GB2293513A

GB2293513A - Downhole video camera and video recorder assembly

Info

Publication number: GB2293513A
Application number: GB9418882A
Authority: GB
Inventors: Colin Scott Boyle
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-09-20
Filing date: 1994-09-20
Publication date: 1996-03-27
Also published as: GB9418882D0

Abstract

A downhole camera assembly lowered into a well bore by means of surface mounted cable and winch provides a method of visually recording the sidewalls of a well bore. Mounted within a pressure resistant steel walled tubular housing the assembly includes a wide angle video camera 9, a power/transmission section 13, a video recorder 11 and tape mechanism and a lighting section 10. An optically clear, pressure resistant glass viewport allows the well bore to be illuminated and the visual image 1 recorded. Thermal transmission from well bore fluid to camera mechanism is minimised by evacuating the camera housing and shrouding components in reflective foil. On retrieval to surface, playing the recorded video tape allows visual inspection of the well bore. An electrical timing device 14 allows the switching on of the apparatus to be predetermined. The operator uses this time to establish the pressure vacuum within the camera assembly and run it to the desired depth prior to filming. <IMAGE>

Description

TITLE: DOWNHOLE CAMERA ASSEMBLY BACKGROUND OF THE INVENTION The present invention relates to the visual recording and logging of a bore hole or well bore.

A borehole or well bore is an artificially excavated hole made to extract minerals and elements from beneath the earth's surface.

Holes are also drilled for the purpose of locating said mineral deposits and for determining the integrity of the rock structure to predict instabilities.

Visual inspection of boreholes can be of benefit to geologists in recognising the presence of mineral bearing rock formations.

In oil, gas and water wells which may be steel clad, visual inspection can be used to determine, wear, corrosion and scale build up on the steel surface. It is common for tools to be dropped or become stuck in such wells. Visual inspection can be used to locate stuck tools and help determine the best method by which they can be retrieved.

To carry out visual inspection of well bores a number of downhole camera apparatus have been developed. Two such examples are as follows.

Barbour US Patent 4,855,820 Hitwell International Application PCT/US92/00037 Both systems are similar in that a camera and light source contained in a pressure retaining steel sheath are lowered into the wellbore on an electrical cable. The image from the camera is transmitted via the cable to surface where it is visually displayed and recorded. Both systems allow real time viewing of the borehole. The barbour system is powered from surface, the Hitwell system has a battery power source mounted in the steel housing.

While both systems are capable of producing visual images at surface, they have a number of limitations. The camera has to be capable of running to significant depths. This requires long lengths of cable through which the signal is transmitted. The cable length does not change with camera depth. The breakdown in signal over the cable length impairs the resolution of the display on surface. It is often difficult to determine the images that the camera is transmitting.

Both systems require dedicated equipment for deploying the camera into the well bore. This significantly increases operating costs and introduces logistical problems in shipping and storing said equipment.

The purpose of this invention is to provide a down hole camera assembly which overcomes the limitations and disadvantages of the above described systems.

DESCRIPTION This invention pertains to a downhole video camera and recording system which will primarily be used for the inspection of Oilfield well bores.

It will be deployed into the well on slickline, a single strand wire cable which is incapable of transmitting electronic signals. Slickline is typically available at the wellsite on a wireline unit.

Details of the camera assembly are portrayed in figure 1. Specific components are individually numbered and are described in full below.

The camera assembly includes an outer housing 1 formed from high strength steel tubing which is capable of withstanding the wellbore pressures to which the camera assembly may be subjected. The outer housing 1 contains the remaining components of the camera assembly which are attached to an inner frame 2.

The inner frame 2 allows the internal components to be installed or removed from the outer housing 1 in one simple operation. When the inner frame 2 is installed within the outer housing 1 it is retained by the top sub 3. the top sub 3 has an external thread which mates with an internal thread on the upper end of the outer housing 2.

On top of the top sub 3 is an external thread 3a. This allows the camera assembly to be attached to the slickline for deployment in the wellbore.

Mounted on the top sub 3 are 'O'-ring seals 5 which seal against the internal seal surface of the outer housing 1. This allows the internal components to remain at a fixed pressure whilst the outer housing 1 is subjected to full well bore pressure.

The fixed internal pressure is less than atmospheric pressure and is produced by attaching a vacuum pump to the valve 4 mounted in the top sub 3.

Prior to deploying the camera the outer housing 1 is evacuated leaving all the internal components within a vacuum. This vacuum prevents heat transfer by conduction and convection from the wellbore fluids through the outer housing 1. To further reduce thermal conduction between outer housing 1 and inner components, contact between outer housing 1 and inner frame 2 is limited. Thermal isolating materials are used on the inner frame 2 at points of contact.

To further reduce thermal transfer between the outer housing 1 and the internal components, the components are shrouded in reflective foil. This foil will reflect any heat transmitted from the outer housing inner wall as radiation.

Adopting these designs allows the internal components to operate reliably at lower temperatures compared to the well bore environment.

Mounted at the lower end of the outer housing 1 is the viewing port 6. This is a cylindrical section of optically clear impact resistant glass. It is capable of resisting the wellbore pressure to which the camera assembly will be subjected. The viewing port 6 is held in place by a retainer ring 7 which threads into the outer housing 1. It is sealed off by two O-rings 8.

Mounted in the inner frame 2 directly above the glass viewing port 6 is a video camera 9. This has a wide angle lens of fixed focal length. Surrounding the video camera 9 is a ring of lights 10.

The lights illuminate the bore hole wall through the view port allowing the reflected light to be collected by the video camera 9.

The signal from the video camera 9 is transmitted to the video recording mechanism 11. This transfers the video signal onto video tape 12. On retrieval of the camera the video tape 12 can be played back to reveal the visual image of the well bore.

Electrical power to run the video camera 9, lights 1 and video recording mechanism 11 is provided by a battery pack 13 mounted on the inner frame 2.

The appliance of power is governed by an electronic timer 14 tied into the electrical system.

This can be preset to determine the time delay before the camera 9, lights 10 and video recording mechanism 11 are switched on.

This allows the operator sufficient time to establish the vacuum within the camera assembly and to lower the camera to a desired depth in the well bore prior to filming.

Claims

1. A downhole camera and recording apparatus for continuously observing and recording images of the interior of a borehole, comprising: a housing; a camera and recording means for capturing and recording images,

2. The camera apparatus set forth in claim 1, further including a light source to provide illumination of said borehole.

3. The camera apparatus set forth in claim 1, wherein said camera means includes a power section to provide remote supply of electricity for operation.

4. The camera apparatus set forth in claim 1, wherein said housing includes a lower and upper housing.

5. The camera apparatus set forth in claim 1, wherein the upper housing incorporates a valve mechanism.

6. The valve mechanism in claim 5 , whereby after assembly the housing can be evacuated for thermal isolation.

7. The camera apparatus set forth in claim 1, wherein the recording mechanism which incorporates a tape to store the recorded information, allowing replay upon retrieval to surface.

8. The camera apparatus set forth in claim 1, wherein the power section incorporates a timer device.

9. The camera apparatus set forth in claim 1, wherein the upper housing incorporates an external threaded connection to allow said apparatus to be connected to single strand wire for deployment into said borehole.

10. The valve mechanism set forth in claim 5 whereby after retrieval the vacuum can be broken to allow disassembly and recovery of recording tape.