Method for offshore production of hydrocarbons concurrently with the installation of a structure therefor

A method is provided for producing usable hydrocarbon product from an offshore reservoir. The method includes the economically desirable step of producing a valuable hydrocarbon product from the formation, soon after its being discovered. The product is then extracted from its reservoir, long prior to, and during the period when a marine structure is being fabricated and installed to more fully develop the reservoir and to receive a flow of the product.

BACKGROUND OF THE INVENTION 
In any offshore discovery of a hydrocarbon containing reservoir such as one 
holding crude oil and/or gas, a considerable time elapses between the 
actual time of discovery and the date when a flow of usable hydrocarbon is 
realized. The primary causes of delay are the necessary factors that go 
into preparing the site and the equipment so that wells can be drilled and 
the product extracted from the reservoir. 
Essentially, the reservoir or the formation and its environment must be 
tested to determine the condition of the soil, and as near as possible the 
conditions at the hydrocarbon formation or reservoir. Thereafter, and with 
this material in hand, a marine structure can be designed to be installed 
at the offshore site. The usual structure is capable of holding equipment 
for drilling the necessary wells and handling the resulting flow of 
product from these wells. 
An essential facet of any such structure or platform is the presence of 
drill conductors which function to guide a drill string as well as to form 
a conduit for drilling fluids. Said conductors normally comprise a series 
of tubular members which are incorporated into the offshore structure as 
it is being constructed. Under some circumstances the conductors can be 
driven into the formation by the drilling rig or vessel. 
Frequently, the marine structure is provided with a series of vertically 
aligned and spaced apart conductor guides. Thereafter, when a well is to 
be drilled, a conductor is lowered through the respective guides to assure 
a generally vertical disposition in anticipation of a drill string being 
passed therethrough. 
The design and building of an appropriate offshore structure is contingent 
to a large extent on the availability of facilities where the structure 
will be fabricated. This often requires that a reservation be made months 
in advance for use of said facilities in order to commence the physical 
building of the structure. 
Thereafter, when the structure has been completed, it is installed by being 
either floated to its offshore site, or by being barged. When it is 
properly positioned, it is fixed in place. With the structure's basic 
jacket located and piled, the remainder of the platform can be completed. 
The latter includes the positioning of well drilling equipment which is 
arranged cooperatively with pre-set drill conductors so that the necessary 
wells can be drilled. 
In any event the time schedule for the above noted design, building, 
installation and ultimate operation of the platform can extend into 
several years. 
During this extended period the reservoir or productive subterranean 
formation will remain untapped and serve no useful purpose. 
The herein disclosed method provides means whereby the offshore hydrocarbon 
containing formation or reservoir can be tapped or provided with a number 
of producing wells within a relatively limited time period. While at least 
some of the wells are thereafter provisionally producing usable product, 
the support structure can be designed, built and subsequently installed to 
facilitate further drilling and production. 
The disclosed offshore structure is thus adapted to utilize an auxiliary 
drilling vessel or ship to commence the production process. This however 
will be a temporary expedient until drilling equipment on the permanent 
platform can be utilized. 
The method herein disclosed resides in the use of a composite marine 
structure that can be built and installed on a piecemeal basis. This 
avoids the usual time delay which would otherwise result were the 
productive field or hydrocarbon containing formation to be provided with a 
drilling and producing structure in the usual manner. 
Physically, a relatively simple drilling template is fabricated which 
includes a plurality of upright drilling conductors. The function of the 
latter is to extend downwardly into the ocean floor, and upward for a 
predetermined distance beyond the water's surface. In such a position they 
will receive a downwardly moving, rotating drill string such that the 
latter can penetrate the substrate and concurrently confine a flow of 
drilling mud. 
In any platform utilized for offshore drilling, normally a drilling 
conductor is inserted into a platform slot only at such times as it is to 
be used. Thus, and as noted herein, the structure is provided with a 
series of vertically spaced drilling conductor guides which serve to 
properly position the conductor as it is lowered from the deck down toward 
the ocean floor. 
As a well is drilled through a prepositioned conductor, the well is 
subsequently completed, provided with well head equipment, and turned into 
a producing facility. 
In the present arrangement, a provisionally placed drilling vessel is 
utilized in conjunction with the initially installed drilling template. 
This is achieved by positioning or anchoring the vessel adjacent to the 
template. Thereafter, the vessel such as a jack-up rig which is provided 
with an overhung or outboard drilling platform, can extend over the 
installed template. The vessel's drilling equipment will thus be in 
position to penetrate the ocean floor by way of one of the conductors. 
Following this procedure, one or more wells can be drilled through a 
plurality of conductors, at least some of which wells can be producers. 
These will be connected to the shore or preferably to fluid separating 
equipment. The latter function to separate the liquid and gaseous products 
before each is transferred to shore or to a storage facility. 
Eventually, the above noted marine structure will be completed at the 
fabrication yard such that it can be installed in conjunction with the 
preinstalled drilling template. The platform, following normal design, 
will include a drilling deck having facilities thereon for continuing the 
drilling of the wells through the remaining conductors. Thus, the need for 
the auxiliary drilling vessel will be lessened, even obviated and the 
further drilling of wells can proceed from the platform itself. 
It is therefore an object of the invention to provide a method for 
facilitating the extraction of hydrocarbon products from an offshore 
formation in a manner which will permit rapid realization of a usable 
product without the immediate need for use of an expensive drilling and 
producing structure. 
A further object is to provide means for extracting a hydrocarbon fluid 
from an offshore reservoir or formation on a provisional basis during the 
interim period when the permanent marine structure or platform jacket is 
being fabricated and installed.

Producing hydrocarbons from an offshore subterranean reservoir or formation 
initially necessitates that corings be taken and tests be made to 
determine the composition of the substrate and the parameters of the 
productive area. This is achieved through a number of methods known to the 
prior art and exercised widely by the petroleum industry. 
When an approximate definition and scope of the reservoir has been 
determined, and the depth of water is known, a suitable drilling template 
can be designed and fabricated. 
Referring to FIGS. 1, 2 and 3, a drilling template 10 of the type 
contemplated is designed to fasten to the ocean floor 11 and to 
accommodate a number of drill conductors 12 and 13. The latter will extend 
above the water's surface 14 to be accessible for a drill string to be 
registered therein to drill a well. Normally the conductor is held 
substantially vertical, with its lower end buried in the formation 11. 
As shown in FIGS. 2 and 3, drilling template 10 comprises primarily 
vertically spaced apart upper tier 16 and lower tier 17. Each of the 
levels includes a plurality of conductor guides 18 and 18' which generally 
assume a wide mouth conical configuration. Thus, a downcoming conductor 12 
will be directed through the guide center opening 19 and be aligned with 
the next lower guide 18'. 
While only two levels or tiers are here shown, it is understood that 
drilling template 10 can embody any number of vertically spaced apart 
tiers depending on water depth. Each tier, however, will include a series 
of aligned conductor guides capable of guiding, and supporting a conductor 
in an upright position prior to a drilling operation. 
Drilling template upper tier 16 is comprised of a set of transverse 
stringers 21 and 22 which terminate at spaced apart terminal members 23 
and 24. Corresponding braces 26 and 27 extend between adjacent stringers, 
each pair forming a support seal for a conical guide element 18. The 
latter includes, as noted, a central passage 19 which is capable of 
slidably registering a downwardly moving tubular drilling conductor. 
Drilling template 10 lower level 17 is comprised of a base 28 having a 
series of conductor guides 18' which correspond to the arrangement of the 
guides in upper tier 16. Base 28 further includes corner columns 29 and 30 
which extend between the upper and lower levels. These columns can be 
embedded into substrate 11 a limited distance or they can accommodate 
anchoring piles when the drilling template 10 is set into place at a 
drilling site. 
Normally, upper and lower level conductor guides 18 and 18' respectively, 
are disposed in substantial vertical alignment. However, in the instance 
of the need to drill one or more diverted wells, the respective guides can 
be offset one from the other. This arrangement causes a downwardly moving 
conductor to be bent to assume a predetermined progressive curvature. 
Referring to FIG. 1, to facilitate movement of produced hydrocarbon from 
the various wells formed in the respective conductors 12 and 13, a second 
structure 31 is embedded adjacent to the drilling template 10. Said second 
structure includes a plurality of downwardly extending legs 32 and 33 
which support a deck 34. The latter is provided with processing means 36 
to receive one or more flows of produced hydrocarbon fluid. Here the fluid 
can be separated into components prior to transporting the hydrocarbon 
either as gas or liquid to the shore, to a tanker, or to other storage 
means. 
After drilling template 10 has been properly positioned and fastened into 
place with piles 37 and 38 to maintain its stability, it is ready to 
receive a drill string from an adjacent drilling vessel 41. The latter can 
be comprised of any one of a number of drilling ships or vessels familiar 
to the industry. These include both floaters and floor anchored platforms. 
In the present arrangement, drilling vessel 41 comprises a jack-up type rig 
wherein a deck 42 holds the necessary drilling and operating equipment for 
an offshore site. The vessel is provided with a plurality of operably 
positioned support legs 43 and 44. Deck 42 in effect comprises a hull 
which permits it to be floated into position for a drilling operation as 
desired. 
When properly positioned, the respective support legs 43 and 44 are urged 
downwardly through deck 42 until they contact the floor 11. Thereafter the 
deck elevating mechanism is activated to climb up the respective legs to a 
predetermined height above the water level. Deck 42 can now be utilized 
for drilling purposes in conjunction with template 10. 
In the present arrangement, the drilling vessel deck 42 includes an 
outboard drilling platform 46 which is positioned to extend from one side 
of the vessel's hull 42. It can thereby overlie drilling template 10 in 
contemplation of a drilling operation. As here shown, drilling platform 46 
is provided with the usual equipment for achieving a drilling operation. 
Such equipment usually comprises a derrick 47, a rotary table, necessary 
mud circulating pumps, draw works and the like. Said equipment is carried 
in a manner to permit a drill string to be lowered through the drilling 
platform 46 and into waiting conductor 12. 
As the drilling operation proceeds, eventually the hydrocarbon productive 
substrate will be reached and the well will be completed to include the 
usual well head, flow control equipment 48. The latter is operable to 
regulate the outflow of hydrocarbon fluid whether it be crude oil, gas or 
a combination thereof. As each well is completed, drilling platform 46 and 
derrick 47 are adjusted to be in alignment with another conductor in the 
template 10 and the drilling operation proceeds. 
As each well is completed, it will be connected by conduits 49 to 
processing means 36 on the adjacent structure 31. The latter usually 
comprises a manifold platform on which the various segments of processing 
and storage equipment are carried to receive produced product. Thus, the 
processed hydrocarbon, after leaving said equipment 36, can be moved by 
pipeline 51 to the shore, or alternately loaded onto an adjacent tanker to 
be carried away. 
During the period between the commencement of the various wells and the 
subsequent flowing of hydrocarbon product, the permanent enclosing jacket 
52 and platform can be designed and built. This latter segment will then 
be cooperatively placed about drilling template 10 and manifold platform 
31. 
Referring to FIG. 4, an offshore platform of the type herein contemplated 
is comprised primarily of jacket 52 which is comprised of a plurality of 
upstanding or battered legs 53 and 54 which extend from a point above the 
water's surface, downward to the ocean floor 11. The respective support 
legs are connected with intermittent braces 56 and 57 to give the unit 
structural integrity. 
To lower the completed jacket 52 into position, it is necessary to suspend 
the drilling operation through drilling template 10. This is followed by a 
retraction of legs 43 and 44 on drilling vessel 41 so that the latter can 
be floated on its hull 42 and removed. 
Jacket 52, which can be shipped by barge or floated to the drilling site, 
can now be readied to be guidably placed about drilling template 10. It is 
thus lifted with the aid of a crane and lowered about both drilling 
template 10 and the manifold platform 31 to assure a protective barrier 
and support means about these preinstalled members. 
As shown in FIG. 5, after jacket 52 is piled into place it is provided with 
means to align and receive an operating deck 61 on the jacket upper side. 
Jacket 52 is thus provided with a series of upstanding posts 58 and 59 
into which corresponding deck columns 62 and 63 can be stabbed whereby to 
properly align and engage the supporting jacket to the deck. 
Jacket 52 can be fastened to the ocean floor by pilings 64 and 66 or by 
similar means. The latter is achieved directly, by registering one or more 
piles 64 and 66, through a leg such as 53. Alternately, exterior piles 
which connect to a leg's outer surface can be utilized as the anchoring 
mechanism. 
With the enclosing jacket 52 and operating deck 61 fully installed, 
additional producing wells can be drilled and the production received on 
processing equipment carried on said deck. Thereafter, any equipment which 
was provisionally installed on manifold structure 31 can be disconnected 
and removed. 
Although modifications and variations of the invention can be made without 
departing from the spirit and scope thereof, only such limitations should 
be imposed as are indicated in the appended claims.