FEATURE

Technical Field

The present invention relates generally to thread forms of the type used for tubular connections, and, more specifically, to threaded connections of the type used for securing flow conduits to form a desired continuous flow path in oil and gas country tubular goods.

Description of the Prior Art

A variety of threaded connections are known in the prior art for joining flow conduits in an end-to-end relationship to form a continuous flow path for transporting fluid. For example, such threaded connections are used in pipe strings employed in the oil and gas industry for the production of hydrocarbons and other forms of energy from subsurface earth formations. Examples of such pipe strings indude drill pipe, well casing and production tubing, known commonly as "oil country tubular goods ^* (OCTG). While OCTG’s are foe primary intended use for the threaded connections of the invention, other applications for the threaded connections of foe invention indude other earth drilling and completion applications, for example, horizontal/trench less drilling operations or non-oilfield applications associated with the construction industry. All of throe type goods employ threaded connections of the type under consideration for conneding adjacent conduit sections or pipe joints. in the case of oil field casing and tubing, it is a common practice to use metal pipes of a definite length, with sections of pipe joined to form a string. The string of pipe effectively creates one lengthier pipe, intended to provide a means to reach the depth at which foe reservoirs of gas or oil are found In order for extraction to the surface. The pipe sections are secured together at their ends by an externally threaded connector, or "pin" that is threadedly received within an internally threaded connector or "box". Each pipe section has a pin on one pipe rod and a box at foe opposite pipe rod. Some pipe has an internally threaded coupling secured to one end of a double pin pipe section to produce foe box. The individual pipe sections are frequently referred to as a "pipe joint”. Tubing and casing pipe joints are usually 30 ft. in length but can vary in length from 20 ft. to 40 ft. or longer.

The various pipe strings used in constructing a well are usually assembled on fee floor of a drilling or workover rig. The pipe string is lengthened and lowered into fee well as succeeding pipe joints are added to fee string. During this assembly procedure, the pipe joint being added to fee string is lowered, pin down or pin up, into an upwardly or downwardly facing box projecting from fee drilling rig floor. This procedure is commonly referred to as "stabbing" the pin into fee box. After being stabbed, fee added pipe joint is rotated to engage the threads of the pin and box, securing the joint to the string. The process is basically reversed in or to disassemble the pipe string. Once free of the box, the removed joint is moved to a storage location.

There have been numerous advances in thread technology of the type under consideration in recent years. The so-called “premium threaded connections* are widely known and well used in the oil and gas industries. These threads, such as by way of example the wedge thread, the dovetail thread, fee multifaceted thread and others, provide an unusually strong connection, while controlling the stress and strain in the connected pin and box members of the connection. Some of these connections have included a gas resistant thread seal feature capable of withstanding the extreme conditions encountered in the oil and gas well environment. These structures will be referred to as “sealing threads” in the discussion which follows. In some cases, fee gas seal feature was a metal-to-metai seal region incorporated into fee pin and box members. Metal-to-metal seals of this general type are discussed, for example, in U.S. Patent No. 6,254,146, issued July 3, 2001 , to Kris L. Church and in U.S. Patent No. 6,832,789, issued to Kris L. Church. Other sealing threads of a simpler nature are known. For example, fee traditional “API 8 Round Thread’' is a “thread fit ^* seal which is screwed together wife pipe dope to provide the sealing capability. Despite the improvements in connection design discussed above, a need continues to exist for a threaded connection which is capable of coupling tubular pipe sections quickly and efficiently, which forms a secure connection, and which is economical to produce. A need also exists for such a threaded connection which provides a more versatile design than existing designs and which achieves different purposes depending on the «id application, such as providing a grain size filtering function for the connection. A need also exists for such a thread form which is extremely easy to machine versus other known threaded connections in the industry.

A need also exists for an improved connection design for the coupling of tubular pipe sections that allows machining using an advantageous feed rate using different cutting tool geometry in the machining operation to thereby achieve an improved overall production rate.

Disclosure of the Invention

The present invention has as its object to provide a further modification of the basic threaded connection design features discussed above which provides improved design characteristics and performance over the prior art and which meets the variously enumerated needs of the prior art discussed above.

A special feature of the present invention is a special machined surface adjacent the primary thread region of the pin and box members which serves as a "grain sizing feature" in actual use of the threaded connection in a pipe string. The "grain sizing filter” region is designed to filter unwanted and harmful particles, as will be more fully described. It is designed to fitter out unwanted particles, for a possible example, those with grain sizes 0.002 inch and greater.

One special performance consideration of the filter region of the threaded connection is that it is not intended or required to be a commonly used as a fluid or gas pressure resistant seal in the oil country tubular goods field of use. The purpose of the filter is strictly to eliminate the migration of unwanted and harmful particles beyond the outer lip of the box member of the connection but not to necessarily eliminate foe pressure flow from one side of foe filter to the other. in one preferred form , the thread form of the invention is intended for use in a tubular connection having a pin member adapted to be made up with a box member to form a pipe connection, foe pin member having an exterior surface, interior surface a longitudinal axis, and an end face adjacent a mouth opening thereof. The pin member has pin threads with thread crests and thread roots which are adapted to be made up with a mating box member having a complimentary thread structure to form a secure connection. The pin threads extend from the outer face of the pin member inwardly in a longitudinal direction generally parallel or on a taper to the longitudinal axis of foe pin member. The pin threads end at a thread run-out region on the exterior surface of the pin member which may or may not be close to the face of the pin.

A special filter region is formed beginning at the thread run-out region on the exterior surface of foe pin member which extends for a given length longitudinally further inward in a direction opposite to the pin threads. The filter region has a machined filter surface formed thereon which when mated with a mating filter surface of companion box member forms an unwanted and harmful solid particle resistant feature, keeping such particles or particulates from penetrating through the length of the filter region and reaching foe thread run-out region and ultimately foe pin threads. The filter region in a completed connection ads to prevent unwanted and harmful particles from penetrating the connedion and jacking the connedion apart due to connection ovality, especially during bending that occurs in typical completion operations.

The filter region is a special and uniquely designed machined surface or “finish” which constitutes a scalloped surface with alternating crests and valleys, as measured in a radial direction along the length of the connection. The valleys constitute a lower surface measured radially along the connection length. A peak on an opposite side of a selected valley defines a crest of the scalloped surface.

The mating box member which makes up the other part of the threaded connection also has a filter region which overlies foe pin filter region, as will be more fully described. Thus, the filter region on the box member also has a machined surface or finish with a scalloped surface with alternating crests and valleys. In some cases, the filter regions of the pin and box members are designed to have a predetermined amount of clearance between foe machined scalloped surfaces thereof. Just by way of example, the height between the valleys and crests of the scallop surface could range between about 0.0004 and 0.0009 of an inch. With these type specified combined pin and box dimensions, he threaded connection of the invention is designed to filter out particles sized approximately 0.002 inch and greater and permits lessor sized particles to flow through.

The machined surface finish which makes up the filter region is machined using a given machined feed rate measured in inches or millimeters per revolution of he cutting tool being used. In a preferred example practice of he invention, the machine feed rate used to form the machine surface finish of the filter region is normally greater than approximately 0.004 inches per revolution, which is typical of liquid and gas sealing structures used in the industry. For example, in one trial run, he machine feed rate is 0.014 to 0.021 inches of feed per revolution. In another trial run, he machine feed rate is0.020 to 0.030 inches of feed per revolution. Specially designed tooling can increase he feed rates even further.

The machine feed rate determines, in part, a production rate for the connection being machined. For the above machine feed rates, the filter region of he threaded connection of he invention increases production on the order of 350 to 750 percent over he manufacture of a typical liquid or gas pressure seal. Specially designed tooling can increase production rates as high as 2000 percent.

Additional objects, features and advantages will be apparent from he written description which follows.

Brief Description of he Drawings

Figure 1 is a perspective view of he pin end of a tubular member employing the unwanted harmful particle resistant feature of he invention. Figure 2 is a side, quarter sectional view of he pin end of he tubular member of Figure 1 employing he thread form of he invention. Figure 3 is a quarter sectional view similar to Figure 2 of the coupling member of the connection, again showing the filter surface that is included as a part of the threaded connection. Figure 4 is a view of another pin end of a tubular member of the invention which employs a crown seal.

Figure 5 is a partial, sectional view showing one box and pin helical feed rate and one pressure direction affecting a completed connection.

Figure 6 is a view similar to Figure 5, but showing a different box and pin helical feed rate and pressure coming from a different direction.

Figure 7 is a side, quarter sectional view of toe pin end of a different thread style which also illustrates the pin helical particle resistant filter gap.

Description of the Preferred Embodiment

The present invention provides a unique type of threaded connection which meets the foregoing described objectives. Problems relating to the migration of particles of unwanted and harmful grain size beyond the outer lip of the box member are eliminated by a specially machined surface or finish on the pin and box members of the connection. This and other features of the improved threaded connection of the invention will be described herein and the various features and advantageous details thereof are explained more Hilly with reference to the non-limiting examples which are illustrated in toe accompanying drawings and detailed in the following description. Descriptions of well- known components and processes and manufacturing techniques are omitted so as to not unnecessarily obscure the workings of the invention. The examples used herein are intended merely to facilitate an understanding of ways in which the invention herein may be practiced and to further enable those of skill in toe art to practice toe invention. Accordingly, the examples should not be construed as limiting the scope of the claimed invention. The thread forms of the invention can be used for making a threaded pipe connection capable of being screwed together and subsequently unscrewed and are well adapted for use as Oil Country Tubular Goods (OCTG) connections. The thread forms are used on a connection which includes a pin member having external threads with stab flanks and load flanks and crests and roots for mating with the mating internal threads of a box member to make up a pipe connection. The threaded connections of the invention feature a unique "filter" region, which will be described in greater detail hereafter. The “filter* is a particle resistant feature that is designed to filter out unwanted and harmful particles which are sized to a particular grain size.

The filtering action of the connections of the invention will be described in the discussion which follows as a “grain sized" particle resistant feature where the grain sizes are described in the U.S. Corps of Engineers Soils Grain Size Chart, published by the Coastal Engineering Research Center, Kingman Building, Fort Be!voir, VA, 1980, reproduced below:

Using the above Soils Grain Size Chart, the filter regions of the threaded connections of the invention are designed to filter out silt, sand and gravel, white generally allowing clay and colloidal grain sizes to pass. In other words, with reference to the above chart, particles in toe size range from about 0.074mm or 0.002 inches are toe target particles under consideration.

It is important to point out that the “filter” feature of the threaded connections of toe invention is not required to be a commonly used as a fluid or gas resistant pressure seal in toe OCTG field of use. The purpose of toe filter is strictly to eliminate the migration of unwanted harmful particles beyond the outer lip of toe box member of the connection but not necessarily to eliminate toe pressure flow from erne side of the filter to toe other. It has been discovered through experimental analysis that toe buildup of material consisting of particles sized 0.002” and greater in the outer extents of a connector can induce stress raisers in the connector material during bending and rotation. This is particularly true in toe case of connections which are run into the tong reach, horizontally drilled sections of oil and gas wells drilled in shale rock formations. Analysis also suggests that pressure balance across the filter is beneficial in minimizing stress raisers.

One particular advantageous aspect of the invention is that fact that, since the "filter* is not defined as a seal, the filter surface can have a very high feed rate in the machining operation during the manufacture of the connections. It has been found that the machining rates can be significantly increased, thus lowering manufacturing costs. Normal feed rates for fluid and gas resistant pressure seals are approximately 0.004 inch per revolution. The "fifter" has a specification that is governed by feed rate range depending on the cutting tod geometry used. The feed rates specified create a scallop type surface. The lower surfer» of toe radius is toe valley and the peak on the opposite side of the valley is the crest. The height or distance between toe valleys and the crests of the scallop is calculated and in one application preferred to be between 0.0004 and 0.0009 of an inch to "filter" unwanted and harmful solid particles. This will filter any unwanted and harmful solids that otherwise might be able to penetrate through toe filter length, thereby exposing the threads and the annulus area to those particles. However, toe threads of toe connection can be designed to seal off smaller grain size particles, fluids and gasses from traversing through the rest of toe connection's length. Two examples of the required feed rates with different standard cutting tool radii taken from actual experimental runs are as follows: 1. With a 1/16-inch radius cutting tool, the feed rate could be 0.014 to .021 inch feed per revolution.

2. With a 1 /8-inch radius cutting tool toe feed rate could be .020 to 0.030 feed per revolution. However, as will be apparent to those skilled in toe relevant arts, the feed rates can have even preferred higher feed rates with special geometry tooling.

The feed rate range will enable the machinist to fine tune toe manufacturing process to produce the best finish for the different grades of OCTG material commonly used. As can be seen by just these two examples, production rates for the fitter area increase from 350 to 750 percent over toe manufacture of a typical liquid or gas pressure seal. This leads to a significant reduction in manufacturing cost and leads to lowering the cost of completing a horizontal oil and gas well.

Since toe primary purpose of the invention does not necessarily allow toe filter to be gas or fluid resistant to well pressures, this invention will likely be used in conjunction with some type of “thread seal.” In other words, a connection where the threads are screwed together tightly with pipe dope to provide the sealing action against liquid or gas pressures. Such a connection is described, for example, in issued U S. Patent No. 10,246,948, issued April 2, 2019, to A!aria et a!., at Column 2, lines 28 et seq. and at other places in the document. There are numerous other references to this type sealing action. It will also be appreciated by those skilled in the relevant arts that a special "premium thread" can be used in those situations where pressure must be kept from traversing through toe entire connection. This term is defined in toe Schlumberger Oilfield Glossary, On-Line Edition, 2019, as follows:

“A class of high-performance thread types that are commonly used in modem oil well and gas well completions. Premium threads are available in a number of configurations and are typically designed to provide superior hydraulic sealing, improved tensile capacity and ease of make-up. Unlike conventional threads, the sealing areas in premium diread connections are independent of the thread profile... ” Such threads are in common use in the OCTG trades and are thus available to take advantage of the additional benefits of toe filter feature of this invention.

Turning now to Figure 1 of the Drawings, there is shown a portion of the pin member of one of the threaded connections of toe invention, designated generally as 11. The pin member 11 has an exterior surface 13, an interior surface 15, a longitudinal axis 17, and an outer face 19 adjacent a mouth opening 21 thereof. The pin member 11 has a threaded region comprised of pin threads with thread crests and thread roots which are adapted to be made up with a mating box member having a complimentary thread structure to form a secure connection. The pin region is illustrated generally at 23 in Figure 1. The pin threaded region extends from toe outer face 19 of toe pin member in a direction away from toe face 19 in a longitudinal direction generally parallel to the longitudinal axis 17 of the pin member. The threaded region ends at a thread run-out region (generally at 25 in Figure 1) on the exterior surface 13 of the pin member. The special filter region begins at the thread run-out 25 and extends longitudinally cm the external surface of the pin member in a direction opposite the outer face 19 of the pin member.

The exact nature of the threaded region 23 will depend upon a number of factors including the exact end application for toe pipe string in question. However, the "filter" feature of the invention will work with any number of a different thread forms. These could range from toe more exotic "premium threaded connections* that will be familiar to those skilled in the relevant arts to simpler thread forms. In the exemplary drawings, toe thread region 23 is a standard "API 8~rd or API 8 Round” thread. This type thread will be readily familiar to those skilled in the present arts. The "8-rd* means 8-round or eight threads per inch and a slightly rounded profile. The profile can be a V or wedge-shape but slightly rounded at the crest and valleys of the threads. These type threads can be, for example, cut on a tapered profile, and made up until a prescribed torque is attained. However, at full makeup torque, the threads do not achieve a pressure seal, because toe threads do not meet in the base of each groove. However, the 8 round threads can be made to seal and prevent pressure leaks with the use of thread lubricant that fills the voids between the thread roots. The gap is very small and its length is quite long due to the number of turns at a pitch of eight per inch, so the lubricant forms an adequate seal in most cases. They may be referred to amply as a "sealing thread ^* in the literature.

Turning now to Figures 2 and 3 of the drawings, the “filter" aspect of foe threaded connections of the invention will now be described in greater detail with respect to foe quarter sectional view of foe pin member 11. Figure 3 of foe drawings is a similar quarter sectional view of foe box end which is adapted to be made up with the pin end shown in Figure 2 to form one of the threaded connections of the invention. The filter region of foe pin 27 is formed beginning at the thread run-out region 25 on the exterior surface of the pin member and extends for a given length longitudinally in a direction opposite to foe pin threads 23. The filter region 27 has a machined filter surface formed thereon which, when mated with a mating filter surface (29 in Figure 3) of a companion box member 12, forms an external solid particle resistant feature. This solid resistant feature filters out harmful and unwanted solid particles, keeping such particles from, in foe particular case shown, from penetrating through foe length of the filter region and reaching the thread run-out region and ultimately foe pin threads after foe connection has been made up. The areas needing to be filtered on the pin and box members are indicated as “A1” and “A2" in Figures 2 and 3, respectively.

Further detail of the API 8 Round thread form used to illustrate the principles of foe invention are shown in Figures 2 and 3. The pin thread crests 31, 33, and roots 35, 37, are shown, for example, in greater detail in Figure 2. The crests and roots of foe pin member 11 are adapted to be made up with a mating box member (illustrated as 12 in Figure 3), having a complimentary thread structure. The box end threads are essentially a mirror image of the pin «id. Thus, foe box thread crests (39 in Figure 3) are formed between a stab flank 41 and a load flank 43 of foe box thread. In the case shown, the thread crests of foe pin and box members are on an axis which is approximately parallel to the thread roots. As used herein, the term "toad flank" will be understood to designate that sidewall of a thread that faces away from foe outer end from foe respective male or female member on which foe thread is formed, and the term "stab flank" will be understood to refer to that sidewall surface that faces toward the outer end of the respective male or female member as the connection is made up.

With reference again to Figure 3, it will be appreciated that the filter region 29 is a machined surface finish comprising a scalloped surface with alternating crests and valleys, as measured in a radial direction along the length of the connection. For example one of the crests is illustrated in Figure 3 as 45 with one of the corresponding valleys being designated as 47. The valleys 47 constitute a lower surface measured radially along the connection length, while a peak on an opposite side of the valley defines a corresponding crest 45. The pin filter surface length is designated as "I1" in Figure 2 while the box filter region length is designated as "I2” in Figure 3. The direction of filtration for the particular connection shown is indicated by the arrows “D1” and “D2” in Figures 2 and 3, respectively. It will be appreciated from Figures 2 and 3 that the filter region 29 of the mating box member 12 is again a scalloped surface of the type described with respect to the pin filter region 27. It comprises a machined surface finish with a scalloped surface with alternating crests and valleys as has been described.

In one aspect of the present invention, the filter regions of the pin and box members 11 , 12, are design to have a predetermined amount of distance between the machined scalloped surfaces thereof. Thus, in one preferred form, the height between the machined valleys and crests of the scallop surfaces are calculated to be in a preferred range between about 0.0004 and 0.0009 of an inch. Figure 4 illustrates this in greatly amplified fashion by showing a preferred maximum combined height gap 49 of 0.002 inch. These measurements will allow the threaded connections to filter out harmful and unwanted particles sized about 0.002 inch and greater.

As has been discussed, the machined surface finishes 27, 29, which make up the filter regions are machined using a given machined feed rate measured in inches per revolution of the cutting tool being used. Figure 2 shows the filter cutting tool radius as “R1". The helical filter cutting tod feed rate per revolution is indicated as "FPRi" in Figure 2. Figures 5 and 6 two connections having pin and box members, 51, 53, and 55, 57, respectively, machined as described. Note the difference in the spacing of the scalloped surfaces with one set of feed rates, denoted as FPR2 and FPR3 in Figure 5 and FPR4 and FPR5 in Figure 6. The special scalloped surfaces 27, 29, which make up the filter surfaces of the invention can be machined at considerably fester rates titan the typical normal feed rates for external fluid and gas pressure seals, i.e., 0.004 inches per revolution. Production rates are greatly increased over the manufacture of typical liquid or gas pressure seals. This should lead to a significant reduction in manufacturing costs and consequently a lowering of the cost of completing a horizontal oil or gas well.

The invention offers other advantages as well. Since the filter is not intended to be a gas or fluid resistant seal which is resistant to well pressures, the filter can be coupled to a simple thread form such as an API 8 Round thread. Alternatively, a special thread design can be used in those situations where well pressure must be kept from traversing through the entire connection and entering the well borer. Such threads are in common use in the OCTG trades and are available to take advantage of the additional benefits of tire filter feature of the threaded connections of the invention. Figure 7 shows a pin member 59 which, for example, has a different style geometry. The pin helical gap is illustrated as “G1. "

The above discussion has primarily been directed to threaded connections where the filter region is acted upon by an external pressure, indicated as “P1” in Figure 5. However, in some situations, it may be envisioned that the filter region could be positioned so as to be acted upon by internal pressures, as indicated by “P2" in Figure 6.

While tiie invention has been shown in several of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof, as described in the claims which follow.