Wells – Processes – Placing or shifting well part
Patent
1995-08-09
1997-08-12
Dang, Hoang C.
Wells
Processes
Placing or shifting well part
166187, 1663324, 166387, E21B 33127
Patent
active
056556071
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a downhole tool, e.g. for pressure testing of oil and gas wells, comprising a generally tubular main tool which is provided with an internal passage and is arranged to be attached between a drill pipe string and a drill bit or the like, said main tool on its outside being provided with an inflatable packing element which may be supplied with and relieved of inflating medium via an annular slide valve arranged internally in the main tool, said slide valve being movable against the action of a valve spring from a closing initial position to a first position wherein inflating medium may be supplied to the packing element and a second position wherein the inflating medium is permitted to leave the packing element, by means of at least one auxiliary tool which is lowerable through the drill pipe string at the end of a cable, the slide valve being provided with a central, through-going passage which has an inwardly extending shoulder against which a portion of the auxiliary tool may be brought to sealing abutment and by means of pressure move the slide valve in the direction towards the drill bit or the like to said first position.
Such a downhole tool is known e.g. from U.S. Pat. No. 3,529,665. Here, the slide valve is divided into two mutually axially movable parts, the lower part having a smaller internal diameter than the upper part. When the packing element is to be inflated, a first auxiliary tool is lowered which passes the upper part of the slide valve and comes to sealing abutment against a shoulder on the lower part, whereupon pressurizing of the drill string causes the first auxiliary tool to displace the lower part of the slide valve downwards against the action of the valve spring, so that a passage to the packing element is opened for inflating it. Upon completed pressure testing the first auxiliary tool is raised and replaced by an auxiliary tool having larger diameter, which upon being run down comes to rest against a shoulder on the upper part of the slide valve. Upon pressurizing the drill string, both the upper and lower parts of the slide valve are moved downwards against the action of the valve spring, thus opening a relieving passage from the packing element to the outside of the main tool via an annular space in the upper part of the slide valve. This structure is not known to be used in the oil industry, a possible explanation being that it is too complicated to use or that it cannot satisfy the strict reliability requirements imposed in offshore oil drilling. Furthermore, it will be difficult or impossible to use in deviation drilling or in horizontal wells.
It is therefore common to undertake formation strength testing only at the shoe of the casing pipe of the well. If, nevertheless, it is necessary to test an open hole, this is done by pulling the drill string out of the hole, dismantling the drill bit etc. and attaching an inflatable packing element to the drill string, which is again run down into the hole to the desired depth. The packing element is subsequently inflated in order to close the hole, whereupon pressure testing of the hole below the packing element may be performed. When the test has been performed, the packing element is deflated and the drill string is pulled out. The packing element is removed, the drill bit etc. installed and the drill string again run down into the hole to continue the drilling. This is a very time consuming and expensive process which therefore often is omitted, i.a. leading to reduced safety.
Thus, it is an object of the present invention to provide an improved tool of the above mentioned type which is well suited for horizontal wells and which, nevertheless, has a simple and reliable structure and is easy, safe and quick to use. It is also an object of the invention to provide a tool which has a wide field of application so that it i.a. may be used for selective pressure testing above or below the tool in an open hole, selective pressure testing above or below the tool in casing pipe, pressure testing of hole s
REFERENCES:
patent: 2862562 (1958-12-01), Hughes
patent: 3335802 (1967-08-01), Seyffert, III
patent: 3529665 (1970-09-01), Malone
patent: 3941190 (1976-03-01), Conover
patent: 4648448 (1987-03-01), Sanford et al.
Aadn.o slashed.y Bernt Sigve
Freyer Jan
Mellemstrand Jone
ritsland Svein
Dang Hoang C.
Smedvig Technology AS
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