SENSOR FOR MONITORING INORGANIC SCALES

Abstract

The present invention relates to the development of equipment capable to monitor the deposition of inorganic compounds in saline solutions in high ion concentration conditions. This invention uses the principle of difference in electrical conductivity that the saline solution and the scale present. In this way, applying the electrical potential to the aqueous solution, through a pair of electrodes, generating an electric current that will be proportional to the conductivity of the compounds present in the medium.

Claims

1. SENSOR FOR MONITORING INORGANIC SCALE, characterized by being a compact equipment for monitoring the deposition of inorganic compounds in saline solutions under high ion concentration conditions composed of: (1) function generator; (2) pair of electrodes; (3) electrical current-potential conversion circuit; (4) symmetrical power supply; and (5) oscilloscope.

2. SENSOR FOR MONITORING INORGANIC SCALE, according to claim 1, characterized in that the function generator (1) generates a low alternating electrical voltage amplitude as input signal, using a 1 V amplitude signal with 10 Khz frequency and 0 V offset level, this signal is sent for the saline solution, maintained in a jacketed reactor with controlled temperature, through a conductor wire, connecting the generator output of functions to one of the electrodes of the electrode pair (2) that is immersed in saline solution, then the circuit is closed with a second electrode of the electrode pair (2), also immersed in solution, which is directly connected to another conductor wire.

3. SENSOR FOR SCALE MONITORING INORGANIC, according to claims 1 and 2, characterized in that the conductor wire is connected to the input of the electrical current-potential conversion circuit (3) generates a closure of the circuit through of a virtual ground, converting the electrical current that passes through the solution in an electrical voltage value, proportional to the resistance electricity from the saline solution.

4. SENSOR FOR MONITORING INORGANIC SCALE, according to claim 1, characterized in that the inverter circuit is symmetrically fed with 15 V through the power supply (4) and response signals are directly sent to the oscilloscope (5) which is connected to a computer for real-time visualization of response signals.

5. SENSOR, according to claims 1 and 4, characterized by coupling the electronic circuit (3) developed with the oscilloscope (5) with analog-to-digital conversion equal to or greater than 100 MS/s and maximum detection amplitude above 15 V with the probe connected to the circuit output and the grounding cable connected to the GND of the entire current-voltage circuit for signal measurements.

6. SENSOR, according to claim 1, 2, 3, 4 or 5, characterized in that the electronic part of the sensor connects the two electrodes (3), of any conductive material and with high resistivity to corrosion, in rods for vertical fixation for immersion in saline solutions and electrical conduction between the electronic circuit and the emerged electrodes, the first electrode must be connected directly to the output of the function generator (1), while the second electrode must be connected to the input inverting the operational amplifier, the connections of these rods with the circuit and function generator must be carried out by means of electrical cables.

7. MONITORING INORGANIC SCALES, according to claim 1, characterized in that the detection of inorganic scales consists of a (A) reactor, magnetic stirrer and pair of electrodes, (B) thermostatic bath, (C) electrical potential injection circuit and response current/voltage conversion, (D) symmetric voltage source, (E) function generator and oscilloscope, (F) computer.

8. MONITORING INORGANIC SCALES, according to claim 1, characterized by inserting saline solution into the reactor (A), which features a magnetic stirring system with an adjusted speed of 500 rpm, to promote the precipitation of salts and possible formation of scale, with the temperature controlled by means of the thermostatic bath (B) which is connected to the jacketed reactor (A), the electrodes are connected to the electrical current-potential conversion circuit (C) and with the function generator (E), the input signal was adjusted to a frequency of 10 kHz, 1 V amplitude and 0 V offset, the conversion circuit is powered through the symmetrical source (D), the output of the electrical current-potential converter is connected to the oscilloscope (E) which sends to the computer (F) real-time response signals, both the function generator and the oscilloscope are present in the multifunctional equipment (E).

9. MONITORING INORGANIC SCALES, according to claim 1, characterized in that the operation is through the input of an alternating electrical potential into a sample which presents a certain electrical resistance, this electrical current passes through current-potential conversion, which also acts on the amplification of the output signal (E), according to the value of the resistor used in the operational amplifier.

Description

DESCRIPTION OF THE FIGURES

[0014] FIG. 1. Schematic diagram of the experimental unit for detection of inorganic scales. (A) reactor, magnetic stirrer, and pair of electrodes, (B) thermostatic bath, (C) electrical potential injection and response current/voltage conversion circuit, (D) symmetrical voltage source, (E) function generator and oscilloscope, (F) computer.

[0015] FIG. 2. Schematic diagram of the detection sensor of inorganic scale. (1) Function generator, (2) pair of electrodes, (3) electrical current-potential conversion circuit, (4) symmetrical power supply, (5) oscilloscope.

[0016] FIG. 3. Result of the drop in electrical response potential due to the number of batches. At each experimental point, analyzes of scanning electron microscopy (SEM) to check the progressive increased scaling on the electrodes.

[0017] FIG. 4. SEM images of electrodes with frontal view during second batch (A) and fourth batch (B) and average measurement of the thickness of the scales.

SUMMARY OF THE INVENTION

[0018] The present invention aims to create equipment for monitoring scale formation in high concentrations of saline solutions. For this, the principle of difference of electrical conductivity that the saline solution and the scale present. In this way, an electrical potential will be applied to the aqueous solution, through a pair of electrodes, generating an electric current that will be proportional to the conductivity of the compounds present in the medium.

[0019] The main advantage of this invention is the possibility of identifying the formation of any type of inorganic scale in systems that present high concentrations of salts (as in production waters found in oil wells, for example). This may result in a great technological advance in the scope of research, as such results of equipment can be correlated with physical properties of the scale, such as layer thickness, which may disclose a greater understanding of the process of scale formation. In addition to research, this tool can also contribute to oil fields with insertion of electrodes in the most diverse production stages of hydrocarbons, for real-time monitoring of the deposition of scales. Since this sensor can identify scales with thicknesses on the micrometric scale, this would be essential to warn field operators the presence of these solids, still at an early stage. This would make the scale removal steps more optimized.

DETAILED DESCRIPTION OF THE INVENTION

[0020] In this section all operating and operation details of the SENSOR FOR MONITORING INORGANIC SCALES, the objective of which is to describe, in a clear way, how equipment works to detect inorganic scale in saline solutions with high concentrations of ions.

[0021] The sensor for monitoring the formation of scale in solutions saline salts at high concentrations, shown in FIG. 2, of the invention here proposed is divided into: [0022] (1) Function generator; [0023] (2) pair of electrodes; [0024] (3) electrical current-potential conversion circuit; [0025] (4) symmetrical power supply; and [0026] (5) oscilloscope.

[0027] The function generator (1) is responsible for generating a low amplitude alternating electrical voltage signal as input signal. In this case, a 1 V amplitude signal with 10 Khz frequency and 0 V offset level was used. This signal is sent to the saline solution, kept in a jacketed reactor with temperature control, through one of the electrodes of the pair of electrodes (2) which is immersed in the saline solution. The circuit is closed with a second electrode of the pair of electrodes (2), also immersed in solution, both positioned vertically by means of a pair of rods and which, together with wires, conductors attached to each rod, serve as connectors for electrical conduction between the electronic circuit and the pair of electrodes. This second electrode is connected to the input of the electrical current-potential conversion circuit (3), generating a closure of the circuit through a virtual ground. Furthermore, this circuit aims to convert the electrical current that passes through the solution in an electrical voltage value, proportional to the electrical resistance of the saline solution. Thus, the sample is treated as an electrical resistor that has variable resistance. In a first instance, the solution presents a low value of electrical resistance, due to the significant amount of ions present in the solution and the absence of scales on the electrodes.

[0028] With the gradual appearance of scales on the surface of electrodes, there is a significant increase in electrical resistance due to insulating characteristic of the scales, preventing the electric current to pass the electrodes. This causes the response signal from the inverter circuit fall as deposits grow on the electrodes. The entire inverter circuit is symmetrically supplied with 15 V via the power supply (4) and the response signals are directly sent to the oscilloscope (5), which has detection of signals up to 15 V. This equipment (5) carries out the acquisition of these signals through an AD converter at a sampling rate of 100 MS/s. This oscilloscope is connected to the output of (3) and the ground cable is connected to the GND of the entire current-voltage conversion circuit (3). The output of (5) is connected to a computer for real-time visualization of signal response, in addition to allowing saving the results for later analysis. It is worth noting that both the function generator (1) and the oscilloscope (5) are inserted into a single piece of equipment, ensuring a more compact sensor.

[0029] Tests to guarantee the proper functioning of the sensor in conditions of high concentrations were carried out in batches (represented by FIG. 1) using synthesized water with the same characteristics as an oil well in the Brazilian pre-salt region, wherein the composition and ion concentration can be viewed in Tables 1 and 2.

[0030] The entire unit is composed of a jacketed reactor (A) with a total volume of 160 mL, attached to a lid that aims to fix the set of rods for passing signals to the pair of electrodes (stainless steel 316) for checking measurements. The saline solution is inserted into the reactor (A), which features a magnetic stirring system with an adjusted speed of 500 rpm, to promote the precipitation of salts and possible formation of scale. The reactor (A) is temperature controlled through the thermostatic bath (B) which is connected to the jacket of the reactor (A). The electrodes are connected with the electric current-potential conversion circuit (C) and with the function generator (E). The sign of input was adjusted to a frequency of 10 kHz, amplitude of 1 V and 0 V of offset, and this configuration can be changed depending on the application of the equipment. The conversion circuit is fed through the symmetric source (D). The output of the electrical current-potential converter is connected to the oscilloscope (E) that sends response signals to the computer (F) in real time. In this equipment configuration, both the function generator and the oscilloscope are present in the multifunctional equipment (E).

[0031] The operating principle occurs with the input of a potential alternating electrical current in a sample that presents a certain electrical resistance. When electrical potential is applied to the analyte, it generates an alternating electrical current that passes through the sample and follows the principle of Ohm's law. This electrical current passes the current-potential conversion that also acts to amplify the output signal (E), according to the value of the resistor used in the operational amplifier. This conversion of current to potential is made for greater ease of measurement by the oscilloscope. When the current passes only through the saline solution, there is a greater flow of current (due to low electrical resistance), reflected in the higher response signal. Throughout the formation of scales on the electrodes, there is greater difficulty in passing the electrical current in the solution (due to the high electrical resistance that scales have), generating a progressive drop in the measured signal.

[0032] To verify the functioning of the present invention, a test using water synthesized from a Brazilian oil well was carried out. The test begins with the preparation of synthetic water to detect the scales. This water is divided into anion water and cation water to simulate well injection water and water produced by the reservoir. Once these waters are mixed, there is an incompatibility between them which leads to the formation of scale. All compounds of the two waters, seen in Table 1, were properly weighed on a precision balance and then dissolved in ultrapure water. The volume of each water used in a single batch was 70 mL and the composition of the water can be seen in Table 2.

TABLE-US-00001 TABLE 1 Materials used in evaluating the sensor for scale detection Preparation of synthetic saline solution Product Purity Manufacturer Ultrapure water Sodium chloride 99% Synth Calcium chloride 99% Synth Potassium chloride 99% Synth Magnesium chloride 99% Synth Barium chloride 99% Synth Strontium chloride 99.7%.sup. Synth Sodium bicarbonate 99.7%.sup. Synth Sodium acetate 98% Synth Potassium bromide 99% Sigma-Aldrich Sodium sulfate 99% Dinamica

TABLE-US-00002 TABLE 2 Composition of the synthetic saline solution used in the sensor operation tests Salts Concentration (ppm) Cation Solution Na.sup.+ 50496 Sr.sup.2+ 252 Ba.sup.2+ 284 Ca.sup.2+ 792 Mg.sup.2+ 305 K.sup.+ 391 Cl.sup.? 79229 Anion Solution HCO.sub.3.sub.? 1544 SO.sub.4.sub.? 46 C.sub.2H.sub.3O.sub.2.sub.? 138 Br.sup.? 0

[0033] After preparing the water, both were placed inside the reactor (A) and the pair of electrodes was immersed into the solution to detect the scales. The measurement was carried out at the initial moment of the immersion and these data were collected and sent to an excel spreadsheet for later assembly of the signal response graph. After collecting the results for the first batch, the pair of electrodes was completely submerged to the bottom of the reactor (A), where it remained for a period of 2 hours so that there was greater accumulation of scale. Immediately afterwards, the electrodes were removed from the reactor (A) and placed in an oven at 90? C. for 12 hours for greater adhesion of solids to the pair of electrodes. After the drying stage, the electrodes were taken to the scanning electron microscopy (SEM) to assess the coverage and distribution of scales on the electrodes. With the end of the analyzes via SEM, the same encrusted electrodes, were taken to the next batch to observe the presence of scale from the previous batch. This process was done by 4 times and aims to accumulate, with each batch, a greater quantity of scales on the electrodes.

[0034] Finally, the results of the response signal for each batch were placed on a graph (FIG. 3) to analyze the results. It is possible to observe a drop in the response signal throughout the batches, showing the increasing accumulation of scale on the electrode. This is confirmed through the SEM analysis that revealed the successive increase in the inorganic deposit area on the electrodes. More detailed images of a small fraction of the electrode also reveal the way in which different materials deposited are distributed throughout the batches, with the main deposits being calcium carbonate and barium sulfate. In FIG. 4 it is also observed a relationship between the thickness of the scale and the results of the sensor developed, wherein the image on the left refers to the second batch and reveals an average thickness of 8.6?2.5 ?m. With the increase in number of batches, it was possible to observe the formation of a layer of more uniform scale with a greater thickness (29.6?5.5 ?m) such a process being detected by the present equipment developed. The tests were carried out in duplicate, also showing the reproducibility of the equipment for monitoring scale.