Wells – Above ground apparatus – With means facilitating connecting or disconnecting...
Reexamination Certificate
2001-09-25
2002-11-05
Schoeppel, Roger (Department: 3672)
Wells
Above ground apparatus
With means facilitating connecting or disconnecting...
C166S085100, C166S079100, C166S092100, C166S241700, C166S242100
Reexamination Certificate
active
06474411
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a metallic protector for the hydraulic seal surfaces located at the threaded ends of drill pipes, used for drilling of oil, gas and geothermal wells, which protect the critical hydraulic seal surfaces on the drill pipe's side pinion and side box joints, collectively referred to as drill pipe's female and male adapters. This protection of the seal surfaces against accidental external impacts using the metallic protectors, is provided during the final stages of drill pipe fabrication which includes sandblasting, painting and application of epoxy coating on the inside surface of the drill pipe assembly, and during transportation, handling and maneuvering in the wells.
DESCRIPTION OF BACKGROUND AND PRIOR ART
References:
D1: GB865 175A
D2: U.S. Pat. No. 2,627,877A
D3: Partial reference information. API (American Petroleum Institute)
Wells for oil, gas and extracted geothermal heat in form of steam or liquid having elevated temperatures, are typically drilled using a drill attached to a drill pipe or drill pipe strings which consist of a number of drill pipes attached together by use of threaded joints. These joints include two seal surfaces, one on each of the joining ends of the drill pipes. These seal surfaces are located perpendicular relative to the center line of each pipe assembly and at the entrance to the threaded end of the female pipe adapter, and below the threaded end of the male pipe adapter. When two drill pipe sections are screwed together, the two seal surfaces meet and join, and when the two pipe sections are properly torqued, the two seal surface a form a joint which is typically labeled a metal to metal seal joint. This joint is herein referred to as the drill pipe hydraulic joint.
This hydraulic joint is an extremely critical interface between the drill pipe section as the drill pipe is the rotational connection between the drill bit and the wellhead motor, and also serves as a conduit to transfer a variety of chemical slurries, also called mud, to the drill bit for the purpose of lubricating, flushing drill residue back out of the drilled well, and for cooling the drill bit and the attached drill pipe string which is exposed to elevated temperatures from friction induced heat. Drilled wells can reach a depth of 6 kilometers or 3.7 miles, and the slurry pumped through the drill pipe string must reach the point of the drill bit for the above stated purposes. The pressure of the pumped slurry and thus the internal pressure of the drill pipe string, can be up to 3,000 PSI or 210 Kg/cm
2
. Unit pipes come in a variety of different diameters from a few inches and up to 18 inches, or 46 centimeters, and with a length of up to 60 feet, or 20 meters. Drill pipe assemblies are typically fabricated from alloy steel SAE 4137H, equivalent UNS number G41370, and have a Rockwell hardness of 30~32 HRC. The hydraulic joint between each drill pipe section must be capable of withstanding extreme pressure and high torsional loading without leaking. Any leaks across two mating seal surfaces caused by an abnormal surface condition can very rapidly destroy the threaded connection and seal surfaces by erosion caused by high velocity of the leaking and escaping fluid, and consequently, the volume of fluid reaching the drill bit is reduced and this can have adverse consequences, and the drilling fluid may eventually break the drill pipe of the point of leakage, it can be a very expensive operation to recover the drill pipe lengths already in the ground, in both terms of time and money.
A drill pipe section is normally a three piece assembly, consisting of a pipe section where the side pinion, or main adapter, is welded to one end of the pipe, and the side box, or female adapter, is welded in the other end. To preclude hydraulic seal failure of the drill piping during operation, the drill pipe fabrication is concluded with a hydraulic testing, where the drill pipe assembly is internally pressurized to a pressure of between 5,000 to 10,000 PSI or 351 to 703 Kg/cm2. Furthermore, to preserve and protect critical areas on the drill pipe assembly, caps or other devices are normally attached to the ends of the assembly to provide protection during the final treatment of sandblasting and painting, and application of epoxy coating of the inside surfaces of the assembly, and during transportation, handling and maneuvering in the well.
At the present, there exist in the market a number of thread and seal protectors having different shape, form and functions. A common type of protector comprise a bell shaped form and with internal threads for adaptation to the drill pipe's male adapter, and having a flat compressed cardboard washer installed as an interface between the lower edge of the projector bell and the hydraulic seal surface on the drill pipe adapter. A protector plug comprising a collar being formed perpendicular to the center line of the protector and flared outward, and with external threads on the plug body for adaptation to the drill pipe's female adapter, and having a flat compressed cardboard washer installed as an interface between the lower surface of the protector collar, and the hydraulic seal surface on the drill pipe adapter. It is generally recognized that the concept or using compressed cardboard washers as a seal surface protector, provides partial protection, only. Furthermore, these washers deteriorate under extreme weather conditions, and are considered for one time use, only.
Reference 1, patent number GB855 175A, provides a concept for a single use die-cast screw thread protector for the screwed or pin ends of oil well sucker rods, with the main objective of sealing and protecting the pin or threaded ends of the sucker rod during painting and oven drying and handling and to prevent the entry of moisture into the critical threaded area. Sucker rods are used as the interfacing connection between the reciprocating driver motor, and the pump piston in the well. Sucker rods are typically connected together using an internally threaded coupling screwed to the sucker rod's external threaded pin ends. Sucker rod or sucker rod strings, with multiple sucker rods connected together, are operated in vertical reciprocating movement and are under pull and tensional levels of loading, which vary from moderate to extremely high, dependent on the depth of the well. Sucker rods or strings are exposed to external pressure from the pumped liquid, and there are no hydraulic leak paths within the adjoining sucker rod ends and interfacing coupling. There is a high failure rate in the industry of sucker rods in operation. The majority of the incidents are associated with threaded pin ends failure caused by metal fatigue from high pull and tensional loading, and induced operating vibrations. On the contrary, a drill pipe or drill pipe string operates at moderate to extremely high torsional loading and internal hydraulic pressure, relative to the depth of the well. The most common cause of drill pipe failure is associated with high friction loading between the drill pipe or drill pipe string and the well wall which can cause a reduction of the pipe diameter of up to 0.275 inch or 7.0 millimeter, leaks at the hydraulic joint between pipe adapter sections with consequent failure of the joint from high liquid velocity erosion, and last, stress induced metal fatigue from violent shock, torsional loading and vibrations during the drilling operation.
To alleviate some of the causes for a drill pipe and sucker rod strings failure in the well, it is imperative that precautions be employed, which includes care during the last phases of drill and sucker rods fabrication, handling and transportation to the well site. Last minute inspections of critical areas are carried out prior to the insertion of a sucker rod or drill pipe into the well. Such inspections and evaluations are commonly prone to human errors, causing unexpected situations at a well site. Precautionary measures include the use of various type of screw-on protect
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