Mobile offshore drilling and production platform

Abstract

The present invention relates to a mobile offshore oil drilling and production platform ( 10 ) that allows a field operator to cope with uncertainty and economically develop a small or marginal oil filed typically located in a remote location. More particularly, the invention relates to a versatile platform which includes a hull ( 12 ) extending above the level of sea to house hydrocarbon extracting and scale up or scale down hydrocarbon processing system modules and equipment with provisions to drill new wells and work-overs using modular portable vertical drilling rigs or conventional rigs, connected to a mat acting as the foundation resting on the seabed which may or may not incorporate storage, using tubular legs, and provision to even abandon the field with minimal costs and disruption. The present invention also relates to a method of installing and de-installing the oil drilling and production platform ( 10 ).

1 . A mobile offshore oil drilling and production platform ( 10 ) wherein the platform includes:
 (a) a hull ( 12 ); and   (b) a mat ( 14 ), wherein the mat ( 14 ) is connected to at least one connecting leg ( 16 ) substantially vertical upstanding from the mat ( 14 ) to the hull ( 12 ) and the mat ( 14 ) includes at least one ballast compartment to be filled with sea water or compressed air in the platform;   characterized in that:   a drilling template ( 22 ) attached to the hull ( 12 ) and mat ( 14 ) by connecting means wherein a drilling template ( 22 ) is removeably attached to the hull ( 12 ) and mat ( 14 ); and   the at least one connecting leg ( 16 ) is provided with at least a stiffener, wherein the load of the platform ( 10 ) is transferred over a substantially large area of the mat ( 14 ), then to seabed.   
   
   
       2 . The platform as claimed in  claim 1 , wherein the platform ( 10 ) includes storage facilities. 
   
   
       3 . The platform as claimed in  claim 2 , wherein the mat ( 14 ) includes at least one ballast compartment ( 20 ) for storing processed oil. 
   
   
       4 . The platform as claimed in  claim 1 , wherein the drilling template ( 22 ) consists of a wellhead deck ( 24 ) that is removeably attached to the hull ( 12 ) and a subsea clamp or a removably attached conductor ( 26 ) subsea support frame ( 32 ) that is attached to the mat ( 14 ). 
   
   
       5 . The platform as claimed in  claim 1  wherein the drilling template ( 22 ) supports conductors ( 26 ) or a caisson ( 28 ) to contain drilling casings. 
   
   
       6 . The platform as claimed in  claim 5  wherein the caisson ( 28 ) is pre-installed by clamping it to the mat ( 14 ) and securing it to the wellhead deck ( 24 ) during towing of the platform. 
   
   
       7 . The platform as claimed in  claim 1  wherein the platform ( 10 ) is relocated to a different location without the drilling template ( 22 ) after the completion of the drilling process. 
   
   
       8 . The platform as claimed in  claim 1  wherein the platform ( 10 ) is attachable to another drilling template ( 22 ) or a wellhead platform at a different location. 
   
   
       9 . The platform as claimed in any one of the preceding claims, wherein the platform ( 10 ) is constructed and fully assembled at a fabrication yard and its quayside before towing to an offshore installation site as an integrated unit. 
   
   
       10 . A method of installing a mobile offshore oil drilling and production platform ( 10 ) as claimed in  claim 9 , wherein the method includes the steps of:
 (a) adjusting ballast levels in the hull ( 12 ) and the mat's ballast chambers to achieve all required conditions for the platform to be towed to an offshore installation site;   (b) securing parts of the platform such as the legs ( 16 ) and caisson ( 28 ) by securing means such as sea-fastening for the tow;   (c) towing the platform to the site;   (d) removing the securing means such as seafastening;   (e) adjusting the ballast levels to achieve all required conditions;   (f) activating the heightening means so that the mat ( 14 ), legs ( 16 ) and the caisson ( 28 ) or the conductor subsea support frame ( 32 ) to be lowered from underneath the hull ( 14 ) to the seabed;   (g) de-activating a subsea clamp holding the caisson to the mat ( 14 ), to allow the caisson ( 28 ) to self-penetrate;   (h) re-activating the clamp to provide lateral support for the caisson ( 28 );   (i) fully de-ballasting the hull ( 12 ); and   (j) activating the heightening means to elevate the hull ( 12 ) to a desired height.   
   
   
       11 . The method as claimed in  claim 10 , wherein the platform ( 10 ) includes storage facilities. 
   
   
       12 . The method as claimed in  claim 11 , wherein the mat ( 14 ) includes at least one ballast compartment ( 20 ) for storing processed oil. 
   
   
       13 . The method as claimed in  claim 10 , wherein the extracted hydrocarbons are transported to the hull ( 12 ) for separation and stabilization. 
   
   
       14 . The method as claimed in  claims 12  and  13 , wherein the processed oil is transported to the mat ( 14 ) and stored in the at least one oil storage compartment. 
   
   
       15 . The method as claimed in  claim 14 , wherein when the at least one oil storage compartment is full of the processed oil, a shuttle tanker is mobilized and the processed oil is offloaded using transporting means such as hoses. 
   
   
       16 . A method of de-installing a mobile offshore oil production and processing platform ( 10 ) which has been installed according to a method as claimed in  claim 10 , wherein the method of de-installing includes the steps of:
 (a) securing the wellhead deck ( 24 ) to the caisson ( 28 ) or conductors ( 26 ) by a securing means;   (b) detaching the drilling template ( 22 ) from the hull ( 12 );   (c) de-activating a subsea clamp holding the caisson ( 28 ) or the securing means to release the subsea support frame from the mat ( 14 );   (d) activating the heightening means so that the hull ( 12 ) is lowered to substantially the sea level;   (e) removing any adhesion caused by soil-in areas surrounding the mat;   (f) activating the heightening means so that the mat ( 14 ) and the legs are returned from the sea-bed to underneath the floating hull ( 12 ); and   (g) re-adjusting the platform to required conditions for towing to the next destination.   
   
   
       17 . The method as claimed in  claim 15 , wherein the platform ( 10 ) includes storage facilities. 
   
   
       18 . The method as claimed in  claim 16 , wherein the mat ( 14 ) includes at least one ballast compartment ( 20 ) for storing processed oil.