The goal is to accelerate development and deployment of “intelligent well completion” technologies to optimize production of natural gas resources. The purpose of this project is to develop and test a wireless system for communicating downhole pressure and temperature data to the surface via acoustic waves, employing the tubing as a medium and a downhole electric power generator to drive low power electronics that acquire, process and transmit the data in real time.
Tubel Technologies, Inc. – Project management and all research products
The Woodlands, TX 77381
“Intelligent” wells have the capability for real-time downhole process control incorporated into their construction. This control relies on real-time, downhole pressure and temperature monitoring to optimize production performance and reservoir management. The task of incorporating a reliable, accurate and cost-effective system for acquiring this data and communicating it to the surface is a critical challenge to the widespread use of intelligent well completions. A wireless communication system driven by a downhole generator could allow intelligent completion sensors to be placed anywhere in the wellbore, without the need for cables to supply power or transmit data.
The system being developed under this project creates an acoustic signal from electrical pulses generated from digitized sensor information. The acoustic waves are coupled to the production tubing and travel up the pipe to the surface in a compression mode. The downhole electronics samples and digitizes information from temperature and pressure gauges at specific time intervals programmed before the tool is deployed in the well. The data is processed and encoded for transmission to the surface to minimize the number of bits of data required. A downhole microprocessor then generates the electrical pulses used to drive the acoustic generator. After transmission of the information to the surface, the processor places the tool in a power saver mode until it is time to perform the data acquisition tasks at the next pre-programmed interval. The system can also receive acoustic commands from the surface.
The power for operation comes both from batteries and a power generation module. The primary power generator employs piezoelectric (PE) wafers to generate electricity from the flow of hydrocarbons through the area in the wellbore where the tool is deployed. A total of 40 ceramic PE wafers are electrically connected in parallel and compressed into a single generator assembly. The batteries are used to provide backup power to enable the tool to operate continuously for 3 years in the event the primary power generator does not supply enough power.
A surface system comprised of three modules provides data acquisition, processing, storage and display capabilities for the data received from the wellbore. The first module is attached to the wellhead at or just below the surface, to detect the signal transmitted from downhole and convert it from an acoustic wave into digital electrical pulses. This acquisition module also converts electrical pulses into acoustic commands to be sent into the well. The pulses received from the wellbore are sent via a cable to a second module that interfaces to a pump controller or computer. Here the data received from the acquisition module is conditioned and pre-processed to eliminate noise. The third module is a PC that interfaces with the processing module to extract the downhole information for viewing in a graphical or tabulated format.
The flow of produced fluids is not restricted because the tool provides for full tubing inside diameter. Since the signals are carried by stress waves in the production tubing, the data is virtually unaffected by the fluid in the well. All hardware for the wireless gauge is held within an atmospheric pressure chamber located outside of the 4½-inch diameter production tubing.
The key element of this system, the Downhole Power Generation System, will potentially impact the development and application of intelligent well technology in several ways. The generator is a solid state system that uses the energy from fluid/gas flow and vibration generated during production to harvest electricity. During production, the generator is capable of powering downhole gauges such as pressure sensors that monitor production and formation parameters to optimize and automate the production process. The result is that an increased amount of hydrocarbon can be extracted from the formation due to the optimization of production equipment. In addition, the generator eliminates cables that are normally deployed on the outside of the production tubing for powering downhole sensors. These cables are quite expensive and can be crushed and/or cut during the deployment of the completion hardware. The high cost and low reliability of cables have been major barriers to the deployment of sensors in most wells and this feature of the new technology will enable the wider application of intelligent well technology. Finally, the generator can be used to power downhole hardware that would otherwise need to rely on hydraulic lines or the deployment of setting tools to actuate those devices. This will result in reducing the cost of the completion systems significantly and the potential risk of accidentally deploying setting tools at the wrong place inside the wellbore. Future applications for the generator include its deployment as part of fracture assemblies for monitoring of the fracture stimulation process in real time, thus potentially improving the process and increasing the production of hydrocarbons. The generator could conceivably also be used to power diagnostic and control systems during the drilling process.
A new downhole gauge has been developed for monitoring deep well gas production. The system is self sufficient where power, sensors and communications are all built as one tool. The new system can provide pressure and temperature measurements and generate power inside the well. A power storage module is capable of capturing, conditioning and storing the energy generated for utilization during the data transmission to the surface. A surface to downhole communications module was also developed to transmit information to the downhole gauge to provide the ability to change data rates or to ask for data in a master-slave configuration. A new digital signal processing module for the downhole tool has been proven to work in the wellbore environment and capable of differentiating signal from noise and also capable of detecting and processing the commands issued at the surface.
Future development would include replacement of the software tone detector with a dedicated hardware tone detector. This would greatly increase the dynamic range for signal acquisition in the downhole pressure gauge. It would also increase noise rejection. With that enhancement along with a change of location of our downhole accelerometer, it can be expected that the range of the tool would be extended many thousand feet.
This project has been completed.
Final Report [PDF-4.59MB] - September, 2005
Summer 2004 GasTIPS article - Real Time Half Duplex Communications Wireless Guage with Downhole Power Monitors Deep Well Gas Production [PDF-361KB]