CA1114624A - Offshore structure carrying a plurality of curved conductor casings and method of installing a curved conductor casing on an offshore structure - Google Patents
Offshore structure carrying a plurality of curved conductor casings and method of installing a curved conductor casing on an offshore structureInfo
- Publication number
- CA1114624A CA1114624A CA303,973A CA303973A CA1114624A CA 1114624 A CA1114624 A CA 1114624A CA 303973 A CA303973 A CA 303973A CA 1114624 A CA1114624 A CA 1114624A
- Authority
- CA
- Canada
- Prior art keywords
- casing
- curved
- platform
- offshore structure
- level
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000004020 conductor Substances 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000003466 welding Methods 0.000 claims description 2
- 239000004576 sand Substances 0.000 abstract 1
- 238000005553 drilling Methods 0.000 description 9
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
- E21B7/043—Directional drilling for underwater installations
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B17/02—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto
- E02B17/027—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto steel structures
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Geochemistry & Mineralogy (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Earth Drilling (AREA)
- Revetment (AREA)
Abstract
OFFSHORE STRUCTURE CARRYING A PLURALITY OF CURVED
CONDUCTOR CASING SAND METHOD OF INSTALLING A CURVED
CONDUCTOR CASING ON AN OFFSHORE STRUCTURE
Offshore structure carrying a plurality of curved conductor casings, which structure is situated on the bottom of a body of water and supports a platform at a level above the said body of water, each conductor casing comprising a curved part and a non-curved part, the non-curved part being inclined to the vertical and extending from a level below the seabottom to a level between the seabottom and the platform, and the curved part consisting of a pre-curved tubular element that is connected to the top of the non-curved part and has the central axis of the top opening thereof substantially vertically arranged. The ease covers, moreover, a method of installing a curved conductor casing on an off-shore structure supporting a platform.
CONDUCTOR CASING SAND METHOD OF INSTALLING A CURVED
CONDUCTOR CASING ON AN OFFSHORE STRUCTURE
Offshore structure carrying a plurality of curved conductor casings, which structure is situated on the bottom of a body of water and supports a platform at a level above the said body of water, each conductor casing comprising a curved part and a non-curved part, the non-curved part being inclined to the vertical and extending from a level below the seabottom to a level between the seabottom and the platform, and the curved part consisting of a pre-curved tubular element that is connected to the top of the non-curved part and has the central axis of the top opening thereof substantially vertically arranged. The ease covers, moreover, a method of installing a curved conductor casing on an off-shore structure supporting a platform.
Description
1$~4~i;Z~ ~
OFFSHORE STRUCTURE CARRYING A PLURALITY OF CURVED
CONDUCTOR CASINGS AND METHOD OF INSTALLING A CURVED ;
CON~UCTOR CASING ON AN OFFSHORE STRUCTURE
The invention relates to an offshore structure carrying a plurality of inclined or curved conductor casings, said structure being placed on the bottom of a body of water and supporting a platform at a level above the said body of water.
Offshore structures of this type are applied for drilling underwater wells and for subsequently recovering oil and/or gas from such wells. Normally, a plurality of wells is drilled from a single platform, these wells penetrating into oil and/or gas containing formations that are located below the seabottom, Since more than one well is to be drilled from the plat~orm, measures should be taken to obviate a well that is being drilled from passing through a previously drilled well and damaging the casing and tubing in such well as well as to avoid damage to the foundation of the offshore structure.
Thereto, drilling of each well is initiated by guiding the drill string into the seabottom via a conductor casing that extends ~rom the platform into the seabottom (over a depth of say 100-200 ft within the earth). The conductor 1~14~2~ ~
is straight inside t-he platfcrm structure and is curved over that part between bracing and platform deck and arranged such ;~
that the central axis of the entry thereto at the level of the platform is vertically positioned. Since the casing is 5 curved, the central axis of the exit thereof (which exit is ~-situated at say 100-200 ft below the seabottom) is conse-quently inclined with respect to the vertical (say at an angle between about 1-10 degrees). By arranging the various conductor casings such that the central axes of their exits deviate from each other, the wells that are being drilled through these casings will not interfere with one another.
Object of the invention is a structure carrying a plurality of curved conductor casings, which casings can be easily installed on the structure.
Another object of the invention is a method of installing a curved conductor casing on an offshore structure in a simple manner which guarantees a s~ooth continuous bore over the curved part of the conductor casing.
The offshore structure according to the invention carries a plurality of curved casing conductors, is situated on the bottom of a body of water and supports a platform at a level above the said body of water, each conductor casing comprising a curved part and a non-curved part, the non-curved part being inclined to the vertical and extending from a level below the seabottom to a level between the seabottom and the platform, and the curved part consisting of a pre-curved tubular element that is connected to the top of the non-curved part and has the central axis of the top opening there-~4 of substantiall~ verticall~ arranged.
The method of installing a curved conductor casing onan offshore structure supporting a platform co~prises the steps of arranging a substantially straight casing with part thereof in the seabottom such that the top end is below the platform, and mounting a pre-curved casing element on top of said straight casing such that the central axis of the entry ;
opening of the curved ele~ent is su~stantially vertically arranged and the connection between the two casing parts consists of a continuous smooth bore.
Since the casing element that is mounted on the ~traight casing has been curved to the desired curvature prior to being mounted on the straight casing, this curved casing element can be manufactured with great care and will have an uninterrupted smooth internal bore. The free passage of the drilling tools and well casing through the conductor casing is warranted hereby.
The straight casing is driven into the seabottom by pile driving means that are situated on e.g. the platform.
The straight casing is guided during this driving procedure by guide means that are arranged with the axes thereof coinciding and supported by the offshore structure. The straight casing ~ay be driven to a depth such that the uoper entry of this casing part is at a level between the sea level and the platform. In an alternative manner, this u?per entry i9 situated above the platform after the casin~ has reached a sufficient deoth, whereafter the upner part thereo is cut off at a level between the sea level and the platform.
4 :`
The invention will be descri~ed by way o~ example in more detail with reference to the drawing which shows a side view of an offshore structure carr~ing a plurality of curved conductor casing.
Offshore structure 1 is situated on the seabottom 2 and connected thereto ~y piles 3 driven through the legs 4 of the structure. If desired the piles 3 ~ay be cemented in holes 5 that have been drilled into the seabottom.
The structure 1 carries a platform 6, on which the drilling operations take place by drilling equipment, such as a derrick, rotary table, etc. Such eauipment is known per se and not shown in the drawing for sake of simplicity.
Parts 7 of the offshore structure 1 extending between the le~s 4 thereof act as reinforcements of the structure and at the same time support guide means 8 through which the conductor casing is passed when ~eing installed. The guide means may - in their most simple embodiment - consist of tubular elements that are welded to parts 7 or other parts tnot ~hown) o~ the structure 1, such that the central axes ; ;;
of a plurality of guide means arranged for guiding a single conductor casing, coincide with one another and are inclined at an angle between say 1-10 with respect to the vertical.
To install a conductor casing, a plurality of straight casing segments (that are interconnected at their adjoining ends by screw couplings, welds or the like) are assembled to form a straight caslng 9. The lower part of said straight casing is driven into the seabottom 2 in a known manner such as by using a pile driving hammer (in case of a relatively 6~ :
soft seabottom) or by drilling a hole b~T means of a drill bit that is lowered through the casing by means of a drill ~-string.
Subseauently, the u~per part of the straight casing is cut off at a level 10 below platform 6. This level 10 is preferably chosen between the sea level 11 and the platform 6 to obviate the use of divers. The upper part is removed and replaced by a precurved casing element. Such pre-curved casing element 12 is shown on the straight conductor casing 13 that has been installed through the guide elements 14. The curvature of the pre-curved casing element 12 has been chosen to allow an easy passing of casing strings and drill strings such that the central axis of the entry 15 thereto is sub-stantially vertical when the element 12 is mounted on the upper end of the straight casing 13. The element 12 and ~he casing 13 are interconnected by welding or in any other suitable manner such that the connection between these two tubular elements shows a smooth inner surface.
Subsequently, a rotary table (not shown) together with all other equipment required for drilling is placed above the entrance 15 to the curved conductor casing consisting of the straight part 13 and the pre-curved part 12.
As observed already hereinabove, the ~art 12 is curved at the desired radius prior to being installed on the structure 1, and therefore can be made in a manner such that it has a smooth curvature as well as a constant radius of the inner surface, thus ensuring the free, un-interrupted passage of drilling tools and tubulars that are being lowered there-4~2~
through during the drilling o~erations to allow an easy ~assing of casing strings and drill strings.
OFFSHORE STRUCTURE CARRYING A PLURALITY OF CURVED
CONDUCTOR CASINGS AND METHOD OF INSTALLING A CURVED ;
CON~UCTOR CASING ON AN OFFSHORE STRUCTURE
The invention relates to an offshore structure carrying a plurality of inclined or curved conductor casings, said structure being placed on the bottom of a body of water and supporting a platform at a level above the said body of water.
Offshore structures of this type are applied for drilling underwater wells and for subsequently recovering oil and/or gas from such wells. Normally, a plurality of wells is drilled from a single platform, these wells penetrating into oil and/or gas containing formations that are located below the seabottom, Since more than one well is to be drilled from the plat~orm, measures should be taken to obviate a well that is being drilled from passing through a previously drilled well and damaging the casing and tubing in such well as well as to avoid damage to the foundation of the offshore structure.
Thereto, drilling of each well is initiated by guiding the drill string into the seabottom via a conductor casing that extends ~rom the platform into the seabottom (over a depth of say 100-200 ft within the earth). The conductor 1~14~2~ ~
is straight inside t-he platfcrm structure and is curved over that part between bracing and platform deck and arranged such ;~
that the central axis of the entry thereto at the level of the platform is vertically positioned. Since the casing is 5 curved, the central axis of the exit thereof (which exit is ~-situated at say 100-200 ft below the seabottom) is conse-quently inclined with respect to the vertical (say at an angle between about 1-10 degrees). By arranging the various conductor casings such that the central axes of their exits deviate from each other, the wells that are being drilled through these casings will not interfere with one another.
Object of the invention is a structure carrying a plurality of curved conductor casings, which casings can be easily installed on the structure.
Another object of the invention is a method of installing a curved conductor casing on an offshore structure in a simple manner which guarantees a s~ooth continuous bore over the curved part of the conductor casing.
The offshore structure according to the invention carries a plurality of curved casing conductors, is situated on the bottom of a body of water and supports a platform at a level above the said body of water, each conductor casing comprising a curved part and a non-curved part, the non-curved part being inclined to the vertical and extending from a level below the seabottom to a level between the seabottom and the platform, and the curved part consisting of a pre-curved tubular element that is connected to the top of the non-curved part and has the central axis of the top opening there-~4 of substantiall~ verticall~ arranged.
The method of installing a curved conductor casing onan offshore structure supporting a platform co~prises the steps of arranging a substantially straight casing with part thereof in the seabottom such that the top end is below the platform, and mounting a pre-curved casing element on top of said straight casing such that the central axis of the entry ;
opening of the curved ele~ent is su~stantially vertically arranged and the connection between the two casing parts consists of a continuous smooth bore.
Since the casing element that is mounted on the ~traight casing has been curved to the desired curvature prior to being mounted on the straight casing, this curved casing element can be manufactured with great care and will have an uninterrupted smooth internal bore. The free passage of the drilling tools and well casing through the conductor casing is warranted hereby.
The straight casing is driven into the seabottom by pile driving means that are situated on e.g. the platform.
The straight casing is guided during this driving procedure by guide means that are arranged with the axes thereof coinciding and supported by the offshore structure. The straight casing ~ay be driven to a depth such that the uoper entry of this casing part is at a level between the sea level and the platform. In an alternative manner, this u?per entry i9 situated above the platform after the casin~ has reached a sufficient deoth, whereafter the upner part thereo is cut off at a level between the sea level and the platform.
4 :`
The invention will be descri~ed by way o~ example in more detail with reference to the drawing which shows a side view of an offshore structure carr~ing a plurality of curved conductor casing.
Offshore structure 1 is situated on the seabottom 2 and connected thereto ~y piles 3 driven through the legs 4 of the structure. If desired the piles 3 ~ay be cemented in holes 5 that have been drilled into the seabottom.
The structure 1 carries a platform 6, on which the drilling operations take place by drilling equipment, such as a derrick, rotary table, etc. Such eauipment is known per se and not shown in the drawing for sake of simplicity.
Parts 7 of the offshore structure 1 extending between the le~s 4 thereof act as reinforcements of the structure and at the same time support guide means 8 through which the conductor casing is passed when ~eing installed. The guide means may - in their most simple embodiment - consist of tubular elements that are welded to parts 7 or other parts tnot ~hown) o~ the structure 1, such that the central axes ; ;;
of a plurality of guide means arranged for guiding a single conductor casing, coincide with one another and are inclined at an angle between say 1-10 with respect to the vertical.
To install a conductor casing, a plurality of straight casing segments (that are interconnected at their adjoining ends by screw couplings, welds or the like) are assembled to form a straight caslng 9. The lower part of said straight casing is driven into the seabottom 2 in a known manner such as by using a pile driving hammer (in case of a relatively 6~ :
soft seabottom) or by drilling a hole b~T means of a drill bit that is lowered through the casing by means of a drill ~-string.
Subseauently, the u~per part of the straight casing is cut off at a level 10 below platform 6. This level 10 is preferably chosen between the sea level 11 and the platform 6 to obviate the use of divers. The upper part is removed and replaced by a precurved casing element. Such pre-curved casing element 12 is shown on the straight conductor casing 13 that has been installed through the guide elements 14. The curvature of the pre-curved casing element 12 has been chosen to allow an easy passing of casing strings and drill strings such that the central axis of the entry 15 thereto is sub-stantially vertical when the element 12 is mounted on the upper end of the straight casing 13. The element 12 and ~he casing 13 are interconnected by welding or in any other suitable manner such that the connection between these two tubular elements shows a smooth inner surface.
Subsequently, a rotary table (not shown) together with all other equipment required for drilling is placed above the entrance 15 to the curved conductor casing consisting of the straight part 13 and the pre-curved part 12.
As observed already hereinabove, the ~art 12 is curved at the desired radius prior to being installed on the structure 1, and therefore can be made in a manner such that it has a smooth curvature as well as a constant radius of the inner surface, thus ensuring the free, un-interrupted passage of drilling tools and tubulars that are being lowered there-4~2~
through during the drilling o~erations to allow an easy ~assing of casing strings and drill strings.
Claims (8)
1. Offshore structure carrying a plurality of curved conductor casings, which structure is situated on the bottom of a body of water and supports a platform at a level above the said body of water, each conductor casing comprising a curved part and a non-curved part, the non-curved part being inclined to the vertical and extending from a level below the seabottom to a level between the seabottom and the platform, and the curved part consisting of a pre-curved tubular element that is connected to the top of the non-curved part and has the central axis of the top opening thereof sub-stantially vertically arranged.
2. Offshore structure according to claim 1, wherein the non-curved part of the conductor casing extends from a level below the seabottom to a level between the body of water and the platform.
3. Offshore structure according to claim 1, wherein the non-curved part of the conductor casing is laterally supported by guide means having the central axes thereof coinciding with one another.
4. Offshore structure according to claim 1, 2 or 3, wherein the non-curved part of the conductor casing is inclined to the vertical at an angle between 1 and 10 degrees.
5. Method of installing a curved conductor casing on an offshore structure supporting a platform, said method comprising the steps of arranging a substantially straight casing with part thereof in the sea-bottom such that the top end is below the platform and mounting a pre-curved casing element on top of said straight casing such that the central axis of the entry opening of the curved element is substan-tially vertically arranged and the connection between the two casing parts consists of a continuous smooth bore.
6. Method according to claim 5, wherein the straight casing is arranged so as to have its top end at a level between the sea level and the platform.
7. Method according to claim 5, including the step of mounting the straight casing such that it extends from a level above the platform to a level below the sea-bottom, and subsequently removing the upper part thereof such that the top end of the straight casing is situated below the platform.
8. Method according to claim 5, 6 or 7, wherein the pre-curved part is mounted on the top end of the straight casing by welding.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2405977 | 1977-06-09 | ||
| GB24059/77 | 1977-06-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1114624A true CA1114624A (en) | 1981-12-22 |
Family
ID=10205718
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA303,973A Expired CA1114624A (en) | 1977-06-09 | 1978-05-24 | Offshore structure carrying a plurality of curved conductor casings and method of installing a curved conductor casing on an offshore structure |
Country Status (7)
| Country | Link |
|---|---|
| AU (1) | AU528812B2 (en) |
| CA (1) | CA1114624A (en) |
| DK (1) | DK251978A (en) |
| GB (1) | GB2000211B (en) |
| NL (1) | NL186921C (en) |
| NO (1) | NO781988L (en) |
| NZ (1) | NZ187481A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0910708B1 (en) * | 1996-06-17 | 2003-04-09 | Shell Internationale Researchmaatschappij B.V. | Lightweight offshore platform structure |
| NO338564B1 (en) * | 2013-01-28 | 2016-09-05 | Neodrill As | Device at inclined guide tubes |
| DE202019104155U1 (en) * | 2019-07-29 | 2019-09-18 | Thyssenkrupp Steel Europe Ag | Support structure, in particular for on- and / or offshore wind turbines |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3687204A (en) * | 1970-09-08 | 1972-08-29 | Shell Oil Co | Curved offshore well conductors |
| GB1399715A (en) * | 1972-06-10 | 1975-07-02 | Texaco Development Corp | Marine drilling structure |
| US3987639A (en) * | 1975-06-26 | 1976-10-26 | Brown & Root, Inc. | Methods and apparatus for installing a drill conductor from an offshore tower |
| US4027734A (en) * | 1975-12-11 | 1977-06-07 | Hebert & Co., Inc. Gurtler | Deviated conductor driving system |
-
1978
- 1978-05-24 CA CA303,973A patent/CA1114624A/en not_active Expired
- 1978-06-07 AU AU36891/78A patent/AU528812B2/en not_active Expired
- 1978-06-07 NL NLAANVRAGE7806186,A patent/NL186921C/en not_active IP Right Cessation
- 1978-06-07 NO NO781988A patent/NO781988L/en unknown
- 1978-06-07 NZ NZ187481A patent/NZ187481A/en unknown
- 1978-06-07 GB GB7826495A patent/GB2000211B/en not_active Expired
- 1978-06-07 DK DK251978A patent/DK251978A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NZ187481A (en) | 1981-04-24 |
| DK251978A (en) | 1978-12-10 |
| AU3689178A (en) | 1979-12-13 |
| GB2000211B (en) | 1982-01-13 |
| AU528812B2 (en) | 1983-05-12 |
| NL186921C (en) | 1991-04-02 |
| NO781988L (en) | 1978-12-12 |
| NL7806186A (en) | 1978-12-12 |
| GB2000211A (en) | 1979-01-04 |
| NL186921B (en) | 1990-11-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |