Wells – Processes – Placing or shifting well part
Reexamination Certificate
2000-09-25
2002-08-20
Suchfield, George (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S207000, C166S208000, C166S242200, C166S242800
Reexamination Certificate
active
06435281
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of this invention of that of liner hangers for the isolation of the well bore of oil and gas wells from the earth formations through which the oil or gas well is being drilled.
As different producing, water, and other formations through which the drilled well will pass must be isolated from each other, a casing string must be cemented in place to isolate each zone. An oil or gas well is typically drilled by first deciding the minimum bore of the production string of casing, or the last pipe to be cemented in place and will be continuous from the surface all the way down to the oil or gas producing formations. This production string of casing must be large enough to allow the production tubing landed inside it to flow enough oil or gas to make the well economic.
Each casing set point requires that an additional concentric casing string be set. A typical set of casing strings in a subsea environment from the inside out would be 7″ 9.625″ 11.750″, 13.375″, and 16″ set within an 18.750″ bore blowout preventer stack, and 20 and 30″ casing strings set before the 18.750″ bore blowout preventer stack is installed. Each casing string occupies a certain amount of radial space, requiring that the next string of pipe be progressively smaller. That program provides a maximum of 5 casing set points with blowout preventer protection during drilling.
Typically, a casing string, i.e. 11.75″ outer diameter, is installed in a drill well bore suspended from the surface to a depth such as 10,000 feet deep. After cementing the 11.750″ casing in place, a hole is drilled with a bit through the 11.750″ casing, i.e. 10.50″ diameter hole to 12,000 feet deep. Into this hole a 9.625″ outside diameter casing can be landed and cemented in place. If the 9.625″ casing string is suspended from the surface and is therefore 12,000 feet long, it is called a casing string. If, however, the 9.625″ casing is only 2000′ long and is suspended by a hanger from the lower end of the 11.750″ casing string, it is called a liner. The use of a liner can save substantially on the cost of casing and cement, e.g. 10,000 feet of casing not purchased. The well program would be followed with a 7.000″ casing string continuous from the surface to the bottom of the well as the production casing string.
The 9.625″ liner in the example above would have saved the operator the 10,000 feet of pipe not purchased, with the cost of a conventional liner hanger being generally offset by the cost of the surface casing hanger. The liner still “costs” the drilling company the “radial space”, forcing the next string to be progressively larger.
In this conventional scenario, if an unexpected pressured formation is encountered and requires that an extra casing string is set, it would probably be 5.500″ in size. With the 5.500″ size, the tubing string landed inside would be reduced from 3″ to 2″, substantially restricting the flow of production from the well. Flow from wells is especially important offshore where the high cost of drilling and producing wells demands a high flow rate to be economic. Cases have been seen of abandonment of wells when an extra pressurized reservoir zone was encountered and the driller realized that his final well bore size would be too small to be economic.
SUMMARY OF THE INVENTION
The object of this invention is to provide a liner which does not occupy “radial space” in the well bore and therefore does force each previously set casing hanger to be a step larger in diameter.
A second object of the present invention is to provide the capability of installing multiple liners in a drilling program to compensate for unforeseen well control situations.
A third object of the present invention is to provide a liner that can be rolled up for compact storage and shipment.
Another object of the present invention is to provide a liner assembly that is compact enough to be airlifted out to an offshore drilling vessel.
Another object of the present invention is to provide an expandable liner which is metallic in construction and impervious to fluid flow.
REFERENCES:
patent: 3104703 (1963-09-01), Rike et al.
patent: 3354955 (1967-11-01), Berry
patent: 3746092 (1973-07-01), Land
patent: 4673035 (1987-06-01), Gipson
patent: 4715443 (1987-12-01), Gidley
patent: 5337823 (1994-08-01), Nobileau
patent: 5794702 (1998-08-01), Nobileau
patent: 5833001 (1998-11-01), Song et al.
patent: 6112818 (2000-09-01), Campbell
patent: 6253850 (2001-07-01), Nazzai et al.
“Reeled Expandable Casing Creates Single Diameter Well”, Offshore Magazine, p. 32, May 1997.*
“Cold-forged Connector Ties Back Well Risers in Congo Field”, Oil & Gas Journal, p. 90, May 5, 1997.*
“Use of Bi-Center PDC Bit Reduces Drilling Cost”, reprinted from Oil & Gas Journal, Nov. 13, 1995.
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