US3331441A - Well screen and method for making same - Google Patents

Description

July 18, 1967 5. R. SWEENEY WELL SCREEN AND METHOD FOR MAKING SAME Filed March 5, 1965 INVENTOR. J4MR SWEENG'Y BY I a ,q/s flTTOE/VGYS United States Patent assignor to Eixby- Galesburg, 11]., a

This invention relates to a well screen of the type comprising parallel wire elements defining axially extending slots for the transmission of a fluid, and more particularly to a well screen having an enhanced torsional strength and to the method of producing the same.

A preferred type of well screen construction employs a tubular array of spaced and parallel wire elements assembled between end fittings and defining axially extending slots for the transmission of fluid through the screen. This construction is desirable for the reason that the screen can be forcefully inserted into a water bearing formation and, as the screen is driven into position, the screen moves axially through the formation, whereby the formation wipes and cleans the slots so as to prevent clogging of the slots. Frequently, however, the screen is inserted with a twisting driving motion such that the wire elements are subjected to a torsional load as the screen is inserted into the water bearing formation.

An object of the present invention is to provide an improved well screen of the type having axially parallel wire elements defining slots therebetween and characterized by an enhanced torsional strength.

Another object of the present invention is to provide a well screen having an enhanced resistance to torsional and radial loading Without increase to the cost or weight thereof.

Still another object of the present invention is to provide a new and improved method for constructing well screens.

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

In the drawings:

FIGURE 1 is a fragmentary perspective view of a well screen embodying the present invention.

FIGURE 2 is a fragmentary perspective view, with a portion broken away, illustrating a modification and further illustrating in exploded detail end fittings for the modification.

Referring to the drawings in greater detail, a preferred embodiment of the present invention is illustrated in FIG- URE 1. This embodiment includes a tubular array of axially parallel linear wire elements 12, each having a triangular cross sectional shape as illustrated at 13. The tubular array of wire elements 12 is divided into quadrants by four axially extending support elements 18. The several support elements are constructed of a flat bar stock and have a radial penetration into the cavity defined by the tubular array of wire elements 12 which substantially exceeds the penetration by the individual wire elements 12.

The support elements 13 are notched at each end thereof, as shown at 20, for attachment to suitable end fittings as will be described subsequently. These support elements, being substantially stronger than the wire elements 12, transmit axial loading between the end fittings for the screen and thereby shield the individual wire elements 12 from such loading.

In the preferred construction the individual wire elements 12 are equally spaced between the support elements and the wire elements adjacent said support elements are spaced a distance from the adjacent support elements Patented July 18, 1967 equal to the spacing between adjacent wire elements. Thus, the assembly of wire elements 12 and support elements defines a tubular array having a plurality of axially extending slots, each of equal width, spaced about the periphery of said array.

In this first embodiment, the shape of the screen and the spacing between the individual wire elements 12 and support elements 18 thereof is fixed by means of annular weld ribbons 14. Each ribbon 14 encircles the screen, contacting and being fused to each of the wire elements and support elements of the screen. The ribbons 14 each occupy a plane which is perpendicular to the axis of the screen and are spaced distances materially greater than the separation between adjacent wire elements 12.

The screen illustrated in FIGURE 1 has been broken oif at one end to indicate that the screen may have an indefinite length and therefore may have an indefinite number of weld ribbons 14.

A well screen having axially extending wire elements assembled in quadrants defined by axially extending support elements and secured by annular weld ribbons occupying planes perpendicular to the axis of the screen is known to be old in the art. A difliculty encountered with screens of such construction results from the fact that the screens are frequently inserted into a water bearing formation by advancing the screen axially into the formation and at the same time twisting the screen about its own axis. This subjects the individual wire elements 12 to a torsional loading inducing bending movements of the wire elements between the securing weld ribbons. In the past, the possibility of distortion of the wire elements 12 due to such twisting movements has been reduced by increasing the number of annular weld ribbons employed in the screen so as to decrease the axial separation between the weld ribbons.

This, of course, increases the cost of the screen, especially the labor cost, and more importantly increases the possibility of clogging as the screen is inserted into the water bearing formation. Thus, each weld ribbon represents a barrier to a relative axial flow of earth along the slots between wire elements. The smaller the separation between the annular weld ribbons, the greater the possibility of clogging by a build-up of earth at the margins on the weld ribbons. Where the weld ribbons are too close together, the build-up of earth at the advancing margins of the annular weld ribbons can sometimes bridge the gap between adjacent weld ribbons with the result that blocking of the screen openings will seriously impair the operating efficiency of the screen.

With the present invention the foregoing problems are relieved by adding a plurality of helical ribbon portions 16 to the screen. Each ribbon portion 16 is preferably continuous along the length of the screen but does not necessarily contact all wire elements 12 in the screen, since, depending upon the screen length, a full convolution about the screen may not be executed by any of the helical portions.

FIGURE 1 illustrates four helical ribbon portions 16a, 16b, 16c and 16d coiled about the screen, the ribbon portions being spaced at intervals about the periphery of the screen. Obviously, if the screen length is less than the axial separation between adjacent convolutions in each ribbon portion 16, no one ribbon portion Will fully encircle the screen so as to contact all wire elements 12 in the screen. On the other hand, whenever the screen length exceeds one quarter of the pitch between adjacent convolutions, the four ribbon portions 16, taken collectively, will contact and thereby support all wire elements in the screen. Ordinarily at least two axially spaced points of torsional support for each wire element are desired and, accordingly, it is preferred that the screen length exceeds one half the pitch between adjacent convolutions of the helically coiled ribbon portions Where four helical portions are employed as shown.

in the use of the screen the helical ribbon portions are subjected to tension or compression loading depending upon the direction of twist applied to the well screen as it is driven into the water bearing formation. In either case, it is found that the helical ribbon portions function ethciently to transmit the torsional loading directly to the fittings at the end of the well screen and to relieve the individual wire elements 12 from excess torsional loading.

At first glance it may appear that the helical ribbon portions offer little advantage, if any, over an increase in the number of the annular weld ribbons 14. Thus, it would appear that the helical weld ribbons increase the number of points of interference to an axial flow of earth past the screen in the same fashion as would additional annular weld ribbons. However, in the practice of the present invention it is found that the helical weld ribbons, in addition to providing an enhanced torsional support, also contribute to the rigidity of the screen under radial loading with the result that the number of annular weld ribbons ltd can be reduced. Thus, the use of a number of helical weld ribbons, as shown, permits a proportionate reduction in the number of annular weld ribbons 14 with the result that the total number of weld ribbons need not increase although, nevertheless, an improved screen is produced. The number of helical ribbon portions and annular weld ribbons and the spacing therebetween is varied depending upon the nature of the water bearing formation into which the screen is to be inserted, the depth of the insertion, and the loads to which the screen will be subjected during use after the insertion.

Where a structural reinforcement greater than that achieved in the embodiment of FIGURE 1 is required, further reinforcement may be employed in the manner illustrated in the modification of FIGURE 2. In this modification, annular weld ribbons 14 and helical ribbon portions 16 are utilized as in the preceding embodiment. These weld ribbons are supplemented in the modification by additional helical ribbon portions 22 coiled oppositely to the helical ribbon portions 16.

The reinforcement of the screen is further supplemented by means of interior weld ribbons underlying the weld ribbons deposited on the outer periphery. Thus, annular weld ribbons 24 underlie corresponding weld ribbons 14 in the outer periphery. Also helical ribbon portions 26 underlie corresponding helical ribbon portions 16 in the outer periphery and oppositely coiled helical ribbon portions 28 underlie corresponding helical ribbon portions 22 in the outer periphery. The several interior ribbons 24, 26 and 28 are each continuous through quadrants and are interrupted only by the inwardly projecting support elements it, against which they terminate.

In addition to illustrating a screen having increased reinforcement, FIGURE 2 also illustrate representative end fittings suitable for well screens of the type described herein. The fitting 30 is a conical driving point which is used to lead the advance of the well screen into the water bearing formation. This fitting has a rearward projection 32 adapted to fit inside the tubular well screen and engage in the notches 20 formed in the support elements 18 of the well screen. The point 36 is welded in place by depositing a weld ribbon around the interface between the point and the wire elements 12. With such construction it will be noted that the driving point 30 shields the forward ends of the wire elements 12, as the well screen is driven into the water bearing formation.

The fitting 34 in an adapter which adapts the rearward end of the well screen for attachment to a standard well casing. To this end, one end 33 of the fitting 34 is threaded for engagement to a well casing. The other end of the fitting 34- has a projection 36 of reduced diameter adapted to fit into the rearward end of the well screen. The projection 36 also seats against suitable notches in the support elements 18, the notches being similar to the notches 20 previously described.

The projection 36 is also welded in place by depositing a weld ribbon at the interface between the rearward ends of the wire elements 12 and the fitting 34.

In view of the substantially increased reinforcement of the FIGURE 2 modification as compared to the FIGURE 1 embodiment, it will be apparent to those skilled in the art that, depending upon the loading to which the well screen will be subjected in use, the axial separation between the several weld ribbons illustrated in FIGURE 2 might be substantially increased. Thus, under similar loading conditions the axial separation between the several weld ribbons used in the FIGURE 2 modification can be much greater than the separation required in the FIGURE 1 embodiment.

Although the preferred embodiments of the device and method have been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described my invention, I claim:

1. In a well screen, a plurality of linear wire elements and means supporting said wire elements in a tubular array wherein said wire elements extend parallel to the longitudinal axis of said array and cooperate to define elongated axially extended slots in the outer surface of said array, said supporting means including a first fitting disposed at one end of said array and adapted for attachment to a Well pipe and a second fitting disposed at the opposite end of said array, a portion of said wire elements having an extended thickness in the direction normal to the outer surface of said array, the ends of said portion of wire elements being fixedly attached to said first and second fittings, and a plurality of weld portions extending helically about said array and fixed to all wire elements of said array, said weld portions being spaced axially one from the other a distance exceeding the spacing between adjacent wire elements in said array.

2. In a well screen, the assembly according to claim 1 wherein said plurality of weld portions comprise at least one continuous weld ribbon executing at least one full revolution about said array.

References Cited UNITED STATES PATENTS 8/1906 Cook 166-234 3/1932 Lange 166-234

Claims (1)

1. IN A WELL SCREEN, A PLURALITY OF LINEAR WIRE ELEMENTS AND MEANS SUPPORTING SAID WIRE ELEMENTS IN A TUBULAR ARRAY WHEREIN SAID WIRE ELEMENTS EXTEND PARALLEL TO THE LONGITUDINAL AXIS OF SAID ARRAY AND COOPERATE TO DEFINE ELONGATED AXIALLY EXTEND SLOTS IN THE OUTER SURFACE OF SAID ARRAY, SAID SUPPORTING MEANS INCLUDING A FIRST FITTING DISPOSED AT ONE END OF SAID ARRAY AND ADAPTED FOR ATTACHMENT TO A WELL PIPE AND A SECOND FITTING DISPOSED AT THE OPPOSITE END OF SAID ARRAY, A PORTION OF SAID WIRE ELEMENTS HAVING AN EXTENDED THICKNESS IN THE DIRECTION NORMAL TO THE OUTER SURFACE OF SAID ARRAY, THE ENDS OF SAID PORTION OF WIRE ELEMENTS BEING FIXEDLY ATTACHED TO SAID FIRST AND SECOND FITTINGS, AND A PLURALITY OF WELD PORTIONS EXTENDING HELICALLY ABOUT SAID ARRAY AND FIXED TO ALL WIRE ELEMENTS OF SAID ARRAY, SAID WELD PORTIONS BEING SPACED AXIALLY ONE FROM THE OTHER A DISTANCE EXCEEDING THE SPACING BETWEEN ADJACENT WIRE ELEMENTS IN SAID ARRAY.

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