Electricity: measuring and testing – Of geophysical surface or subsurface in situ – By aerial survey
Reexamination Certificate
1999-04-01
2001-07-03
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
By aerial survey
C324S326000, C324S345000
Reexamination Certificate
active
06255825
ABSTRACT:
This invention relates generally to techniques for locating pipelines and ferromagnetic objects located at or just under the surface of the ground, and has to do particularly with a method and apparatus for detecting, locating, and resolving such objects.
BACKGROUND OF THIS INVENTION
It is essential for human activity that pipelines be laid, in order to transport gases, (usually natural gas), liquids (water, crude or refined hydrocarbons) and even slurries (e.g. coal, etc., in a liquid carrier). Commonly, these pipelines are buried, for protection against surface traffic, etc. After some years, surface vegetation or weathering may effectively mask the location of the pipelines. In some instances, there may be no information about the precise path of a pipeline, either due to the fact that its path was never accurately surveyed, or that the documentation about its path has since been lost. This may be true even if the pipeline is still being actively used for its original purpose.
In the event of further activity in the vicinity, which may necessitate the disturbance of the surface, it becomes a vital matter to precisely determine the location of the pipelines in the area, in order to avoid the possibility of inadvertent rupture of a pipeline. The consequences, in terms of personal injury or financial loss, of the rupture of a gas or oil pipeline, for example, could be very serious.
A common occurrence, for example, is the need to conduct further seismic tests, utilizing new technology, in the vicinity of a producing oil field. Seismic tests require the detonation of explosive charges, or the use of heavy vibrators, whose sites must be well clear of existing pipelines.
It may also occur, in the case of an oilfield or network of water wells where a series of wells feeds a system of collection by pipes, that the precise location of the individual wells is no longer known but must be determined, to facilitate further activity in the field.
Although means are known for locating buried pipes by ground measurements, such means usually rely on the ability to contact the pipe at one known point and, in any case, are slow and labour intensive if a large area, encompassing multiple pipelines, is to be mapped.
Pipelines are commonly made of steel, as an inexpensive, strong and durable material. Where the metal of the pipe comes into direct contact with groundwater, however, corrosion may occur, due to electrochemical action. To help guard against such corrosion, pipelines are usually covered with an impervious coating before burial. In addition, the electrical potential of the pipe is often lowered relative to the ground by use of a suitable DC generator, thus providing “cathodic protection” against corrosion, but causing DC current to flow along the pipe.
Wellheads are usually characterized by having rather long lengths of near-vertical steel casing, in order to maintain the integrity of the well and to allow gases or fluids to be brought to the surface.
Other ferrous objects, such as buried drums, submerged vessels, buried ordnance, etc. may themselves be the targets of interest for detection and precise positioning. These are usually much more limited, dimensionally, than pipelines or wellhead castings.
GENERAL DESCRIPTION OF THIS INVENTION
In view of the foregoing, it is an aim of one aspect of this invention to provide a method and apparatus whereby to precisely map the location of pipelines and wellheads, very quickly and inexpensively, from the air. It is the aim of a further aspect of this invention to provide a diagnostic means whereby the response from the pipelines and wellheads may be distinguished from one another and from responses due to geological features and other cultural sources.
It is well known that steel objects can cause changes (anomalies) in the Earth's natural magnetic field in their vicinity. These changes have often been observed in accurate surveys of the Earth's total magnetic field, whose primary objective is geologic information, and are usually regarded as “noise” on the surveys. Such magnetic “noise” may be generated by pipelines, buildings, bridges, and wellheads, etc., all of which contain significant amounts of steel.
There are really three sources of such magnetic noise, namely:
1) induced magnetization of the steel objects, in the Earth's field, due to their high magnetic susceptibility;
2) remanent (permanent) magnetization, created in the steel when it was initially formed at high temperatures, and then cooled; and
3) the magnetic field of the cathodic protection current flowing in the pipelines. Even in the case of pipelines which are not under active cathodic protection, there may be currents flowing, due to electrochemical cells set up between dissimilar ground contact points on the pipe.
In the present invention use is made of these “noises” in the Earth's magnetic field to detect and precisely locate their sources, and to resolve these sources into useful categories, such as pipelines, wellheads and local steel objects (buildings, bridges, ordnance. etc.).
More particularly, this invention provides an apparatus for mapping the ground location of pipelines and wellheads from the air, comprising:
a framework adapted to be transported above the ground, the framework having a prescribed orientation relative to the transport direction,
first and second magnetic field sensors supported on the framework so as to be in substantially the same horizontal plane and spaced apart transverse to the direction of transport when the framework is being transported in said prescribed orientation,
a third magnetic field sensor supported by said framework,
altimeter means for determining the elevation of the sensors above the ground,
and computing means for receiving signals from all of the sensors and the altimeter, and for determining field gradients by operations based on the received signals.
Further, this invention provides a method of mapping the ground location of pipelines and wellheads from the air, utilizing a framework on which are supported:
first and second magnetic field sensors positioned so as to be spaced apart transversely in the same horizontal plane when the framework is in a prescribed orientation relative to the direction of transport and to the vertical, a third magnetic field sensor located so as to be substantially vertically aligned with the mid-point between the first and second sensors when the framework is in said prescribed orientation, and
altimeter means supported on said framework for determining the elevation of the sensors above the ground,
the said method including the steps:
A. transporting the framework spaced above the ground such that the framework maintains said prescribed orientation relative to the direction of transport and to the vertical,
B. during transport, causing said sensors and said altimeter means to emit signals,
C. utilizing the said signals to determine a) the total field variations and b) the magnetic field gradients in three mutually perpendicular directions, and
D. interpreting said variations and gradients to determine the presence of pipelines and wellheads on or under the ground.
In addition, this invention provides a method of mapping the ground location of pipelines and wellheads from the air, utilizing a framework on which are supported:
first and second magnetic field sensors positioned so as to be spaced apart transversely in the same horizontal plane when the framework is in a prescribed orientation relative to a direction of transport and to the vertical,
a third magnetic field sensor supported by said frame in a location where it is substantially equidistant from said first and second sensors, and is located substantially vertically under the mid-point between the first and second sensors when the framework is in said prescribed orientation,
a fourth magnetic field sensor located in the same horizontal plane as the first and second sensors and equidistant therefrom, but spaced away from the mid-point between the first and second sensors in the direction of flight, and altim
McConnell Terrence
Ryder-Turner Alastair
Seigel Harold O.
Scintrex Limited
Sim & McBurney
Strecker Gerard R.
LandOfFree
Method and apparatus for detecting, locating and resolving... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for detecting, locating and resolving..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for detecting, locating and resolving... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2517020