MXPA06000674A - Apparatus and method for measuring concentrations of scale-forming ions - Google Patents

Abstract

This invention relates to methods and apparatus for determination of ion concentrations, particularly in downhole water from hydrocarbon wells, aquifers etc. It is useful in a wide range of applications, including predicting the formation of scale and fingerprinting waters from different sources. More particularly, the invention relates to the use of ligands whose electronic configuration is altered by the binding of the scaling ions within a water sample. These alterations are detected, for example by electrochemical means, and are indicative of the concentration of scaling ions in the sample.

Description

WO 2005/014977 Al lili II ll! L l! GM, KE, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, ZM, Published: ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), - with mternational search report European (AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, Fl, FR, GB, GR, HU, IE, _T, LU, MC, NL, PL, PT , RO, SE, SI, For two-letler codes and other abbreviations, refer to the "Gutd-SK, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, ance Notes on Codes and Abbrevialions "appearing at the begin- GW, MI., MR, NE, SN, TD, TG). ntng regular ofeach iswe ofthe PCT Gazette.

APPARATUS AND METHOD FOR MEASURING INCONFIGENT ION CONCENTRATIONS Field of the Invention The present invention relates to the determination of ion concentration in water below the borehole of hydrocarbon wells, aquifers, etc. This is useful in a wide range of applications, including the prediction of scale formation and marking waters from different sources. Background of the Invention The prediction of the location and type of mineral scale that can be formed around or within the production facilities or surface of an oil well is an important factor, both in the design of the well and in the formulation of strategies for deal with mineral inlays. Current methods for the prediction of mineral scale formation include the recovery of samples from the well, which are then either analyzed on the surface or also sent out to laboratories for analysis. Out of this analysis, errors and delays may arise. Electrochemical methods have previously been developed for the measurement of the concentration of a number of different metal ions, and some have been employed in flat holes, lakes and ocean waters. However, the application of these methods for the operations of the oil fields has been limited, since the high temperatures (up to 175 ° Celsius), and the pressures (up to 1529.57 kg / cm2 (1500 bars)) common for the Most of the wells make their use impractical. In addition, many electrochemical methods can not distinguish between the main metal ions (Ca2 +, Ba2 + and Sr2 +), responsible for the formation of scale. This problem is compounded by the low concentrations of these ions (approximately 10s mg / L) in the formation water, which is often highly saline. The ability to quickly and conveniently distinguish fouling ions can also find application, for example, in marking waters that flow into the hydrocarbon well of different production zones. This information, which indicates the connectivity between different zones of the production well, can allow the optimization of production strategies for the recovery of oil in the place. SUMMARY OF THE INVENTION An object of the present invention is to provide improved methods for the measurement of fouling ions, which are suitable for use at the site, ie in a continuous connection for a fluid flow. Accordingly, a first aspect of the present invention provides an apparatus for determining the concentration of fouling ions in the water below the well; the apparatus comprising a ligand which binds the fouling ions of the fluid that is flowing, which could be the water below the perforation, said ligand having an electronic configuration which is altered at the time of the binding of an encrusting ion, and a detector for determine the alterations in said electronic configuration, indicating the amount of said alterations the concentration of the encrusting ion in the sample. Preferably the ligand is contained within an electrochemical cell and changes in the electroactivity of the ligand are determined, for example, by means of an ammeter or a voltmeter. In other modalities, the binding of the encrusting ion can alter the fluorescent properties of the ligand. Changes in ligand fluorescence at the time of ligand binding can be determined using any of a range of conventional techniques. The apparatus may comprise a single ligand which binds specifically to a single encrusting ion, so that changes in the electronic configuration of the ligand are directly related to the concentration of the encrusting ion in the water sample. More preferably, the apparatus may contain two or more different ligands, for example, three, four or five or more. Alterations in the electronic configuration of each ligand can be determined independently, either simultaneously or consecutively. In some embodiments, each ligand can bind specifically to a different encrusting ion. Changes in the electronic configuration of each ligand are directly related to the concentration of the corresponding fouling ion in the water sample. In other embodiments, each ligand can be linked to two or more different scavenging ions. The changes in the properties (ie the electronic configuration) of each ligand are directly related to the concentration in the water of the sample of two or more fouling ions to which that ligand is bound. The different electronic response of the ligand to different ions can be translated into respective concentration measurements, for example, by locating the peaks in a voltagram. Alternatively, each ligand can bind to a different combination of fouling ions, so that the concentration of each individual fouling ion of the water sample can be calculated from the measurements determined for two or more different ligands.

An advantage of the apparatus is that it allows on-site analysis to be performed, thereby avoiding the problems associated with transporting the samples to the surface for off-site analysis. The present invention is partially based on the realization that electrochemical techniques can be adapted for drilling operation, i.e. in hostile and relatively demanding conditions. Preferably the detector is operably connected to a processor to determine the concentration of fouling ions of the current or potential in the cell. In some embodiments, the apparatus is adapted to be used in drilling (ie, in a hydrocarbon well or aquifer). The processor may also be adapted for use in drilling, or alternatively, it may be intended to be used for a remote installation, for example, on the surface. For example, the processor can be a properly programmed computer. A further aspect of the present invention provides the use of the apparatus as described herein for the measurement at the site of the concentration of fouling ions. In another aspect, the present invention provides a method for monitoring the concentrations of fouling ions in the water of the drilling which comprises: contacting a sample of the water in the drilling with a ligand, which binds selectively to the fouling ions , wherein the binding of the incrusting ions in said sample to the ligand alters the electronic configuration of the ligand; measure changes in the electronic configuration of the ligand; and determining the concentration of the encrusting ion of said changes in the electronic configuration. BRIEF DESCRIPTION OF THE DRAWINGS The specific embodiments of the present invention will now be described with reference to the following drawings, in which: Figures 1A and 1B show examples of an apparatus according to the present invention. Figures 2 to 5 show examples of ligands suitable for use in accordance with the present invention. Figure 6 shows a voltagram measured using a ligand of Figure 5 in an ion-free fluid, and in a fluid with Ba ions. Figure 7 shows a flow chart of a method according to an example of the present invention. Figure 8 shows an example of an inlay sensor in an application in a borehole. Detailed Description of the Invention In general terms, the present invention relates to the measurement of the ion concentration in drilling water, in particular, of the ions responsible for the formation of scale by means of changes in the electronic configuration of a ligand which binds to the encrusting ions. A preferred method comprises the use of an electrochemical cell containing a ligand which changes electroactivity at the time of bonding with an encrusting ion. Changes in the electroactivity of the ligand at the time of ion binding alter the electrochemical properties of the cell and can be measured using a detector. Other methods may comprise the use of a ligand whose fluorescent properties change at the time of the binding of an encrusting ion. The water of the drilling may be comprised within a production fluid of a well or deposit of hydrocarbons, which may comprise hydrocarbons, drilling mud, etc. Water from the well can, for example, be innate water. Inerting ions are ions which are responsible for the formation of scale. The main fouling ions in the drilling water are Ca2 +, Ba2 + and Sr2 + ions. A suitable ligand can be selectively linked to one or more of these fouling ions, for example, a ligand can bind to Ca2 +, Ba2 + and Sr2 +. Preferably, a ligand substantially does not show binding to other ions. In some modalities, the ligand may have a different binding affinity for each of the three major scaling ions (Ca2 +, Ba2 + and Sr2 +), allowing the levels of each individual ion in the water of the perforation to be determined. Discrimination between different ligands can be achieved, for example, by determining the characteristic redox properties of each ligand at different potentials. The ligand may be present in the cell in an aqueous solution in a concentration of 0.1 to 10 mM, preferably 1 to 10 mM, or it may be dispersed within a porous polymer membrane. Ligands suitable for use in accordance with the present invention are stable and can bind to fouling ions under the conditions of perforation, for example, at high temperatures (e.g., up to 175 ° C), and high pressures (for example, up to 175 ° C). example, up to 1529.57 kg / cm2 (1500 bars)). A class of suitable ligands has the formula (I): wherein R1 is a C- | .5 alkyl (including, for example, C..5 unsubstituted alkyl, and C-1-5 substituted alkyl) or C-? _ 8 aryl (including, for example, C - [_ 8 unsubstituted aryl, and C? .8 substituted aryl); and from R2 to R9 can independently be H, halogen, (F, Cl, Br, I); a group C..5 alkyl; an O-C1-5 alkyl group; COOH; NH2; -CONH2; a CO-C1-5 alkyl group; or a fluorophore group such as carboxy-X-rhodamine (ROX), tetramethylrhodamine (TAMRA) and fluorescein (FAM). The "C -? - alkyl" belongs to a monovalent moiety obtained by the removal of a hydrogen atom from a hydrocarbon compound having 1 to 5 carbon atoms, which may be aliphatic or alicyclic, or a combination thereof, and which can be saturated, partially unsaturated or completely unsaturated. Examples of suitable ligands according to formula I are shown in Figure 2. In some embodiments, the aromatic rings of suitable ligands may comprise substitutions at the ortho, meta or para positions (ie, at one or more of the positions of R2 to R9), in order to change the redox characteristics of a ligand to allow the exploration of different ions in spectrum windows separated from the well, in order to avoid interference. For purposes of the present invention, the foregoing class of ligand is referred to as O, O'-Bis (2-aminophenyl) ethylene glycol-N, N, N ', N'-tetraacetic acid, or BAPTA derivatives. Other suitable ligands may include cryptans (Lehn &Sauvage (1975) J. Am. Chem. Soc. 97 23 6700), for example, a ligand shown in Figure 3, and thymolphthalein and its derivatives (Qing and Yuying (1987) Talanta 34 6 555), for example, the ligands shown in Figure 4. Other suitable ligands may include neutral ionophores (Simon et al Anal, Chem. 1985, 57, 2756), specific crown ethers (DJ Cram et al. J. Am. Chem. Soc. 1973, 95, 3021) or antibiotics, such as valinomycin. An additional ligand of the cryptand family is shown in Figure 5. The crypting is derived by a redox-active group or M-portion. Entity M can be selected from the example of a group consisting of Fe, Ru, Co, V, Cr, Mo, and W ynym can have a range of 1 to 3. For purposes of the present invention, ligands of the type of Figure 3 and 5 are referred to as crypting derivatives. The apparatus may further comprise a porous membrane or a porous electrode block which allows the ions within the piercing water to pass into the cell to contact the ligand. A suitable porous membrane can be made of zeolite or a ceramic material. A block of epoxy material can be made as a basic material. The membrane can be contacted with separate samples or batches of water from the perforation, or the membrane can be contacted with a continuous flow of water from the perforation. The apparatus may comprise one or more liquid guiding channels for directing water from the borehole to the membrane and for removing water from the bore after contacting it with the membrane.

The detector may comprise one or more electrodes which make contact with the ligand. Various electrode adaptations can be used, as is conventional in electrochemistry. It can be conveniently used, an adaptation of three electrodes consisting of a working electrode, a reference electrode and a counter electrode. Preferably, the working electrode is composed of a fault-resistant material, such as a diamond enriched with boron, or a glassy carbon, the counter electrode is platinum, and the reference electrode is Ag / AgCl. Other suitable electrode materials such as Ag, are known to those skilled in the art. The electrodes can be used to detect changes in the electroactivity of one or more of the ligands. For example, changes in electroactivity caused by the presence of encrusting ions can alter the current or voltage flow between the electrodes. The current or voltage can be detected or measured by the detector. For example, the potential of the electrodes can be varied and the measured current or vice versa. The current or potential difference associated with the electroactivity of each of the one or more ligands can be measured by the detector and correlated with the concentration of fouling ions in the water sample of the perforation. In the presence of target ions, the peak currents must increase in proportion to the concentration of the target species. A power source can be connected to the electrodes to operate the current between the electrodes. The power source can be an integral part of the apparatus, and, for example, it can be comprised within the detector. In some embodiments, the power source can be separated from the apparatus and connected to it. The apparatus may comprise an appropriate circuit system for connection to the power source.

The ligand may be contained within the apparatus in any of a number of ways. In some embodiments, the ligand can be dispersed in an aqueous solution within a chamber of the apparatus. In other embodiments, the ligand can be dispersed within a porous polymer membrane. The binding of the fouling ions by the ligand occurs within the pores of the membrane and the resulting changes in the current or potential are detected by the circuit system directly connected to the membrane by means of the working electrodes, counter and reference. The use of a porous membrane is convenient to allow the miniaturization of the voltammetric or amperometric sensor, thus knowing in a faster response time, a lower consumption of reagents and lower costs of the unit. In other embodiments, the ligands can be adhered to conductive solid particles, such as carbon or metal particles (eg, gold), which are incorporated within the surface of one or more of the electrodes, preferably the working electrode. The accumulation of particles with the attached ligands forms a conductive pore electrode with the ligand attached to the walls of the pores. Suitable techniques for fixing the particles to the electrode surface include epoxy resin adhesion or abrasive immobilization. For example, a porous electrode for the determination of hydrogen sulphide is disclosed in the published UK Patent Application GB-A 2391314. For example, the ligand (I) above can be designed so that the R8 group is a amine (-NH2), which can be reacted with nitrous acid to form the diazonium ion -N + = N and subsequently be connected to carbon particles by reducing the diazonium group by hypophosphorous acid. Therefore, the ligand chemically bonded in this manner to the carbon particles and are can be incorporated into the working electrode 4, as described above. In other embodiments, the ligand (I) above can be coupled to gold particles with one of the groups from R2 to R9 being an amine (-NH2) or a thiol (-SH). As described above, the detector can be operably connected to a processor that determines the concentration of fouling ions in the sample from the difference in current or potential measured by the detector. The processor may be separated from or be part of the detector. The processor may also be adapted for use under the conditions of drilling (e.g., high temperature, high pressure and high salinity). Alternatively, it can be intended for remote installation, for example, on a surface. For example, the processor can be a properly programmed computer. The measurement of the concentration of the encrusting ion as described in the present description, can be useful in the sampling of perforations, the production record to characterize the flow within the well, and therefore, help remedy or production strategies, and in permanent monitoring applications, where the accumulation of scale or penetration / flooding of water from the tank could be calibrated. Figure 1A shows a cross-sectional diagram of an apparatus according to an embodiment of the present invention. The apparatus is shown separated within an upper part and a lower part as in a stage that is being assembled. The inlets 11 and the outlets 12 for the water of the sampling hole are indicated by arrows pointing in the direction of the flow. The water sample makes contact with a membrane 13a, which allows the passage of the ions inside the cell 14. The ligand solution in cell 14 comes into contact with the reference electrode Ag / AgC1 15, a counter electrode. 16 platinum ring and a glassy carbon working electrode 17. The electrodes 15, 16 and 17 detect changes in the electroactivity of the ligand in cell 14, which are related to the concentration of fouling ions. In the variant of Figure 1B, the scale sensor 20 is shown connected to a flow line 23. The body 21 of the sensor is fixed within the end section of an opening 22. The body bears a microporous epoxy matrix 211 which embedded catalyst 214 and contacts 212 providing the connection points to the voltage supply and measurement through a small channel 221 at the bottom of the opening 22. A sealing ring 213 protects the contact points and electronic components of the perforation fluid passing under operating conditions through the sample channel 23. In an example according to one embodiment of the present invention, the four ligands (2A to 2D) shown in Figure 2 can be present in solution in cell 14 or be embedded in block 211. These ligands have different binding properties; Ligand 2A binds to Ca2 +, Sr2 + and Ba2 +; ligand 2B binds to Ca2 + and Sr2 +, ligand 2C binds to Sr2 + and Ba2 +, and ligand 2D binds to Ba2 +. The level of Sr2 + of the water in the sample can be determined, for example, by measuring the alterations of the electroactivities of the 2C and 2D ligands in the cell and then subtracting the value obtained from the 2D ligand from the value obtained from the 2C ligand, to provide a value which represents the concentration of Sr2 +. (That is, 2C - 2D = [Sr2 +]). As above, the mark of the figure is taken as a representative of the respective ligand and / or the concentration measurement associated therewith. The level of Ca2 + in the sample water can be determined by measuring the alterations of the electroactivities of ligands 2B, 2C and 2D in the cell. The values of ligands 2B and 2D are aggregated together and the value obtained from ligand 2C is subtracted from this combined amount, to provide a value which represents the concentration of Ca 2+. (That is, 2B + 2D - 2C = [Ca ++]). The level of Ba2 + in the sample water is determined by measuring the alterations of the electroactivities of ligands 2A and 2B in the cell and then subtracting the value obtained from ligand 2B from the value obtained for ligand 2A, to produce a value which represents the concentration of Ba2 +. (That is, 2A - 2B = [Ba2 +] or 2D ligand). The chemical structure of the additional examples of ligands is shown in Figures 3 and 4. The indices n and m of the ligand of Figure 3 can be 1 or 2. Figure 5 shows the example of a modified cryptan with an active redox portion. Entity M can be selected from the group consisting of Fe, Ru, Co, V, Cr, Mo, and W and n and m can be in a range of 1 to 3. Figure 6 shows the response of the ligand of Figure 5 with M = Fe and n = m2 in the presence of Ba2 +. The solid line 51 is the typical electrochemical response of the pure ligand, while the dotted line 52 is the same response in the presence of Ba cations. The ligand of Figure 5 is sensitive to more than one species of fouling ions and the presence of different ions can be easily detected from the determination of peak locations on the voltam. Therefore, this ligand alleviates the need to use multiple ligands. Square wave voltammetry can be used, instead of the full cycle voltammetry shown. The flow chart of Figure 7 summarizes the steps of an example method of the present invention, including step 71 of contacting a sample of, for example, water from the perforation with a ligand which selectively binds to the fouling ions, the step 72 for measuring the changes in the electronic configuration of the ligand, and the step 73 for determining the concentration of the encrusting ions from the change in the electronic configuration. The results of the measurement can be fed in a model 74 that predicts the accumulation of scale in tubular equipment and other equipment exposed to the flow, for example, the production line or the pumps of the perforation. One application of the sensor is illustrated in Figure 8. This figure shows a Venturi type 810 fluidometer, which is well known in the industry and which is described, for example, in U.S. Patent No. 5,736,650. The flowmeter is installed mounted on the production line or tubing 812, at a location within the well 811 with a wired connection 813 to the surface, following known procedures as described, for example, in U.S. Patent No. 5,829,520. The fluidometer consists essentially of a restriction or groove 814 and two pressure switches 818, 819 located conventionally at the entrance and in the position of the maximum restriction, respectively. Generally, the Venturi fluidometer is combined with a densitometer 815 located beyond, either up or down. The innovative inlays sensor 816, preferably it is located below the fluidometer 20 to take advantage of the mixing effect that the fluidometer 20 has on the flow. A recess 817 protected by a metal mesh provides an entrance to the unit. During production, the drilling fluid enters the recess 817 and is subsequently analyzed using a sensor unit 816. The results are transmitted from the data acquisition unit to the surface, by means of the cables 813. Although the present invention has been described in conjunction with the exemplary embodiments described above, those skilled in the art will appreciate many modifications and equivalent variations when they have this description. Accordingly, the exemplary embodiments of the present invention set forth above are considered as illustrative and not limiting. Various changes can be made to the described embodiments, without departing from the spirit and scope of the present invention.

Claims (31)

1. CLAIMS 1. An apparatus for determining the concentration of encrusting ions; the apparatus comprising: a ligand which binds to encrusting ions in a fluid sample, the ligand having an electronic configuration, which is altered at the time of the binding of an encrusting agent, the ligand being placed in the vicinity of a flow of said fluid; a detector to determine the alterations in the electronic configuration, being indicative the amount of said alterations of the concentration of incrustating ions in the sample.
2. 2. An apparatus as described in claim 1, characterized in that the encrusting agent is selected from a group consisting of Ca2 +, Ba2 + and Sr2 + ions.
3. An apparatus as described in claim 1 or claim 2, characterized in that the detector comprises one or more electrodes for determining changes in the electroactivity of said ligand.
4. 4. An apparatus as described in claim 3, characterized in that the ligand is immobilized in conductive particles adhered to one or more of said electrodes.
5. The apparatus as described in claim 4, characterized in that the conductive particles are carbon or metal particles.
6. 6. The apparatus as described in claim 5, characterized in that the metal particles are gold particles.
7. The apparatus as described in any of claims 4 to 6, characterized in that the particles with ligands immobilized therein form a conductive porous electrode.
8. 8. An apparatus as described in claim 1, characterized in that a ligand comprises oxygen and / or nitrogen.
9. 9. An apparatus as described in any of the preceding claims, characterized in that the ligand is a derivative of BAPTA.
10. 10. The apparatus as described in any of the preceding claims, characterized in that the ligand is a derivative of crypting.
11. The apparatus as described in any of the preceding claims, which comprises a processor for calculating the concentration of fouling ions in the sample water from alterations in the electronic configuration of the ligand.
12. 12. An apparatus as described in claim 11, which comprises a ligand that binds to two or more different scavenging ions and generates a different electronic configuration in response to said binding.
13. 13. An apparatus as described in claim 11, which comprises two or more different ligands, being adapted to the detector to independently determine the alterations in the electronic configuration of each ligand.
14. 14. An apparatus as described in claim 13, characterized in that each of said two or more ligands is linked to a different combination of fouling ions.
15. 15. An apparatus as described in any of the preceding claims, which comprises a porous membrane which allows the ions of the fluid to make contact with the ligand.
16. 16. An apparatus as described in claim 15, characterized in that the membrane is ceramic or zeolite.
17. 17. An apparatus as described in any of the preceding claims, which comprises ligands embedded in a block of porous material, the block being exposed to a fluid flow.
18. 18. An apparatus as described in any of the preceding claims, characterized in that the fluid is an effluent from a perforation.
19. 19. An apparatus as described in any of the preceding claims, characterized in that the fluid leaves a production flow of a drilling well.
20. 20. An apparatus as described in any of the preceding claims, which is adapted to be placed in an underground location.
21. 21. A method for monitoring fouling ion concentrations which comprises: contacting a fluid flow with a ligand which selectively bonds to fouling ions, characterized in that the binding of the fouling ions in the sample to the ligand alters the configuration ligand electronics; the measurement of changes in the electronic configuration of the ligand; and the determination of the concentration of fouling ions from said changes in the electronic configuration.
22. 22. The method as described in claim 21, characterized in that the fouling ions are selected from the group consisting of ions of Ca,: 2 + Ba2 + and Sr2 +.
23. 23. A method as described in claim 21 or claim 22, characterized in that the change in the electronic configuration is determined by measuring the alterations in the electroactivity of the ligand.
24. 24. A method as described in any of claims 21 to 23, characterized in that the ligand is a derivative of BAPTA.
25. 25. A method as described in any of claims 21 to 23, characterized in that the ligand is a derivative of crypting.
26. 26. A method as described in any of the preceding claims, characterized in that the ligand binds two or more different scale ions and generates a different electronic configuration in response to the link.
27. 27. A method as described in any of the preceding claims, which comprises contacting the sample with two or more different ligands and determining the alterations in the electronic configuration of each ligand.
28. 28. A method as set forth in claim 26, characterized in that each of said two or more ligands is linked to a different combination of fouling ions.
29. 29. A method as described in any of the preceding claims, which includes the step of monitoring the production of a drilling well.
30. 30. A method as described in any of the preceding claims, which includes the step of predicting the scale in hydrocarbon production equipment or tubes.
31. 31. A method as described in any of the preceding claims, which includes the step of monitoring the scale in the equipment or tubular hydrocarbon production components in a location of a borehole.