In the hydrocarbon production industry a large number of wells in close proximity are often constructed beneath a single platform. The direction of each well must be accurately controlled to allow it to access a specific area of the field. The final position of the wells at their deepest points may be several kilometres apart.

The wells consist of a number of concentric, decreasing diameter tubes known as conductors, casings, and at the lower end of the well, liners. Each tubular string is of smaller diameter than its predecessor and is installed to a greater depth. In the early stages of well construction, it is common practice to install the first tubular string (s) to relatively shallow depths by driving with a pile-driving hammer. Deeper in the well, casings are installed into drilled bore holes. The closed end directional driving shoe, according to the present invention, is used in the early stages of the well construction where the first pipes, known as conductors or surface casings, are installed by driving.

The principal benefit of driving, with respect to drilling, is that soil disturbance is reduced. This may be important to preserve the integrity of the foundations beneath a platform.

Due to the large number and close proximity of wells beneath a platform, directional control of the conductors and surface casings while they are being installed is particularly important. It is necessary to follow a pre-determined well path that

avoids existing wells and foundation piles and will not compromise the construction of future wells. One of the principal disadvantages of driving, with respect to drilling, is that it is more difficult to accurately control the direction and path of the pipe or pile as it is driven into the ground. Previous methods use an open ended directional shoe, which consists of either a bent joint of pipe or a short section of pipe (about 2 m long) welded to the end of the driven pipe at a small angle (offset with respect to the pipe axis at the tip by about 10 to 20 mm).

It is known to use boring equipment for forming relatively small holes for utility conduits using moling devices which have an external boring face constructed to apply an asymmetric boring force. Typically, these slanted nose members are 6 to 9cm in diameter and are used in the soil near the surface. A conductor of an oil or gas well is significantly larger, e. g. in excess of 60 cm, and may have to be pushed or driven many metres into the ground, without the use of drilling equipment. The present invention provides a driving shoe for use in installing a conductor or casing for an oil or gas borehole that enables the direction and path of the conductor or casing to be controlled.

The present invention relates to a closed end directional driving shoe for use in installing a conductor or casing into an oil or gas borehole having a shaped nose that during the driving operation generates a resultant force that is perpendicular to the longitudinal axis of the driven pipe. This lateral force causes the pipe to deviate from its initial direction. The shoe can be designed to deliver higher or lower lateral forces depending on the degree of deflection desired. Similarly, the direction of the deflection can be selected by rotating the pipe and shoe to the desired orientation direction prior to and/or during the driving process.

Another advantage of the closed end directional driving shoe of the present invention is that a directional survey may be recorded either continuously or at regular intervals using a directional surveying tool, for example a gyroscope. Thus, a survey profile may be provided in the interior of the shoe to locate and orientate the directional surveying tool. The survey tool can be a conventional wireline-deployed survey instrument. Accordingly, the orientation of the shoe can be recorded to predict the path that will be taken by the pipe during its installation.

Suitably, the closed end directional driving shoe for use in installing a conductor or casing into an oil or gas borehole (hereinafter termed"shoe") comprises a tubular

body that is connectable either directly or indirectly to the base of a pipe that is to be installed into the ground (for example, by lowering, pushing or driving the pipe).

Preferably, the tubular body is comprised of steel. Typically the tubular body is provided with a threaded connection for connecting the tubular body to the lower end of the pipe that is to be installed into the ground. Alternatively, the tubular body may be welded to the lower end of the pipe. Preferably, the interior of the tubular body is provided with the survey profile for locating and orientating the directional surveying tool.

The nose of the shoe may comprise single or multiple, planar or curved external surfaces that are orientated such as to generate a resultant force, a component of which is perpendicular to the longitudinal axis of the pipe. This resultant force deflects the pipe in a predetermined direction during its installation into the ground or below the seabed.

Preferably, the nose of the shoe may comprise a first and a second angled planar surface that meet to form an edge at the tip of the nose. This edge is offset from the central longitudinal axis of the tubular body of the shoe. Typically, the first and second planar surfaces are at an angle of from 30 to 60° from the longitudinal axis of the tubular body of the shoe. Typically, the ratio of the surface areas of the first angled planar surface to the second angled planar surface is in the range 60: 40 to 80: 20, preferably 65: 35 to 70: 30, for example, 67: 33.

Preferably, the nose of the shoe is made of a non-ferrous material, for example, aluminium, to allow the nose of the shoe to be completely or substantially removed by an internal drilling or milling action that can be supplied by a conventional drilling rig.

Removal of the nose of the shoe may be required for any of the following reasons: a. To allow well construction activities to continue through the installed pipe. b. As a corrective measure should the desired inclination be reached prior to the intended depth. Thus, removal of the shoe substantially reduces or removes the force causing the pipe to deflect. c. In the event that it is not possible to install the pipe to the desired depth without removing the shoe.

Advantages of the closed end directional driving shoe of the present invention

include: a. The shoe is closed or substantially closed, such that the formation through which the pipe is installed is prevented from entering the pipe. b. A directional surveying tool may be deployed inside the pipe, to measure the inclination and azimuth of the driven pipe close to the shoe. c. A survey profile may be mounted on the inside of the shoe to measure the orientation of faces of the drive shoe close to the tip of the shoe.

The present invention will now be illustrated with respect to Figures 1 and 2.

Figure 1 shows a shoe according to the present invention comprising a steel body 1 and a nose 2 having first and second angled planar surfaces 3,4 that meet to form an edge 5 that is offset from the central longitudinal axis of the steel body 1. A survey profile 6 is provided in the interior of the tubular body 1 for orientating a directional surveying tool (not shown). The surveying tool is generally located in the tubular portion 7 of the survey profile 6. The interior of the shoe below the survey profile may be filled with a filler 8. The upper portion of the steel body 1 has a thread or weld preparation 9 for connection to the pipe to be forced into the ground.

Figure 2 illustrates the first and second angled planar surfaces 3,4 of the nose 2.

The profile of the nose generates a net lateral force to deflect the pipe that is connected to the tubular body of the shoe, for example, via a threaded connection or a welded joint.