WO1993007356A1

WO1993007356A1 - Method, toolstring and tubing element for downhole operation

Info

Publication number: WO1993007356A1
Application number: PCT/NO1992/000166
Authority: WO
Inventors: Roger Tailby
Original assignee: Den Norske Stats Oljeselskap A.S.
Priority date: 1991-10-11
Filing date: 1992-10-06
Publication date: 1993-04-15
Also published as: NO179112C; NO179112B; NO913990L; AU2791592A; NO913990D0

Abstract

Method of performing a toolstring operation in horizontal oil or gas wells comprising tubing means (5) with no-go means (20), followed by extension tubing (6) throughout the horizontal well part. There is employed a toolstring comprising an elongate, tubular toolstring element (7) being connected to a surface installation (1). The toolstring is first moved down through a substantially vertical part of the well by supplying power from said surface installation (1), then through a bend part and into the horizontal part of the well, establishing a stationary seal between sealing means (10) on said toolstring and said no-go means (20) and a slide seal internally between said sealing means (10) and said toolstring element (7) passing therethrough. The well pressure is increased to perform a piston action to scope or push said toolstring element (7) further into said extension tubing (6) through said sealing means (10) until reaching a point of desired operation within said extension tubing. After performing said operation, such as by applying pressure, a pulling force is exerted from said surface installation (1) so as to return said toolstring (7, 8) to the surface.

Description

•METHOD, TOOLSTRING AND TUBING ELEMENT FOR DOWNHOLE OPERATION

This invention concerns a method and toolstring for downhole operation such as performing well maintenance tasks in an oil or gas well which has a long horizontal or highly- deviated section passing through the producing formation. The invention also comprises a tubing element for installation in connection with this method.

Horizontal oil and gas wells are being drilled to lengths which are too long for conventional well servicing with coiled tubing. This coiled tubing buckles when being pushed along a horizontal well tubing or casing, and the extra friction thus generated quickly becomes large enough to prevent further movement into the well.

Prior art patents within this field are mainly concerned with carrying out logging or other electric line services in the horizontal section, notably U.S Patents 4,484,628, 4,349,072 (Re. 32,336) and 4,729,429, whereas the present invention will enable both mechanical and hydraulic tasks as well as conveying electric lines inside coiled tubing to the bottom of a horizontal well-.

The present method can be used in two different well configurations with radically different operating charac¬ teristics and limitations. One involves fluid circulation back up the annulus to the surface, denoted configuration A, while the other requires a limited amount of injection of wellbore fluid back into the formation, and is referred to as configuration B.

Thus, more particularly this invention is directed to a method of performing a toolstring operation downhole in horizontal or high-deviation oil or gas wells comprising tubing means within the well casing, and no-go means installed at the lower end of said tubing means, which is followed by an extension tubing of considerable length throughout the horizontal or high-deviation well part. The novel and specific features provided by this invention in such method and in an associated toolstring as well as in a tubing element, are recited in the appended claims. The various aspects of this invention, including the technique and apparatus required to perform the said well maintenance are explained more in detail below with reference to the drawings, in which:

Fig. 1 schemicatically shows the well configuration A referred to, when circulation up the annulus is utilised, Fig. 2 shows the installation of a circulation control valve for the above well configuration A during normal production operations.

Fig. 3 schematically shows the well configuration B, when injection into the producing formation is utilised. Fig. 4 shows in axial section a seal adapter connected to a toolstring on the end of the coiled tubing as it would be run into the well, and

Fig. 5 shows the coiled tubing being scoped through the seal adapter in fig. 4 when performing its sealing functions within a tubing element.

Fig. 1 schematically shows a surface installation 1, for example an offshore production platform, a well or casing 2 having a substantially vertical section and a substantially horizontal section, production tubing 5 and packers 2A, 2B for one or more production formations. At 20 a tubing element is inserted between the main production tubing 5 and extension tubing 6 penetrating into the horizontal or high- deviation part of the well.

In the above case A, when the well is configured for annulus circulation, as shown in Fig. 1, there is installed a tubing element 20 with a port or ports in the tubing immediately above the production packer 2A, which should be set at a deviation substantially equal to the well section or extension tubing 6 continuing downwards through the producing formations. Tubing element 20 preferably takes the form of a no-go nipple assembly so that a circulation control valve 55 can be installed, as shown in Fig. 2. This valve can be similar to that described in U.S. Patent 4,513,764, which is set and retrieved by pumpdown methods, or it can be a simple straddle sleeve which is run and pulled with coiled tubing or even wireline. One or more radial ports 28 are provided in tubing element housing 20A, within which valve 55 is installed. Its function is to seal closed the port 28 during routine well production operations. When this valve or sleeve is removed, it may be necessary to circulate heavy, particle- free fluid into the well in order to establish another barrier to well flow in the annulus. Alternatively, the well may have been equipped with an annulus safety valve for this purpose.

In order to protect the producing formation from excessive fluid injection during subsequent pumping operations, standing valves may be installed lower in the well opposite the isolated producing intervals shown in Fig. 1. These standing valves may also perform valuable tasks in their own right by controlling the influx of produced fluid from the individually isolated formation intervals, provided they can be reliably maintained.

As shown in Fig. 1 an elongate toolstring element or coiled tubing 7 is connected at its top end to surface installation 1 and its downhole end is provided with a bottom-hole assembly or tool unit 8 for performing a tool¬ string operation downhole. Fig. 1 shows a situation during scoping of toolstring element 7 with assembly 8 into extension tubing 6, with ^Ja seal adapter 10 positioned within tubing element 20 and performing a very important function for making such scoping possible.

As the coiled tubing moves into the horizontal section of the well, it is assumed that all displaced fluid is expelled into the well's annulus and retrieved at the surface, this volume being equal to the volume of the length of coiled tubing and its contents below the port or ports in tubing element 20. These ports 28 are seen in fig. 2. Further details are explained below with reference to Figs. 4 and 5.

The other well configuration, B, shown in Fig. 3, does not allow fluid access to the annulus. In this case, all the volume of the coiled tubing 7 and its contents must be displaced through perforations 44 or otherwise into the formation matrix. This possibility must be present or the method will not work. It follows therefore that no work may be done in a cased well before it is perforated or after it is plugged back, or if standing valves are installed. This configuration requires that a no-go nipple 40 incorporating a seal bore is installed at the bottom of the production tubing 5 or the top of the liner, again at a point where the well has a deviation substantially equal to that of the rest of the well which penetrates the producing formation, i.e. with extension tubing 46. Other elements and units shown in Fig. 3 correspond to those found in the configuration (A) of Fig. 1.

The apparatus which allows the method to be utilised in both configurations A and B is functionally the same, although its dimensions may be different for each configu¬ ration, and is shown scematically in Fig. 4, and referred to as the seal adapter 10. This seal adapter is detachably fixed to the toolstring on the bottom of the coiled tubing 7 with one or more shear pins 15. It encloses the coiled tubing and contacts it through two moulded seal packing elements 12, 14, but is otherwise free to slide on the coiled tubing when not attached to the toolstring, i.e. when shear pin 15 has been broken. The inner cylindrical surface 17, 17A, 17B has a varying diameter so designed as to not constrain or stress the coiled tubing 7 under conditions of buckling, bending or other elastic or non-critical plastic deformation during normal operations.

The seal adapter 10 also has an external moulded seal 11, which is smaller than any part of the tubing string 5 above the ported nipple assembly or tubing element 20 (Figs. 1, 2, 5) or no-go nipple 40 (Fig. 3) . This seal 11 will fit .into the upper seat or packing bore 21 of the ported nipple assembly 20 (configuration A) or a seal bore of the no-go nipple 40 (configuration B) when the lower shoulder 13 of the seal adapter 10 seats on the no-go shoulder 22 of the respective nipple.

Fig. 5 shows somewhat in detail an axial section the seating of seal adapter in tubing element 20 being here in the form of a ported nipple assembly. This element or assembly in principle is the same as the one shown in Fig. 2. The situation illustrated in Fig. 5 is the same as configu¬ ration A, corresponding to Fig. 1. Thus, as indicated with arrows 28A and 28B in Fig. 5, a return flow path for displaced well fluid is established through the ports 28 to the outside of production tubing 5 as a whole (Fig. 1) and accordingly up the well's annulus, during scoping of the toolstring element 7 into the extension tubing 6. It will be seen that ports 28 in housing 20A in association with no-go or stop shoulder 22 therein, is an essential feature in this connection. A stationary seal is established between seal adapter 10 and seat 21 within housing 20A, and a slide seal is provided internally in seal adapter 10 against the tool¬ string element or coiled tubing 7 passing therethrough during scoping.

In operation, the toolstring is run into the well on the coiled tubing with the seal adapter 10 pinned to the tool¬ string element 7 or tool unit 8. The coiled tubing 7 is run ^■ into the well 5 in a conventional manner, except that the toolstring is such that the end of the coiled tubing 7 is sealed, at least temporarily. This continues until the seal adapter 10 meets the no-go 22 in the nipple, where the string stops, usually at the beginning of the horizontal section 6, 46. Downward compressive force is then applied to the coiled tubing 7 resulting in the pin 15 connecting the seal adapter 10 shearing. A compressive load of about 1000 lbf (5kN) will be sufficient in a practical embodiment contemplated.

At this point, the seal adapter 10 has created three pressure chambers, one consisting of the coiled tubing 7, both on a reel in surface installation 1 and in the well, one consisting of the coiled-tubing-to-tubing annulus, and the third consisting of the well volume below the seal adapter 10, minus the coiled tubing, but including either the well annulus (configuration A) or the pores of the formation matrix. (configuration B) .

The coiled tubing 7 may then be run further into the well extension 6 until helical buckling begins to cause excessive friction. At this time, pressure may be applied to the coiled-tubing-to-tubing annulus. Further slacking off of the coiled tubing at the surface will then result in the coiled tubing being pushed further into the well by the force applied by the differential pressure across the cross- sectional area of the coiled tubing in the seal, adapter. This force may have a tendency to buckle the coiled tubing only below the seal adapter, not above.

Upon reaching the effective end of the horizontal well, the same technique may be used to apply compressive force on the toolstring in excess of that which could be transmitted mechanically by the coiled tubing. Alternatively, a circu¬ lation valve as known per se could be opened by coiled tubing pressure and various fluids could be circulated into the well. If the coiled tubing carried an electric line, then certain measurements could be made, depending on the nature of the toolstring, while running into the well or while pulling out.

Retrieval of the coiled tubing 7 and the toolstring 8 is achieved by simply pulling the coiled tubing from surface installation 1, after releasing the pressure in the coiled- tubing-to-tubing annulus. The seal adapter 10 will be pulled off seat in tubing element 20 or 40 by the toolstring 8 at the end of the coiled tubing 7 when it reaches the tubing element, i.e. ported nipple 20 or no-go nipple 40.

As shown more in detail in Fig. 2 the essentially cylindrical housing 20A of tubing element 20 has an axial passage 24 in which circulation control valve 55 or another component may be installed. In the example of Fig. 2 such installation comprises a mandrel or lock unit 50 having keys adapted to engage in lock recesses 29 in the axial passage 24 for the positioning of components such as valve 55 in the passage. Seals 51 and 52 are provided for sealing against seat 21 and a seal bore 27 respectively in passage 24. Seat 21 has the form of a substantially cylindrical bore and at the inner end of this bore a stop shoulder 22 serves to block against further downward movement of component or unit 50 into passage 24. In other words, the stop shoulder 24 performs a no-go function.

From Fig. 2 it is further seen that seat 21 is located rearwardly of the radial ports 28, whereas seal bore 27 is positioned forwardly of these ports. With these and other geometrical relationships appearing from Fig. 2, the ported nipple assembly or tubing element 20 will be able to have functions as intended both in connection with the install- ation of a component such as a circulation control valve 55 with unit 50 and the seal adapter described above.

In the method described the downhole operation concerned may comprise the use of a circulation valve as for example being in principle known per se, incorporated as a tool component at the leading end of the toolstring element 7, preferably as the rearward component of the bottomhole assembly or toolstring 8. Application of an increased pressure exceeding a predetermined magnitude through the toolstring element, can break mechanical locking means in the circulation valve so as to open the valve for allowing fluid flow through it.

Claims

1_ Method of performing a toolstring operation downhole in horizontal or high-deviation oil or gas wells comprising tubing means within the well casing, and no-go means installed at the lower end of said tubing means, which is followed by an extension tubing of considerable length throughout the horizontal or high-deviation well part, characterized by employing a toolstring comprising an elongate, tubular toolstring element being at least temporarily closed at its leading or bottom end and being connected to a surface installation at the opposite or top end, said toolstring being first moved down through a . substantially vertical part of the well by supplying power from said surface installation, then through a bend part and into the horizontal or high-_^deviation part of the well, establishing a stationary seal between sealing means on said toolstring and said no-go means and a slide seal internally between said sealing means and said tool¬ string element passing therethrough, increasing the well pressure to perform a piston action to scope or push said toolstring element further into said extension tubing through said sealing means until reaching a point of desired operation within said extension tubing, performing said operation, such as by applying pressure, and exerting a pulling force from said surface installation when said operation has been terminated so as to return said toolstring to the surface.

2. Method according to claim l, characterized by establishing a return flow path outside said tubing means and up the well's annulus for displaced well fluid during said scoping of the toolstring element into said extension tubing, by providing port means in association with said no-go means.

3. Method according to claim 1, characterized by utilizing an escape flow path for displaced well fluid during said scoping of the toolstring element into said extension tubing, through casing perforations or via other access to a surrounding (production) formation, thereby maintaining the normal isolation of said annulus from said tubing means.

4. Method according to claim 2, characterized in that said downhole operation comprises use of a circulation valve being in principle known per se, incorporated as a tool component at said leading end of the toolstring element (7) , whereby application of an increased pressure exceeding a predetermined magnitude through said toolstring element is adapted to break mechanical locking means in said circulation valve so as to open the valve for allowing fluid flow therethrough.

5. Toolstring for performing operations requiring application of power downhole in horizontal or high- deviation oil or gas wells, and adapted to be moved down in tubing means (5) within a casing (2) in the well from a surface installation, comprising an elongate toolstring element (7) , with a top end of the toolstring element (7) being connected to said surface installation, characterized in that said toolstring element (7) is tubular and has a leading or bottom end adapted to be closed, that sealing means (10) is detachably connected to said toolstring element and has external seal means (11) for co-operation with seat means (21) associated with no-go means (20, 40) at the bottom end of said tubing means (5) , from which extension tubing means (6, 46) extend further into said horizontal or high-deviation well, - that said sealing means (10) comprises internal seal means (12, 14) to sealingly surround said toolstring element (7) and allow sliding of the toolstring element therethrough when engaging said seat means (21).

6. Toolstring according to claim 5, characterized in that said elongate toolstring element consists of coiled tubing (7) .

7 Toolstring according to claim 5 or 6, characterized in that said external' seal means has at least a substan¬ tially cylindrical outer surface (11) adapted to sealingly engage a substantially cylindrical seal bore (21) in said no-go means (20) .

8. Toolstring according to claim 7, characterized in that said cylindrical outer surface (11) extends substantially adjacent to a front end face (13) of said sealing means (10) adapted to come to a stop against a stop shoulder (22) at the bottom of said seal bore (21) .

9. Toolstring according to any one of claims 5 to 8, characterized in that said internal seal means (12, 14) is incorporated into an internal profile (17) of said sealing means (10) having a shape such that said toolstring element (7) may be subjected to bending to a certain degree of curvature through said sealing means,

• while a sufficient sealing effect is maintained by said internal seal means (12,14) during such bending.

10. Toolstring according to claim 9, characterized in that said internal seal means consist of two annular seals (12, 14) being located at a mutual axial distance within said sealing means (10) , and that said internal profile (17) between the annular seals comprises a widened recess of significantly increased diameter in relation to the inner diameter of said internal annular seals (12,14) and preferably widened end portions (17A, 17B) between the respective annular seals and the adjacent ends of said sealing means.

11. Tubing element for installation at the lower end of single tubing means adapted to accomodate a toolstring according to any one of claims 5-10, characterized by comprising: an essentially cylindrical housing (20A) having an axial passage (24) , interior seat means (21) in said axial passage (24) ^■ for providing a-fluid seal against said toolstring element sealing means (10) and preferably another component (50, 55) set by said toolstring (7) or other means into said passage, and stop means (22) in said passage (24) at a position adjacent to said seat means (21) for blocking against movement of said sealing means (10) or said component (50, 55) further into said passage.

12. Tubing element according to claim 11, characterized in that said seat means comprise a substantially cylindrical bore (21) and that said stop means is formed by a shoulder (22) of reduced diameter at the forward end of said cylindrical bore (21) .

13. Tubing element according to claim 11 or 12 for use in carrying out the method according to claim 2, characterized in that from said axial passage (24) at least one radial port (28) is provided to the outside of said housing (20A) , and that said interior seat means (21) is located at a rearward position in relation to said at least one radial port (28) .

14. Tubing element according to claim 13, characterized in that a seal bore (27) is provided in said axial passage (24) at a forward position in relation to said at least one radial port (28) .

15. Tubing element according to claim 14, characterized in that at least one lock recess (29) is provided in said axial passage (24) still further rearwards from said seat means (21), for the positioning of said component (50, 55) in said passage.

16. Tubing element according to claim 14 or 15, characterized in that said passage (24) is shaped to also accomodate a component in the form of a circulation control valve (55) provided with seal means (51, 52) for engagement with said seat means (21) and said seal bore (27) respectively.