularly by rotation, in order to cause the pad to engage the formation and then, upon completion of the test, to permit the stem to be further manipulated in a manner to equalize pressure across the stem to facilitate disengagement of the pad.

Other objects, advantages and features of this inven tion will be apparent to one skilled in the art upon consideration of the written specification, the attached claims and the annexed drawings.

These and other objects are accomplished, in accordance with the illustrated embodiment of the present invention, by a drill stern tester which has a tubular housing closed at its lower end and connectable at its upper end to a drill stem and carries a pad for vertical reciprocation with respect thereto while the pad is sealed against the formation. In this manner, the buoyant effect of formation fluid within the drill stem may be detected by a lessening of the tension in the stern, which will in turn permit the operator to lower the stem to sufliciently compensate for such effect. Thus, the operator may cause the pad to be sealed against the formation and produce formation fluid through the stern without fear that the buoyancy of such fluid will pull the pad loose from the formation.

Since the operator need not be overly concerned with the buoyancy problem, there is no necessity for positively wedging the pad tightly against the formation and I replace the conventional device of this type with a means which merely urges the pad against the formation and permits it to be effectively held thereagainst by the pressure differential across it. In fact, I provide my tester with a large pad not only to increase the volume, but also to provide a more effective seal, because, as noted below, my tester is operable to remove the differential upon completion of the test in order to free the pad from the information.

This greater flexibility in operation, and particularly the actual production of the formation fluid through the drill stem, is also made possible by the use of a housing and drill stern modified in a manner to reduce the likelihood of their becoming stuck by differential pressure. That is, as shown in my copending application, Serial No. 797,180, filed March 4, 1959, now patent No. 2,999,552, and entitled Tubular Drill String Member," each may have one or more shallow, spiral grooves thereabout. Also, the housing of my drill stem tester includes a clutch which frees the upper end thereof from the portion which carries the pad so that, when the pad is sealed against the formation, the stem may be worked periodically, as by rotation or vertical reciprocation, to further lessen the likelihood of their becoming stuck.

I also propose to operate my drill stem tester in such a way that the pad may be unstuck regardless of the force due to the pressure differential across it. Thus, as my tester is lowered into the well bore, the pad is open to the flow of drilling mud into the stem, which not only facilitates running of the tool, but also leaves it open for circulation purposes. When the pad is at least approximately opposite the formation, the hydrostatic head of the well fluid within the stem is reduced, as by its displacement, so that when the pad is engaged against the formation, the pressure above the well fluid in the stem may be reduced to induce flow of the formation fluid. Then, when an adequate sample has been taken, the pressure across the housing may be equalized by the opening of a valve in the wall of the housing, so that there is only a low pressure differential remaining across the pad and the tester may be easily pulled from the formation.

The means for urging the pad against the formation is operable merely in response to rotation of the stem so that the pad need not be moved longitudinally out of a position opposite the formation. Preferably, the pressure equalizing valve is similarly operable, but only upon sealing of the pad against the formation, and, more particularly, only after production of the formation fluid has begun.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIGS. 1A and 1B show the upper and lower ends of a formation tester constructed in accordance with the present invention and lowered into a well bore with the pad thereof opposite the formation to be tested;

FIG. 2 is a view of the tester of FIGS. 1A and 1B after the pad has been urged into sealing engagement with the formation and the clutch has been manipulated to permit the upper end of the tester housing and the drill stem to be rotated with respect to the pad;

FIG. 3 is a view of the tester similar to FIG. 2, but with the pad pulled away from the formation and urged to a position substantially centrally of the well bore, and during raising of the tester to the surface;

FIGS. 4A and 4B are views, partly in cross section, of the upper and lower ends of the clutch in a position freeing the drill stem with respect to the lower end of the tester;

FIGS. 4C and 4D are views, also partly in section, of the upper and lower ends of the valve located below the clutch and in closed position;

FIGS. 4E and 4F are views, again partly in cross section, of the upper and lower ends of a spring assembly beneath the valve and above the pad for alternately centering the latter and urging it into engagement with the formation;

FIGS. 4G and 4H are views, again partly in cross section of the upper and lower ends of the pad of this tester;

FIG. 5 is a cross-sectional view of the clutch, as seen along broken line 5-5 of FIG. 4A;

FIG. 6 is a cross-sectional view of part of the spring assembly, as seen along broken lines 6-6 of FIG. 4F;

FIG. 7 is a cross-sectional view of the pad, as seen along broken line 7-7 of FIG. 4G; and

FIG. 8 is a view of the valve similar to FIG. 4D, but with the valve in open position.

With reference now to the details of the above-described figures, and as shown in FIGS. 1A and 1B, the well bore extends downwardly from the surface level 21 beneath a derrick 22 or other means for raising and lowering the drill stem for the purposes here to be described. As is common in this art, the upper end of the well bore is lined with a casing 23 (FIG. 1A) having a blowout preventer 24' or other pressure control apparatus at its upper end for sealing about the stem, if necessary. As also shown in FIG. 1A, there are outlets 26 from the casing 23 above the surface level 21 and below the preventer 24 for connection with conventional well head equipment used in controlling the fluid column within the well bore annulus. As shown in a portion of FIGS. 1A, 1B, 2 and 3', the lower end of the well bore 20 is uncased and penetrates a formation F which is to be tested in the manner described hereinafter.

As is also well known in the art, the well bore 20 is filled with a drilling mud which is heavier than the formation fluid to prevent it from flowing into the well bore. The face of the formation which is penetrated by the well bore is usually covered with a coating of mud cake which also tends to restrict the fiow of formation fluid into the well bore. Obviously, the well bore may penetrate other formations from which samples are to be obtained, although the utility of the present invention may be understood in connection wit-h its use in obtaining the sample from the single formation F.

The drill stern tester T is run into and pulled from the well bore by means of a drill stem 27 connected to its upper end and extending through the preventer 24. During a stage of the testing procedure to be described below, a test head 28 is connected to the upper end of the drill stem 27 by means of a swivel 25 which permits the stem to be rotated relative to the head by any conventional means (not shown) on the derrick floor 22a. This head may be of any suitable construction including a conduit forming a continuation of the drill stem as well as lateral connections therewith, each such conduit and connection being controlled by a conventional valve 28a. As will be understood from the description to follow, this test head 228 permits the passage of fluid into and out of the drill stem and also enables the operator to control the pressure of same.

The lower end of the drill stem 27 may include one or more joints 29 of pipe modified in the manner previously mentioned, and particularly provided wit-h one or more shallow, helical grooves 30 to reduce the area thereof over which pressure will act in the event pipe is held against the well bore 20. Preferably, these special joints of pipe extend from that portion of the drill stem 27 beneath the well casing 23 to the connection of the stem with the upper end of the tester T.

As shown in FIGS. 1A, 1B, 2 and 3, the tester comprises a tubular housing forming a continuation of the stem and including a clutch 31 at its upper end and a valve 32 beneath the clutch. A pad 33 is carried on the housing beneath the valve and intermediate an upper spring assembly 34 and a lower spring assembly 35. Obviously, two or more such pads may be carried on the housing for various purposes, such as the testing of two or more formations or the testing of a single formation at isolated levels. The lower end of the tester includes a tubular section 36 which is closed on its lower end and which may contain instruments for accumulating reservoir data. As shown, each of the clutch, valve and lower end of the tester T may also be provided with shallow, helical grooves 37 thereabout, similarly to-the lower joints of the drill stem 27, in order to lessen the likelihood of differential pressure sticking.

As shown in FIGS. 1A and 1B, the clutch 31 includes upper and lower

tubular sections

38 and 39, respectively, which are vertically slidable with respect to one another between the extended position of FIGS. 1A and 1B and the contracted position of FIG. 2. In their extended position, the

clutch parts

38 and 39 are engaged for rotation with one another so that, with the upper part 38 connected to the lower end of the drill stem 27, rotation of the stem will impart rotation to the lower clutch part 39 and thus to the valve 32 connected thereto. On the other hand, in the contracted position of the clutch parts, the upper part 38 and thus the entire drill stem 27 is free to rotate with respect to the lower part 39. As previously mentioned, this permits the drill stem to be rotated while the pad 33 is sealably engaged against the formation F, thereby further lessening the likelihood of pressure dilferential sticking of the stem. Also, of course, since the clutch parts are reciprocable between opposite positions, the stem may be worked vertically from time to time.

The valve 32 also includes upper and lower

tubular sections

40 and 41, respectively, which are connected by left-hand threads 43 (opposite to those connecting the drill stem joints) for vertical reciprocation between a contract-ed position (FIGS. 1B and 2) and an extended position (FIG. 3). In the contracted position thereof, the

valve parts

40 and 41 close ports 42 in the upper part 46 to flow between the inside and outside of the tester housing. However, in the extended position of the valve parts shown in FIG. 3, the ports 42 are opened for the purpose of equalizing pressure across the tester. For reasons apparent from the description to follow, the valve sections are locked by the parts 4311 against relative rotation and in closed position as the tester is run into the bore and until the test begins, at which time they are unlocked for relative rotation to open position.

The pad 33 includes a substantially cylindrical body 44 having a sealing face 45 thereon and surrounding a tubular member 46 which is connected at its upper end to the lower valve part 41 and at its lower end to the lower tubular end 36 of the tester body. More particularly, and as will be described below, the tubular member 46 is vertically reciprocable with respect to the pad between limits defined by stops (to be described) below the upper spring assembly 34 and above the upper end of lower spring assembly 35. At the same time, the pad body 44 is held against rotation with respect to tubular member 46 so that rotation of the latter is imparted to the pad. As will also be described hereinafter, the face 45 of the pad is slotted for communication with the interior of tubular member 46, and thus the interior of the drill stem 27, in any relative vertical position with respect to the tubular member.

Each spring assembly includes bow springs 47 held at opposite ends between an upper collar 48 and a lower collar 49, each of which is disposed about the tubular member 46 for vertical movement with respect thereto. A coupling 50 connecting sections of the tubular member 46 at the lower end of the spring assembly 34 and a coupling 51 connecting sections thereof at the upper end of spring assembly 35 provide the aforementioned stops engageable with the pad during vertical reciprocation of the tubular member with respect thereto.

The upper collar 48 of each spring assembly is connected to a section on tubular member 46 having lefthand threads 52 so that it will move downwardly with respect thereto when the tubular member 46 is rotated to the right relative to the bow springs 47. As is well known in the art, the outward urging of these springs against the well bore will resist their rotation with the tubular member, thereby permitting the aforementioned relative rotation which is required in order to move the upper collar and thus the bow spring downwardly along the tubular member 46.

In the elevated position of each spring, as shown in FIG. 1B, the lower collar 49 is disposed just above a portion 53 of the tubular member which is bent in a direction radially opposite from the face 45 of the pad. Thus, in the positions shown in FIG. 1B, such assemblies will center the tester in the well bore and maintain the pad away from the formation. However, as the spring 47 is moved downwardly, its lower collar 49 moves over the bent portion 53 of the tubular member 46, as shown in FIG. 2, thereby urging the face 45 of the pad radially against the formation F. Upon completion of the test, and this will be described more fully hereinafter, the lifting of the tubular member 46 will permit the lower collar 49 of each spring section to move downwardly from the bent portion 53 of the tubular member and thereby bring the bow springs 47 into substantially their original relationship with respect to the tubular member 46, which will in turn urge the face 45 of the pad away from the formation and the tester into a central position for pulling purposes.

With reference now to the operation of the tester T, it is first lowered within the well bore 20 upon the drill stem 27 to a position (not shown) in which the pad 33 is disposed a relatively short distance, such as 20 or 30 feet, below the formation F. As previously indicated, this as well as other vertical locations of tester pad may be accomplished with electrical or radioactive logging tools suspended within the stern. At this time, the

clutch parts

38 and 39 may be in a position intermediate expanded and contracted positions, the valve 32 will be closed, and the

spring assemblies

34 and 35 will be disposed in their uppermost positions to maintain the tester housing substantially centrally of the well bore. Also, the drilling mud within the well bore will flow into the slotted pad face 45 and thus into the drill stem so that the pressure across the tester housing is equalized.

When the pad face has been lowered to the position above described, the testing head 28 is installed on the upper end of the drill stem 27, as shown in FIG. 1A, and gas, water or other fluid lighter than the drilling mud is pumped downwardly into the drill stern. This will, of course, displace mud from within the stem out to the slot in the pad face 45, but not directly against the face of the formation. As in production practices, suflicient displacing fluid is pumped into the drill stem to lower the hydrostatic head of the well fluid below the pressure of the formation fluid. The valves on the testing head are then closed in order to maintain this pressure on the hydrostatic head of mud, and the stem is then raised to dispose the pad face 45 oposite the formation, as shown in FIG. 1B.

This lowering and subsequent raising of the stem insures that the

clutch parts

38 and 39 are extended and therefore engaged for rotating the lower clutch part and thus the tubular member 46 with the drill stem in a right-hand direction. This rotation, which'is imparted to the stern while it is held against longitudinal movement will cause the bow springs 47 above and below the pad to move downwardly to the position of FIG. 2 and thus urge the pad into engagement with the formation.

The

valve parts

40 and 41 remain locked against rotation and thus reciprocal movement as long as the pressure across the housing is equalized due to the mud column within as well as without the valve body. As previously mentioned, the outer body 44 of the pad 33 rotates with the tubular member 46 as the bow springs 47 are being moved downwardly and continues until there is obvious torque indicated at the well head, at which time the operator knows that the pad face has sealably engaged with the formation and that rotation of the stem may be discontinued. During this rotation, the pad face 45 will wipe against the mud cake over the face of the formation and thus increase its permeability prior to becoming sealably engaged therewith.

When the pad face has become so engaged with the formation, it will, of course, be held thereagainst by the pressure differential across it due to the hydrostatic mud pressure opposing the force of the lower pressure formation fluid. It will be noted, in this respect, that the bow springs 47 provide only a light force for holding the pad against the formation, and particularly do not positively wedge the pad thereagainst. At this true, the test head 28 is manipulated to relieve the pressure on the mud column within the drill stern so that the formation fluid will flow freely up through the stern. As previously mentioned, this production may be continued for an indefinite time without necessarily increasing the possibility of wall sticking. Thus, the operator is permitted to obtain a large volume of formation fluid for testing purposes. Also, and as will be described more fully hereinafer, the operator can obtain truly representative production data from the formation since the slot in the pad face 45 eX- tends a considerable longitudinal distance.

Preferably, the drill stem is now lowered a few feet in order to lower the upper clutch part 38 from the fully extended position with respect to lower clutch part 39 and thereby free the upper clutch part and the drill stem for rotation with respect to the remainder of the tester including the sealed pad 33. This is useful in providing further assurance that the stem shall not become stuck 1 against the well bore because it permits the operator to rotate as well as to reciprocate the drill stem from time to time. As will further be described in connection with a detailed description of clutch 31, the

parts

38 and 39 are also operable, upon reciprocation, to provide a jarring effect which may be useful in unsticking the pad from the formation in some cases.

When suificient test data has been obtained, and the operator is ready to pull the tester from the well bore, he raises the drill stem in order to fully extend the upper clutch part 38 with respect to the lower part 39. This engages the clutch parts in order to impart rotation of the stem to the remainder of the tester housing, and particularly to the upper part 40 of the valve 32. As previously mentioned, the upper and

lower parts

40 and 41 of the valve are released for rotation with respect to one another when there is a pressure differential thereacross. Obviously, this differential occurs as soon as the formation fluid flows into the tester housing so that the upper valve part 40 is automatically released for rotation with respect to the lower valve part just as soon as the test begins. As a result, when the clutch is engaged, right-hand rotation of the stem will move the upper and lower valve parts from the contracted position of FIG. 2 to the extended position of FIG. 3, in which latter position the ports 42 are opened.

This opening of the ports 42 will permit the well fluid about the outside of the tester housing to flow into the interior thereof and thereby equalize pressure across the pad. As previously mentioned, this permits the pad to be easily pulled away from the formation wall merely upon raising the drill stem. If there is any tendency to stick, the clutch parts may be reciprocated to jar the pad. At any rate, when the drill stem is raised to pull the pad face away from the formation, the bow springs 47 above and below the pad will move downwardly over tubular member 46 to the position of FIG. 3, and thus urge the pad away from the well bore and into the substantially central position it occupied as the tester was run into the bore. As can be seen in FIG. 3, and as will be described more fully hereinafter, the upper collar 48 on the

spring assemblies

34 and 35 will abut, in this latter position, with

rings

34a and 35a, respectively, on the tubular member 46 so as to maintain them in the centralizing position.

When the tester is disposed in the position of FIG. 2, and while a sample of the formation fluid is being produced through the tester housing, the lighter formation fluid will have a buoyant effect thereon which, in the ordinary drill stem tester of this type, would tend to pull the pad face 45 loose from the formation. However, since the body 44 of the pad 33 is freely reciprocable over the tubular member 46, this buoyant effect is first reflected by a lessening of tension in the tubular member without vertical force on the pad 33. In other words, as shown in FIGS. 1B, 2 and 3, the coupling 51 on the tubular member 46 is disposed beneath the lower end of the pad 33 a distance sufficient to indicate to the operator that there is a buoyancy problem.

When this is detected, the operator may lower the upper end of the stem to counteract the tendency and prevent the collar 51 of the tubular member 46 from engaging and pulling the pad 33 loose from the formation. As previously mentioned, this tester construction makes it practical to hold the pad face against the formation merely by pressure differential and without the aid of positive wedging devices which impose a heavy force on the pad against the formation, thereby making it difiicult to free the pad from the formation wall when the test has been completed.

The opening of the valve 32 will not only substantially equalize pressure across the face of the pad, but will also displace the formation fluid within the tester housing and the drill stem upwardly to the surface. This fluid may be bled off by .the opening of a surface valve and the maintaining of a full column of fluid in the annulus between the drill stem and well bore, as by control of the side outlet 26. When the fluid has been displaced from the drill stem and good mud and safe conditions are present at the surface, the test head 28 can be removed and the stem and tester pulled from the well bore. Obviously, during this pulling of the tool, the springs 47 will maintain the portion of the tester housing and particularly pad face 45 in central position.

With reference now to the details of the above-described tester, and with particular reference to FIGS. 4A and 4B, the upper end of upper tubular clutch part 38 is threadedly connected at 54 to the lower end of bottom drill stem joint 29, and the lower end of lower tubular clutch part 39 is threadedly connected at 55 to the upper end of upper tubular valve part 40. The lower part 39 is telescopically received within the upper part 38 and has a bore 56 therethrough of substantially the same diameter as the bore through the drill stem. The lower end of upper clutch part 38 carries packing 57 for sealably engaging the outer diameter of lower clutch part 39 during vertical reciprocation therebetween. In this manner, the connection between the clutch parts is sealed against the flow of fluid between the inside and outside of the tester housing.

The inside of the upper clutch part 38 is counterbored at 58 above the packing 57 to slidably receive the enlarged upper end 59 on the lower clutch part 39. More particularly, and as best shown in the cross section of FIG. 5, the part 39 is provided with ribs 60 just below the enlargement 59 for vertical reciprocation in its lowermost position within slots 61 formed within the upper clutch part 38 beneath the counterbore 58 therein. This, of course, engages the clutch parts so that, upon rotation of the upper part 38, the sides of the slots 61 will engage the sides of the ribs 60 to also rotate the lower clutch part 39. On the other hand, when the clutch parts are contracted to the position of FIG. 4A, or any other position in which ribs 60 are above slots 61, the upper clutch part 38 may be rotated with respect to the lower part, as previously described. In the lower limit of reciprocation of the upper part 38 with respect to the lower part 39, a downwardly facing shoulder 62 on the outside of the former will engage an oppositely facing shoulder 63 on the lower part to provide a jarring effect, when desired.

As shown in detail in FIGS. 4C and 4D, the upper tubular part 40 of the valve 32 comprises an upper portion 40a to which the lower clutch part 39 is threadedly connected at 55 (FIG. 4B) and a lower portion 40b threadedly connected thereto. The bore through the upper end of the tubular portion 40a forms a substantial continuation of the bore through lower clutch part 39, while the lower end thereof and the lower portion 49b have enlarged bores to telescopingly receive the upper end of lower valve part 41. This lower valve part has a bore therethrough forming a substantial continuation of the bore through the clutch.

As shown in FIG. 4D, the threads 43 on the lower valve part 41 and the mating threads 64 on the inside of the lower end of the valve part 40 are coarse and of a relatively low pitch to permit accurate alignment of the ports 42 in valve part 40 with ports 65 in the lower valve part 41 when the two valve parts are moved with respect to one another to the open position of FIG. 8. The lower valve part 41 carries packing 66 above and below the opening 65 therethrough to seal between the valve parts during their relative reciprocation between opened and closed positions. As shown in FIG. 4D, the upper valve part 40 also has a smaller port 67 therethrough above the port 42 for alignment with the ports 65 during movement of port 42 in position. If desired, the upper valve part 40 may be rotated to align the smaller port 67 to provide a more restricted flow between the well annulus and the inside of the tester housing.

As previously described, the tubular valve parts are held against reciprocation with respect to one another until there is a pressure drop across the tester housing, which would occur as formation fluid enters the housing at the beginning of a test. These lock parts 43a comprise pistons which, in their locking position, extend within aligned

openings

68 and 69 in the upper and lower valve parts. As can be seen from FIGS. 4D and 8, these openings extend through the parts in question so that the inner end of the piston 43a is exposed to pressure of the fluid within the tester housing while the outer end thereof is exposed to the pressure of the fluid Within the annulus. More particularly, the piston carries an O-ring 70 sealably slidable within the opening 69 which renders it responsive to the aforementioned pressure drop. As shown in FIG. 8, when the piston 43a is moved inwardly by virtue of the pressure drop within the tester housing, its outer end is moved entirely free from the opening 68, which frees the upper valve part 40 for rotation and vertical movement with respect to the lower valve part 41.

Each piston 43a carries another O-ring 71 outwardly of the O-ring 70 and within a shallower groove so that, in the locking position of piston 43a shown in FIG. 4D, a radially outer portion of the O-ring 71 abuts against the outer edge of opening 69. This prevents the piston 43a from being accidentally moved inwardly to unlocking position until there is a substantial pressure difierential thereacross, at which time the outer O-ring 71 is compressed inwardly for sliding into the opening 69. Obviously, the tight fit of this outer O-ring will have a tight fit within the opening 69 which serves to prevent the piston 43a from being accidentally displaced outwardly.

The piston 43a is also prevented from accidentally dropping out of its locking position shown in FIG. 4D by the head of a shear pin 72 comprising a nail driven into openings 74 through the sides of valve part 41. As will also be apparent, the shear pin also bridges the separation between the lower end of valve part 40 and the adjacent portion of valve part 41 to further insure against accidental unlock-ing of the

valve parts

40 and 41, although the pin is shearable when torque is applied thereto by rotation of upper valve body part 40.

As shown in FIG. 40, the valve part 41 has a downwardly racing shoulder 75 adapted to abut with an upwardly facing shoulder 76 on valve part 40 in order to locate the port 42 in the open position of FIG. 8. As will also be appreciated from the drawings, the packing 66 seals between the interior of the tester housing and the annulus thereabout in all relative vertical positions of the valve parts. This packing may be assembled about the lower valve part in any suitable manner, such as by a removable upper portion 41a thereof which enables the packing to be lowered over the lower portion 41b tor seating upon an upwardly facing shoulder 41c. rings 77 are held down upon makeup of the separate portions 41a and 41b. As shown in FIG, 4D, a portion of the opening 65 through one spacer ring 77 is aligned with the remainder of such opening through the lower portion 41b of valve part 41 by means of a removable pin 78.

With reference now to the details of the upper spring section 34 shown in FIGS. 4E, 4F and 6, and identical to the lower spring section 35, the bow springs 47 comprise four separate and equally spaced-apart blades 47a, each having its opposite ends connected within the

collars

48 and 49 by means of pins 79. away portion of *FIG. 4F, these pins are removably fittable within shallow recesses in the sides of each spring blade. As shown in FIGS. 4E and 4F, the inside 80 of each collar adjacent the connection of the spring blade thereto is curved to allow the collars a certain amount of flexibility with respect to the tubular member 46 as they are moved thereover. The upper collar 48 of spring section 34 is located in its upper position by a stop ring 81 (FIG. 4E) while the upper collar of the lower spring section 35 is located in its upper position by means of a similar stop ring 82 shown in FIGS. 1A, 1B and 3.

The upper collar 48 of each spring section has spacedapart threaded sections 83 fior connection with and movement over the coarse threads 52 on tubular member 46.

Spacer.

As shown in the broken Thus, as previously described, the urging of the springs 47 against the well bore will at least hold the collar 48 against rotation with the tubular member 46 whereby the latter may be rotated with the drill stem to move the spring downwardly irom the position of FIGS. 1B, 4B and 4 F to the position of FIG. 2. As best shown in FIGS, 4E and 4F, the tubular member 46 includes upper and lower sections intermediate valve part 41 and coupling 50 which are axially aligned with one another and the bore through the remainder of the tester housing.

As previously described, the portion 53 of the tubular member is bent radially away from the afiace 45 of the pad so that when the lower ends of the springs 47 move with the collar 49 onto the bent portion 53 of the tubular member, the springs will urge the pad cfiace oppositely firorn the direction of the bend. During this downward movement of the spring sections, the lower collar 49 will slide over the gradually bending portion of the tubular member 46 until it reaches approximately the position of groove 84 on the outer side of the bent portion. When the inner curved side of the collar 49 is disposed opposite to this groove, the spring has been moved to a position to provide its maximum urging effect upon the pad tiaoe 45. The groove 84 thereby permits the operator to locate each spring section in its optimum position, and rfurther tends to hold the spring assembly in such position because, assuming the spring section has moved this far, the upper threaded section 83 of the collar 48 has disengaged from the threads 52 on the tubular member 46'.

On the other hand, the pad ffiace 45 may become sealed against the formation before the spring assembly reaches this position. In fact, neither spring assembly may reach this maximum posit-ion prior to sealing of the pad (face. Still further, one spring assembly may have moved downwardly a distance further than the other, particularly in the event that the pad seals against a iormation surface which is angled with respect to the vertical. This would occur, [for example, in the event the springs 47 of one assembly slipped more than the other, because the springs 47 will not remain absolutely stationary as the tubular member 46 is rotated with respect thereto.

In any event, however, rotation of the tubular member 46 can be continued in order to release the upper collar 48 of each assembly from threaded engagement with the tubular member 46. Thus, as previously described, when the test sample has been taken, and the tester is to be removed from the well bore, raising of the drill stem 27 will lifit the tubular member 46 within the

collars

48 and 49 to permit the lower collar 49 to move downwardly over the lower side of bent portion 53 and into the posi tion shown in FIG. 3. At this time the entire tester is again centered because the lower collar is disposed over a section of tubular member 46 which is axially aligned with respect to the remainder of the tester housing bore. As previously mentioned, in this lower pulling position, the collars 48 will be located by engagement with ring 34a in the case of the upper spring section 34, and the ring 35a in the case of upper spring section 35.

As previously mentioned, the outer body 44 of the pad is held against rotation with respect to the tubular member 46. The bent portions 53 in tubular member 46 are assembled in diametrically opposed relationship thereto by means of aligning parts on the

couplings

50 and 51 where they connect with opposite ends of the tubular member 46 on which pad body 44 is carried as well as the sections of the tubular member on which the upper.

make-up with the threaded socket of the coupling. 1111 order that the sections of tubular member 46 above and below the pad may be interchangeable for use with either the upper or lower spring section, they are provided with aligning recesses 85 at each opposite end.

As shown in FIGS. 4G, 4H and 7, the face 45 of the pad is disposed on a radially enlarged portion of the body 44 and is covered with a sheet 88 of vulcanized rubber or the like curved to fit as closely as possible with the face of the formation F. As previously described, my invention contemplates that this area of the tester sealably engageable with the formation may be of large extent so as to permit the use of a large opening to provide a maximum of flow of the formation fluid into the tester housing. For this purpose, the opening through the tester face comprises a slot 87 extending vertically thereof and covered with a perforated screen 89. As shown, the outer face of the screen is recessed slightly with respect to the cover 88 on the pad face.

As shown in FIG. 46, the tubular member 46 is provided with a threaded opening to receive a plug 90 having an L-shaped opening 90a therethrough to connect the slot 87 with the bore of the tester housing. More particularly, the plug is made up within the opening in the tubular member to abut at its inner end with the opposite side of the bore and to project outwardly on its outer end 90b within the slot 87. As shown in FIG. 7, this outwardly projecting end of the plug 90 is received fairly closely within the slot 87 to prevent any substantial rotation of the pad body 44 with respect to the tubular member 46.

As shown in FIG. 46, the hollow plug 90 is disposed toward the lower end of slot 87 when the tubular member 46 is in its lowermost position with respect to the pad body 44. Thus, the plug 90 is free to move upwardly with respect to the sealed pad in order to reflect the buoyancy effect of the formation fluid within the drill stem. More particularly, the slot 87 is of at least substantially the same length as the spacing between the lower end 92 of the pad body and the upper end 93 of coupling 51. In the lowermost position of the tubular member 46 with respect to the pad, the underside 94 of coupling 50 rests upon the upper end of pa-d body 44 so as to locate the remainder of the tester vertically within the well bore.

The pad body 44 is preferably made up of threadedly connected

sections

44a, 44b and 440 which enable packing 95 to be assembled thereabout for sealably engaging the tubular member 46 above and below the slot 87 and the hollow plug 90 in any relative vertical position of the tubular member 46 and the pad.

From the foregoing it will be seen that this invention is one Well adapted to attain all of the ends and objects herein-above set forth, together with other advantages which are obvious and which are inherent to the method and apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth and shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1s:

1. A formation tester, comprising a pad having a face sealably engagea'ble against a formation on the side of a well bore; and a tubular housing connectable at its upper end to a drill string and carrying the pad for movernent with respect thereto to permit the housing to reciprocate when the pad is sealed against the formation, said pad face and housing having means therein to fluidly connect the well bore with the interior of said housing as said housing and pad are lowered into the bore and to fluidly connect the formation with the interior of said housing when said pad face is sealably engaged against the formation.

2. A formation tester, comprising a tubular housing connectable at its upper end to a drill string; a pad surrounding the tubular housing for axial reciprocation with respect thereto when a face of the pad is sealed against the formation, said pad face having an opening therein fluidly connecting with an opening in the housing as said pad and housing are lowered into the well bore as well as when said pad is sealably engaged against the formation; and means sealing between the pad and housing above and below said openings.

3. A formation tester as in claim 2 wherein said pad opening is a vertical slot and the housing opening is formed in a hollow plug carried by the housing for guided reciprocation in the slot.

4. A formation tester, comprising a tubular housing adapted to be connected to the lower end of a drill string; a pad carried by the housing and having a face with an opening therethrough to receive fluid from the well bore as said pad face and housing are lowered into the well bore and being .sealably engageable with a formation on the side wall of a well bore to receive formation fluid therefrom into the housing; and means for maintaining the pad face spaced from the side wall of the well bore as it is lowered therein and urging it against said side wall of the bore when said face is adjacent the formation, said housing being vertically reciprocable with respect to the pad while the face thereof is urged against and sealed with respect to said formation to indicate changes in the vertical force on the housing due to the formation fluid therein.

5. A formation tester, comprising a tubular housing having separate slidably connected upper and lower ends, means on the upper end connectable to a drill string; a pad carried by the lower end and having a face sealably engageable against a formation on the side of the well bore to fluidly connect said formation with the interior of said housing; and means connecting the upper and lower housing ends for rotation with one another to permit the pad to rotate with the drill string and also connecting the upper and lower housing ends for movement relative to one another to permit manipulation of the drill string with respect to the pad. when said pad is so engaged against the formation.

6. A formation tester, comprising a tubular housing having separate slidably connected upper and lower ends, means on the upper end connectable to a drill string; and a pad carried by the lower end and having a face sealably engageable against a formation on the side of the well bore to fluidly connect said formation with the interior of :said housing, said upper and lower housing ends being vertically reciprocable with respect to one another and having oppositely disposed faces for jarring upon said reciprocation.

'7. A formation tester, comprising a tubular housing having separate upper and lower ends, means on the upper end connectable to a drill string; and a pad carried by the lower end of the housing and having a face sealably engageable against a formation on the :side of the well bore to fluidly connect said formation with the interior of said housing, said housing including a clutch selectively operable to engage the lower housing end with the upper housing end for rotation therewith and to disengage said upper end from said lower end for rotation relative thereto while said pad is engaged.

8. A formation tester of the character defined in claim '7, including means for urging the pad face against the formation in response to rotation of said lower housing end with said upper housing end.

9. A formation tester of the character defined in claim 7, wherein said clutch includes parts on the upper and lower 'housing ends which are separate and vertically reciprocable with respect to one another between engaged and disengaged positions.

10. A formation tester, comprising a tubular housing connectable at its upper end to a drill string; a pad carried by the housing and having a face sealably engageable with a formation on the side wall of the well bore to fluidly connect said formation with the interior of the housing; and means including at least one spring assembly carried by the housing to maintain the pad face out of engagement with the side wall of the well bore as it is lowered therein and operable upon rotation of said housing to urge said pad face against the formation on the side wall of the well bore as said pad is held opposite thereto.

11. A formation tester, comprising a tubular housing connectable at its upper end to a drill string; a pad carried by the housing for vertical reciprocation with respect thereto when -a face of the pad is sealably engaged with a formation on the side wall of the well bore; and means including a pair of spring assemblies about the housing above and below the pad, respectively, to maintain the pad face out of engagement with the side wall of the Well bore as it is lowered therein and responsive to rotation of the housing to urge said pad face against the formation without vertical movement of said pad.

12. A formation tester, comprising a tubular housing connectable to the lower end of a drill string; a pad car- 'ried on the housing and having a face sealably engageable with a formation on the side of the well bore to fluidly connect said formation with the interior of the housing, said housing having separate parts which are connected to one another for relative movement with respect to one another and valve means which is normally closed and adapted to be opened in responseto said relative movement of said parts; and means preventing said relative' movement until the pressure of fluid on the exterior of said housing is a predetermined amount greater than that of the fluid within said housing, said last-mentioned means being operable, when the fluid pressure on the exterior of said housing reaches said predetermined amount greater than the fluid pressure within the housing, to permit said relative movement of said housing parts.

13. A formation tester, comprising a tubular housing having an upper end connectable to the lower end of a drill string and a lower end threadedly connected to the upper end for longitudinal movement with respect there to; a pad carried on the housing and having a face sealablyengageable with a formation on the side of the Well bore to fluidly connect said formation with the interior of said housing; valve means in the housing adapted to be opened in response to said longitudinal movement between the upper and lower ends thereof; and means preventing longitudinal movement of the upper housing end with respect to the lower housing end until the pressure of fluid outsideof the housing is greater to a predetermined extent than that within the housing, and operable, when the fluid pressure outside of the housing is greater by a predetermined extent than the fluid pressure within the housing, to permit said longitudinal movement between the upper and lower ends of the housing.

14. A formation tester, comprising a tubular housing connectable at its upper end to a drill string; a pad carried on the housing and having a face sealably engage- :able with a formation on the side of the well bore to fluidly connect said formation with the interior of said housing; means responsive to" initial rotation of the hous ing in one direction for urging the pad face against the formation; valve means for communicating the interior and exterior of said housing; and means for locking the valve means in closed position during said initial rotation and until the formation fluidly connects with the interior of the housing and then unlocking said valve means for opening in response to further rotation of the upper end of said housing in said one direction.

15. A formation tester of the character defined in claim 14, wherein the lower end of the housing is separate from the upper end and said urging means and valve means are located on the lower end of the housing, and there is a clutch between the upper and lower housing ends for engaging and disengaging them for rotation with one another in response to vertical reciprocation therebetween.

16. In a formation testing tool, a tubular member having an intermediate portion carrying a pad having a face for engagement with a formation on the side of a Well bore, said member having a pair of sections on one end of the intermediate portion which are at least substantially axially aligned with the intermediate portion, said member also being bent between said sections in a direction radially opposite said pad face; a spring assembly about the member for resiliently engaging the side wall of the well bore and adapted to surround one of said sections of the tubular member to maintain the pad face out of engagement with the side wall of the well bore as it is lowered therein; and means on the spring assembly threadedly connected to the tubular member for moving a portion of said spring assembly Over the bent portion, upon rotation of said member relative to said string assembly, to thereby urge said pad face toward the side of the well bore.

17. In a testing tool of the character defined in claim 16, wherein the assembly includes a collar at each upper and lower end of bowed springs for surrounding said sections of the tubular member, one such collar being threadedly connected to said member to move the other collar over the bent portion.

18. In a testing tool of the character defined in claim 16, wherein the spring assembly threadedly disconnects from the tubular member when the portion thereof moves over said bent portion, whereby said portion is slidable about the other section on one end of the tubular member upon reciprocation of said member relative thereto to return the spring assembly to a position for maintaining the pad face out of engagement with the well bore.

19. In a testing tool, a tubular member disposable in a drill string and including a pair of separate telescopically related tubular sections, each section having an opening aligned with an opening in the other section in one relative position of the sections; a piston moveable within said openings for reciprocation between a first position connecting the sections for movement together and a second position releasing the sections for movement from said one relative position to another relative position, said sections having ports therein positionable for fluidly connecting the interior and exterior of said tubular member with one another when in said another relative position; and means sealing between said sections to prevent such fluid connection through said ports in said one relative position of the sections.

20. In a testing tool of the character defined in claim 19, wherein there are two ports in one tubular section sequentially fluidly connectable to a single port in the other tubular section, the first port in said one section to be fluidly connected being smaller than the second port.

21. In the testing tool of claim 19, including deformable means on the piston engageable with one of said openings to resist movement of the piston to its second position.

22. In the testing tool of claim 19, including a shear pin connecting the sections in their one relative position to prevent the piston from moving from its first position in a direction away from its second position.

23. In a method of obtaining fluid from a well formation, comprising the steps of lowering a pad on a drill stem into the Well bore while permitting well fluid to flow upwardly therein; displacing the well fluid in the stem with a lighter fluid to reduce the hydrostatic head of the Well fluid within the stem to below that of the fluid in the formation and locating the pad in a position adjacent the formation; urging a face of the pad into sealing engagement 15 against the formation; and then reducing the pressure on side lighter fluid above the well fluid within the stem to permit formation fluid to flow upwardly through said stem.

24. A method of the character defined in claim 23 including the further steps of communicating the interior and exterior of the stem to equalize the pressure across the stem to permit the pad face to be raised from engagement with the formation after a desired quantity of formation fluid has been obtained.

25. A method of the character defined in claim 23, including the steps of first lowering the pad to a position beneath the formation prior to displacement of well fluid from within the stem; and then raising the pad to a position adjacent said formation after such displacement and prior to urging the pad face into sealing engagement with said formation.

26. A method of the character defined in claim 23, including the steps of maintaining the pad face out of sealing engagement with the well bore until it is located adjacent the formation; and then urging the pad face against the bore without moving it vertically from its position adjacent the formation.

27. In a method of obtaining fluid from a well formation, comprising the steps of lowering a pad on a drill stern into the Well bore and locating it in a position adjacent the formation; simultaneously rotating the stem and pad and urging the face of the pad into sealing engagement with the formation in order to obtain fluid therefrom; and then freeing the stem for movement with respect to the pad when said pad face is sealed against the formation.

28. In a method of obtaining fluid from a well formation, comprising the steps of lowering a pad on a drill stem into the well bore and locating it in a position adjacent the formation; urging the face of the pad into sealing engagement with the formation for receiving fluid therefrom into the stem; and locating the stem relative to the pad so that it may move vertically upwardly with respect thereto, whereby the change in the buoyant effect of the formation fluid on the stem as said fluid is received therein may be observed and compensated for to prevent the pad face from being disengaged from the formation.

29. A formation tester, comprising a pad having a face sealably engageable against a formation on the side of a Well bore; a tubular housing connectable at its upper end to a drill string and carrying the pad for movement with respect thereto to permit the housing to reciprocate vertically when the pad is sealed against the formation, said pad and housing having means therein to fluidly connect the well how with the interior of said housing as said housing and pad are lowered into the well here and to fluidly connect the formation with the interior of said housing when said pad face is sealably engaged against the formation, and means on the tester for moving the pad into sealing engagement with the formation.

30. A formation tester, comprising a tubular housing having separate slida-bly connected upper and lower ends, means on the upper end connectable to a drill string; a pad carried by the lower end and having a face sealably engageable against a formation on the side of the well bore to fluidly connect said formation with the interior of said housing; means connecting the upper and lower housing ends for rotation with one another to permit the pad to rotate with the drill string and movement of said upper and lower housing ends relative to one another to permit manipulation of the drill string with respect to the pad when said pad is so engaged against the formation, and means on the tester for moving the pad face into sealing engagement with the formation.

31. A formation tester, comprising a tubular housing having separate slidably connected upper and lower ends, means on the upper end connectable to a drill string; a pad carried by the lower end and having a face sealably engageable against a formation on the side of the well bore to fluidly connect said formation with the interior of said housing, said upper and lower housing ends being vertically reciprocable with respect to one another and having oppositely disposed faces for jarring upon said reciprocation, and means on the tester for moving the pad into sealing engagement with the formation.

32. A formation tester, comprising a tubular housing having separate upper and lower ends, means on the upper end connectable to a drill string; a pad carried by the lower end of the housing and having a face sealably engageable against a formation on the side of the well bore to fluidly connect said formation with the interior of said housing, said housing including a clutch selectively operable to engage the lower housing end with the upper housing end for rotation therewith and to disengage said upper end from said lower end for rotation relative thereto while said pad is engaged, and means for moving the pad into sealing engagement with the formation.

33. A formation tester, comprising a tubular housing connectable at its upper end to a drill string, a pad carried by the housing and having a face sealably engageable with a formation of the side wall of the well bore to fluidly connect said formation with the interior of the housing, and means on the housing for maintaining the pad face out of engagement with the side wall of the well bore as it is lowered therein and operable in response to rotation of said housing to urge said pad face against the formation on the side wall of the bore as said pad is held opposite thereto.

34. In a method of obtaining fluid from a well formation, comprising the steps of lowering the pad on a drill stem into the well bore and locating it in a position adjacent to the formation, rotating the stem to urge the face of the pad into sealing engagement with the formation in order to obtain fluid therefrom, and then freeing the stern for movement with respect to the pad when said pad face is sealed against the formation.

35. In a method of obtaining fluid from a Well formation, comprising the steps of lowering a pad on a drill stem into the well bore and locating it in a position adjacent the formation, urging the face of the pad into sealing engagement the formation for receiving fluid therefrom into the stem, locating the stem in relation to the pad so that it may move vertically upwardly with respect to the pad in response to the change in the buoyant elfect of the formation fluid on the stem as the fluid is received therein, and lowering the upper end of the stem to compensate for the buoyant effect to prevent the pad face from being disengaged from the formation.

References Cited by the Examiner UNITED STATES PATENTS 2,262,655 'l1/41' Seale l66-l00 2,688,369 9/54 -Br0yles 166l00 2,892,501 6/59 Boller 166-l00 2,905,247 9/59 Vestermark 166-l00 2,935,133 5/60 Eckel et a1 1664 XR 2,947,361 8/ Hyde 166100 3,104,7'12 9/63 Whitten 16634 XR CHARLES E, OCONNELL, Primary Examiner.

Claims

34. IN A METHOD OF OBTAINING FLUID FROM A WELL FORMATION, COMPRISING THE STEPS OF LOWERING THE PAD ON A DRILL STEM INTO THE WELL BORE AND LOCATING IT IN A POSITION ADJACENT TO THE FORMATION, ROTATION THE STEM TO URGE THE FACE OF THE PAD INTO SEALING ENGAGMENT WITH THE FORMATION IN ORDER TO OBTAIN FLUID THEREFROM, AND THER FREEING THE STEM FOR MOVEMENT WITH RESPECT TO THE PAD WHEN SAID PAD FACE IS SEALED AGAINST THE FORMATION.