Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Reexamination Certificate
2001-08-28
2003-06-17
Lefkowitz, Edward (Department: 2862)
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
C324S239000, C324S227000
Reexamination Certificate
active
06580268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed toward artificial lift systems used to produce fluids from boreholes such as oil and gas wells. More particularly, the invention is directed toward apparatus and methods for measuring dimensions and flaws in coiled sucker rod as the rod string is removed from or inserted into the borehole.
2. Background of the Art
Oil and gas wells are typically drilled with a rotary drill bit and a circulating drilling fluid or “mud” system. Subsequent to the drilling of a well, or alternately at intermediate periods during the drilling process, the borehole is cased typically with steel casing, and the annulus between the borehole and the outer surface of the casing is filled with cement. The casing preserves the integrity of the borehole by preventing collapse or cave-in. The cement annulus hydraulically isolates formation zones penetrated by the borehole that are at different internal formation pressures. Producing zones are typically produced through tubing suspended within the casing.
Fluids can be produced from oil and gas wells by utilizing internal pressure within a producing zone to lift the fluid through the well borehole to the surface of the earth. If internal formation pressure is insufficient, artificial fluid lift means and methods must be used to transfer fluids from the producing zone and through the borehole to the surface of the earth.
The most common artificial lift technology utilized in the domestic oil industry is the sucker rod pumping system. A sucker rod pumping system consists of a pumping unit that converts a rotary motion of a drive motor to a reciprocating motion of an artificial lift pump. A pump unit is connected to a polish rod and a sucker rod “string” which, in turn, operationally connects to a rod pump in the borehole. The string can consist of a group of connected, essentially rigid, steel sucker rods sections (commonly referred to as “joints”) in lengths of 25 or 30 feet (ft), and in diameters ranging from ⅝ inches (in.) to 1¼ in. Joints are sequentially connected or disconnected as the string is inserted or removed from the borehole, respectively. Alternately, a continuous sucker rod in diameters ranging from ¾ inches (in.) to 1¼ in. (hereafter referred to as COROD) string can be used to operationally connect the pump unit at the surface of the earth to the rod pump positioned within the borehole. A delivery mechanism rig (hereafter CORIG or any injector) is used to convey the COROD string into and out of the borehole.
A prior art borehole pump assembly of a sucker rod operated artificial lift systems typically utilizes a progressing cavity pump (hereafter PCP) positioned within wellbore tubing. The PCP consists of a rotor operating within a stator, and is positioned at or near a formation to be produced. The sucker rod string is rotated from surface of the earth by a rotary well head drive, thereby imparting rotation to the rotor element of the PCP to provide desired fluid lifting. This system has proven to be an effective means of lifting primary heavy oil formations where sand is suspended within the produced fluid. As the sand laden oil mixture rises in the tubing string, the fluid acts like abrasive slurry that abrades the sucker rod string. This abrasion can be general over a length of the rod thereby altering the cross section area of the rod string over an extended length. Abrasion can be localized to form a groove or a ring around a limited vertical extent of the sucker rod string. Significant abrasive wear can lead to mechanical failure of the rod. In addition, produced fluids are often corrosive. These corrosive fluids can attack the sucker rod surface causing pitting that may lead to fatigue cracking and subsequent rod failure.
To summarize, fluids produced with a PCP operated with a COROD sucker rod system can adversely alter the sucker rod string. The fluid can abrade the sucker rod string over an extended length thereby reducing cross sectional area of the string. The fluid can “incise” groves or rings in vertically localized sections of the rod string thereby forming localized flaws. Corrosive fluid can pit or otherwise distort virtually any portion of the rod string that it contacts. All of these alterations can adversely affect the physical integrity of the sucker rod string that can lead to costly system failures. From an economic, operational and safety viewpoint, it is of prime importance to monitor the sucker rod for all types of alterations so that proper remedial action can be taken. More specifically, it is desirable to monitor sucker rod for alterations as the string is being removed from or inserted into the well borehole.
Electromagnetic Inspection (EMI) systems as well as eddy current surface inspection systems have been used to detect incised type flaws in sucker rod during manufacture and also during field use. Linear transducers have been used to measure sucker rod cross sectional dimensions, thereby providing a means of detecting wear type alteration of rod dimensions over extended lengths. These measurements have been limited to conventional sucker rod joints in the prior art. ICO Shearer (http:// www.icoshearerinc.com) offers an inspection service for continuous sucker rods. An inspection head assembly is used which will allow a 2 in. diameter rod which is pined and coupled to pass there through. This service is performed while the rod string is being removed from a well borehole. These prior art systems are, however, not practical for monitoring the condition of a conventional sucker rod string in “real-time” as it is pulled from or inserted into a well borehole.
Eddy current systems are very effective for at detecting surface defects such as cracks, grooves, gouges and the like. EMI systems have been used to detect localized defects or flaws in sucker rods. All of these systems require that a magnetic flux be induced within the rod. Surface defects result in magnetic flux leakage. Sensors measure the leakage and are thereby used to locate and even quantify the surface defect. An EMI system has been used to detect localized flaws in joints of tubulars, wherein the system employs Hall effect transducers and an energized coil that induces the magnetic flux within the tubular. Again, these measurements have been limited to inspecting the body of conventional sucker rod joints in the prior art, and are therefore are not practical for monitoring the condition of a conventional sucker rod string as it is pulled from or inserted into a well borehole. This limitation is partly due to forged pins at each end of a conventional sucker rod joint, and the non-consistent speed at which a rig crew pulls a conventional sucker rod string from a well borehole.
Several prior art systems are available for the inspection of continuous sections of wire rope. As examples, inspection systems wire rope inspection systems are disclosed in publications and several U.S. Patents to Noranda. An inspection system is offered by NDTech (http:///www.ndtettech.com
dtbro.pdf). Prior art wire rope inspection systems are summarized in the publication “Inspection of Wire Ropes in Service: A Critical review”, Frank A. Iddings and G. P. Singh, Materials Evaluation, Vol. 43, No. 13, pp. 1592-1605 (1985). The systems are typically portable, use permanent magnets to create a magnetic flux within the rope section being inspected, and all use the measure of magnetic flux leakage for flaw detection. Some systems measure the total magnetic flux to determine the effective cross-sectional area of the wire rope. This measurement is based upon the principle that for a saturated ferromagnetic rope, the magnetic flux is proportional to the cross-sectional area of the rope. A measure of magnetic flux can, therefore, be used to calculate the cross sectional area of the rope. Although not suitable for conventional sucker rod strings comprising joints, this technique can be adapted to measure the cross sectional area of continuous sucker rod strings, namely COROD str
Lefkowitz Edward
Moser, Patterson & Sheridan L.L.P.
Weatherford / Lamb, Inc.
Zaveri Subhash
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