SKTsS-01 Well Cementing Logging Station.

 

 

SKTsS location and operation at well cementing.

 

The Well Cementing Process Control System SKTsS-01 manufactured by Electrotech, Izhevsk, is intended for density, flow, pressure, and temperature logging during various operations involving injection of variable-density fluids.

Let us review operation of the station on a typical example of well cementing. Let's assume that single-stage reservoir annulus cementing is required. Based on parameters of the well structure, a work plan shall be executed specifying injection phases and amounts. Initial planned parameters are entered into the station's application.

 

 

 

 

 

The station's measuring tube is mounted in the discharge line downstream of the manifold unit immediately upstream of the cementing head. Everything that enters the well passes through the measuring tube. Signals from sensors of monitored parameters are converted with a controller into a digital electric signal, which goes to the operator's workstation. Data are transmitted either via a power supply cable through the power supply unit or via a radio communication line.

 

The computer application displays process parameters as plots on the monitor screen and on the remote digital display (indicator). It is possible for the cementing engineer to monitor the injection parameters throughout performance of works.

 

 

Piping of the ground equipment at the cementing head closed is followed by pressure testing. A pressure plot shows a values of the proof-test pressure. There is no water motion through the pipeline; therefore, the flow plot remains at zero.

 

After the cementing head opens, a displacement fluid is pumped into the well in order to prevent mixing of the drilling mud and the cement slurry and to clean the well walls. As the displacement fluid only separates fluids, its volume is relatively small.

 

The next stage consists in injection of the first cement slurry—gel-cement. Gel-cement is intended for cementing of the casing's upper part to a specific height; therefore, thorough monitoring of the injected fluid volume is required.

 

Cement-slurry injections begins at a low speed of the pump and subsequently goes to higher speeds. The flow plot records a mode change of cement-slurry feed into the well. The cement density is the main cementing parameter. A density plot allows the cementing engineer to execute operational control of the injection process.

After discharge of the top plug in the cementing head, the squeeze process begins. A displacement fluid is fed into the casing string. Squeeze of the cement slurry begins at high pump speeds and then slowly goes to low speeds, which is related to a growth of the squeeze pressure. This considers compression of the displacement fluid. The application simulates penetration of the cement slurry into the annulus.

 

 

The displacement fluid volume injected into the well is under continuous monitoring. When 1 to 2 cubic meters of the displacement fluid remains until the end of squeeze, the feed intensity shall be dramatically decreased. To do so, only one cementing unit shall be left operating in order to smoothly approach a "STOP" depth. A pressure surge indicates that the plug has seated on the stop ring. Cement-slurry squeeze into the annulus is completed.

 

The final stage of works consists in flushing of the discharge line and equipment.

 

The logging station's operator shall draw up a Well Cementing Report on the basis of data obtained during cementing works.

 

 

Physical principles of density and flow measurement in the SKTsS-01

 

The logging station measures 4 parameters of a fluid flowing through the measuring tube: density, flow, pressure, and temperature. Time integration of the flow is used to calculate the volume of the fluid injected.

 

The measuring tube is protected with a robust enclosure. The system is a direct-flow type and contains no elements preventing the fluid's flowing through.

The density of the fluid being inside the tube is measured by a vibration method. In order to prevent an impact of external vibrations, relative oscillations between two symmetrical flow-through tubes shall be excited. An electromagnets builds up oscillations of the system with short pulses. The instrument automatically maintains oscillations in the resonance mode on the basis of readings by relative tube displacement sensors. A resonance-oscillation frequency depends on the mass, which makes it possible to calculate the fluid density in a set tube volume.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The fluid flow rate passing through the tube is measured in different ways for different versions of the station design. In order to measure the flow rate of a conducting fluid, Electrotech supplies electromagnetic flowmeters.

 

The operating principle of an electromagnetic flowmeter is based on the electromagnetic induction law. Faraday's law says: if an electric conductor crosses force lines of the magnetic field, an electromotive force proportional to the conductor speed is induced in this conductor. A magnetic field is created in the flowmeter, and a difference of potentials on the opposite tube walls is measured. The flowmeter typically operates jointly with the density meter, which allows you to calculate both mass and volume flow rates based on the fluid density and speed in the tube.

 

 

 

 

 

 

 

 

 

 

 

 

 

Electrotech also supplies advanced vibration flowmeters, which measure flow rates of any liquids, irrespective of whether they are able to conduct the electric current or not. The operating principle of the vibration flowmeter is based on the Coriolis effect. When a fluid is flowing in measuring tubes of the density meter, it is experiencing an inertia force known as a Coriolis force. As a result, the tube oscillation profile is no longer symmetric about the centreline. The mass flow of the fluid is calculated according to the oscillation phase difference at symmetric points.

 

The measuring tube of the logging system has a rigid enclosure, which ensures reliable operation in the most extreme conditions. Indications of temperature and pressure sensors are used to perform thermal compensation and take into account the strain under high pressure. Small dimensions allow the station to be rapidly delivered and integrated into any process chain of fluid pumping. The station's software issues a useful signal on the background of external disturbances, which make it possible to use the equipment under high vibration conditions.

 

 

PC software (ETCservice.exe)

 

The service computer application of the logging station collects and records the data transmitted by the measuring tube and processes them in real time with solution of operational process tasks. In addition, the application forms cementing process databases, displays information as graphs and on the remote display, and does warning whenever parameters go beyond the established limits.

 

Every time the station is used to monitor parameters of some well operations, the application creates a new project. To do so, the Project Manager is used to enter source data on the well and planned injection parameters. The entire work is divided into stages. For example: pressure test, displacement fluid, gel-cement, cement, squeeze.

 

Parameter logging begins as soon as the "Start operation" button is pressed in the Project Manager. A monitoring module appears on the screen. The screen top contains a display with parameters being measured. Either a digital or pointer version of instrument reading display can be selected, as desired. A field to display plots against time occupies the most of the screen. All five plots (density, flow, pressure, temperature, and volume) are built simultaneously and differ in conventional colours. Respective graduated scales are shown on the side.

 

The operator begins parameter logging upon the cementing engineer's command. To do so, they press the on/off switch of the relevant stage. The button colour changes during works. Green means that the stage has not been performed yet; yellow means "ready to work"; red means that the stage has begun and the parameter logging is in progress. After the stage is chosen (the button lights in yellow), the recording begins automatically: upon the fact that the fluid began actual movement through the measuring tube. The beginning of the stage is marked on the plot with a vertical line and a corresponding text.

 

The plot of the pumped fluid volume for each work stage is built separately, i.e., starts from zero.

Logging of all the parameters is continuous during the entire time of work at the well to display actual conditions of process operations. Based on the station measurement results, the colour printer prints out a Well Cementing Report with plots of all parameters and a summary table of injection data immediately after completion of the works.

 

 

 

SKTsS-01 configuration versions

Depending on technologies used, the logging stations can be supplied both as separate measuring tubes and as integrated in mobile systems.

 

 

The basic package of the SKTsS-01 includes a density meter, an electromagnetic flowmeter, a power supply unit, a laptop with a colour printer, a remote display, connecting cables and reel units.

 

The portable station version is convenient for operational works, when equipment can be delivered to the well by any transport (including by car).

 

The stationary variant of station installation on the manifold unit ensures comfortable conditions for equipment mounting on the discharge line.

 

 

 

 

The operator's workstation can be located in a vehicle cabin, an auxiliary room, or in a separate KUNG (unified body of normal dimension).

 

The SKTsS-01 logging station can be used in automatic well cementing systems.