Nowadays the increased rates of the oil production volumes and the urgent request of the oil companies to reduce operating costs lead to necessity of so-called Smart Wells creation. The complex of surface and downhole equipment, including as a rule VSD switchboard and telemetry system built in ESP motor, that allows the pump unit operating parameters' logging is usually called the "Smart" well. Than, on the basis of logging information, according to the special algorithm, the switchboard controller should manage the operating mode setting, for example, bottom-hole pressure supporting.
In the middle of the 90-ies the VSD Elekton-05 Switchboards for all power ranges of ESP motors, which are applied in petroleum industry were designed and settled production-run manufacturing by Elekton enterprise. More than 800 switchboards of this type are successfully running on the oil fields of Russia. Since the end of 2002 the production-run manufacturing of Submersible Telemetry System Elekton-TMS was started. So the second component of the Smart Well complex equipment appeared.
The design of Elekton own Submersible Telemetry System has been caused by the fact that systems offered by domestic manufacturers did not provide reliable and accurate data. Besides the downhole units of such systems had operating temperature range limited by the top value not more than 90?C. At the same time the oil production intensification process, accompanied by increase of pump units' running depth and, accordingly, formation water temperature growth, puts forward more rigid requirements to the downhole parts of telemetry system. The Downhole Unit of Elekton-TMS system does not contain active electronics; therefore the top border of its operating temperature range is 150°C.
The Submersible Telemetry System Elekton-TMS transfers data on pump's suction pressure (up to 320 atm) and the ESP oil motor temperature, to the switchboard's Elekton-05 controller. There is the mode of preset pressure value maintenance in controller's program, for that purpose the special algorithm of proportional-integral (PID) regulator was designed. In case of measured pressure value deviation from preset value, the controller corrects the output voltage value in such a way, that deviation become minimally possible to within an accuracy of the measured pressure processing. Regulation discreteness is set by controller's settings. The PID-regulator's operation is influenced by first - coefficient of proportionality and second - integral coefficient. The more value of the coefficient of proportionality, the more is frequency variation. The integral coefficient determine the system's speed (time) of response on pressure change.
Based on coefficient of proportionality and integral coefficient preset values, PID-regulator determines frequency variation pace of the switchboard. Productivity of the pumping unit varies respectively to the output frequency. Thus the continuous rematching of the pumped-out liquid volume from the hole and its inflow from the formation is carried out.
It allows to keep up the bottom-hole pressure preset value and to operate of the pump unit in rate of optimal fluid withdrawal. And it will secure against barring the degassing process on the pump unit's suction. The bottom-hole pressure, at which preset well production rate is provided, is determined by:
Ðbot = Ðform - Q/Êprod
Ðbot - bottom-hole pressure;
Ðform - formation pressure;
Q - specified well production rate
Êprod - well production factor.
Nowadays the CJSC ELEKTON has running experience of the Smart Well equipment complex on the oilfields of the oil-production enterprise "Kogalymneftegaz", CJSC "Slavneft-Megionneftegaz", CJSC "Orenburgneft". As an example, look at the pressure change plot (Figure 1). The equipment is running in the Povhovskoe oilfield of the oil-production enterprise "Kogalymneftegaz".
The value of supported pressure is equal 85 atmospheres. At the initial moment of time (the plot's start), the current pressure (the curve's top) is above preset value. Output frequency (the curve's bottom) at this time has the maximum value of 55 Hz and further cannot increase, as ESP motor works in a nominal mode, and the further increase of rotation frequency will lead to increase in power input and ESP motor's operating current and, as consequence, overload protection triggering. After pressure has fallen up to the value less than preset, output frequency has started to decrease and decreased until pressure again has not grown up to the value, a little bit greater than preset, that has caused the output frequency increase.
Further is clear, the frequency varies near to some average value, supporting pressure about the preset value. In spite of the fact that the equipment is mounted on a well with unstable characteristics of the buttonhole formation zone, the continuous coordination of the pumped liquid volume with fluid entry has been provided, thanks to what the pump unit worked without a stop from the moment of start. So, the daily production in comparison with estimated was grown on 12-15 %.
The achieved results confirm stable work of pump unit with a frequency-adjustable drive at discharge of pump unit's range extension and allow forecasting its lifetime prolongation in comparison with non-adjustable drive. Besides the equipment can be used for such characteristics' specification of reservoir, as reservoir pressure and productivity factor that will allow to select the submersible equipment for the given well correctly.
The above complex allows optimizing and coordinating in an independent mode the downhole equipment's operation with characteristics of reservoir's bottomhole formation zone. The operating parameters of pump unit and switchboard, which for usability of equipment's data analysis can be represented in a tabulated or graphic kind, are fixed in controller's memory. Besides the software allowing creation of various databases on the basis of fixed parameters has been developed.
The presence of the interface RS-485 and standard ModBus RTU protocol in switchboard's controller allow to integrate the complex into telemechanics system (Fig. 2) existing in the oil fields and to solve more challenges of automation and optimization of oil production process. One can control and receive operating data of the complex by means of communication system "Elekton-CK2" with CDMA technology on the basis of 48 low-orbital satellites Globalstar.
The production-run Elekton-05 Switchboard adaptation to the operating within Smart Well complex equipment required essential software and hardware updating of the controller. That was the reason of additional indexes, which were entered into a designation of Elekton-05 PP Switchboard (the parameter maintenance mode).
Closed Joint Stock Company ELEKTON, having begun more than 10 years from design and manufacture of electro technical equipment for the oil industry, now uses the state- of- the - art technology in manufacturing of the wide spectrum of artificial lift surface equipment. Quality management system of CJSC ELEKTON has been certified for conformance to ISO 9001-2000. All production-run equipment has certificates of conformance and is covered by patents.
Lepekhin V.I. (CJSC ELEKTON)
Vidyakin N.G. (CJSC ELEKTON)
Valeev A.S. (JSC LUKoil-Western Siberia)
Kan A.G. (TNK-ÂÐ JSC Orenburgneft)