Texas Tech, Permian Basin operators and service companies monitor sucker rod pump performance.

Because of huge investments in production equipment, operators should expect reliable information about equipment performance and vital downhole conditions. The ideal production monitoring and control system offers programmable control, downhole and surface data acquisition, and data memory with the capability for real-time data analysis. The goal is to facilitate proactive knowledge-based decision-making to optimize well maintenance and production performance on a continuous basis.
An economical system that measures pressure, temperature, vibration and sensor current leakage in progressive cavity pump (PCP) or rod pump wells was installed in a 4,000-ft (1,220-m) well located at Texas Tech University Test Well Facilities. The Department of Petroleum Engineering is supervising this joint industry project (JIP).

In addition to the measured downhole parameters, the system allows real-time monitoring of various surface parameters, local and remote data logging as well as full Web-based communication and control via any computer, phone link or SCADA system (Figure 1). Wood Group Production Technology (WGPT) provided the system and installation services as a fully integrated package.

Conventional downhole gauges employ expensive quartz-based and, more recently, fiber-optic technology. This new system is comprised of more economical pressure and temperature strain sensors coupled with an intelligent remote terminal unit (RTU)/programmable controller. The sensor is a variant of a reliable and successful system used to monitor and control thousands of electric submersible pump (ESP) wells worldwide. Over the expected 9-month test period, the system will provide information on wellbore parameters and three-phase electrical load data, which will be used by the research team to establish the dynamic slippage of sucker rod pumps with different clearances. It is believed this project will provide the industry with a more accurate predictive model for determining the volumetric efficiency of sucker rod pumps.

Downhole

The sensor installed on the Texas Tech test well measures pump intake pressure, pump intake temperature, vibration, sensor current leakage and pump discharge pressure.

The sensor is based on strain transducer technology that has a proven track record in permanent and memory gauge production logging use. Before dispatch, the completed sensor and housing are functionally tested over expected operating pressure and temperature ranges. Metal work for sensor parts is compatible with the wellbore environment according to NACE MR01-75. The downhole cable termination is metal-sealed between the cable sheath and the sensor. Pressure testing is carried out on the sensor to termination seal during manufacturing and in the field, once the cable has been made up to the sensor.

The downhole electronics package, including pressure and temperature transducers, is housed inside a 13 chrome stainless steel (or 4140, 1026 carbon steel) tubing conveyed housing (Figure 2). The housing is available in sizes to meet each customer's tubing requirements. The sensor is connected to the surface by means of a ¼-in. tubing encased conductor (TEC) cable, which is secured to the outside of the production tubing by either cable protectors or steel bands. The cable is made up of four main parts: an insulated electrical conductor, a filler material, the cable sheath and an outer encapsulation material.
After the production tubing has been run, the TEC is fed through the tubing hanger and then through the wellhead, where it is terminated to a pressure retaining feed-through system. Once terminated, the system is connected to the intelligent RTU/programmable controller (or other available surface interface units/data loggers).

On the surface

The RTU/controller (Figure 3) can be permanently installed at the surface. Real-time data can be gathered and analyzed continuously. Using the latest advances in hardware, software and telecommunications technology, the controller offers function control of production equipment, data acquisition and, most importantly, data analysis capabilities previously unavailable. The modular construction and add-ons allow the RTU to be configured as a simple pump controller, a component of a SCADA system or as a full-function stand-alone device addressable from anywhere in the world via software. Data gathering and handling is provided by a microprocessor, which directly inputs data into the customer's data gathering system.

The system architecture of the controller consists of three primary components: hardware, firmware and software. The hardware provides the basic system functionality via its multiple communications channels, expandable memory and input/output flexibility. The firmware is the programming located in the microprocessor. The firmware can be addressed via software either locally or remotely. The software resides on a remote computer and is used to communicate to the surface interface unit via a variety of communication methods.

A number of other surface interfaces are available from basic data loggers to state-of-the-art satellite links. This enables the gathered data to be immediately available for analysis. Alternatively, where power/logistics are an issue, regular well site surveys can be conducted using a portable data logger or laptop computer.

Communications

The controller and all other surface interface units provide flexible communications capabilities. An onboard phone modem is standard. The communication ports are located on the side of the selected NEMA 4 enclosure. They may be utilized to configure, change or modify set points, analog outputs, alarms, etc. These ports are weatherproof and accept quick-connect, six-pin female connectors. Configurable communication parameters include: data speed, parity, controller address, data bits and transmission delay. The surface units support data rate speeds from 300 to 28,000 BPS. The communications setup is performed at the well site via the surface interface display or remotely using software which has English, Spanish and Russian language capabilities.

If telephone communications exist, the system may be interfaced with a standard modem package. This can then provide an alarm call-out notification (a feature that can automatically dial a digital beeper, pager and/or telephone answering service to advise of down production).

The flash memory employed by surface interface units allows re-configuration of the system using software to turn hardware on or off. Options may be added at any time in this manner and can be sent over the Internet. Once system parameters are set up and downloaded into a surface interface unit, it will retain its parameters even in the event of a power loss or when equipment is taken out of service.

Conclusion

This monitoring and control technology has been proven on ESP wells around the world and has been extended to rod pump and progressive cavity pump applications. Over the next 9 months, the system is expected to deliver reliable information about equipment performance and vital downhole conditions, which the JIP partners will use to extend the accuracy of sucker rod dynamic slippage correlations.

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