Radial tie back assembly for directional drilling

#1. Field Of The Invention

#The apparatus of the present invention relates to directional drilling for oil and gas. More particularly, the present invention relates to a novel assembly for the recovery of oil or gas from multiple radials which have been drilled from either a horizontal or vertical well, so that each of the radials can be produced simultaneously.

#2. General Background

#For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein:

#FIG. 1 is an overall view of the radial tie back assembly positioned within a cased borehole;

#FIG. 2 is an overall cross sectional view of the radial tie back assembly positioned within the borehole including the collet assembly positioned therein and the drill string positioned therein drilling a radial borehole;

#FIGS. 1-7B illustrate the preferred embodiment of the system utilized to carry out the process of the present invention. In the process of the present invention, the radial tie back assembly is illustrated in the figures, is utilized in order to produce a plurality of radially drilled wells from a single vertical or horizontal borehole, in such a manner that the wells may be produced simultaneously from different points along the length of the borehole. In the method of the present invention, there is provided a cased horizontal or vertical borehole drilled within the earth to a predetermined depth. Utilizing the system of the present invention as will be described in FIGS. 1-7B further, the radial tie back assembly is lowered into the borehole and is sealed in place with an upper and lower seal assembly, and a packer on its lowermost end. The radial tie back assembly is lowered into the hole through a combination of a muleshoe J lock sub and a gyro orienting tool at its upper end, so that when the assembly is placed at its predetermined depth, the gyro orienting tool orients a whipstock contained within the assembly to a specific orientation, and the muleshoe J lock sub is then disengaged from the assembly after the top and bottom seals of the assembly are sealed into place against the wall of the casing, and the packer on its lower end is expanded to grip the casing at the lowermost end. Following this step, a collet latch assembly is engaged into the radial tie back assembly and a radial drill string is then lowered into the assembly and contacting the whipstock bores through the wall of the casing and drills out the formation of a first radial well. Following this step, the drill string is then retrieved from the hole, and a production liner is lowered into the hole and the packer 15 engaged below the collet latch assembly, with the production liner serving to case off the production zone inside the radial bore. The running string is then released from the packer and retrieved to surface. The collet latch assembly is then disengaged within the radial tie back assembly and retrieved to surface. The well is now ready to be produced from its lowermost point through this assembly. Should subsequent radial wells want to be produced above this point, then each well would require an additional radial tie back assembly undergoing the same series of steps as was described above. In order to accommodate production flow from the lowermost assembly upward, in the event there are other radial tie back assemblies in place, each radial tie back assembly is provided with a flow bore throughout its length, so that as production flow reaches the next upper radial tie back assembly, the production flow flows through the flow bore from its lowermost end up out of its uppermost end and into the cased borehole until the flow engages another higher positioned radial tie back assembly and the flow would continue therethrough until the series of radial tie back assemblies are producing from different points along the length of the wellbore to the surface.

#In order to accomplish the method of the present invention, reference is made to FIGS. 1-7B in the drawings. As seen in FIG. 1, the radial tie back assembly 10 is positioned within a primary borehole 12, with the casing 14 extending therethrough. The assembly 10 would include a bottom seal assembly 16, having a pair of upper annular seals 18 and 20, and a lower packer 22 set beneath the bottom seal assembly 16 for holding the assembly 10 at its lowermost point so that nothing will be able to flow past the seals 18, 20, between tie back assembly and the cased bore hole. There would also be provided a top seal assembly 24, having a pair of lower annular seals 26 and 28, which would when expanded seal against the inner surface 15 of the casing 14, so that there would be a seal on both the upper and lower ends 30, 32 respectively of the radial tie back assembly 10. During the process of setting the radial tie back assembly 10, it would be lowered into the borehole 12, with the use of a muleshoe J lock sub 34, which is illustrated in its entirety in FIGS. 7A and 7B. FIGS. 7A and 7B illustrate a muleshoe J lock sub 34. As illustrated in 7A, muleshoe J lock sub includes a body portion 35, having a lower end 36 with a pair of latching members 37, 37A. The upper end 39 of lock sub 34 would be attached to the gyro-orienting tool 40. The latching members 37, 37A, of the muleshoe J lock sub 34 would lock into the upper end 11 of the radial tie back assembly 10 and lowered into position as seen in FIG. 1. Once the assembly 10 is in the proper orientation and seals and packer set, the J lock sub 34 would be disengaged and brought up to the surface with the assembly 10 set in place downhole. The assembly 10 is set in the proper orientation within the borehole through the use of the gyro orienting tool 36, as illustrated in FIG. 1.

#The purpose of orienting the assembly 10 within the hole and the proper orientation is the fact that the main assembly would include a whipstock 41 as one portion of the assembly 10. Such a whipstock 41 is known in the art and includes an angulated floor portion 42, so that when a drill bit makes contact with the floor portion 42, the drill bit is angulated into the wall of the cased hole and bores through the wall and out to begin a radial borehole. Therefore, the whipstock surface 42 must be oriented in the precise orientation so that when the drill bit makes its exit through the wall of the casing 14, it is oriented in the direction as was predetermined at the floor of the well. Further, the radial tie back assembly 10 would include a series of flow bores 40 extending from its upper end 30 through its lower end 32, for allowing hydrocarbons to flow upward through the assembly during the production, in the direction of arrow 43 as seen in FIG. 1. This flow bore will be discussed further.