Denver Unit Well Surveillance and Pump-Off Control System
Authors: Hunter J.C. , Hubbell R.S. , Reiter C.R. 
Published: December 2007

This paper describes a prototype system that demonstrates the technicalfeasibility of installing and operating an on-line, computer-based wellsurveillance and control system. This system provides a much higher levelof surveillance and control than possible with conventional equipment.Expansion of the system will include all wells and facilities in the DenverUnit of Wasson Field.

Introduction

Approval was obtained in Oct. 1974 to install a pilotcomputer production control (CPC) system to serve abattery (Battery 3) of the Denver Unit, Wasson Field.The test battery area contained 76 beam pumped wells, four satellite separation and test facilities, andtreating and storage facilities in the battery.

The pump-off control portion of the system, whichmonitors and controls the individual wells, becameoperational in June 1976. Automatic well testing becameoperational in Feb. 1977. The system basically consistsof a small wellhead remote unit at each well, a largerremote unit at each satellite, and the battery. Thewellhead remote units take signals from the load andposition transducers on the pumping units and transmit position transducers on the pumping units and transmit the data to the pump-off control (POC) computer locatedin the production office at Denver City, TX. The largerbattery and satellite remote units communicate with adisc-based field computer located in the production office(see Fig.1).

About 94,000 ft of six-pair cable was installed toconnect the wells, satellites, battery, and productionoffice. Microwave communication links the productionoffice with Shell computers located in Houston.Few problems have been encountered with this fieldcommunications network. Supervisory hardware, whichincludes all remote and computer interface units, alsohas performed satisfactorily. The first line amplifiers(repeaters) furnished by the hardware manufacturer wereunsatisfactory and had to be redesigned. The POCcomputer, which is a new model, had many problems earlier;however, recent changes seem to have improved itsreliability, Early problems also were experienced with loadcell transducers. The cables were constructed so that asmall strain on the cable caused it to tear out of the loadcell. This problem has been reduced substantially byusing a better method for connecting the cable to theload cell. Thus, the cable fails instead of damaging theload cell.

The pump-off control technique has proven a reliablemethod for determining when a well is pumped off.The computer uses data from a well to calculate energy inputto the rod string during a certain portion of the stroke.When the energy drops below a specified limit, the well isconsidered pumped off. A limit can be set so that the wellshuts down for any degree of pump-off. The POC programalso checks for abnormal load conditions and eithershuts the well down or alerts the operator. To enhancewell surveillance, a sucker-rod diagnostic program wasimplemented in the field computer. Data can be transferredon request from the POC computer to the field computer foranalysis. Results normally are returned to the operator ina few seconds. From the results, the operator can determinehow the pump is performing and also detect any abnormal conditions that might be occurring in the well. The"on-line" combination of POC, automatic well testing, andsucker-rod diagnostics gives the field a powerful surveillancetool.

JPT

P. 1319