A drilling rig, in particular for the offshore industry, in the form of a jack-up platform on which a cantilever is mounted so as to be movable at least substantially horizontally and in a first direction, with the cantilever projecting more or less outside the jack-up platform. On the cantilever a drilling platform is present, which drilling platform is movable relative to the jack-up platform in a second direction, different herefrom. This drilling platform is fixedly mounted on the cantilever while the latter is movable relative to the jack-up platform in both abovesaid directions.

FIELD OF THE INVENTION
 The present invention relates to a drilling rig in the form of a jack-up
 platform on which a cantilever is mounted so as to be movable at least
 substantially horizontally and in a first direction, with the cantilever
 projecting more or less outside the jack-up platform, while a drilling
 platform is further present on the cantilever, said drilling platform
 being movable relative to the jack-up platform in a second direction,
 different herefrom.
 BACKGROUND TO PRESENT INVENTION
 In the conventional drilling rigs, the cantilever is movable only in its
 longitudinal direction relative to the jack-up platform, and the drilling
 platform is movable relative to the cantilever in a direction transverse
 thereto. Due to the resulting movement of the drilling platform relative
 to the jack-up platform, the drilling point of the drilling rig can reach
 any point located in a rectangle of which the lengths of the sides are
 determined by the travel of the cantilever relative to the jack-up
 platform and the travel of the drilling platform relative to the
 cantilever. However, in the transverse direction, the size of this
 rectangle is limited by the distance between the cantilever beams
 extending in the longitudinal direction, which beams determine the width
 of the cantilever. Located under the drilling platform is a grid of
 drilling points. The drilling platform with the blow-out valve and a part
 of the equipment, tools and materials for drilling that are further
 required moves from one drilling well to the other. The transverse
 movement of the drilling platform is limited by the cantilever beams. As a
 consequence, the drilling pattern is limited to drillings within said
 rectangle. To obtain a drilling pattern which is nevertheless acceptable,
 the cantilever should be of a relatively wide design. If the drilling
 platform has moved over the maximal distance in the transverse direction,
 the cantilever beam on the side to which this movement took place is
 subjected to a considerably heavier load than the other cantilever beam.
 Because of such asymmetric load on the cantilever beams occurring in
 practice, these beams should be of a relatively heavy construction. A
 further drawback of the conventional rigs is that between jack-up platform
 and cantilever, as well as between cantilever and drilling platform,
 flexible connections should be provided for pipes, cable work, etc.
 SUMMARY AND OBJECTS OF THE INVENTION
 The object of the invention is to provide a drilling rig wherein the
 above-mentioned drawbacks are avoided at least to a considerable extent.
 To this end, according to the invention, the drilling rig as described in
 the opening paragraph is characterized in that the drilling platform is
 fixedly mounted on the cantilever and said cantilever is movable relative
 to the jack-up platform in both abovementioned directions.
 As a result, the drilling point always remains in the same place relative
 to the cantilever, viz. preferably centrally between the two cantilever
 beams. This leads to a symmetric load on the cantilever beams and offers
 the possibility of giving them a lighter construction. Now, the width of
 the cantilever can be selected independently of the displacement in the
 transverse direction and can be slighter without the drilling pattern
 being limited thereby. On the contrary, by increasing the movement
 possibility of the cantilever in the transverse direction, a larger
 drilling pattern can be obtained than is possible with the conventional
 drilling rigs. The construction according to the invention further has the
 advantage that flexible connections for pipes, cable work, etc. must only
 be provided between the jack-up platform and cantilever.
 Although the cantilever with the drilling platform is movable in two
 directions by extending the cantilever in its longitudinal direction and
 rotating it about a fixed point on the jack-up platform, the cantilever is
 preferably constructed for movement in its longitudinal direction with the
 cantilever projecting more or less outside the jack-up platform, and in a
 direction relative to the jack-up platform which is transverse hereto. To
 enable these movements in an efficient manner, supporting members for the
 cantilever are present, which supporting members are movable with the
 cantilever in the transverse direction over rails secured on the jack-up
 platform, while the cantilever is supported by the supporting members for
 movement in the longitudinal direction.
 In a concrete embodiment, the supporting members are slidable by means of
 relevant operating cylinders over rails secured on the jack-up platform
 and extending in the transverse direction, relative to slide members which
 can be secured on these rails, when they are at least secured thereon.
 When the supporting members slide over the rails on the jack-up platform or
 the rails of the cantilever slide over the supporting members,
 considerable shearing forces occur. In order to at least partially relieve
 the parts sliding over each other in this regard, at least the two
 supporting members that are movable over the rail located closest to the
 edge of the jack-up platform may comprise friction-reducing means which
 are operative in the longitudinal direction as well as in the transverse
 direction, to take up at least a part of the frictional forces between the
 supporting members and the relevant rail and between the rails of the
 cantilever and the relevant supporting members. In a concrete embodiment,
 these friction-reducing means are formed by pairs of rollers which are
 freely movable between the supporting members and the rails in the
 direction of the rails and pressed thereagainst. In this regard, it is
 advantageous when the pressure exerted on the relevant rails by the
 friction-reducing means is settable.
 It may sometimes be desirable to provide the drilling platform on a
 separate support platform. With the drilling rig according to the prior
 art, this is possible by providing a separate support construction on the
 separate support platform, onto which support construction the drilling
 platform can be slid from the cantilever. In practice, this proves to be a
 fairly difficult operation. For that reason, according to another aspect
 of the present invention, coupling means may be present whereby the
 drilling platform is detachably connected to the cantilever so that it can
 be positioned on a separate support platform. Due to the movability in
 height direction of the jack-up platform and the movability of the
 cantilever, both in the longitudinal direction and in the transverse
 direction, an accurate positioning of the drilling platform coupled to the
 cantilever is possible. By moreover constructing the coupling means such
 that the drilling platform can be hooked on laterally by the cantilever,
 it becomes possible, after the drilling platform has been placed on the
 separate support platform by a downward movement of the jack-up platform,
 to uncouple the drilling platform from the cantilever through a further
 downward movement of the jack-up platform and, subsequently, a withdrawing
 movement of the cantilever.
 In the drilling rig according to the prior art, the high-pressure dredge
 pumps associated with such rig are typically arranged on the jack-up
 platform and relatively costly flexible high-pressure lines are necessary
 both between the jack-up platform and the cantilever and between the
 cantilever and the drilling platform.
 Because according to the invention, the drilling platform is fixedly
 connected to the cantilever, one set of flexible high-pressure lines can
 be replaced by so much cheaper fixed high-pressure lines.

DETAILED DESCRIPTION OF THE INVENTION
 A drilling rig, in particular for the offshore industry, in the form of a
 jack-up platform on which a cantilever is mounted so as to be movable at
 least substantially horizontally and in a first direction, with the
 cantilever projecting more or less outside the jack-up platform. On the
 cantilever a drilling platform is present, which drilling platform is
 movable relative to the jack-up platform in a second direction, different
 herefrom. This drilling platform is fixedly mounted on the cantilever
 while the latter is movable relative to the jack-up platform in both
 abovesaid directions.
 More particularly, embodiments of the invention are now described with
 reference to the Figures.
 FIG. 1 is a top plan view of a cantilever 1 which, relative to a jack-up
 platform 2, is movable in its longitudinal direction as indicated by the
 arrow A, and in its transverse direction as indicated by the arrow B. The
 cantilever 1 and the jack-up platform 2 form part of a drilling rig
 capable of being moved by tugs to a specific location at sea, after which
 the jack-up platform can be positioned on the seabed by posts that can be
 moved downwards. Located on the jack-up platform are various spaces,
 accommodations, cranes, a helicopter platform, equipment and further
 accessories that may be important for a marine drilling rig. Located on
 the cantilever 1 is the drilling platform 3 with the derrick, the blow-out
 valve and further equipment, tools and materials required for drilling. In
 the embodiment according to the invention, the drilling platform 3 is
 fixedly arranged relative to the cantilever 1 and hence moves along
 therewith in the directions indicated by the arrows A and B. Provided on
 the deck of the jack-up platform 2 are rails 4 and 5 extending in the
 direction B. Over the rail 4, supporting members 6 and 7 are movable and
 over the rail 5, supporting members 8 and 9 are movable. These supporting
 members act as carriers for the cantilever 1; the cantilever 1 is movable
 over these supporting members in the direction A. Hence, with the
 interposition of the supporting members 6-9, the cantilever 1 is movable
 back and forth along the edge of the jack-up platform 2 through a distance
 determined by the end positions 6', 7', 8' and 9' that can be reached by
 the supporting members over the rails 4 and 5, and further over the
 supporting members 6-9 into a position in which the drilling platform 3
 more or less projects outside the jack-up platform 2. Through the movement
 that can be made by the cantilever 1 with the drilling platform 3
 positioned thereon, a rectangle is described centrally below the drilling
 platform 3 within which rectangle the drilling pattern will be located.
 The point from which the drilling takes place is indicated by P in FIG. 1;
 by moving the cantilever in the directions A and B, this drilling point P
 can be moved to all desired locations within said rectangle and the
 desired number of drillings at the desired mutual distances can take
 place. The size of the drilling pattern can be enlarged by increasing said
 rectangle or, in other words, by increasing the distance through which the
 cantilever 1 can be shifted in the directions A and B.
 The means whereby the supporting members 6 and 7 can be shifted over the
 rail 4 are indicated in the rear view given in FIG. 3, while one of these
 means is depicted in an enlarged view in FIG. 5. The means whereby the
 supporting members 8 and 9 can be shifted over the rail 5 are indicated in
 the front view given in FIG. 4, while one of these means is depicted in an
 enlarged view in FIG. 6. The means whereby the cantilever 2 can be shifted
 over the supporting members 6, 7 and 8, 9 are indicated in the side
 elevation given in FIG. 2, while these means are depicted in an enlarged
 view in FIGS. 7 and 8 respectively. The cantilever 2 is shifted over the
 supporting members 6-9 by means of rails 10 and 11 arranged under the
 cantilever. The manner in which the supporting members 6-9 slide over the
 rails 4 and 5 and the manner in which the rails 10 and 11 slide over the
 supporting members 6-9 is always the same, to the effect that the slide
 means for the rails 10 and 11 are provided in the supporting members so as
 to be rotated through 90.degree. relative to the slide means for the rails
 4 and 5. These slide means are formed by vertical side plates 12 (FIG. 6)
 and 12' (FIG. 8) respectively, mounted below and against a deck plate 13
 and on a bottom plate 13' respectively, between which side plates 12, 12'
 a horizontal plate 14, respectively 14' is provided. The plates 14 and 14'
 are fixedly interconnected by a tubular section 15 extending through the
 supporting members. Both in the deck plate 13 and in the bottom plate 13',
 a slot has been provided through which the supports 16 and 16'
 respectively for the rails 10, 11 and 4, 5 respectively pass. The plates
 12, 13 and 14 constitute a housing through which the rails 10, 11 of the
 cantilever 2 can move. Provided in this housing are support plates 17 and
 18, which, like the plates 12, comprise slide plates 19. The rails 10 and
 11 are movable through the supporting members 6-9 while contacting these
 slide plates. The slide plates 19 are made from a material having good
 wear and corrosion properties, preferably an aluminum-bronze alloy. In the
 same manner, the plates 12', 13' and 14' constitute a housing whereby the
 supporting members can move over the rails 4, 5. In this housing, too,
 support plates 17' and 18' are again provided, which, like the plates 12',
 comprise slide plates 19' of the same material as the slide plates 19.
 By means of the supports 16', the rails 4, 5 are secured on the jack-up
 platform 2, while by means of the supports 16, the rails 10, 11 are
 secured on the side beams 20 thereof extending in the longitudinal
 direction of the cantilever.
 The supporting members 6-9 are shifted in the transverse direction by
 hydraulic cylinders 21, 22, activated in synchronization. By means of
 connecting pieces 23, 24, 25 and 26, these operating cylinders are
 arranged between the relevant supporting members 6-9 and slide members 27,
 28 which can be secured on the rails 4, 5. Here, these slide members are
 constructed as a slide block which can be secured on the rails 4, 5 or
 released from these rails respectively by a number of hydraulic cylinders.
 Likewise, the cantilever is shifted in the longitudinal direction over the
 supporting members by hydraulic cylinders 21', 22' activated in
 synchronization. These operating cylinders, too, are arranged by means of
 connecting pieces 23', 24', 25' and 26' between the relevant supporting
 members 6-9 and slide members 27', 28' which can be secured on the rails
 10, 11. These slide members 27', 28' are again identical to the slide
 members 27 and 28 respectively. In FIGS. 5-8, the operating cylinders are
 all shown in their retracted positions.
 When in FIGS. 3 and 4 the slide members 27 and 28 have been secured on the
 rails 4 and 5 respectively, and the cylinders on the left-hand side are
 retracted while the cylinders on the right-hand side are extended, the
 supporting members 7-9 will, through the extension of the cylinders on the
 left-hand side in synchronization with the retraction of the cylinders on
 the right-hand side, be moved leftwards through a distance corresponding
 to the travel of the cylinders. When the slide members 27 and 28 are
 subsequently released relative to the rails 4 and 5, and the cylinders on
 the left-hand side are extended, in synchronization with the retraction of
 the cylinders on the right-hand side, the slide members 27, 28 are shifted
 rightwards through a distance corresponding to the travel of the
 cylinders. After that, the slide members can again be secured on the
 relevant rails and the supporting members can again be displaced. In this
 manner, the supporting members and, accordingly, the cantilever can be
 displaced stepwise in transverse direction. By operating the slide members
 27' and 28' and the cylinders 21' and 22' in the same manner, the
 cantilever can be displaced stepwise over the supporting members 6-9 in
 the longitudinal direction.
 Because of the weight of the drilling platform with accessories, reactive
 forces will occur in the supporting members. These reactive forces will be
 considerably greater in the supporting members 6 and 7 than in the
 supporting members 8 and 9. As a consequence, the frictional forces
 experienced by the supporting members 6 and 7 during shifting over the
 rail 4 and the frictional forces occurring in these supporting members
 during a displacement of the cantilever in the longitudinal direction will
 be considerably greater than the frictional forces experienced by the
 supporting members 8 and 9 during shifting over the rail 5, respectively
 the frictional forces occurring in the latter supporting members during a
 displacement of the cantilever in the longitudinal direction. For this
 reason, the supporting members 6 and 7 are provided with friction-reducing
 means 40 and 29 which are operative both in the longitudinal direction and
 in the transverse direction (see FIGS. 5 and 7). These friction-reducing
 means are formed by pairs of rollers which are freely movable between the
 supporting members 6 and 7 and the rails 4, 10 and 11 in the direction of
 the rails and pressed thereagainst. The pressure exerted by these pairs of
 rollers on the relevant rails is hydraulically settable.
 Although the drilling platform may be fixedly connected to the cantilever,
 the drilling platform 3 shown in the present exemplary embodiment is
 detachably connected to the cantilever 2. The drilling platform 3 is at
 the top side hooked on the cantilever 2 around shafts 30 which are both
 arranged in a space at the end of an upper beam 31 of the cantilever. For
 this purpose, the drilling platform 3 is provided, at the top side
 thereof, with a forwardly and downwardly extending portion 32 movable over
 these shafts, while in the coupled condition the drilling platform 3 finds
 support, by its bottom side, against the cantilever and can at the support
 location 33 be bolted against the cantilever 1. Because of the
 height-movability of the jack-up platform and the movability of the
 cantilever 2 in the directions A and B, the drilling platform can
 accurately be positioned above a separate support platform and be placed
 thereon.
 The movability of the cantilever and the fixed positioning thereon of the
 drilling platform render it more attractive to place the high-pressure
 dredge pumps conventional in drilling rigs on the cantilever. Now,
 flexible high-pressure lines are entirely avoided. Between the jack-up
 platform and the cantilever, low-pressure connections are now sufficient;
 fixedly mounted on the cantilever, they extend in the longitudinal
 direction towards the drilling platform.
 The invention is by no means limited to the exemplary embodiment described
 hereinabove, but comprises various modifications hereto, in so far as they
 fall within the scope of the following claims.