GB2247260A - Injector head for wells - Google Patents

Abstract

An injector device for driving a conduit into an orifice comprises a drive mechanism 13, 15 contact means 17, 19 for advancing the conduit in a given direction by frictional engagement with the exterior of the conduit, wherein the advancement path 7 of the conduit has an arcuate section in which section the conduit is contacted and driven under control of the drive mechanism. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO INJECTOR HEADS This invention relates to improvements in or relating to injector heads suitable for introducing conduits downhole, more particularly to an improved injector head for injection of coil tubing into an off-shore oil well.

In the off-shore search for hydrocarbons, drilling is now taking place at progressively greater depths. Such oil and gas wells require servicing to increasingly higher standards as demand for higher production increases.

When a new oil well is brought 'on-stream' for the first time, it is generally accepted that at this point the well is flowing at its optimum production level. This production level falls through time due to a variety of reasons, such as the deposition of sand, wax, formation of scale, etc. on the internal surface of the well which reduces the effective diameter of the well and thus inhibits the productivity of the well. Traditionally, the well would be the subject of an extremely costly workover process which involves the complete renewal of all production components in the well. The downtime during workover, costs of component overhaul and interruption of production is no longer acceptable to the industry.

In recent years, the accepted answer to the problems encountered by the complete workover process has been to use coiled tubing. This is a small bore conduit which is stored on a reel and is fed through an injection head which is raised above the well by an on-deck crane. The tubing is then driven through the injection head into the live well to enable the pumping of treatment chemicals into the well to dissolve blockages and flush out the contaminants described above, thus restoring the well to a condition approaching its previous best production capability and prolonging the life of the well. This tubing is commonly described as "coil tubing" in this field and it will be so described and referred to herein.

As production equipment has increased in size, and with much deeper wells, so, over recent years, coil tubing equipment has increased in size, whilst being fundamentally unchanged in design, thus becoming larger, clumsier and more complicated to use. Several problems have developed with this type of equipment, not least of which is the lack of space which is a major factor in the design and production of off-shore equipment. As the dimensions of traditional coil tubing have grown to meet each new application, the storage room, manpower and resources required to schedule operations involving the equipment can create enormous planning problems.

Furthermore, the weight of the equipment is especially important on older production platforms where the cranes used to hoist the injector heads above the productions wells have been down-rated to a limit of eight tonnes. The weight of most traditional components now exceeds this limit which creates difficulties in servicing wells on these platforms, which obviously require the most maintenance to maintain satisfactory production levels.

Difficulties also arise with maintenance and adaptation of such equipment in that spare parts are not always readily available in the UK market and skilled personnel may have to be called in from USA to undertake repair work.

Further problems caused by operator errors are associated with the traditional equipment. There are difficulties in monitoring injection and retrieval of the tubing which means that tubing 'hang-up' within the well may occur and initially go unnoticed until a serious problem has developed. Complicated and time consuming 'rig-up' and 'rig-down' procedures for equipment may need to be carried out, for an error in judging the weight and length of coil tubing required could lead to permitted loadings being exceeded with risks of accidents possibly resulting in a well being damaged, perhaps irretrievably so, requiring it to be closed. There is also the risk of injury to rig personnel as a result of equipment failures arising from such errors producing hazardous working conditions for the crew of the rig.

Furthermore, there are many hydraulics hoses, cables and control lines required to run the equipment which are individually totally exposed to damage from the environment.

These hoses, if severed or snapped out of the couplings, could cause equipment failure with the risk of the coil tubing being ruptured and an extremely dangerous spillage of acid, escape of nitrogen etc. could occur.

In the accompanying drawings the figure identified as PRIOR ART illustrates the general layout of a typical known injector system. In this system a pair of endless drive chains carrying a plurality of gripper blocks are connected to a drive mechanism and driven in counter rotary-fashion to provide between opposed regions of said chains a throughpassage wherein said blocks are presented in such a manner as to contact a portion of the conduit and by frictional engagement therewith cause advancement thereof vertically through the injector drive mechanism. The driven conduit is then guided around a gooseneck prior to injection into a well. The whole injector system is installed in the drilling derrick by means of deck cranes.

The present invention aims to provide an improved injector head apparatus which obviates or mitigates, the above described disadvantages associated with traditional equipment.

Thus according to this invention there is provided an injector device for driving a conduit into an orifice comprising a drive mechanism, contact means for advancing the conduit in a given direction by frictional engagement with the exterior of the conduit, wherein the advancement path of the conduit has an arcuate section in which section the conduit is contacted and driven under control of the drive mechanism. Hitherto, the driving of a conduit such as coil tubing around a curved section in which the conduit is positively contacted and driven in that curved section has not been contemplated. The injector of the invention by adopting this approach surprisingly achieves the requisite compactness for reduced height working conditions (even below deck) without loss of utility nor introduction of undue complexity of design.

Preferably the contact means are carried on a continuous drive surface and include contact blocks for engagement of the conduit surface and guide shoes and/or rollers for maintenance of the preselected contact pressure on the conduit and guidance thereof in the arcuate path.

Conveniently the drive surface is provided by at least one drive chain or belt having tensioner means located about the arcuate path section to urge the drive surface to maintain the contact means in frictional engagement with the conduit surface.

The drive mechanism may comprise two endless drive chains passed around driven sprockets, with idler sprockets or wheels as required, arranged such that an arcuate path is defined between two adjacent portions of the respective chains, and the spacing of the adjacent portions is such as to allow the respective chains to bring contact blocks into frictional engagement with a conduit to be driven therethrough.

Preferably, the injector device is confined within a custom built compact lifting frame enabling the whole to be installed as a module for operation and repair below deck.

This has the advantage that the drilling and pipe deck surface operations of the platform need not be interrupted since the top deck main rig derrick is not utilised for the coil tubing operations of a particular well. This represents a significant improvement in space utilisation and enables more efficient use of the equipment on the upper decks.

According to the invention there is also provided a storage drum for conduits, such as coil tubing, which is formed from components enabling the transportation thereof and lifting within weight restrictions for off shore installation deck cranes, or lifting barge tenders, in a compact disassembled form. Conveniently the drum may be split into two part- cylindrical halves, symmetrically or asymmetrically. The drum is provided with a detachable spooling reel to provide a unique assembly for storage of conduits, particularly coil tubing, on site within a production installation.

Further according to the invention there is provided a multi-tasking control system operable from a control point, e.g. a control cabin on a well-deck, comprising a single umbilical within which is confined a plurality of fluid and electrical lines in communication with power systems, both hydraulic and electrical, and the actuators for the injector, handling system and blow-out preventor.

In order that the present invention may be more readily understood and so that further features thereof may be appreciated, reference will now be made to the accompanying drawings, in which : FIGURE 1 is a schematic view of the general layout of a typical known injector system; FIGURE 2 is a schematic view of an injector head apparatus according to one aspect of the present invention FIGURE 3 is a schematic view of the injector head of FIGURE 2 as in use in a coil tubing injector system of the invention; FIGURE 4 is a side view of a reel for storing coil tubing to be injected for downhole use by means of the injector head of FIGURE 2 , and FIGURE 5 is a schematic view of both the injector heads of FIGURE 1 and FIGURE 2 in normal operative positions.

Referring now to the drawings, an injector head apparatus 1 according to one aspect of the present invention comprises an injector head 3 having a substantially triangular body 5. The body may be formed of any suitable material. The body 5 is bisected by an arcuate pathway 7 which divides the body in the vertical plane into two asymmetrical sections 9, 11, the upper section 9 having a generally triangular shape with a concave base, whilst the lower section 11 is in the form of a segment having an upper convex surface.

First and second drive sprocket mechanisms 13, 15 are provided at end portions of the first and second body sections 9, 11. Sprockets 13 are associated with the first body section 9 and sprockets 15 are associated with the second body section 11.

An endless chain drive 17, 19 is mounted for advancement about each set of sprockets 13, 15 and thus for travel around each body section 9, 11, the chains each passing through the arcuate pathway 7 to line the respective walls of the pathway which are formed by the body sections 9, 11.

The endless chains 17, 19 are kept taut by chain tensioners 21 which are preferably hydraulically controlled and which can be adjusted to take-up any slack in the chains 17, 19 due to changes in operating conditions. Hydraulic hoses 23 for controlling the tensioners (see figure 3 ) lead from a control cabin 25 to a control point 27 on the injector head apparatus.

A guide shoe 29 is provided adjacent the lower pair of sprockets 13, 15. The guide shoe 29 is provided within the path of the first endless chain 17 and is hydraulically controlled, in a similar manner to the chain tensioners A tubing tension guide 31 is adapted to be mounted adjacent the upper pair of sprockets 13, 15 on the injector head apparatus 1. The tubing tension guide 31 comprises a substantially cylindrical body formed of a plurality of overlapping cylindrical sections 33 which are hingedly connected together to allow axial movement of the body.

Such movement of the body is controlled by a further hydraulic tensioner 35. A plurality of pairs of rollers 37 are provided within the cylindrical body 33, one pair of rollers being provided within each of the overlapping cylindrical sections 33.

Reference will now be made to figure 3 which illustrates a storage reel 37 for use with the injector head apparatus 1. The storage reel 37 comprises a drum 39 upon which the coil tubing is wound. The drum of this invention is formed of two releasable, interlocking sections 41 which enable the drum to be transported off-shore in two sections to meet the weight restrictions for lifting apparatus on off-shore platforms, and . then to be assembled once the sections 41 have been lifted on the off-shore platform.

The storage reel 37 is located on a spindle 43 which is journalled in two uprights 45, and the complete reel is housed within a cage 47. A tensioner 51 is mounted on the cage 47 at a position to enable the coil tubing to pass through the tension guide 51 when the tubing is being drawn into the injector head apparatus.

Adjustment of the tensioner 51 is controlled from the control cabin 25 via the control line 53.

In use of a injector head apparatus 1 according to one aspect of the present invention, the injector head is mounted in a frame 55 which is positioned above the well head. The frame removes the need for the injector head apparatus 1 to be lifted above the well head by a crane and enables work over processes to be carried out on lower levels of the off-shore platform while production is maintained on the upper level of the platform.

The coil tubing wound around the drum 39 is fed through the tensioner 51 and into the tubing tension guide 31. The coil tubing is passed between the pairs of rollers in the tubing tension guide and into the passageway between the two sections of the injector head.

Upon counter-rotation of the two endless chains 17, 19 of the injector head 3 , the coil tubing is drawn from the drum 39 through the apparatus. When the coil tubing exits the injector head apparatus 1 it is passed into a standard stuffing box 57 and directed into the production well 59.

Chain tensioners 21 are controlled from the control cabin and are adjusted to compensate for any loss of tension in the two endless chains 17, 19 The apparatus as described provides a compact, selfcontained injector head which overcomes problems such as lifting and 'rig-up' and 'rig-down' times associated with traditional coil tubing apparatus.

It is further envisaged that the apparatus described above could be controlled by a microprocessor from the control cabin. This would give a greater capability to controlling the operation.

Furthermore, the size of bundles of hydraulic hoses running between the apparatus and the control cabin could be reduced by using remote controlled hydraulic valvepacks mounted on the injector, storage reel and further equipment such as a blow-out preventor.

The microprocessor would provide more accurate monitoring and control of the system as it is operating than is available at this time with traditional equipment e.g.

the line tension between the injector head and the storage reel could be controlled continuously to avoid over tensioning or shock loading.

Similarly, by monitoring the chain travel and the tube travel in the injector head, any slip that occurs could be very quickly corrected ensuring smooth operation and minimising wear on the coil tubing.

As a safety feature, the microprocessor could monitor the injector load cell and record the loads on the systems.

This would allow for continuously automated fatigue life assessment using specially developed tubing management software. Problems such as tubes getting 'hung up' in the well could be registered by the microprocessor and the injector apparatus stopped very rapidly. This helps to remove operator error and delay and would prove to be a more reliable means of preventing buckling of the tube in the well.

Depth control could be preset on the computer which would be programmed to include stretch deviation etc.

Downhole operations carried out at depth would be greatly enhanced using this system compared to the mechanical counter-head systems in use at this time.

Furthermore, by using a microprocessor control a complete history of the coil tubing would be available, giving a continuous fatigue life information programme.

Claims (8)

Claims

1. An injector device for driving a conduit into an orifice, the injector device comprising a drive mechanism, contact means for advancing the conduit in a given direction by frictional engagement with the exterior of the conduit, wherein the advancement path of the conduit has an arcuate section in which section the conduit is contacted and driven under control of the drive mechanism.

2. An injector device according to claim 1, wherein the contact means are carried on a continuous drive surface and include contact blocks for engagement of the conduit surface and guide shoes and/or rollers for maintenance of the preselected contact pressure on the conduit and guidance thereof in the arcuate path.

3. An injector device according to claim 2 wherein the drive surface is provided by at least one drive chain or belt having tensioner means located about the arcuate path section to urge the drive surface to maintain the contact means in frictional engagement with the conduit surface.

4. An injector device according to claim 1, 2 or 3 wherein the drive mechanism comprises two endless drive chains passed around driven sprockets, with idler sprockets or wheels as required, arranged such that an arcuate path is defined between two adjacent portions of the respective chains, and the spacing of the adjacent portions is such as to allow the respective chains to bring contact blocks into frictional engagement with a conduit to be driven therethrough.

5. An injector device according to any preceding claim wherein the injector device is confined within a custom built compact lifting frame enabling the whole to be installed as a module for operation and repair below deck.

6. A storage drum for conduits, such as coil tubing, which is formed from components enabling the transportation thereof and lifting within weight restrictions for off shore installation deck cranes, or lifting barge tenders, in a compact disassembled form.

7. A storage drum according to claim 6 wherein the drum is split into two part-cylindrical halves, symmetrically or asymmetrically and is provided with a detachable spooling reel to provide a unique assembly for storage of conduits.

8. A multi-tasking control system operable from a control point, comprising a single umbilical within which is confined a plurality of fluid and electrical lines in communication with power systems, both hydraulic and electrical, and the actuators for the injector, handling system and blow-out preventor.