Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
2001-07-20
2004-03-30
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S721000
Reexamination Certificate
active
06714018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrical heating of subsea pipelines. More particularly, the invention relates to method for commissioning and operating a pipe-in-pipe pipeline.
2. Description of Related Art
Offshore hydrocarbon recovery operations are increasingly moving into deeper water and more remote locations. Often satellite wells are completed at the sea floor and are tied to remote platforms or other facilities through extended subsea pipelines. Some of these pipelines extend through water that is thousands of feet deep, where temperatures of the water near the sea floor are in the range of 40° F. The hydrocarbon fluids, usually produced along with some water, reach the sea floor at much higher temperatures, characteristic of depths thousands of feet below the sea floor. When the hydrocarbon fluids and any water present begin to cool, phenomena occur that may significantly affect flow of the fluids through the pipelines. Some crude oils become very viscous or deposit paraffin when the temperature of the oil drops, making the oil practically not flowable. Hydrocarbon gas under pressure combines with water at reduced temperatures to form a solid material, called a “hydrate.” Hydrates can plug pipelines and the plugs are very difficult to remove. In deep water, conventional methods of depressurizing the flow line to remove a hydrate plug may not be effective. Higher pressures in the line and uneven sea floor topography require excessive time and may create operational problems and be costly in terms of lost production.
The problem of lower temperatures in pipelines has been addressed by a variety of heating methods, including electrical heating. Most of the proposals for electrical heating of pipelines have related to pipelines on land, but in recent years industry has investigated a variety of methods for electrical heating of subsea pipelines. (“Direct Impedance Heating of Deepwater Flowlines,” OTC 11037, May, 1999). One electrical heating method is the pipe-in-pipe method. In one configuration of a pipeline using this method, a pipe-in-pipe subsea pipeline is provided by which a flow line for transporting well fluids is surrounded concentrically by and electrically insulated from an electrically conductive outer pipe until the two pipes are electrically connected at the distal or remote end of a heated segment by a bulkhead. Voltage is applied between the inner and outer pipes at the proximate or electrical input end and electrical current flows along the exterior surface of the inner pipe and along the interior surface of the outer pipe. This pipe-in-pipe method of heating is disclosed, for example, in U.S. Pat. No. 6,142,707. Other variations of the general pipe-in-pipe method exist. The electrical power is supplied through an electrical isolating joint at the power input end of a segment of line to be heated. Alternating current, normally at about 60 Hz, is used. The voltage across the annulus is highest at the isolating joint and falls linearly to zero at the bulkhead. The current is essentially constant along the entire length of the pipe segment that is heated. Two key electrical effects, the skin effect and the proximity effect, confine the current flow largely to the annulus surfaces. Consequently, most of the current is effectively isolated from the produced fluids and the seawater around the pipeline.
Phenomena related to the commissioning (starting-up) and operation of pipe-in-pipe pipelines may cause loss of electrical isolation between the inside and outside pipes. This may be a result of water-induced arcing or a direct short because of inadvertent water or other contaminants entering the annulus or external mechanical damage. There is a need for methods that allow detection of any condition change in the pipeline that could cause an electrical fault upon application of power for heating and to allow operation of the pipeline by applying high voltages while minimizing risk of electrical faults.
SUMMARY OF THE INVENTION
In one embodiment, a method for determining electrical properties of a pipeline is provided. A base curve of impedance over the full range of operating voltages at a range of temperatures is developed. The curve may be used to measure thermal properties of the pipeline by measuring cooling rate. A method for applying voltage to the line provides increasing increments so that risk of damage from arcing is decreased.
REFERENCES:
patent: 972308 (1910-10-01), Williamson
patent: 1231202 (1917-06-01), Saylor
patent: 2217857 (1937-04-01), Byck
patent: 2096279 (1937-10-01), Karcher
patent: 2178720 (1939-02-01), Daniels
patent: 2206831 (1940-03-01), Betrhelsen
patent: 2224403 (1940-12-01), Lines
patent: 2306831 (1942-12-01), Proctor
patent: 2660249 (1953-11-01), Jakosky
patent: 2678377 (1954-05-01), Justiz
patent: 2714930 (1955-08-01), Carpenter
patent: 2757738 (1956-08-01), Ritchey
patent: 2851197 (1958-09-01), Colton
patent: 2982354 (1961-04-01), Green
patent: 3184958 (1965-05-01), Eaton
patent: 3388724 (1968-06-01), Mowell et al.
patent: 3423570 (1969-01-01), Trabilcy
patent: 3432186 (1969-03-01), Braun
patent: 3439075 (1969-04-01), Bauer et al.
patent: 3507330 (1970-04-01), Gill
patent: 3515837 (1970-06-01), Ando
patent: 3547193 (1970-12-01), Gill
patent: 3556218 (1971-01-01), Talley, Jr. et al.
patent: 3605888 (1971-09-01), Crowson et al.
patent: 3614986 (1971-10-01), Gill
patent: 3620300 (1971-11-01), Crowson
patent: 3630038 (1971-12-01), Ando
patent: 3642066 (1972-02-01), Gill
patent: 3706872 (1972-12-01), Trabilcy
patent: 3789188 (1974-01-01), Rudbarg
patent: 3859503 (1975-01-01), Palone
patent: 3885595 (1975-05-01), Gibson et al.
patent: 3933031 (1976-01-01), Uhlarik
patent: 3935632 (1976-02-01), Maxson
patent: 3944262 (1976-03-01), Stiner et al.
patent: 3958636 (1976-05-01), Perkins
patent: 3975617 (1976-08-01), Othmer
patent: 3981181 (1976-09-01), Ochiai
patent: 3983360 (1976-09-01), Offermann
patent: 4010799 (1977-03-01), Kern et al.
patent: 4011652 (1977-03-01), Black
patent: 4017102 (1977-04-01), Henderson
patent: 4140179 (1979-02-01), Kasevich et al.
patent: 4142093 (1979-02-01), Offermann
patent: 4319632 (1982-03-01), Marr, Jr.
patent: 4401162 (1983-08-01), Osborne
patent: 4450711 (1984-05-01), Claude
patent: 4496174 (1985-01-01), McDonald et al.
patent: 4522578 (1985-06-01), Jameson et al.
patent: 4553023 (1985-11-01), Jameson et al.
patent: 4590971 (1986-05-01), Webster et al.
patent: 4644780 (1987-02-01), Jeter
patent: 4645906 (1987-02-01), Yagnik et al.
patent: 4667505 (1987-05-01), Sharp
patent: 4684786 (1987-08-01), Mann et al.
patent: 4716960 (1988-01-01), Eastlund et al.
patent: 4768455 (1988-09-01), Maxson et al.
patent: 4831324 (1989-05-01), Asakura et al.
patent: 4839644 (1989-06-01), Safinya et al.
patent: 4861074 (1989-08-01), Eastlund et al.
patent: 4874925 (1989-10-01), Dickenson
patent: 4970467 (1990-11-01), Burnett
patent: 4992001 (1991-02-01), Harrison
patent: 4996879 (1991-03-01), Kruka et al.
patent: 5072622 (1991-12-01), Roach et al.
patent: 5172730 (1992-12-01), Driver
patent: 5189374 (1993-02-01), Burnett
patent: 5270661 (1993-12-01), Burnett
patent: 5289561 (1994-02-01), Filho
patent: 5421675 (1995-06-01), Brown et al.
patent: 5464307 (1995-11-01), Wilkins
patent: 5490562 (1996-02-01), Arnold
patent: 5605798 (1997-02-01), Koster
patent: 5801953 (1998-09-01), Thoma et al.
patent: 5836719 (1998-11-01), Martin et al.
patent: 5905194 (1999-05-01), Strong
patent: 6000438 (1999-12-01), Ohrn
patent: 6049657 (2000-04-01), Sumner
patent: 6058979 (2000-05-01), Watkins
patent: 6114857 (2000-09-01), Kohl
patent: 6142707 (2000-11-01), Bass et al.
patent: 6171025 (2001-01-01), Langner et al.
patent: 6179523 (2001-01-01), Langner et al.
patent: 6264401 (2001-07-01), Langner et al.
patent: 6278095 (2001-08-01), Bass et al.
patent: 6278096 (2001-08-01), Bass
patent: 6292627 (2001-09-01), Gilchrist, Jr. et al.
patent: 6305429 (2001-10-01), Welch et al.
patent: 6315497 (2001-11-01), Wittman et al.
patent: 6364401 (2002-04-01), Kim
patent: 6371693 (2002-04-01), Kopp et
Lair Donald M.
Le N.
Shell Oil Company
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