Boring or penetrating the earth – Boring a submerged formation
Patent
1996-12-18
1999-02-02
Dang, Hoang C.
Boring or penetrating the earth
Boring a submerged formation
166358, 175 61, E21B 712, E21B 704
Patent
active
058652604
DESCRIPTION:
BRIEF SUMMARY
This application claims priority to and the benefit of PCT International Application No. US/96/13960, filed Aug. 30, 1996, and U.S. Provisional Application Ser. No. 60/003,163, filed Sep. 1, 1995, now abandoned.
FIELD OF THE INVENTION
The present invention is directed to apparatus and a method for substantially reducing the costs of drilling and producing petroleum from underwater reservoirs.
More particularly, it relates to increasing the number of wells that can be drilled from a deep water platform having limited facilities to drill single wells through a multiplicity of "slots" by providing multiple wells in close proximity to one another (close proximity wells or "CPWs") in individual slots.
SUMMARY OF THE INVENTION
In accordance with the present invention, a facility or platform having a limited number of circular well-drilling slots is converted to provide additional well-drilling locations on the platform while protecting the platform from the hoisting and lowering loads normally required to drill deep water wells. This load protection is accomplished by transferring such loads to an underwater competent earth formation. To utilize a competent formation, an annular shroud (also referred to as a caisson or a drive pipe) having an outer diameter slightly smaller than the generally circular slot but large enough to accommodate multiple close proximity wells is extended downwardly through a platform slot and typical unconsolidated, underwater formations.
The wall thickness of the shroud is adequate to provide a heavy-wall pipe structure that can be driven to a "refusal" depth by an underwater hammer alone, or with aid of a rotary excavator. Preferably, the driven end of the shroud includes a surrounding "shoe" to aid and protect the driven edge of the shroud. In this way, the outer surface of the shroud is vertically supported over the full penetration depth in the competent formation. The upper end of the shroud can pass through the slot, but it is not connected thereto.
After the shroud is driven to its final depth, the enclosed detritus is excavated to form clear interior open space within the shroud. This open space is then configured to provide weight-bearing support for two or more separate CPWs. A series of internal guides are inserted within the excavated shroud. These guides each carry two or more axially-oriented parallel cylindrical apertures, one for each of the CPWs to pass through. The guides are locked in place with guide locks against the internal wall of the shroud. The guides are spaced apart from each other vertically over the length of the shroud and are aligned with one another so that their two or more apertures together define a series of two or more separate and distinct parallel cylindrical paths running from the lower end of the shroud to the drill platform. A multiple bore drill head is then installed, supported on the upper end of the shroud. Casings (also referred to as conductor strings) for the individual CPWs are then run through the distinct parallel paths defined by the guides. The weight of the conductor strings is suspended from the shroud. The largest of these conductor strings are generally somewhat less than half the diameter of the outer shroud.
The outer edges of the guides are supported on the inner wall of the shroud with their apertures positioned to create as much space between the two conductor strings as possible. In this way, the two or more conductor strings pass through the boreheads and down through the guides spaced along the shroud to the bottom of the shroud without becoming entangled.
These conductor strings are drilled or driven into the competent formation as the next step of the process. This drilling/driving can take place after one conductor string has been run to the bottom of the shroud or it can be commenced when the several conductor strings have been put in place in the shroud.
To anchor the conductor strings for drilling of the well from the bottom of the shroud, one or more guides generally of the type already described can be pos
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patent: 1900163 (1933-03-01), Dana et al.
patent: 4136996 (1979-01-01), Burns
patent: 4561802 (1985-12-01), Campo
patent: 5458199 (1995-10-01), Collins et al.
patent: 5560435 (1996-10-01), Sharp
Avocato Noel S.
Jackson John R.
Leiper Alan
Wiersma Jan
Chevron U.S.A. Inc.
Dang Hoang C.
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