FR2641319A1 - Cementing head for an oil well - Google Patents

Abstract

The invention relates to the cementing heads for oil wells and the like. The head is mounted on the pipe column 1 and sleeve 2 assembly. It comprises an internal tubular part 3 which cannot move rotationally and an external tubular part 4 which can move rotationally. Each tubular part includes orifices which can be made to coincide alternately by suitable rotation of the component 4. The fluid flows out through the coinciding orifices and drives out the mechanical plugs 5 and then 6.

Description

Oil well cementing head
The invention relates to the technical sector of the annealing of oil wells.

We are fully aware of the principle of this technique which consists in injecting, in an appropriate sequence, into the interior of the casing or "casing" lowered into the wellbore, fluids such as mud, cement slag, separated by a mechanical plug (" plug ") and / or by a separation fluid (" spacer "). One or more mechanical plugs must also be properly launched to isolate certain areas of the well.

All of these operations are carried out under very high pressure (pumping pressure of the fluids in the well).

All these operations are, in principle and their operating mode, part of the routine for the field engineer.

Currently, and for several decades, cement heads are used as shown in Figure 2 attached.

The cementing heads of the prior art operate in the following manner (the fluid arrives at very high pressure at "F"): - first of all the valve V1 is opened (the valves V2 and
V3 being closed) to circulate a first fluid in the well (P) without throwing a plug; this first fluid can be a mud.

- V2 is opened after closing V1, V3 remaining closed and thus admitting a cement slag under very high pressure. Under pressure, the element R1 (calibrated) breaks and the first plug (5) is released and descends into the well. It is followed by the cement slag which we continue to pump. the spring-mounted element T ("tell-tale") detects the passage of the plug.

- when the above phase is finished, we close V1 and V2, we open V3, and we pump a cement slag again. By the same process, the plug (6) is released by rupture of the calibrated R2 element - the element
T detects the passage of the second plug.

- Then we close V3.

The operation of V1, V2 and V3 is carried out manually because remote control would be too complex.

In addition, the cementation head, which must be fully resistant to very high pressures, is extremely heavy. This is a serious additional disadvantage on the one hand because the head must be raised above the "table" of the derrick and on the other hand because the operation of such a mass involves a very high risk of damaging the thread. thin threads of the sleeve (2).

Finally, another serious drawback, the well-known phenomenon of "U - tube" (free fall of the cement slag in the well) which occurs during cementing, causes a passing but abrupt and significant depression. When the first plug has been launched but the second has not yet been launched, this depression is exerted on the plug (6) and can deform the element R2. This deformation can have a serious impact on the launching of the second plug (premature launching, blocking, wedging at an angle in the well, etc.) and / or the geometry or the strength of the plug, which can compromise the cementing operation. .

The invention provides a cementing head integrated into the casing or "casing", as shown in the
Fig. 1 attached.

In Figs. 1, 2, 3 and 4, the same references generate the same elements.

The cementing head according to the invention mainly consists of an outer tubular element (4), an inner tubular element (3), an upper plug or "cap" (7) having an orifice (8) allowing inject the fluids (F) into the cementing head and a part (9) capable of mechanically holding the elements (3) and (4) in position, and which can be screwed onto the sleeve or "collar" (2 ) itself mounted conventionally on the casing (1) or "casing".

The internal element (3) is immobilized in rotation by the part (10) integral with the internal element (3) and which is blocked in rotation by engagement in a suitable groove (11) formed in the part (9).

Seals (12, 13) seal the fluids under pressure as shown in FIG. 1.

The internal element (3) is integral with a part (14) which is therefore also fixed in rotation. The external element (4) movable in rotation has adapted grooves (15) which allow the element (4) to move in rotation despite the presence of the part (14).

The internal element (3) has three holes A, B and
C lines and arranged as shown in Fig. 1, drilled in the wall.

The movable external element (4) has three orifices a, b and c identical to the orifices A, 8 and C (or substantially identical), as well as three orifices of smaller dimensions, x, y and z, intended to allow the pressure equalization as will be explained below.

Fig. 1 corresponds to a nonlimiting example of a cementing head intended for launching two plugs or "plugs" 5 (lower) and 6 (upper).

Obvious modifications relating to the number and the angular localization of the orifices of type A, a, or x make it possible to increase the number of plugs for example up to 3 or 4.

These modifications will not be described here, because they will appear clearly to a person skilled in the art on reading the operating mode of the two-plug version, which will follow.

The implementation and operation of the device according to the invention (Fig. 1 and 3 composed of 3a, 3b, and 3c, Fig. 3 representing plugs adapted according to the invention) will be understood on reading the description which will follow and referring to the accompanying drawing.

Before placing the cementing head (mainly consisting of parts 7 (plug), 3 (internal element fixed in rotation), 4 (external element mobile in rotation), 14 (fixing part of plugs 5 and 6 with respect to the 'element 3) and 9 (connection piece to the sleeve or "collar" 2), the two plugs 6 and 5 are placed on the head, as follows.

First of all, the upper plug (6) is introduced by sliding upwards along the head, the part (14) sliding in the groove (16) of the plug (cf. Fig. 3) and the rotary external element. (4) being in a position such that its plug blocking lug (lug (17)) is in position I2 (Fig. 3a) which allows this lug to slide in the vertical groove (18) of the plug (6).

When the plug (6) is in position, the element (4) is pivoted to Il / V2. This maneuver makes it possible in turn to slide the lower plug (5) strike at the vertical grooves (16) and (19) of this plug (cf. Fig. 3b) and simultaneously blocks the plug (6) because the lug 17 n is more opposite the vertical groove 18. The two plugs (5) and (6j have a horizontal groove (20) opening respectively into the vertical grooves (19) and (18), this groove (20) allowing movement in simultaneous rotation of the two pins (17).

When the plug (5) is in turn in position, the two pins (17) are brought into position V1 / R (Fig 3a) which ensures the locking of the plug (5) without unlocking the plug (6).

The two plugs being thus locked, the cementing head is screwed onto the "collar" (2) as shown in FIG. 1.

The orifices in communication, in this position of the element (4), are a and A on the one hand; x and B on the other hand; and finally y and C.

If a first fluid is injected under high pressure at F, this fluid (circulation of mud, cement slag, brine, etc.) will flow through the orifice (a,
A) (the element (3) is closed by the bottom (f)) and fulfill its function. Simultaneously the orifices (x, B) and (y, C) ensure pressure balancing in all the zones located on either side of the plugs. Thus the plugs are not subjected to any constraint and only the parts (7) and (9) must be qualified "high pressure".

When the first circulation of fluid by (a, A) is complete, the element (4) is pivoted from the rest position (R) to the position (L1) (cf. Fig. 3). This movement simultaneously causes - the disappearance of the coincidence a, A - the coincidence (b, B) - the coincidence (z, C) - the positioning of the pins (17) with regard to the
groove (19) of the plug (5).

It is easy to understand that the pressure drives the plug (5) down (the lug (17) being able to slide in the groove (19)) while the orifice (z, C9 equalizes the pressure in the upper zone this which means that no stress is exerted on the upper plug (6).

Each plug (5) and (6) has on its upper part a shutter valve capable of withstanding the working pressure in the well.

This valve is composed of a rigid or semi-rigid plate (21) capable of pivoting towards the center of the head and downwards under the action of an elastic element (22) (metal blade, rubber blade, etc.) .

See Fig. 1 and Fig. 3.

When the plugs (5) and (6) are positioned on the element (4), the valves are naturally raised. At rest, the valves rest on the element (4) in a slightly inclined inward position, the elastic element 22 being compressed, so that, as soon as the plug is released from the bottom of the element (4) the valve tends to close on the central orifice (23) of the plug. This closing movement is amplified by the pressure of the fluid which is then exerted on the upper face of the plate (21). This pressure causes the plate (21) to be firmly and definitively held against the upper face (24) of the plug. It therefore closes the orifice (23) which allows the plug to fulfill its role as an area insulating element. A boss (25) of suitable geometry makes it possible to fix the plate 21 in the closed position.

To launch the second plug (6), the element (4) is pivoted from position (L1) to position (L2) which - prevents coincidence (a, A) - causes coincidence (c, C) - eliminates the coincidence (z, C) - brings the 2 lugs (17) to the vertical groove (18) of the plug (6): it is therefore driven freely by the fluid passing through the orifice (c, VS).

Fig. 4, which consists of Figs. 4e and 4b, represents a variant of an internal valve plug whose operation is very similar to that which has just been described. (as for the other figures, the same reference numerals designate elements of identical function).

According to another obvious variant, the plug (7) can be divided into a central part secured to the fixed internal element (3), and into a concentric external part secured to the external element (4) and movable in rotation .

In order to make the Figures clearer, the scale was not respected and certain elements were not represented on all the Figures, or only once. For example, the valve (21, 22r has not been shown, in FIG. 1, for the plug 5.

The corrections, in particular of scale, are absolutely obvious and will be imposed on the skilled person.

The invention therefore proposes a cementing head - light - making it possible to launch at least two plugs - reliable (the plugs are not subjected to unnecessary stresses as long as they are not launched); - of a simple implementation (the valves V1, V2, V3 are omitted) - and being able to be controlled and automated remotely (it suffices to control the pivoting of the upper cap - or "cap" (7), which is mechanically secured at (25) to the pivoting element (4), by known mechanical means, which can be simple and reliable (actuator, connecting rod, gear, pneumatic, hydraulic, electromagnetic control) and are well known.

Claims (8)

1. Cementation head for oil, gas, water, geothermal and similar wells, positioned on the sleeve (or "collar") (2) or on any similar high pressure fixing system, itself fixed on the upper end of the casing (or "casing") (1) lowered into said well (P); said head containing at least one plug (or "plug") (5, 6) intended to be launched into said well (P), characterized in that it comprises:  - a connecting piece (9), qualified as high pressure, for its positioning and its fixing on said sleeve (or "collar") (2);  - two concentric tubular elements - one internal (3) being fixed and closed at its lower end (f); The other, external (4) being mobile in rotation- suspended in said casing (or "casing") (1) thanks to said connecting piece (9); said fixed element (3) comprising immobilization means (14) in rotation of (or) said plug (s) (or "plug (s)") (5, 6) in the waiting position in said cementing head and said movable element (4) comprising on its outer wall means for locking in height (17) of said plug (s) (or "plug (s)") (5, 6) in the waiting position;  - an upper plug (or "cap") (7), qualified as high pressure, covering said tubular elements (3) (4), which can cause said movable tubular element (4) to rotate and comprising at least one injection orifice (8 ) fluid (F) in the fixed, internal tubular element (3); and in that the plug (s) (or "plug (s)") (5, 6) is (are) positioned (s), in the waiting position, between the internal wall due casing (or "casing") (1) and the outer wall of the movable tubular member in rotation (4); each of said plugs (or "plugs") (5, 6) comprising a central passage (23) with a diameter substantially equal to that of the external tubular element (4) and being equipped with mechanical means (21) (22) capable of closing said passage (23) under the pressure of the fluid (F) when said plug (or "plug") (5, 6) is launched in the well (P); each of said plugs (or "plugs") (5, 6) further comprising over its entire height two vertical grooves ((18 or 19); (16)) and in its body a horizontal groove (20) opening into one said vertical groove (18 or 19); said first vertical (18 or 19) and horizontal (20) groove being intended to cooperate with said height locking means (17) of the plug (or "plug") (5, 6) carried by said movable element (4) and said second vertical groove (16) being intended to cooperate with said immobilization means (14) in rotation of said plug (or "plug") (5, 6) carried by said fixed element (3); and in that said fixed (3) and mobile (4) elements comprise orifices (A, B, C, a, b, c, x, y, z) which, in each of the volumes delimited by at least one face of the (or) said plug (s) (5, 6), can be placed in coincidence or, on the contrary, offset by a certain angular deviation - thanks to an appropriate arrangement of said orifices and to the possibilities of rotation of L ' movable element (4) relative to the fixed element (3) - so that, by simple (s) successive rotation (s) of said element (4) relative to said element (3), rotation (s ) controlled (s) by the upper plug (or "cap") (7), fluids (F) can be injected under high pressure into the well (P) successively: by the lower end of the elements (3) (4 ); then by each zone immediately above a plug (or "plug") (5, 6) -the pressure equalization then being respected in the upper zones- which then causes the launching of said plug (or "plug" ) (5, 6) in the well (P); the mechanical means (21) (22) immediately closing the central passage (23) of the plug (or "plug") (5, 6) thus launched. 2. Cementing head according to claim 1, characterized in that it contains at least two plugs (or "plugs") (5, 6) intended to be launched into the well (P). 3. cementing head according to one of claims 1 or 2, characterized in that it contains two plugs (or "plugs"> (5, 6) intended to be launched into the well (P) and in that The fixed internal element (3) has three aligned holes (A, B, C), located respectively below the lower plug (or "plug") (5), between said lower plug (or "plug") (5 ) and the upper plug (or "plug") (6), above said upper plug (or "plug") (6); and that the movable external element (4) comprises on the one hand, three orifices (a, b, c) offset, said three orifices (a, b, c) being of dimensions close to those of said orifices (A, B , C) of the fixed internal element (3) and being situated respectively at the same levels and on the other hand, three orifices (x, y, z) offset, of smaller dimensions -destined for The pressure equalization in the volumes delimited by the faces of said two plugs (or "plugs") (5, 6) - located for One (x) at the level of the orifices (B, b) of the volume delimited by Said two plugs (or "plugs") (5, 6) and for the other two (y, z) at the orifices (C, c) above said upper plug (or "plug") (6). 4. cementing head according to any one of the preceding claims, characterized in that each of said plugs (or "plugs") (5, 6) is equipped with a valve (21) -rigid or semi-plate rigid - for closing its central passage (23); Said valve (21) being secured to said plug (or "plug") (5, 6) by means of an elastic element (22); the set elastic element valves (2f / 22) being mounted either in the body of said plug (or "plug") (5, 6) or on its upper surface. 5. cementing head according to claim 4, characterized in that each of said plugs (or "pLugs") (5, 6) is further equipped with means (25) for fixing in the closed position of the valve (21); said means (25) consisting for example of a boss of suitable geometry. 6. cementing head according to one of claims 1 to 5, characterized in that said upper plug (or "cap") (7) is an element of a single piece or that it consists of a part fixed central unit, secured to the fixed internal element (3) and a concentric peripheral part movable in rotation, secured to the movable external element in rotation (4). 7. Plug involved in the cementing head according to any one of the preceding claims, characterized in that it comprises:  - a central passage (23),  - Means (21, 22) making it possible to provide at will the release or the obturation of said central passage (23); said means being located either in its body or on its upper surface;  - two vertical grooves (16, 18 or 19) on either side of said central passage (23), over its entire height, and  - in its body, a horizontal groove (20) opening into one of said vertical grooves (18 or 19). 8. Stopper according to claim 7, characterized in that it is further equipped with means (25) for fixing, in the closed position, means (21, 22) for closing said central passage (23).