Multi-Point Permanent Downhole Measurement System

What Multi-Point PDMS can do

The permanent multi-point measurement system with distributed temperature and pressure sensors and real-time downhole data transfer to the surface through the cable is used to monitor bottom-hole temperature and pressure, control producing intervals in the well and determine relative oil or gas production rates (injection rates) for different reservoir intervals.

Relative oil and gas production rates are quantified by a thermohydrodynamic simulator using distributed temperature sensor data from producing intervals.

The unique quartz sensors without electronic components used for high-precision and wide-range bottom-hole pressure and temperature measurements ensure the reliability and long operating life of the Multi-Point PDMS

Operating principle

Multi-Point PDMS consists of up to 200 measurement modules contained in individual 0.5–6 m long tubes.

What Multi-Point PDMS can do

Encapsulated polymer-coated cable – with metal-to-metal sealing at the connection between the cable and measurement modules and in Wellhead Outlet – is used for voltage supply and data transfer from the measurement modules of Multi-Point PDMS to Surface Recorder. 

If no permanent 220 V power supply is available, an independent power supply system (IPSS) utilising environmental energy from a wind power generator and solar panels can be used. The system is explosion-proof.

Surface Recorder records data from downhole tools to store them in non-volatile memory and is compatible with Supervisory Control and Data Acquisition (SCADA) systems through RS232 and RS485 buses. The system is explosion-proof.

Pressure and temperature data recorded by the PDMS are transferred in real time via modem or satellite communication to a telematic data system at a sampling rate from 1 s. At the same time, data are recorded into the internal memory of the surface recorder. 

In a horizontal well, distributed point temperature sensors are located at fixed points. During production, the thermal field in a horizontal well changes due to thermodynamic effects, such as the Joule-Thomson effect, the adiabatic effect and degassing heat release. Their impact on well temperature distribution depends on various factors: geothermal pattern, reservoir properties, reservoir fluid composition, gas-oil ratio, water cut, wellbore fluid flow rate, bobble-point pressure and well operating conditions.

Joint analysis of these effects and theoretical modelling of hydrodynamic fields by the thermohydrodynamic simulator can locate producing sections in a
horizontal well.

What Multi-Point PDMS can do for a horizontal well:

1. Bottom-hole pressure monitoring under various well operating conditions with different choke sizes or ESP speeds;
2. Temperature profiling along the horizontal section of the well;
3. Location of producing intervals in the horizontal section of the well;
4. Quantification of relative oil and gas production rates for producing intervals;

Real-time temperature profiling with multi-point PDMS allowed to discover inactive reservoir zones which were not involved in the production. Based on these data, it was decided to acidize the inactive layers, and conduct a temperature profiling with multi-point PDMS in other wells.