By Mark Watson, vice president – Middle East North Africa, Tendeka
Despite the best efforts of oil and gas operators and service companies alike, permanently installed pressure and temperature (PT) monitoring systems are sometimes prone to failures for one reason or another. This can leave the operator’s well without any functional real – time permanent monitoring system, unless a costly re-completion is undertaken, which may not be possible for commercial reasons.
To overcome this, Tendeka, the completions solutions provider, has developed a wireline installable wireless downhole Pressure and Temperature Gauge, which now gives the operator a reliable, efficient and cost effective alternative. The technology, which was developed at the company’s base in Stavanger, Norway and was sponsored by the Norwegian Research Council, was recently deployed by Statoil offshore Norway and was deemed a success.
Wireless Technology
The P&T Gauge system uses “Static Pressure Pulses” which are fundamentally different from the “shock wave” type pressure pulses, which are created by technology such as MWD (measurement while drilling) monitoring. The primary role of the gauge is that of a retrofittable alternative to a permanent gauge system, and can be deployed either by wireline or coil tubing.
The system has been designed for simple interfacing and maximum compatibility to the well; the wireless signals travel along the well trajectory in the form of pressure variations that can be read on surface by the customer’s Wellhead sensor. This means that for the majority of operators, the system can be deployed by a single wireline trip, allowing for highly accurate data to be sourced almost instantaneously for a fraction of the cost of a re-completion.
Using a wireline set packer to deploy the system, allows the gauge to be set in blank pipe, therefore giving the optimal freedom with regards to installation depth. The alternative is to set it using a wireline set lock, which is generally more cost effective than the wireline set packer option, however, this does limit the installation location to where there are wireline nipple profiles in the completion.
The company’s wireless technology is not limited to transmitting gauge data and offers significant benefits, compared to other alternatives such as acoustic and electromagnetic systems. The gauge system can be installed as close to the producing interval as required. It also has a very low energy consumption, which does not increase at greater depth, passing on a major benefit to the customer.
Other applications for the wireless technology include the measurement of pressure, temperature and water cut with the system installed between zones to report pressure, temperature and zonal water breakthrough as well as flow rate to the surface. A more advanced version of the system can be installed in inflow control devices (ICD) and completion plugs.
Wireless Gauge Deployment
Statoil recently deployed the wireless Pressure and Temperature Gauge at a depth of 2,200m in a low pressure (32bar) gas well offshore Norway. The existing Wellhead Sensor was used to capture the wireless signal and extract the data, therefore no extra infrastructure was required.
During the installation planning, there were some concerns that the free gas would attenuate the signal,. However, once the Wireless Gauge was installed at depth, the signal pulse proved to be easily distinguishable from the background pressure variation noise. Therefore, the Wireless technology has been qualified to transmit pressure pulse based signals even in low pressure gas wells, thereby demonstrating that the wireless downhole telemetry can be applied in nearly all fluid compositions and flow regimes.
The wireless gauge is unable to transmit signals in either a non-flowing or shut-in well due to an actual flow regime being required to produce the pressure pulses. The tool has been designed to be able to be programmed to record PBU (pressure build up) data during shut-in periods and once well production is restarted; the stored data can be transmitted to surface. During this actual installation, there were periods of shut in while surface maintenance was conducted. The tool successfully recognised the shut in events and entered its power saving hibernation mode. When the well resumed production, the technology re-activated itself and the first telegrams transmitted following the restart, gave accurate shut in pressure data to surface.
This application, and two others undertaken at the time, demonstrated that the system functions not only in oil wells, but also in gas wells and wells with a high gas/oil ratio. During the trials, it was demonstrated the Wireless gauge could function in wells with slug flow and high levels of pressure/noise variations on surface. During shut in periods the tool has successfully recorded the shut in data and transmitted to surface when production was resumed.
Reliable and accurate monitoring is crucial to well operations and when a Permanent Gauge system fails, it is paramount that the means of obtaining real-time data is commenced. Previously, this may have required a costly well re-completion, but with Tendeka’s Wireless retrofittable downhole Pressure and Temperature gauge provides a reliable and cost-effective alternative.
It is expected that the deployment of this system will save significant intervention costs and avoid deferred production caused when conventional Permanent Monitoring are required to be replaced.
