Camera system can be deployed on wireline or coiled tubing for downhole visual inspection under well-control conditions.

A new camera system for real-time downhole inspection can be deployed on wireline or coiled tubing (CT). The CamScanEVO camera system provides real-time downhole imaging with high image quality for use subsea, downhole and during well interventions. A rotate-and-tilt head allows full, hemispherical viewing. Digital recording means that still or moving images are transferrable instantaneously over the Internet. Typical applications include dropped-object investigation, damage assessment and inspection of wellheads, the seal area, threads and the annulus. The system can be run into a live well under well-control conditions, in wells where deployment can only be made on wireline or CT, in installations that cannot run drillpipe or in highly deviated wells.
Real-time images
Currently, it is the only system of its type that offers real-time color or monochrome imaging at depths beyond 6,562 ft (2,000 m). In addition to advances in camera technology, a unique drillpipe running tool was designed that makes it possible to flush the area around the periphery of the camera. This displaces wellbore fluid around the camera to create clear viewing. By employing wellbore cleanup technology, the running tool is the ideal vehicle for delivering filtered sea water, surfactants and flocculants to ensure visibility at the area of interest.
Wireline and CT deployment
The camera system is the first that provides real-time images using wireline as the power, data and video transmission system. In the past, problems have arisen when attempting to use analogue transmission technology. Analogue methods do not have the capability to transmit the large amount of data required for high-resolution, real-time images. These limitations have meant that only still images could be transmitted at intervals. For example, existing technology only allowed black and white images transmitted at approximately one frame per second. In comparison, the new system can transmit in real time (25 frames per second), in high resolution and in color.
Design parameters were established around a typical 7/32-in. monoconductor, representing a new and very high industry standard. This presented technical challenges not only with data compression, but also multiplexing the power, data and video signal on one single copper conductor while using the high tensile steel-armored outer braid as the electrical return. This approach created additional challenges, because the electrical properties of conductance, impedance and resistance change in direct correlation with how much wireline spool is unwound and the amount remaining on the reel. When fully wound on the reel, the electrical return outer sheath actually touches each wrap of the cable, changing the electrical properties.
The development process
The first stage of development investigated the behavior of electrical transmission using custom umbilical in the standard camera inspection system. This has the benefit of being a multi-core copper cable. Coupled with a nominal outer diameter of 11 mm, a lot of copper for both transmission and return can be used in its construction. However, it was still a challenge to ensure that, where lengths exceeded 6,562 ft, there was no degradation in picture resolution, and that there was sufficient power to operate the lights and mechanical drive. Fiber-optic cable was avoided because of its fragility and high cost. When deploying a system on drillpipe through the rotary table, a robust and field-repairable solution is required. Therefore, staying with copper umbilical and a highly developed transmission method that operates effectively on copper was deemed necessary.
Using the multiconductor umbilical, (which electrically is superior to monoconductor wireline) in the initial development trials, the transmission theory was developed into a working prototype. A hybrid system of modulated analogue and digital technology compressed and transmitted the data via a highly specialized radio frequency (RF) communication protocol. As the compression and transmission method was a new development, it was a logical step to develop this technology on multiconductor umbilical so that a detailed understanding of the new transmission characteristics could be assessed before modifying it to run on monoconductor.
Early indications showed that the principle of the technology was sound. However, it was very important to ensure that the picture at surface had the minimum of degradation and artifacts (errors generated from data compression). From lessons learned on the multi-conductor trials, circuitry and software could be modified precisely by matching the modulation and de-modulation process precisely to suit the characteristics of the monoconductor wireline. In effect, the technology that was developed tricked the cable into "thinking" that it was something that it wasn't by using the electronics in the transmission and receiving modules.
Power transmission
Power transmission presented its own set of problems. The power supply compatibility in both in the control unit and the camera module behaved differently depending on cable length. For the long-term aim, where it was likely that the wireline spool would be of a fairly consistent length, it was a case of matching the power supply exactly to the cable length. Up to lengths of approximately 6,562 ft, the system would operate without electrical noise, whether it was running on 1 ft or 6,562 ft.
To achieve overall system performance and ensure image quality, it was critical to select the correct, new-generation complementary metal oxide semiconductor (CMOS) image sensor array that would minimize degradation in image resolution. Units from a wide range of sources were tested to identify whether a specific module was suitable. Following the selection process, units were modified to fine-tune to exact specifications.
Bringing all of these elements together in a sophisticated microprocessor control system using 10 separate microprocessors achieved the desired result. The microprocessor control system was an in-house design that used custom software, thus allowing flexibility and the ability to configure for different types of wireline. The control system features not only monoconductor wireline, but also multicore wireline.
The development of the camera to run on wireline makes it possible to deploy on CT. As with a traditional drillpipe deployed system, this means that flushing can be performed to improve the visibility in the critical zone.
Deployment sequence
The highly portable equipment can be mobilized by helicopter. The camera is mounted in the deployment tooling whether it is a drillpipe running tool, winch, wireline or CT adaptor. The umbilical or wireline is connected to the camera and a function test is carried out. The camera is then deployed through the rotary table on the drill floor and through the stuffing box lubricator if being deployed under well-control conditions.
At all times during deployment, from running in hole to pulling out of hole, the camera is continuously sending real-time images to surface, which allows instant evaluation of conditions downhole. The images are also recorded onto digital media.
Real-time transmission during run-in allows evaluation of the well, casing and riser. If there are concerns at a specific depth, the camera can be deployed to that depth for a more thorough investigation. The camera has a 360° rotate-and-tilt mechanism that allows complete hemispherical viewing. In the event that clarity of the fluid does not allow adequate visibility, then seawater, drilling water, surfactants and flocculants can be introduced into the well bore via the camera running tool. The running tool has been designed to enable fluid introduction while running on drillpipe or CT, and for high turbidity situations, chemical additives have been developed in conjunction with leading wellbore clean-up companies. The additives and flow rates are generally recommended by us in discussion with installation personnel.
Deployment times naturally vary with depth, application, deployment method and wellbore clearances. Drill pipe deployment can be in the range of 750 to 1,000 ft/hour; deployment on wireline can be up to 5,000 ft/hour.
Easier and safer mobilization
As camera use increases in offshore procedures such as workovers, completions and general well interventions, this new technology will open up new opportunities for inspection, most notably under well-control situations. Mobilization will become easier and safer, as bulky items such as umbilical reels need not be shipped because the existing wireline spread is normally present on the installation. This new development also opens up possibilities for cameras and monitors to be based permanently on installations during critical operations. For example, in the event that downhole investigation is required, trained personnel on the installation will be able to operate the equipment immediately. This brings obvious cost- and time-savings benefits. In addition, operations will be able to proceed far more quickly without delays waiting on personnel and equipment.
Beyond capturing real-time images
Data compression and transmission technology need not be limited to real-time image capture. Any wireline electrical process could benefit. This has the potential for enhancing well-logging performance, for example. The application of this new technology could be far-reaching. For the moment, however, the new "wireline" version of this established camera inspection system can offer substantial benefits.