Downhole cable protection device

A device for an underground well, typically a petroleum well (1), wherein, in the uncased inflow portion (2, 4, 6) of the well, there is placed an inflow pipe, possibly in the form of a strainer pipe (8) comprising a strainer/perforated outer mantle (16), a main pipe (12) located within and a number of preferably axial spacer strips (18) spaced apart about the external periphery of the main pipe and arranged to support the strainer mantle (16), whereby there are, in the space defined by the strainer mantle (16) and the main pipe (12), channels 20 between the spacers (18), and in one or more of the channels 20, there extends at least one cable, pipe or hose (34, 38).

CROSS REFERENCE TO RELATED APPLICATION

The present application is the U.S. national stage application of International Application PCT/NO02/00132, filed Apr. 5, 2002, which international application was published on Oct. 17, 2002 as International Publication WO 02/081862. The International Application claims priority of Norwegian Patent Application 20011808, filed Apr. 10, 2001.

BACKGROUND OF THE INVENTION

This invention relates to a device which forms a protected passage for communication cables, pipes or hoses in the well fluid inflow portion of production tubing in wells of the kind used in the recovery of petroleum.

In recent years, in particular when horizontal wells are used, it has become usual to use the so-called “open hole” technique. The technique involves that in a portion of the well, typically in one or more of the petroleum-producing zones of the reservoir, no casing is set. Thus, when the production tubing is to be run, it must be moved into and through an open well bore, within which it lies slidingly against the well formation. To prevent sand from the formation from entering together with the inflowing well fluid, and to support the formation wall and thus prevent the well bore from collapsing, it is common to set so-called strainer pipes in the petroleum-producing zones of the reservoir. In their outer jacket, the strainer pipes are provided with through openings in the form of fine bores or slots designed to admit well fluid but prevent formation sand from reaching the production tubing located within.

The development of the production technique in question has resulted in the discovery of an increasing requirement for using downhole sensors and actuators. Sensors are used, for example, for measuring one or more of the physical properties of the well fluid, whereas actuators may be used, for example, for choking well fluid from one or more of the zones of the reservoir. Communication between such downhole equipment and the surface is normally accomplished by means of electrical cables, whereas energy is supplied by means of electrical wires and/or hydraulic pipe or hose connections.

According to known technique, cables and pipes or hoses of the kind in question are placed in protective channels arranged for the purpose externally on the strainer pipe. It is obvious that when production tubing is being run, as the strainer pipes are subjected to displacement and rotation against the uncased formation, such protective channels are subjected to huge mechanical loads. Experience goes to show that during the running operation damage will occur, to a considerable extent, on these protective channels and the cables, pipes or hoses carried inside the channels.

SUMMARY OF THE INVENTION

The invention has as its object to remedy the drawbacks of known technique.

The object is achieved according to the invention through the features specified in the description below and in the following claims.

A strainer pipe normally comprises an external, relatively thin-walled strainer mantle and an internal, relatively strong perforated load-carrying main pipe. The strainer mantle, which may be constructed from strainer wire, is supported concentrically by spacers, possibly in the form of a number of longitudinal spacer rails spaced along the periphery of the production tubing. The spacer rails are thus within an annular space between the strainer mantle and the main pipe.

During production well fluid enters through the openings of the strainer mantle, through the annular space along the spacer rails and further through the perforations of the main pipe into the cavity of the main pipe, after which the fluid flows to the surface through the production tubing of the well.

To avoid the above-mentioned drawbacks of the known technique, cables and hydraulic connections are placed in one or more longitudinal pipes present in the annular space between the strainer mantle and the main pipe. In such a solution the protective devices of cables and hydraulic connections are subjected to minimal mechanical load, while at the same time they reduce the flow area available for well fluid only to an insignificant degree.

It is common to join together several strainer pipes which may form a length corresponding to the length of the producing zone of the reservoir. The annular space of each of the strainer pipes may be connected to the annulus of the adjacent pipe by means of sleeves of a kind known in itself, wherein the sleeves may be provided with external openings.

In some applications cables and hydraulic connections may be placed in said annular space without the use of longitudinal pipes.

The device is also well suited for use in wells provided with a cemented and perforated liner.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings the reference numeral1identifies a petroleum well, there being placed, in the uncased petroleum-producing zones2,4,6of the well1, a number of interconnected strainer pipes8. Well fluid flows from the well1to the surface through a production tubing10which is connected to the central main pipe12of the strainer pipe8. The production tubing8extends through the casing14of the well1.

In a preferred embodiment, the strainer pipe8comprises besides the main pipe12, a strainer mantle16and a number of continuous or slotted spacer strips18spaced apart about the periphery of the main pipe12and arranged to support the strainer mantle16. In the annular space between the strainer mantle16and the main pipe12there are, depending on the number of spacer strips18, a number of longitudinal channels20, through which well fluid is flowing on its way from the slots22of the strainer mantle16to the perforations24of the main pipe. The slots22may be formed by means of, for example, a spun strainer wire26or a slotted mantle pipe28.

It is common to fill the annulus formed between the uncased well portion and petroleum producing zones2,4,6with gravel30with the aim of contributing to the prevention of sand entrance and formation damage.

The well inFIG. 1is provided with a number of sensors32communicating with the surface through a cable34, and a number of actuators36supplied with hydraulic or electrical energy through pipes, cables or hoses38. In the well portion where a strainer pipe8is used, the cable34and the pipes or hoses38extend through fluid tight protective pipes40located in one or more of the channels20, whereas in the upper portion of the well1they extend through the annulus formed between the casing12and the production tubing10up to the surface. The protective pipe40may possibly replace a spacer rail18.

In another embodiment, essentially based on the technique described above, the strainer pipe8is provided with a perforated mantle pipe42, seeFIG. 5.

By placing the protective pipes40in the channels20, the protective pipes40are only exceptionally subjected to mechanical loads, whereby wires, pipes or hoses34,38located within the protective pipes40are completely shielded from external loads.