GB2349659A - A method of deploying wellbore tools on a slickline - Google Patents

Abstract

A method of deploying a wellbore tool 22 (e.g heavy duty pulling tool, mechanical jar and weight bars) comprises a hollow slickline 20. The tool 22 is suspended from said slickline 20, the slickline 22 being deployed via, a wireline unit.

Description

Flexible Elongate Conveying Element for Use in a Wellbore This invention concerns a method of carrying out drilling-related operations in a wellbore utilising a flexible elongate conveying element to convey a working tool to a required location in the wellbore.

In the petrochemical industries, oil, gas and water wells allow the extraction of products from below the surface of the earth. The wells may be drilled to a great depth and are periodically cased with a large diameter metal pipe called casing, in order to avoid collapse of the newly drilled hole. The wells are normally completed with a pressure sealing conduit called"tubing"which runs inside the casing from the wellhead or xmas tree valve assembly on surface to near the bottom of the well. Both ends are sealed in order to provide a pressure tight communication between the surface facilities and the producing formation (see a typical installation as shown in Figure 1). The wellhead will seal this casing/tubing annulus at the surface and a device called a packer will seal pressure downhole near the producing formations.

Many devices are located in the tubing such as safety valves, nipples, sleeves and injection valves for the safe ongoing operation and maintenance of the well. Occasionally and during installation, these devices require maintenance calling for an intervention in the wellbore. Depending on the severity of the problem which has made the intervention and associated maintenance (or replacement) necessary, different levels of intervention are required. These may include wireline, coiled tubing or drilling rig intervention. The preferred choice is usually the most cost effective and efficient.

Use of a full drilling rig is normally to be avoided due to the great cost and time factors involved. A drilling rig would consist of a large mast around 120 feet high with weight lifting equipment capable of lifting large loads in and out of the well. The rig utilises 30 ft. lengths of pipe which are screwed together to form a conduit which is lowered in and out of the wellbore to perform a variety of tasks. The conduit or drillstring allows large loads to be pulled (or pushed) and also offers the ability to pump fluids down the drillstring and back up the wellbore. Large diameter pressure containing equipment allows the passage of the drillstring into the wellbore whilst providing the facility of closing off the pressure (Blow Out Preventers, B. O. P.'s) should that be required.

The availability of the hydraulic source through the pipe allows tools to be included at the bottom of the drillstring to perform certain functions. The drillstring itself is heavy, clumsy and slow to move. Drilling rigs may normally only work on wells which have been killed, that is a well where there is no pressure imbalance at surface and which is filled with fluid of a weight which can counter any sub surface pressures which may exist. A crew of at least 15 men is required. Transportation, set up and operation of the rig are time consuming and costs are high not only for the daily operation of the rig but also in lost production from the well. Many operations such as installation or replacement of the tubing may only be done with a rig.

It is also known to use"coiled tubing", which is a continuous coil of pipe (commonly two inch O. D.) of a reduced diameter and strength from drillstring, which has been spooled onto a drum to provide a continuous conduit thousands of feet long. Its mobilisation and operation is faster than a rig but it still requires 6 or more men and a certain level of heavy equipment to be utilised. Its deployment in the wellbore is relatively fast compared to a drilling rig.

The termination of the tube to the toolstring also differs from the slickline method. Toolstring weights, jars and other components may be largely as for standard slickline.

According to the invention, there is a method provided of carrying-out drilling-related operations in a wellborn utilising a flexible elongate conveying element to convey a working tool to a required location in the wellbore, in which the elongate conveying element comprises a hollow slickline.

Preferably, the hollow slickline comprises a tube of the type available for use as"control line".

The tube preferably has a nominal outer diameter ouf'S inch.

The hollow slickline may be spooled on to a wireline unit, ready to be withdrawn therefrom for use down the wellbore when required.

The tool which is conveyed by the hollow slickline to the required location in the wellbore may include one or more of the following components: HDPT (heavy duty pulling tool); mechanical jar; and weight bars.

Preferred examples of methods of carrying out the invention will now be described in detail, by way of example only, and with reference to Figures 2 and 3 of the accompanying drawings, in which: Figure 2 is an illustration, partly in longitudinal section, of one example of use of a hollow slickline for use in a method according to the invention; and Figure 3 is a view, similar to Figure 2, showing a further example of use of hollow slickline in a method according to the invention.

Referring first to Figure 2 of the drawings, there is shown a hollow slickline 10 extending to surface, and being used to convey a working tool to a required location in a wellbore. A fitting 11 is carried by the slickline 10, and at its lower end 12 has a connection to a tool string (not shown). A hydraulic pipe 13 also extends to the lower tool string, to provide hydraulic energy to operate the tool, when required. Internally of the fitting 11, there are three sets of twin swage internal fittings 14 for hydraulic pipes.

Referring now to Figure 3, this shows a hollow slickline 20 extending to surface, and used to convey a tool to a required location in a wellbore. In the example shown in Figure 3, a composite tool assembly is coupled with the hollow slickline 20, being designated generally by reference 21. The composite tool assembly includes a lower HDPT (high duty pulling tool) 22, a mechanical jar section 23, and one or more weight bars 24.

Deployment of a hollow slickline (as shown in Figures 2 or 3) is identical to existing slickline methods with two added benefits. The available tensile rating of the wire/tube is doubled and an hydraulic path from surface to downhole has been created. This path may be used for the delivery of large amounts of hydraulic energy to a downhole tool system previously only available with coiled tubing deployed systems but with the ease, flexibility and economic benefits of a slickline unit. One new such tool which may benefit from this method and system of the invention called a heavy duty pulling tool (H. D. P. T.) is described below (see Figure 3). One other option available with this system are the coupling of an hydraulic tractor to the tube end.

Hydraulic fluid pumped from surface as a power fluid allows a downhole tractor device to drag the tube along a horizontal or heavily deviated section of the wellbore to deliver other tools or instrumentation to a specific part of the wellbore. Unlike slickline, these hydraulic tractors do not rely on gravity for conveying tools along horizontal sections and are presently available for coiled tubing useall be it with the disadvantages as stated before.

The heavy duty pulling tool will now be described with reference to Figure 3, by way of example, to demonstrate the increased functionality of a method according to the invention using a hollow slickline, over normal slickline, and its economic and time advantages when compared. with coiled tubing methods.

A Heavy Duty Pulling Tool (H. D. P. T.) is used to release a safety valve or other similar piece of wellbore equipment which is stuck due to foreign body ingress, corrosion, erosion or other locking means forming with time.

Presently, the slickline techniques used to deal with this problem universally consist of imposing ever increasing loads with a slide hammer above the stuck device. Pulling on the wire imparts a blow to the stuck device which is proportional to the weight of the hammer above the device, the stroke of the hammer and the speed of delivery of the blow. The amount of force which may be imparted is finite and is ultimately limited by the physical properties of the wire including its ultimate tensile stress. This may be an impact force of around 40,000 lbs at best. The connection between the hammer and the stuck device is made with a device called a pulling tool (or running tool if the device is being installed).

The H. D. P. T. when used with hollow slickline also fits above the normal pulling tool and below the hammer. A hydraulic pipe extends across the hammer (see Figure 2) providing hydraulic communication to the H. D. P. T. consists of two main parts, a slip assembly and piston assembly. The slip assembly features contact pads which will grip the tubing wall above the stuck device and provide an anchor point in response to applied pressure. The piston assembly may be a multi stage piston which will provide an hydraulic pulling force of many thousands of psi on the stuck device.

This force is regulated by the application of surface pressure and may be as much as hundreds of thousands of pounds, limited only by the ability of the tubing to provide a sound anchor. A similar embodiment of the device may be used in a reversed layout to push the device into a seat.

It comprises a spooling unit to contain the coiled pipe, an injector head to physically push the pipe into the well and pressure containing equipment. Coiled tubing may be used on a live well where there is pressure at surface and the tubing contains a mixture of oil and gas. The injector head is required to push the coiled tubing into the wellbore as the internal pressure will try to push it out.

Coiled tubing provides a means of conveying equipment in and out of the wellbore, a means of exerting a pull on stuck equipment and a means of circulating fluids or chemicals around and into the wellbore. Due to the nature of the spooling unit, the injector head and the pressure containing equipment, only a limited amount of manipulation of the coiled tubing is possible limiting the full range of operations available with this technology. Coiled tubing operations, although much cheaper than a full drilling rig, are still expensive and require considerable well down time.

The equipment is bulky and requires a certain amount of space which is not always easily available at a wellsite.

Substantial cranes are required to lift and position the equipment due to its great weight. Often the coiled tubing unit is positioned on a drilling rig as the combination offers certain advantages. Sometimes due to space considerations, the well may not be accessed without the drilling rig being positioned over it, even although the drilling rig will only be used as a platform for the coiled tubing unit.

Slickline is a known technique utilising a solid wire many thousands of feet long with tools or operating devices on the bottom end. The wire diameter is normally. 108 for normal operations or 3/16"for heavy duties. It is contained on a drum usually around 3 feet in diameter which is part of a hydraulic winch unit. The wire passes through pressure containing equipment which is small and light in weight. Due to the nature of the equipment, it is highly portable, occupies minimum deck space and requires no other support infrastructure for its operation. The wireline tools are lowered down the wellbore and operated by means of wire manipulation (which may be rapid). Devices may be removed or installed into the wellbore. A slide hammer or jar is always included above the tools as a means of increasing the loads applied during installation or retrieval. Slickline requires a two man crew, is fast to mobilise and rig up, does not require the well to be killed prior to its operation and is inexpensive in every respect.

Slickline is the most common and frequently used type of intervention and has a wide range of tools and systems available for a multitude of tasks.

It is an object of the disclosed method of the invention to increase the range of tasks possible with slickline by utilising the method as disclosed, which is referred to for convenience as"hollow slickline".

"Hollow slickline"or control line is a technique where slickline equipment and techniques are used, but the slickline wire is replaced with tube e. g. tube nominally of 1/4"diameter. This tube is commercially available for use in wells and is generally called"control line". Various grades and materials are available but for the purpose of example we will use a 1/4"O. D. with 0.083" wall UNS-S31803 Duplex material. This provides tensile properties of approximately twice that of regular. 108 slickline. The tube may be spooled onto a normal wireline unit and used with all the usual pressure control equipment. A slight modification is required to the stuffing box (the pressure sealing element) to accommodate the different diameter.

Sheaves of at least 50 times the tube O. D. are also required.

Therefore, in general terms the invention is concerned with usage of a flexible elongate conveying element in a wellbore, to convey a working tool to a required location in the wellbore (tubing), in which the conveying element comprises a hollow flexible element, such as flexible tube of the type known in the drilling art as"control line".

Claims (6)

1. CLAIMS: 1. A method of carrying-out drilling-related operations in a wellbore utilising a flexible elongate conveying element to convey a working tool to a required location within the wellbore, in which the elongate conveying element comprises a hollow slickline.
2. 2. A method according to claim 1, in which the hollow slickline comprises tube of the type available for use as control line.
3. 3. A method according to claim 2, in which the tube is nominally of V, inch outer diameter.
4. 4. A method according to one of the preceding claims, in which the hollow slickline is spooled on to a wireline unit, to be withdrawn therefrom for use down the wellbore.
5. 5. A method according to any one of the preceding claims, in which the tool conveyed by the hollow slickline to the required location in the wellbore includes one or more of the following components: heavy duty pulling tool; mechanical jar; and weight bars.
6. 6. A method according to claim 1 and substantially as hereinbefore described with reference, and as shown in Figure 2 or Figure 3 of the accompanying drawings.