Wireline grease head

Abstract

Grease control head utilizing at least one ceramic insert for sealing around wireline, slick-line or braided wire while performing service operations in a well.

Description

FIELD OF THE INVENTION

This invention relates to grease control heads for sealing around flexible wireline, slick-line (solid wire) or braided wire (collectively service line) while performing service operations in a well and more particularly to the use of nonmetallic materials, such as ceramic inserts, in the grease head.

BACKGROUND OF THE INVENTION

Service lines are passed through a grease head as part of wireline pressure control operations. A grease head from the top down may include a line wiper, a grease and liquid overflow housing, one or more grease couplings and one or more flow tubes. Each flow tube consists of an outer rigid tube or body, an internal housing for inserts with the housing being a rigid-cylindrical tube and one or more inserts inside the housing.

When working in a well under pressure, viscous grease is injected into the flow tube through one or more grease couplings at a pressure greater than the existing well pressure. Grease fills the annular space between the inner wall of inserts and the outside surface of the service line forming a liquid seal that contains the well fluids while allowing service line movement. The combination of the inserts, service line and grease provide a pressure barrier to contain the well gas and liquids. The grease barrier is increased by increasing the number of flow tubes and grease couplings. A problem with the present grease heads is the wear that occurs on the inside surface of the metal inserts, which makes it difficult and eventually impossible to maintain the proper pressure barrier to contain the gases and liquids of the well.

The servicing of grease heads, which includes the replacement of the metal inserts, is expensive and time consuming. Additionally, worn inserts abrade braided service lines, which may cause a break in the outer surface and an unraveling of the braid. This hampers or stops the movement of the service line through the grease head and/or other components above and below the grease head.

Grease heads have been made with steel inserts for over 20 years. It has been found that the service line with a metallic surface inside the steel inserts results in particles of steel being pulled from both. As a result, the metal inserts get out of tolerance and grease is pulled down hole with the service line which increases the amount of grease needed for each operation. Additionally, when the wear becomes great enough, the grease head cannot maintain the necessary pressure and fluids from the well, in addition to grease, may escape from the overflow housing at the top of the grease head. As a consequence, the cost of operation increases because of the increase in grease used. Further, the grease that escapes from the grease head and overflow housing gets on trucks, trailers and other devices at the well site which may be an EPA problem.

SUMMARY OF THE INVENTION

This invention involves an improved grease head having a longer life with extended periods between servicing and consists of flow tubes having ceramic inserts. The ceramic inserts have a longer life than the typical steel inserts which results in significant reductions in the costs of operation.

Ceramic inserts and inserts of other non-metallic material do not have the loss of material experienced with metallic inserts. Consequently, there is better control over the well bore pressure. Additionally, not as much grease is required for lower a cost of operation. The EPA concern is significantly reduced and the well site location is kept cleaner. Further, the grease head with ceramic inserts perform as required for over 200 runs of service line through the grease head compared to the typical 20-30 runs with metallic inserts before servicing is needed. Moreover, with ceramic inserts, the service line may be retracted from the well at a much higher speed, such as between 350 feet to 400 feet per minute, as compared to 100 feet to 150 feet per minute with steel inserts.

Objects, features and advantages of this invention will become apparent from a consideration of the foregoing and the following description, the appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a grease head in place for performing service operations in a well, according to the present invention;

FIG. 2 is an elevation view of components of the grease head, partially in cross-section, according to the present invention;

FIG. 3 is a cross-sectional view of the grease head taken along the section lines 3-3 of FIG. 2, according to the present invention;

FIG. 4 is an elevation view of a housing of a flow tube, partially broken away, according to the present invention; and

FIG. 5 is a perspective view of a ceramic insert, according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Wells that produce gas are drilled to various depths, including common depths of 8,000 feet to 9,000 feet and sometimes to depths of 12,000 feet or greater. A solid casing is inserted in the drilled hole to the depth of the hole. Thereafter, many tests are conducted down hole and holes are created in the casing. The instruments for the tests and the tools, including explosives, for creating the holes are inserted in the well and removed from the well by a service line that carries the instrument or tool at its end. The service line may be a solid wire similar to piano wire, a braided wire with internal electrical conductors or braided wire without electrical conductors. In each case, the outer surface of the service line is metallic for strength and durability.

As shown in FIG. 1, a service line 1 passes through a grease head 2 that lubricates the line. Grease fills the annular space between the outer surface of the service line and an inner surface of the grease head to create a pressure barrier to contain the fluids in the well. The grease head 2 includes at least one flow tube 4 and at least one grease coupling 6. The number of flow tubes 4 and grease couplings 6 depends on the desired operating pressure of the grease head, which must be greater than the pressure of the well. The grease head 2 is attached to and extends vertically above a well head 7. The well head 7 extends from a casing 8 which is placed in the hole drilled in the earth. A tool section 10, which has a length to accommodate the instruments and tools (representatively shown by rectangle 11), is located between the grease head 2 and the well head 7. An overflow housing 12 is at the top of the grease head 2 with a line wiper 14 being above the overflow housing.

Grease is inserted into the grease head 2 through one or more fittings 15 which are screwed into a threaded hole (FIG. 2) in the side of a grease coupling 6. Grease is typically inserted into only one of the grease couplings 6, when there are a plurality of couplings. Details of the grease head 2 are shown in FIGS. 2-4. The upper grease coupling 6 of FIG. 2 has the grease fitting 15 inserted into a threaded hole 16 in the side of the coupling 6.

The flow tube 4 includes a cylindrical outer body 19 that is threaded at both ends with threads 20 and is attached to the grease couplings 6 at each end by threads 21 in the ends of the grease couplings 6. The outer body is a rigid metal cylinder with external threads 20 at each end. Inside the outer body 19 is a rigid cylindrical housing 24. Housing 24 has tapers 25 at each end for easy insertion into a recess 27 that has been formed in each end of the grease couplings 6. When the outer body 19 of the flow tube 4 is screwed onto a grease coupling 6 at each end with the housing 24 in place, the housing is held in place.

Ceramic inserts 30 are shown in elevation view in FIG. 2 and in a perspective view in FIG. 5. In one particular grease head the housing 24 has a length of 13½ inches. This length may be greater or less than 13½ inches. Although there may be a single ceramic insert 30 in the housing 24, better results are obtained by employing a plurality of ceramic inserts 30. In one typical grease head, the ceramic inserts 30 have a length of 1.005 inches with an outside diameter 31 of 0.450 inches and an inside diameter 32 of 0.291 inches. The inner diameter 32 is based upon the outer diameter of the service line that passes through the ceramic insert 30. The annular spacing between the outside surface of the service line and the inner surface of the insert 30 is preferably between 0.003 inches and 0.008 inches to provide the desired grease barrier. The outer diameter of a service line varies in use compared to the outer diameter of a service line newly installed on a reel or drum. The annular spacing is designed to be 0.005 inches between the I.D. of the ceramic insert and the O.D. of the service line in use

The annular spacing between the ceramic insert 30 and the inner diameter of the housing 24 is between 0.005 inches and 0.010 inches so that the insert will easily slip into the housing 24. The outer diameter 31 of the ceramic inserts 30 may be a standard size for a number of different sizes of service lines, with the inner diameter being determined by the outer diameter of the service line.

In the assembly of the flow tube 4, a threaded nut 34 is placed into one end of the housing 24 and then the ceramic inserts 30 are slipped into the housing 24. With a 13½ inch long housing 24, 13 ceramic inserts, having a length of 1.005 inches, are placed in the housing. After insertion of the ceramic inserts, a second threaded cap 34, shown in FIG. 4, is threaded into the housing 24 to secure the inserts in place. The threaded nut 34 may have grooves in the top surface to accommodate a tool or may be a solid nut that has a hex-shaped opening for the tool to insert and tighten the nut in place. Once the nut 34 is in place, the center of the nut 34 is drilled out to permit the service line 1 to pass through the nut and through the ceramic inserts 30.

Although the description above contains specificity, this should not be construed as limiting the scope of the invention but merely as providing illustrations of one of the preferred embodiments of the invention. This invention is not limited to the specific embodiments, but rather the scope of the invention is to be determined as claimed.

Claims

1. A grease head for sealing a service line lowered into or raised from a well comprising at least one flow tube having a cylindrical housing for inserts and one or more ceramic inserts aligned inside the housing.

2. A grease head according to claim 1 further comprising a lock-down threaded cap threaded into one end of the housing and engaging the end of the nearest ceramic insert.

3. A grease head for a metallic service line comprising at least one grease coupling, at least one flow tube and at least one nonmetallic insert inside the flow tube.

4. A grease head according to claim 3 wherein the insert is ceramic.