For oil producers, wise automation technology selection is important.
by Jim Gardner, FreeWave Technologies, Inc.
February 5, 2013

The use of plunger lift technologies in the production of natural gas in the U.S. has allowed producers to optimize well production. In fact, during the past 3 years, natural gas production has been so successful that it is experiencing a surplus. Because of this excess, producers have seen a dramatic shift in demand from natural gas to oil and have begun to focus production efforts on oil.

The increased demand for oil brings the need to optimize production methods, such as directional drilling. In turn, producers are continually searching for the most effective and efficient ways to produce oil. Many have found that a reliable communications network helps streamline operations, allowing for system monitoring and control on a real-time basis. Automation is at the forefront of this ideology, but many options are available, making it important for producers to make their choices wisely.

Traditional Methods
The conventional approach of putting a flow computer or a controller, such as a remote terminal unit (RTU) or programmable logic controller (PLC), on each wellhead can become redundant and expensive. Many of the first multi-pad wells used one much larger flow meter or controller that could handle multiple wellheads. Another popular early attempt was to use “hardwire” and direct buried cable from each wellhead to a central controller.

However, the wells were often brought onto the production line at different times and automation technology was added incrementally. This meant that crews were brought to each location at different times, and backhoes were required to dig trenches from each wellhead—which could become costly and time-consuming. In some cases, wiring from a previous installation was damaged during a second installation. With new wells rich in hydrocarbon liquids, producers needed to address increased tank capacities on each pad. Some locations required six or seven tanks to gather liquid for 12 to 16 wells.

Additionally, the wiring from the wellheads to the tank batteries would be placed under the access roads for the trucks required to transport the liquids to other facilities. This became problematic because the heavy weight of the trucks and the high volume of traffic ravaged the buried cables and caused the wiring to become non-functional. Depending on the locations and soils, some producers replaced their buried cable in less than a year, another expensive and time-consuming proposition.

Despite the costly and resource-consuming process of installing cable, most oil producers are accustomed to wired solutions. Because wire is a common solution, it is trusted by many producers. When using newer options, such as wireless data radios, compromised reliability is a common concern for producers. Some believe that the radios will have higher failure rates than wired solutions. However, during the past 5 years, the opposite has proven true. As the use of wireless data radios has increased, many producers have found that they are more reliable and have low failure rates.

Wireless data radios also have an advantage because they are not affected by construction or equipment relocation, which is a risk factor for a wired solution. No device is immune to a loss of signal, though many radio manufacturers have planned accordingly and offer solutions with built-in, fail-safe or default setting configurations.

This allows producers to set parameters around the radio. For instance, if communication is lost, producers can pre-set whether a valve should be closed, opened or left as is. They can essentially choose how long they prefer to wait and what action will take place should communications fail. With wire, these options are not available.

Wireless I/O
What is Wireless input/output (I/O)? Wireless I/O is a mechanism by which analog (4-20mA, 1-5VDC, etc.), discrete and other raw signals are transmitted via radio to and from a central processing device—such as a distributive control system (DCS), programmable logic controller (PLC) or other remote terminal unit (RTU). In the simplest terms, wireless I/O is wire replacement, where the wireless communications link emulates wire in an existing application. No changes are required to the system architecture. Wireless links are used to transmit the same data that the physical wire once carried.

Wireless I/O is a more recent option for automating multiple well pads. Today, wireless I/O is recognized as an effective and reliable way to monitor and control plunger lift, and many producers are adopting it as an option for oil production. Technology manufacturers that have followed industry trends are aware of the decreased need for gas-producing technologies and the increased demand for technologies that can monitor and control multiple wells on one pad to maximize production.

Producers often use advanced production techniques, such as directional wells where oil comes in at high pressures—from 6,000 to 10,000 psi. Wireless I/O radios have the ability to transmit varying data straight to producers’ offices, allowing them to closely monitor casings, tubing, and intermediate and surface pressures. With wireless I/O, producers can view temperatures, pressures and alarms in the system from miles away. Many wireless I/O radios are now capable of transmitting data more than 60 miles with good line of sight communication paths.

These wireless technologies can also control the valve at the wellhead. Because these wells are so prolific, six to 10 tanks and a tank battery may be used at each location. Some wireless I/O providers can transmit tank levels for multiple tanks, allowing for optimal valve control. For example, should one tank become full, a wireless I/O will automatically instruct the valve to close and signal a new tank to open. Essentially, wireless I/O takes the information from the wellhead or the tank back to the controller. The controller then processes the data, reads the algorithms and makes decisions, which the wireless I/O data radio carries back to the valve. The valve opens, closes or remains as is depending on the signal from the radio.

When producers investigate wireless I/O options, they must also consider that some manufacturers offer more variety than others. For example, some manufacturers’ radios offer multiple I/O points, allowing for several temperatures, pressures, etc., to be communicated through one radio. It is more common to have just one I/O point. Depending on how many points are needed, seeking a provider who offers multiple I/O points, also known as I/O expansion, may be beneficial for end users.

For example, a wireless I/O base may have two digital inputs, two analog inputs, two digital outputs and two analog outputs, allowing the user to simply snap a module onto the radio that has up to 16 additional I/O points. For oil wells, the ability to have I/O expansion is crucial because when measuring high-pressure fluids, casing, tubing, surface and intermediate pressures must be monitored. I/O expansion helps increase the overall health of oil production systems by offering producers real-time data that can be analyzed for multiple pressure readings via one communication source.

Image 2. A remote slave with a wireless I/O slave—the box also contains an RTU, battery and a voltage regulator.<br />

Conclusion
In oil production, advancements such as directional drilling allow for multiple wells on a single pad. This increases efficiency and overall production.

However, to keep up with these advancements, a communication solution that can effectively monitor differing data points is essential. Wireless I/O and I/O expansion meet these needs and offer benefits, such as a fail-safe way to handle communication failure. Additionally, wireless I/O can transmit the data needed to control valves on oil tanks, preventing overflow and optimizing production. Choosing the right automation technology can be a daunting task, so producers should be familiar with all the options. Today, wireless I/O radios are available at a fraction of the cost of buried cable, and they can offer the same reliable results in a flexible and easy-to-install package.