Grouting

Abstract

A method of applying grout to an offshore structure, wherein the method includes determining the required volume of grout to be applied to the offshore structure and conveying grout along a grout line connected to a grout application location of the offshore structure. The method also includes inserting a cleaning pig into the grout line and conveying the cleaning pig along the grout line towards the offshore structure so as to evacuate at least a portion of the remaining grout from the grout line to the grout application location.

Description

GROUTINGFIELD OF THE INVENTION

[0001] This invention relates generally to grouting, and more specifically to grouting of offshore structures. More specifically, although not exclusively, this invention relates to a method of, and grouting system for, applying grout to an offshore structure.BACKGROUND OF THE INVENTION

[0002] Offshore structures, commonly present in both the offshore wind and offshore oil and gas industries, most often include a structural jacket supporting a payload above the surface of the water. In the offshore wind industry, the payload is a wind turbine, and in the offshore oil and gas industry, the payload tends to be a processing and / or accommodation platform.

[0003] Normally, the interface between the structural jacket and the pay load and / or between the structural jacket and the seabed is filled with a cementitious material, commonly known as grout. The grout is applied such that the interface is filled. The grout is subsequently left to cure. Conventionally, the grout is applied from pump unit on the surface via a grout line, which is a pipe or hose.

[0004] Conventionally, once the interface is filled the grout line is removed and the excess grout within the line is flushed out. Such a process results in waste material which must be carefully handled and disposed of, increasing the overall cost of a grouting operation.SUMMARY OF THE INVENTION

[0005] It is therefore a first non-exclusive object of the invention to provide a method of applying grout and a grouting system at overcomes, or at least mitigates, the drawbacks of the prior art.

[0006] Accordingly, a first aspect of the invention provides a method of applying grout to an offshore structure, the method comprising: determining the required volume of grout to beapplied to the offshore structure; conveying grout along a grout line connected to a grout application location of the offshore structure; inserting a cleaning pig into the grout line and conveying the cleaning pig along the grout line towards the offshore structure so as to evacuate a portion of the remaining grout from the grout line to the grout application location.

[0007] The method may comprise monitoring the volume of grout being conveyed along the grout line to the grout application location.

[0008] The cleaning pig may be inserted into the grout line when the volume of grout left to be applied to the offshore structure is substantially equal to or is less than a volumetric capacity of the grout line.

[0009] The cleaning pig may be inserted into the grout line when the volume of grout left to be applied to the offshore structure is greater than a volumetric capacity of the grout line.

[0010] The cleaning pig may otherwise be referred to as a scraper.

[0011] The method may comprise determining the volumetric capacity of the grout line.

[0012] The grout line may have a first end connected to a pump and a second end located at a grout application location of the offshore structure. The second end may be connected to a connector of a permanent grout line of an offshore structure.

[0013] The cleaning pig may be inserted into the grout line before disconnecting the grout line, e.g. the second end thereof, from a connection point of a permanent grout conduit of offshore structure.

[0014] The cleaning pig may be inserted into the grout line before disconnecting the grout line, e.g. the second end thereof, from the grout application location of the offshore structure.

[0015] The method may comprise monitoring the volume of grout applied to the grout application location or offshore structure.

[0016] The method may comprise conveying the cleaning pig along the grout line until it reaches a pig catcher or a cleaning pig seat, e.g. of the grout line.

[0017] The pig catcher or cleaning pig seat may be connected or connectable to the second end of the grout line.

[0018] The pig catcher or cleaning pig seat may comprise an abutment or stop along the grout line so as to prevent further movement of the cleaning pig along the grout line.

[0019] The pig catcher or cleaning pig seat may comprise a seat. The cleaning pig may be configured to engage with the seat.

[0020] The cleaning pig and seat may be configured to provide a seal so as to prevent the migration of fluid from upstream of the pig downstream of the seat.

[0021] The method may comprise pumping a purge fluid, purge medium, conveying fluid or conveying medium (hereinafter conveying fluid) upstream of the cleaning pig to convey the cleaning pig along the grout line. The conveying fluid may be a liquid, e.g. water. The conveying fluid may be a gas, e.g. air. The method may comprise pumping conveying fluid using a pump. The method may comprise pumping water using a water pump.

[0022] The volume of conveying fluid pumped may be less than or equal to a volumetric capacity of the grout line.

[0023] The method may comprise monitoring the volume conveying fluid pumped upstream of the cleaning pig as the cleaning pig is conveyed along the grout line. The method may comprise determining the volume per stroke of the pump, e.g. the pump or the water pump, and calculating or tracking the number of pump strokes, e.g. since the beginning of the conveying of the cleaning pig along the grout line.

[0024] The method may comprise stopping the pump, e.g. the water pump, when it is determined that the volume of conveying fluid pumped is less than or equal to a volumetric capacity of the grout line.

[0025] The method may comprise stopping the pump, e.g. the water pump, when it is determined that the volume of conveying fluid pumped is between 50% and 100% of thevolumetric capacity of the grout line, for example between 60% and 90% of the volumetric capacity of the grout line, between 70% and 80%, for example 75% of the volumetric capacity of the grout line.

[0026] The method may comprise pumping conveying fluid from a supply or store. The supply or store may comprise a storage tank. The method may comprise pumping water from a water supply. The water supply may comprise a water storage tank. The water storage tank may have a volumetric capacity substantially equal to or less than a volumetric capacity of the grout line. The water storage tank may contain an initial volume of water less than or equal to a volumetric capacity of the grout line.

[0027] The water storage tank may contain an initial volume of water between 50% and 100% of the volumetric capacity of the grout line. The water storage tank may contain an initial volume of water between 60% and 90% of the volumetric capacity of the grout line, for example between 70% and 80%, for example 75%.

[0028] The water storage tank may have a volumetric capacity between 50% and 100% of the volumetric capacity of the grout line. The water storage tank may have a volumetric capacity between 60% and 90% of the volumetric capacity of the grout line, for example between 70% and 80%, for example 75%.

[0029] The water storage tank may be or comprise an intermediate bulk container (IBC).

[0030] The method may comprise providing indicia on the water storage tank indicative of a fill level corresponding to a volume of water less than or equal to a volumetric capacity of the grout line. The indicia may be a fill line. The indicia may be indicative of a fill level corresponding to a volume of water between 50% and 100% of the volumetric capacity of the grout line, for example between 60% and 90%, or between 70% and 80%, for example 75%. The indicia may be indicative of a fill level corresponding to a volume of water equal to or less than 100%, 90%, 80% 70%, 60% or 50% of the volumetric capacity of the grout line.

[0031] The method may comprise filling the water storage tank with water up to the fill level, fill line, or indicia e.g. prior to inserting the cleaning pig into the grout line, prior to applying grout to the offshore structure or prior to conveying grout along the grout line.

[0032] The method may comprise providing one or more holes or apertures through a side wall of the water storage tank indicative of a fill level corresponding to a volume of water less than a volumetric capacity of the grout line, for example between 50% and 100% of the volumetric capacity of the grout line. The holes or apertures may define an overflow. The method may comprise drilling the holes or apertures. The holes or apertures may have a diameter greater than or equal to 5mm, 10mm or 15mm.

[0033] The holes or apertures may be indicative of a fill level corresponding to a volume of water between 50% and 100% of the volumetric capacity of the grout line, for example between 60% and 90%, or between 70% and 80%, for example 75%. The holes or apertures may be indicative of a fille level corresponding to a volume of water equal to or less than 75% of the volumetric capacity of the grout line.

[0034] The method may comprise filling the water storage tank with water up to the holes or apertures, e.g. prior to inserting the cleaning pig into the grout line, prior to applying grout to the offshore structure or prior to conveying grout along the grout line.

[0035] It will be appreciated that the storage tank of the conveying fluid may comprise the aforementioned features of the water storage tank.

[0036] The method may comprise conveying grout along the grout line using a grout pump, disconnecting the grout line from the grout pump, connecting the grout line to a pump or water pump and pumping water upstream of the cleaning pig using the water pump.

[0037] The grout line may be or may comprise a flexible grout line. The grout line may comprise a plurality of parts or sections. The grout line may comprise a main grout line and a buffer hose or buffer portion (hereinafter buffer hose). The buffer hose may be connected tothe main grout line and located downstream thereof. The buffer hose may be connected between the main grout line and the grout application location. The buffer hose may be connected between the main grout line and a connector of a permanent grout line of an offshore structure. The main grout line may be longer than the buffer hose.

[0038] The pig catcher or cleaning pig seat may be located at the connection between the main grout line and the buffer hose. The pig catcher or cleaning pig seat may be located along the main grout line or the buffer hose. The pig catcher or cleaning pig seat may be located at a downstream end of the buffer hose, e.g. at the connection between the buffer hose and a connector of a permanent grout line of an offshore structure.

[0039] The pig catcher or the cleaning pig seat may be located such that between 50% and 100% of remaining grout is evacuated from the grout line as the cleaning pig is conveyed along the grout line to the cleaning pig seat, for example between 60% and 90% of the remaining grout or between 70% and 80% of the remaining grout.

[0040] The pig catcher or the cleaning pig seat may be located such that less than 100% of remaining grout is evacuated from the grout line as the cleaning pig is conveyed along the grout line to the cleaning pig seat, for example less than 90%, less than 80%, less than 70%, less than 60% or less than 50%.

[0041] The method may comprise monitoring a pressure in the grout line, main grout line or buffer hose upstream of the cleaning pig as the cleaning pig is conveyed along the grout line.

[0042] The method may comprise determining that the cleaning pig has reached the pig catcher or cleaning pig seat by detecting an increase in pressure, e.g. upstream of the cleaning pig.

[0043] The method may comprise stopping the pump, e.g. the water pump, in response to the detected pressure increase.

[0044] The increase in pressure may be due to the cleaning pig engaging with a seat of the pig catcher or the cleaning pig seat and preventing or restricting the flow of fluid from a location upstream of the cleaning pig to a location downstream of the cleaning pig.

[0045] Determining the required volume of grout to be applied may comprise determining a minimum volume threshold of grout.

[0046] The cleaning pig may be inserted into the grout line when the volume of grout left to be applied to the offshore structure such that the minimum volume threshold is met is less than or equal to the volumetric capacity of the grout line.

[0047] Conveying grout along a grout line may comprise pumping grout along the grout line using a pump, e.g. a grout pump.

[0048] Monitoring the volume of grout being conveyed along the grout line to the grout application location may comprise determining the volume per stroke of the pump, e.g. the grout pump, and calculating or tracking the number of pump strokes, e.g. since the beginning of the grouting operation.

[0049] Monitoring the volume of grout being conveyed along the grout line to the grout application location may comprise monitoring the level of grout at the grout application location in relation to reference indicia located on the offshore structure.

[0050] Once the remaining grout or a portion of the remaining grout has been evacuated from the grout line, the method may comprise removing the cleaning pig from the grout line.

[0051] The method may comprise sealing the second end of the grout line, main grout line or buffer portion.

[0052] The method may comprise moving the grout line to a waste site.

[0053] The method may comprise flushing the grout line with a cleaning agent to remove residual grout.

[0054] The cleaning agent may be or comprise water, e.g. from the water storage tank.

[0055] The offshore structure may comprise a monopile and transition piece. The grout application location may be an annulus described between the monopile and transition piece. The method may comprise inserting the cleaning pig into the grout line when the level of grout overflows the annulus between the monopile and transition piece. The cleaning pig may inserted into the grout line when the level of grout overflows the grout application location.

[0056] According to another aspect of the invention there is provided a grouting system for applying grout to an offshore structure, the system comprising a grout line, the system further comprising a cleaning pig configured to clean grout from the grout line, wherein, in use, the cleaning pig is received within a first end of the grout line and conveyed therealong from the first end towards the offshore structure so as to evacuate at least a portion of the remaining grout from the grout line to the offshore structure.

[0057] The grouting system may comprise a grout pump configured to convey grout along the grout line towards the offshore structure.

[0058] The grouting system may comprise a water supply and a water pump. The water pump may be configured to pump water, from the water supply, upstream of the cleaning pig so as to convey the cleaning pig along the grout line.

[0059] The grout line may comprise a pig catcher or cleaning pig seat. The pig catcher or cleaning pig seat may be configured to receive and / or engage the cleaning pig as it is conveyed so as to prevent the flow of fluid from a location upstream of the cleaning pig to a location downstream of the cleaning pig. The pig catcher or cleaning pig seat may be located such that between 50% and 100% of the remaining grout, e.g. volumetrically, is evacuated from the grout line to the offshore structure, e.g. at the point at which the cleaning pig arrives at the pig catcher or cleaning pig seat.

[0060] The pig catcher or cleaning pig seat may be located such that between 60% and 90% of the remaining grout, e.g. volumetrically, is evacuated from the grout line to the offshorestructure, e.g. at the point at which the cleaning pig arrives at the pig catcher or cleaning pig seat, for example between 70% and 80%, for example 75% of the remaining grout.

[0061] The grout line may comprise a main grout line and a buffer hose. The cleaning pig seat may be located at the connection between the main grout line and the buffer hose.

[0062] The grout line may have a first end connected to a pump, and a second end connected to a pig catcher or cleaning pig seat.

[0063] The cleaning pig may be conveyed along the grout line using a pump, e.g. a water pump, from the first end to a pig catcher or cleaning pig seat.

[0064] According to another aspect of the invention, there is provided a water supply system for conveying a cleaning pig along a grout line of a grouting system described above, the water supply system comprising a water supply and a water pump, wherein the water pump is configured to pump water from the water supply upstream of the cleaning pig to convey the cleaning pig along the grout line.

[0065] The water supply volume may be less than or equal to a volumetric capacity of the grout line.

[0066] For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. For example, the grouting system or water supply system may comprise any one or more features of the method relevant to the grouting system or water supply system and / or the method may comprise any one or more features or steps relevant to one or more features of the grouting system or water supply system.

[0067] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless suchfeatures are incompatible. For the avoidance of doubt, the terms “may”, “and / or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that maimer.BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0069] Figure 1 is a schematic showing a grouting system;

[0070] Figure 2 is a schematic showing an alternative grouting system; and

[0071] Figure 3 is a schematic of the grouting system of Figure 2 during a cleaning operation.DETAILED DESCRIPTION OF THE INVENTION

[0072] Referring now to Figure 1, there is shown a grouting system 1 for applying grout to an offshore structure O. The offshore structure O is configured to support an offshore wind turbine and has a top pile TP connected to a monopile MP in this example. The grout is supplied by the grouting system 1 to an annular region A described between the top pile TP and monopile MP. A fixed or permanent grout line or conduit G is located on the offshore structure O, for reversible connection with the grouting system 1.

[0073] The grouting system 1 includes a grout line 2, connected to a pump 5 on onboard a vessel, for conveying grout to the offshore structure O. In the present arrangement, the groutline 2 has a first end 20 connected to the pump 5 via a pig launcher 3, and a second end 21 connected to a pig catcher or cleaning pig seat 4 (hereinafter pig catcher). The pump 5 is a grout pump in this example. The pig launcher 3 is allows a cleaning pig or scraper (not shown) to be loaded into the grout line 2, and conveyed therealong during an operation to clean grout from the line 2. The pig catcher 4 allows removal of the cleaning pig or scraper once it reaches the second end 21. The pig launcher 3 and pig catcher 4 together form part of a line cleaning apparatus.

[0074] The pig launcher 3 has an inlet 30 connected to the pump 5 and configured to receive input therefrom, and an outlet 31 connected to the grout line 2. Between the inlet 30 and outlet 31 is a pressure gauge 32 configured to measure pressure within the grout line 2, upstream of a cleaning pig or scraper (not shown).

[0075] The pig catcher 4 has an inlet 40 connected to the grout line 2, and an open outlet 41 for allowing the passage of grout to the offshore structure O. The outlet 41 is configured to reversibly connect to the fixed grouting line G.

[0076] Proximate the outlet 41 is a seat 42 configured to receive, and engage with, a cleaning pig or scraper. In use, the cleaning pig or scraper and seat are configured to provide a seal therebetween, preventing or impeding the flow of fluid across the cleaning pig or scraper from upstream to downstream.

[0077] The pump 5 has an inlet side 50 for receipt of material to be conveyed along the grout line 2 and an outlet side 51 connected to the pig launcher 3 in this example. The pump 5 is located on a skid 52 onboard a vessel in this example.

[0078] In use, in order to apply grout to an offshore structure O, the required volume of grout to fill or overflow the annular region A between the top pile TP and monopile MP is determined. Further, the volumetric capacity of the grout line 2 is also determined.

[0079] A grout mix is then received at the inlet of the pump 50. The grout is then conveyed from the pump outlet 51, through the pig launcher 3, along the grout line 2 and out of the pig catcher outlet 41 to a grouting location at the offshore structure O.

[0080] The volume of grout applied to the annular region A is monitored, either visually based on the level of grout in relation to reference indicia located on the top pile TP or monopile MP. The volume of grout applied to the annular region A may be monitored to determine when the level of grout overflows the annular region A. Alternatively, the amount of grout conveyed by the pump 5 may be determined by multiplying the volume of grout per stroke of the pump 5 by the number of pump strokes since the beginning of the grouting operation. Additionally or alternatively, the amount of grout conveyed by the pump may be determined using a flow meter located at the pump outlet 51 or located along the grout line 2. Additionally or alternatively, if the grout is stored in a tank upstream of the pump 5, then the amount of grout conveyed by the pump 5 may be determined by monitoring a level of grout in the tank.

[0081] In order to minimise wasted grout, when it is determined that the volume of grout left to be applied to the offshore structure O is less than or equal to the volumetric capacity of the grout line 2, a cleaning pig or scraper is inserted into the pig launcher 3. Water is then pumped, using the pump 5 or an alternative water pump (not shown), upstream of the cleaning pig or scraper in order to convey it along the grout line 2 from the pig launcher 3 towards the pig catcher 4.

[0082] As the cleaning pig or scraper is conveyed, the grout within the grout line 2 downstream of the cleaning pig or scraper is evacuated to the offshore structure O. Therefore, substantially all grout conveyed from the pump 5 becomes useable, rather than being left within the grout line 2 and subsequently going to waste.

[0083] Once the cleaning pig or scraper arrives at the pig catcher 4, it engages with seat 42. Water upstream is prevented from crossing the cleaning pig or scraper. Therefore, as the pump5 continues to operate, the upstream pressure within the grout line 2 increases, and will be shown on the pressure gauge 32.

[0084] The pressure increase provides evidence that the cleaning pig or scraper is seated, and that the grout line 2 is substantially free of grout. The pump 5 can then be switched off and the grout line 2 removed to a waste site and flushed to remove any remaining grout.

[0085] Referring now to Figure 2, there is shown another grouting system 100 for applying grout to an offshore structure O. The offshore structure O is similar to the offshore structure of Figure 1, and like references denote like features and will not be described further.

[0086] The grouting system 100 is similar to grouting system 1, wherein like features are denoted by like references incremented by ‘100’ and only the differences will be described in detail hereinafter. The grouting system 100 includes a grout line 102, connected to a pump 105 on onboard a vessel, for conveying grout to the offshore structure O.

[0087] The grout line 102 differs from grout line 2, in that it is formed of two parts. The grout line 102 has a main grout line 102a and a buffer hose 102b. The main grout line 102a has a first end 120a connected to the pump 105 in the absence of a pig launcher, and a second end 121a connected to a pig catcher or cleaning pig seat 104 (hereinafter pig catcher). The buffer hose 102b has a first end 120b connected to the main grout line 102a and a second end 121b connected to a fixed or permanent grout line or conduit G located on the offshore structure O. Therefore, in this case, the pig catcher or cleaning pig seat 104 is located at the connection between the main grout line 102a and the buffer hose 102b, part way along the grout line 102, rather than at an end of the grout line 102 as is the case in Figure 1. The pig catcher or cleaning pig seat 104 allows removal of the cleaning pig or scraper once it reaches the second end 121a of the main grout line 102a.

[0088] The pig catcher 104 has an inlet 140 connected to the second end 121a of the main grout line 102, and an open outlet 141 for allowing the passage of grout to the buffer hose 102bduring a grouting operation. The open outlet 141 is configured to reversibly connect to the buffer hose 121b.

[0089] Proximate the open outlet 141 is a seat 142 configured to receive, and engage with, a cleaning pig or scraper during a grout line cleaning operation. In use, the cleaning pig or scraper and seat 142 are configured to provide a seal therebetween, preventing or impeding the flow of fluid across the cleaning pig or scraper from upstream to downstream.

[0090] In use, a grout mix is then received at the inlet 150 of the pump 105. The grout is then conveyed from the pump outlet 151, along the main grout line 102a, through the pig catcher 104, along the buffer hose 102b to a grouting location at the offshore structure O.

[0091] Referring now to Figure 3, there is shown the grouting system 100 of Figure 2 configured for carrying out a cleaning operation. In this case, a pig launcher 103 is connected to the first end 120a of the main grout line 120a and allows a cleaning pig or scraper (not shown) to be loaded into the grout line 102, and conveyed therealong to the pig catcher 104 during an operation to clean grout from the grout line 102 after a grouting operation. The pig launcher 103 and pig catcher 104 together form part of a line cleaning apparatus.

[0092] The pig launcher 103 has an inlet 130 connected to the pump 106 and configured to receive input therefrom, and an outlet 131 connected to first end 120a of the main grout line 102. Between the inlet 130 and outlet 131 is a pressure gauge 132 configured to measure pressure within the grout line 102, and in particular the main grout line 102a upstream of a cleaning pig or scraper (not shown).

[0093] The pump 106 is a water pump in this example and has an inlet side 160 for receipt of water to be conveyed along the grout line 102 upstream of a cleaning pig or scraper and an outlet side 161 connected to the pig launcher 103 in this example. The pump 106 is located on a skid 162 onboard a vessel in this example.

[0094] A water storage tank 107, in the form of an intermediate bulk container, is connected to the inlet side 160 of the pump 106 via a conduit 170. In the present example, prior to the cleaning operation taking place, the water storage tank 107 contains a volume of water less than a volumetric capacity of the grout line 102.

[0095] In use, grout is conveyed along the grout line 102 to the offshore structure O as described above respect of Figure 2. The volume of grout applied to the annular region A is monitored, either visually based on the level of grout in relation to reference indicia located on the top pile TP or monopile MP. The volume of grout applied to the annular region A may be monitored to determine when the level of grout overflows the annular region A.

[0096] In order to minimise wasted grout, when it is determined that the volume of grout left to be applied to the offshore structure O is less than or equal to the volumetric capacity of the grout line 102, the pig launcher 103 is connected to the first end 120a of the main grout line 102a. A cleaning pig or scraper is then inserted into the pig launcher 103 which is, in turn, connected to the pump 106. Water is then pumped from the water storage tank 107, using the pump 106, upstream of the cleaning pig or scraper in order to convey it along the grout line 102 from the pig launcher 103 towards the pig catcher 104.

[0097] As the cleaning pig or scraper is conveyed, the grout within the grout line 102 downstream of the cleaning pig or scraper is evacuated to the offshore structure O. Therefore, a portion of the grout conveyed from the pump 105 during the grouting operation becomes useable, rather than being left within the grout line 102 and subsequently going to waste.

[0098] Once the cleaning pig or scraper arrives at the pig catcher 104, it engages with seat 142. Water upstream is prevented from crossing the cleaning pig or scraper. Therefore, as the pump 106 continues to operate, the upstream pressure within the grout line 102 increases, and will be shown on the pressure gauge 132.

[0099] The pressure increase provides evidence that the cleaning pig or scraper is seated, and that the main grout line 102 ais substantially free of grout. The pump 106 can then be switched off and the grout line 102 removed to a waste site. In this case, the buffer hose 102b can be flushed to remove any remaining grout.

[0100] In the present example, the cleaning pig seat 104 is located along the grout line 102 such that between 50% and 100% of the remaining grout is evacuated from the grout line 102 to the offshore structure O.

[0101] It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, it is shown and described in respect of Figure 1 that the grout line 2 has both the pig launcher 3 and pig catcher 4 connected during the entire grouting process. However, this need not be the case. Instead, initially the grout line 2 may be connected to the pump 5 and fixed grouting line G during the initial phase of the grouting operation. Then, when it is determined that the when it is determined that the volume of grout left to be applied to the offshore structure O is less than or equal to the volumetric capacity of the grout line 2, the pig launcher 3 and pig catcher 4 may be connected and the cleaning pig or scraper conveyed as described above.

[0102] It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and / or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

CLAIMS1. A method of applying grout to an offshore structure, the method comprising: determining the required volume of grout to be applied to the offshore structure; conveying grout along a grout line connected to a grout application location of the offshore structure; inserting a cleaning pig into the grout line and conveying the cleaning pig along the grout line towards the offshore structure so as to evacuate at least a portion of the remaining grout from the grout line to the grout application location.

2. The method according to claim 1, comprising monitoring the volume of grout being conveyed along the grout line to the grout application location.

3. The method according to claim 1, wherein the cleaning pig is inserted into the grout line when the volume of grout left to be applied to the offshore structure is substantially equal to or is less than a volumetric capacity of the grout line.

4. The method according to any one of claims 1, 2, or 3, wherein the cleaning pig is inserted into the grout line before disconnecting the grout line from a connection point of a permanent grout conduit of the offshore structure.

5. The method according to claim 1, comprising pumping a conveying fluid upstream of the cleaning pig to convey the cleaning pig along the grout line.

6. The method according to claim 5, wherein the volume of conveying fluid pumped is less than a volumetric capacity of the grout line.

7. The method according to claim 5, wherein the conveying fluid is water.

8. The method according to claim 7, comprising pumping water from a water storage tank having a volumetric capacity substantially equal to or less than a volumetric capacity of the grout line.

9. The method according to claim 7, comprising conveying grout along the grout line using a grout pump, disconnecting the grout line from the grout pump, connecting the grout line to a water pump and pumping water upstream of the cleaning pig using the water pump.

10. The method according to claim 1, comprising conveying the cleaning pig along the grout line until it reaches a cleaning pig seat of the grout line.1 1 . The method according to claim 10, wherein the grout line comprises a main grout line and a buffer hose connected to the main grout line and located downstream thereof, and wherein the cleaning pig seat is located at the connection between the main grout line and the buffer hose.

12. The method according to claim 10, wherein the cleaning pig seat is located such that between 50% and 100% of remaining grout is evacuated from the grout line as the cleaning pig is conveyed along the grout line to the cleaning pig seat.

13. The method according to claim 10, comprising monitoring a pressure in the grout line upstream of the cleaning pig as the cleaning pig is conveyed along the grout line anddetermining that the cleaning pig has reached the cleaning pig seat by detecting an increase in pressure.

14. The method according to claim 13, wherein the increase in pressure is due to the cleaning pig engaging with the cleaning pig seat and preventing the flow of fluid from a location upstream of the cleaning pig to a location downstream of the cleaning pig.

15. The method according to any one of claims 1, 2, or 3, wherein conveying grout along a grout line comprises pumping grout along the grout line using a pump, and wherein monitoring the volume of grout being conveyed along the grout line to the grout application location comprises determining the volume per stroke of the pump, and calculating the number of pump strokes since the beginning of the grouting operation.

16. The method according to claim 2, wherein monitoring the volume of grout being conveyed along the grout line to the grout application location comprises monitoring the level of grout at the grout application location in relation reference indicia located on the offshore structure.

17. The method according to claim 1 , wherein once at least a portion of the remaining grout has been evacuated from the grout line, removing the cleaning pig from the grout line, and sealing an end of the grout line.

18. The method according to claim 17, comprising flushing the grout line with a cleaning agent to remove residual grout.

19. The method according to claim 1, wherein the offshore structure comprises a monopile and transition piece and the grout application location is an annulus described between the monopile and transition piece.

20. The method according to claim 19, comprising inserting the cleaning pig into the grout line when the level of grout overflows the annulus.

21. A grouting system for applying grout to an offshore structure, the system comprising a grout line, the system further comprising a cleaning pig configured to clean grout from the grout line, wherein, in use, the cleaning pig is received within a first end of the grout line and conveyed therealong from the first end towards the offshore structure so as to evacuate at least a portion of the remaining grout from the grout line to the offshore structure.

22. The grouting system according to claim 21 , comprising a grout pump configured to convey grout along the grout line towards the offshore structure.

23. The grouting system according to claim 21 or claim 22, comprising a water supply and a water pump, wherein the water pump is configured to pump water, from the water supply, upstream of the cleaning pig so as to convey the cleaning pig along the grout line.

24. The grouting system according claim 21, wherein the grout line comprises a cleaning pig seat configured to receive and engage the cleaning pig as it is conveyed so as to prevent the flow of fluid from a location upstream of the cleaning pig to a location downstream of the cleaning pig, wherein the cleaning pig seat is located such that between 50% and 100% of the remaining grout is evacuated from the grout line to the offshore structure.

25. The grouting system according to claim 24, wherein the grout line comprises a main grout line and a buffer hose, and the cleaning pig seat is located at the connection between the main grout line and the buffer hose.

26. A water supply system for conveying a cleaning pig along a grout line of a grouting system according to claim 21 , the system comprising a water supply and a water pump, wherein the water pump is configured to pump water from the water supply upstream of the cleaning pig to convey the cleaning pig along the grout line.

27. The water supply system according to claim 26, wherein the water supply volume is less than or equal to a volumetric capacity of the grout line.

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