The Wireless Downhole Monitoring Dream: Now A Reality

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The GEOEM 125 Gauge features advanced wireless telemetry combined with a highly accurate suite of sensors makes for a dependable monitoring solution for even the most critical wells. And with a custom-built carrier design and engineered battery solution, it has been designed from the ground up to survive hostile environments with high vibration and temperatures exceeding 125°C.

Now with over 300+ successful installations around the globe, this proven monitoring solution is changing the way operators optimize their assets providing real-time downhole data in a way that is reliable & cost-effective. This allows real-time optimization for wells where traditional gauges may have never before been feasible.

Figure 1: GEOEM 125 Wireless Downhole Gauge

Solving Client Problems With Wireless Monitoring

The Australian Coal Bed Methane (CBM) industry has prolifically installed traditional wire-based downhole gauge monitoring solutions. Since 2011, conservatively, 12,000 wire-based systems have been installed, predominantly on PCP completions.

One of the challenges with CBM wells is that once dewatered, killing them with fluid during workover damages the coals, decreasing well productivity. Also, due to high near-wellbore permeability, some wells cannot hold a fluid column, and cannot be killed. For both reasons, some workover activity is moving toward the use of snubbing rigs, where live well interventions are preferred.

Live well workovers with snubbing units are not possible with wire-based monitoring solutions. The pressure control on a traditional snubbing unit requires the round profile of tubing to seal effectively. In 2016 clients in Australia approached us here at GEO PSI and Qteq to develop a Wireless based monitoring solution for PCP and SRP completions, that could be utilized on snubbing rigs. In 2017, the GEOEM wireless gauge platform was born and subsequently commercialized.

Figure 2: GEOEM 125 sensor and downhole electronics housing

GEOEM Operating Principle & Deployment

The functional premise behind GEOEM gauges is to provide wireless transmission capabilities delivering data to the surface without using downhole cables. Our GEOEM platform utilizes built-in telemetry electronics to transmit a low-frequency signal that propagates through the earth to the surface.

Figure 3: GEOEM 125 downhole gauge signal propagation visualization

Powered by specialty lithium-ion batteries designed for downhole use, the sensor package includes pressure, temperature, vibration, and inclination, bundled together with signal propagation telemetry. The sensor package and battery are installed inside specially designed carriers, called gap subs.

The gap sub incorporates a non-conductive barrier that creates an electrical insulator in the tubing string. The string above the gap sub is isolated from the casing using nonconductive centralizers, while the signal below is funnelled toward the formation. This configuration ensures maximum signal propagation toward the formation, finally travelling to the surface for processing.

Figure 4: GEOEM 125 gap sub and battery pack visualization

At the surface, the signal is detected at ground stake locations, where it is then decoded and processed for delivery to appropriate data acquisition infrastructure.

Depending on the well and completion design, the GEOEM 125 can be installed on the bottom of the tubing (below completion, below pump), or part of the tubing (in completion, above pump). Certain completions can also be designed to accommodate wireline deployments.

Figure 5: GEOEM 125 wireless signal transmission visualization

GEOEM Capabilities & Features

GEOEM 125 gauge is a highly capable wireless solution packed with powerful capabilities, features, and benefits. Below is a list of just a few of the key advantages of running this gauge:

Altering Sample Rate To Preserve Battery Power

Wireless solutions must be designed to manage the fine balance between battery power and sample rate. Where wired systems have an infinite source of power, batteries only have a limited, stored quantity of power.

When battery power is a fixed variable, what can be altered to influence run life is the sample rate. The GEOEM 125 has two modes to manage sample rate, and therefore power usage.

One of which is ΔT mode. This mode takes a time-based approach to sample management. Users can define the frequency with which samples are transmitted to surface and will send new data at every set fixed interval for the life of the tool.

Another sample mode is ΔP. This functionality delivers fresh sample data based on a predetermined pressure change (ie. ±0.5 psi). So if nothing changes to the downhole pressure the tool will preserve battery life and wait to send a fresh data packet once there is a significant change detected.

Both ΔT and ΔP modes can be used independently, or together to manage sample rate. These features are easily configured before the tool is deployed using the included utility software.

Figure 6: GEOEM utility software gauge configuration window

GEOEM Power vs. Data Case Study

To give greater context to the effectiveness of these two sample modes we have outlined the following calculations and case study.

Where ΔT is used as a sample management tool, the following table indicates the calculated run life.

Where the ΔP sample management tool is used, the following table indicates the savings in total samples over ΔT mode. The table illustrates that by decreasing the number of “redundant” samples using ΔP mode, the run life will dramatically increase.

The practicality of both ΔT and ΔP is highlighted in the following graphs.

This first graph shows production data from a well with a PCP completion, where bottom hole pressure (BHP) data was transmitted using ΔT mode at 10-minute intervals regardless of whether there was a significant change in pressure. The total number of BHP samples was 37,076 samples.

The question is, how many of those samples were redundant where battery power could have been conserved, increasing run life?

Figure 7: Graph showing the total samples and subsequent fluctuation in downhole pressure using a regular pre-determined sample interval

The second graph shows the same well production profile as the top graph, except that both ΔT and ΔP mode were enabled.

The program utilized ΔT mode every three hours, and ΔP every 0.72 psi change in pressure. Utilizing both ΔT and ΔP modes led to 9,684 samples being taken, compared to 37,076 samples when just ΔT mode was used at 10-minute intervals.

This significantly increased the run life without compromising the client’s data acquisition objectives.

Figure 8: Graph showing the total samples and subsequent fluctuation in downhole pressure using a pressure trigger to initiate the transmission of samples

As you can see utilizing both ΔT and ΔP together dramatically reduced the amount of power used, yet the same valuable insights on the downhole environment were able to be presented.

The power utilization case study has proven that ΔT and ΔP are powerful sample modes that allow sophisticated power management, leading to the capture of key production data without losing the granularity of key production pressure profiles.

Conclusion

The GEOEM platform is another high-performance solution in the GEO PSI downhole monitoring toolbox. Where snubbing operations, cable failures or other operational challenges are prevalent, GEOEM can be utilized to meet client downhole monitoring objectives.