The Bryansk based ELECTROAPPARAT factory
developed a new FOC-based monitoring system for oil and gas
wells. The system can control all procedures in wells doth
on the stage of preparation and on the production stage.
Oil and gas wells, FOC, leak detection, pipeline
Relying on the 15 years scientific and practical experience
of the OMEGA Company the Bryansk based Elektroapparat
Company has developed and prepares for production of the
Complex Well Monitoring System (CWMS), the operation of
which is based on fiber-optic technologies. The system
allows receiving real-time critical information on the well
operation which is required for the management of decision
making process. CWMS will be offered on markets in 2019.
Timely acquisition of crucial information about changes of
downhole conditions has fundamental importance for safe and
effective technological maintenance of deposit operation.
That is why leading international oil and gas companies are
promoting the well intellectualization and automation.
The introduction of artificial intelligence technologies has
marked a new stage in the evolution of well operation.
Indeed, there is no possibility of prompt reaction to
changes of downhole conditions with a set of equipment based
on traditional electrical sensors, though segregation of
produced fluid into separate phases (oil, gas and water)
occurs mainly after it comes into the hole mouth.
According to international practice a smart well consists of
three components connected by a logic circuit: a system for
obtaining downhole data on the work of both the formations
and equipment placed into the well, a fully or partially
automated system of decision-making as well as a module of
parameters changes in well operation. All necessary
information about the well and reservoir is provided by
complexes based on fiber-optic technologies: this is the
cornerstone laid down by the Elektroapparat Company
developers which began researches in this field in early
2000s. In close cooperation with the Transneft Company,
world biggest oil and oil products transporter,
Elektroapparat created the OMEGA Company through which more
than five and a half thousand kilometers of Russian
pipelines have been equipped with fibre-optic Leak detection
and activity control system (OMEGA LDACS).
Fiber optic sensors implemented in CWMS and LDACS are based
on the phenomenon of light scattering inside the optical
fiber performing the role of both a sensor and a medium for
signal transmission. The feature of such sensors recording
the scattering is their distribution along a continuous
light-guiding core: straylight reflection occurs throughout
the fiber, and the reflection from each elementary section
determines the state of this area due to temperature or
other physical factors. Meanwhile the registration of the
reflected signals allows estimating the distribution of
temperature or strain along a fiber optical path. Thus, the
Optical Time Domain Reflectometry (OTDR) method allows the
detecting the temperature either at specified points or
continuously along the fiber length.
Control and Measuring Complex for Wells Monitoring
Constantly improving fiber-optic technologies in the
framework of a special research program the developers from
Elektroapparat have created a highly sensitive and selective
control and measuring complex until recent time based on the
application of two distributed sensors: temperature sensor
and vibroacoustic fluctuation sensor. Meanwhile the Complex
Well Monitoring System presented to the oil and gas
community in December 2015 was augmented with a point
pressure sensor as well, which has been already launched
into a serial production, and a distributed temperature
sensor had been adapted for the determination of absolute
temperature values. The measurement module of the absolute
temperature (MMAT) captures changes of temperature
fluctuations along the length of the wellbore in continuous
Figure 1. CWMS pressure measurement module design
Figure 2. CWMS absolute temperature measurement module
The CWMS temperature range varies from -45 to +350°C, and
electronic equipment is capable to provide stable operation
of distributed temperature sensor measuring absolute
temperature at any point along a length of up to 6 km. The
mentioned parameters correspond and partially exceed those
of systems on the market and are result of long research and
practical application: the prototype of CWMS was first
implicated on the Ashalchinskoye field in Tatarstan in 2007.
CWMS essentially consists of a fiber-optic cable placed in
the wellbore, and a logic module, equipped with temperature,
vibration and pressure measurement modules, as well as the
UPS, providing the system functioning in case of
disconnecting the external power supply. Automated workplace
of the operator is connected with the CWMS logic module
through a local network and can use other monitoring systems
at the same time. The PC-based automated workplace displays
the results of well monitoring: the event, localization and
time. The data are being recorded in a real-time mode along
the length of the immersed in the well cable.
Table 1. CWMS DATA SHEET
As a sensor CWMS uses a fiber-optic cable developed by the
Elektroapparat Company and produced according to Technical
Condition 3587-015-51154035-2015. Polymer coating applied
for the cable protection is resistant to both high
temperature (up to 200°C) and high atmospheric pressure (up
to 600 ATM), moreover it withstands aggressive environment
with a high content of hydrogen sulphide (H2S) - up to 26%.
The use of the same specialized submersible fibre optic
cable with multiple optical fibers allows not only to
measure temperature, but also to register the acoustic
impact along the entire wellbore.
Figure 3. Fiber-optic cable design applied by CWMS
Unique Features of Fiber Optic CWMS
- Capability to measure a profile of physical quantities
throughout the length of the borehole in real time mode
without sensor relocation.
- Sensor high stable operation and noise immunity.
- High system reliability and life expectancy due to lack of
sophisticated electronic and mechanical devices as well as
electrical communication channel in the downhole.
- Usage of a single optical fiber for measuring different
- The ability to monitor multiple wells simultaneously using
a single above-ground, mobile or fixed location device.
- Simultaneous measurement of thermal profile throughout the
length of the borehole and the bottomhole formation zone
pressure in real time without sensor relocation.
- Fiber optic sensors’ stable operation in aggressive
environment ensures the functioning of thermometry and
barometry systems for the entire downhole equipment
- Possibility for continuous well monitoring of different
types: inspection wells, injection wells, steam-injection
wells and the wells with a complex scheme of operation -
long-haul horizontal trunks, multilateral wells.
- CWMS provides multiple applicability during tripping
- Free access to electronic equipment simplifies the work on
its modernization and maintenance.
Bottom-hole pressure monitoring is carried out with the help
of a point pressure sensor placed at the lowest point of the
cable. Monitoring the pressure changes in different
intervals is possible with the use of multiple (up to 5 on a
Using three types of sensors allows CWMS improving the event
detection accuracy. So decrease in the number of
interventions into wells to ascertain causes of operational
failures will reduce costs, downtime, as well as maintenance
and environmental risks and security threats.
One of the examples of the system effectiveness is the leak
detection on the production casing in producing well. The
undoubted advantage is the ability to research and monitor
well operation with complex completions, the design of which
does not allow inserting “traditional” GIS devices into the
trunk, including additional horizontal wellbores,
multilateral wells, and smart wells with controllable
equipment and operating devices. It is possible to monitor
the temperature field during the well construction, i.e.
during the drilling of the barrel and mounting both
intermediate and production casings. A fiber optic cable
installed in the zone of conductor cementation (in the
permafrost zones as well) can perform the quality control
function of the column cementing. In this case, local
thermal fields which are formed as a result of the
endothermic reaction in the process of cement stone
formation are recorded. Steady thermal field in the zone of
cementation characterizes high quality of cement stone. Low,
ragged profile of the thermal field shows the low quality of
the cement stone or its absence, which indicates the low
quality of the well cementing in general and requires repair
The Elektroapparat Complex Well Monitoring System will
Monitoring of Mechanical Impurities Concentration in Oil,
Gas and Water Flow
- Temperature fluctuation profile measurement along the
length of the borehole in continuous mode.
- Bottom hole pressure measurement.
- Inflow monitoring along the entire length of the wellbore
horizontal section to determine the effectiveness of its
- Monitoring of productive horizon isolated interlayers in
vertical and directional wells.
- Injectivity profile measurement.
- Well interference testing in continuous mode.
- Injection efficiency monitoring, localization of heat loss
in steam-injection wells.
- Measuring of permafrost lens thawing in the casing
- Monitoring of hydrate plugs formation in gas and gas
- Optimization of fluid extraction from productive stratum
based on received reliable information.
- Effectiveness of the compressed gas injection in
gas-condensate wells and underground gas storages.
- Identification of the production string and tubing
Reverting to the already raised issue of dividing produced
fluids into separate phases it should be noted that the
content of dissolved gas in oil during deposit exploitation
goes towards reduction, though these processes are not
immediate, but spread over the whole period of reservoir
development. Generally gas cut varies in different
productive strata of the same deposit. For the purpose of
determining the concentration of gas, oil, water and
mechanical impurities in fluid flow, samples are
periodically taken from wells.
One of the most important issues in the hydrocarbon
production is accounting of produced oil and gas. Existing
instrument gauges allow determining these parameters of
extracted on the surface raw material with great precision.
However, according to modern requirements in case of
simultaneous operating two or more productive facilities in
a well it is necessary to keep separate records for each
According to the CWMS ideology, if taking the gas content in
the period between the borehole researches as a constant
value and determining average flux density by Elektroapparat
system’s data, then applying the Mendeleev–Klayperon
equation the universal gas constant and knowing the
temperature inversion it is possible to calculate the
concentration of oil, water and mechanical impurities in the
flow. This data allow organizing operational accounting in
the multiphase flow even taking into account the error of
these calculations at the level of 5-10%, which, however,
will give adequate information for operational
decision-making. Besides during the deposit operation
process the information will be automatically accumulated
and stored in the archive. These data will allow deducing
the interdependence of changes in particular parameters that
will eventually help to predict the measurement of phase
concentration in the multiphase flow.
This information is stored in the electronic module of CWMS,
which implements the functionality of the primary data
processing and consists of processing core and
analog-to-digital converter (ADC). Primary data come from
the modules of absolute temperature and pressure.
Figure 4. Pressure sensor calibration process in a
laboratory performed by engineer Xenia Bobrova.
Figure 5. The well with two absorbing horizons equipped with
CWMS point pressure and temperature sensors.
Determining the Acceleration of Intervals
Let us consider the most common engineering task to be
solved when injecting in disparate horizons (two or more)
during reservoir repressuring process management. The task
consists of determining the acceleration of each interval
separately, when only the total injection rate is known Q,
For simplicity of explanation let us take the well with two
absorbing horizons (Picture 5), equipped with the system of
point temperature and pressure sensors, where
- 1 - system of injected fluid delivery;
- 2 - production string;
- 3 - tubing lift;
- 4, 7 – packer;
- 5 – distribution system;
- 6 – absorbing horizon (A);
- 8 – mandrel;
- 9 – pressure and temperature sensors;
- 10 – absorbing horizon (B);
- 11 – annular pressure and temperature sensors.
As it is seen from the proposed scheme, the well is divided
by a packer into two discrete intervals. To solve the
problem, it is enough to equip an absorbing horizon with a
system of sensors, whereas the intensity of acceleration on
the interval (A) will be determined as the difference
between total flow rate and the test interval (B).
The main condition under which we can determine the
acceleration of the formation is the pressure difference
between the tubular (Ptub) and annular (Pan) space.
These data are received in real-time mode from sensors 9 and
11, installed in the studied horizon. In addition, to solve
this task it is necessary to download several additional
parameters in the system:
- ρ - density of the injected liquid;
- S - total cross-sectional area of the holes through which
the liquid flow;
- h - height of the liquid column in absolute values;
- µ - flow coefficient (reference value):
- α- coriolis coefficient;
- ξ- coefficient of local resistance.
As all aforementioned parameters except the density are
constant values for each well, then it is the only time when
it is necessary to download them into the Protocol of
automated working place - before the beginning of injection.
If during injection the density of liquid is unstable, the
system determines it automatically, correcting calculations.
Ultimately, to determine injection intensity (speed) is
necessary to solve the only formula.
If necessary, similar calculations can be applied for
several intervals of pumping, when pre-equipped them with
Ground-based equipment allows you reading information from a
group of wells (4 and more) of the reservoir pressure
maintenance system, equipped with fiber optic sensors, which
facilitates the task of well monitoring in a waterflood
system, when a group of wells is injected with the same
discharge line. In this case, the system allows determining
the injection rate of both defined horizon and each of the
wells. The information obtained reduces the time of taking
prompt technological decisions and increases the efficiency
of reservoir repressuring process management.
System of complex well monitoring, the creation of which
became possible due to the extensive experience of Russian
scientists and workers of oil and gas field, even at the
stage of elaboration has already aroused an active interest
of the Russian oil and gas company representatives. It is
envisaged that applying CWMS can lead to the formation of
“smart deposits”, the operation of which allows optimizing
both equipment efficiency and well productivity, increasing
significantly oil production coefficient and reducing not
only operating costs but ecological damage.
Even not being on the market yet, in 2015 the Elektroapparat
system has been presented to Shell specialists as far as on
the Moscow session of the BRICS financial Committee on