CA1256361A - Measuring sulphide scavenger content of drilling fluid - Google Patents
Measuring sulphide scavenger content of drilling fluidInfo
- Publication number
- CA1256361A CA1256361A CA000479639A CA479639A CA1256361A CA 1256361 A CA1256361 A CA 1256361A CA 000479639 A CA000479639 A CA 000479639A CA 479639 A CA479639 A CA 479639A CA 1256361 A CA1256361 A CA 1256361A
- Authority
- CA
- Canada
- Prior art keywords
- zinc
- drilling fluid
- amount
- scavenger
- solution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
A B S T R A C T
MEASURING SULPHIDE SCAVENGER CONTENT OF DRILLING FLUID
The concentration of unspent zinc-based hydrogen sulphide scavenger in an aqueous drilling fluid is determined by selectively extracting the unspent scavenger in a solvent, such as glacial acetic acid, and measuring the concentration of dissolved zinc, for example, with an X-ray fluorescence spectrograph.
MEASURING SULPHIDE SCAVENGER CONTENT OF DRILLING FLUID
The concentration of unspent zinc-based hydrogen sulphide scavenger in an aqueous drilling fluid is determined by selectively extracting the unspent scavenger in a solvent, such as glacial acetic acid, and measuring the concentration of dissolved zinc, for example, with an X-ray fluorescence spectrograph.
Description
~563~l K 8998 CA~
MEASURING SULPHIDE SCA~ENGER CONTENT OF DRILLING FLUID
The present invention relates to determining the amount of unspent zinc based sulphide scavenger which is present in a water-based drilling fluid. More particularly, the invention relates to a relatively quick and accurate procedure which can be used in field locations.
A state of the art paper entitled "Chemical Scavengers for Sulfides in Water-Based Drllling Fluids" by R.L. Garrett, R.K.
Clark, L.L. Carney and C.K. &rantham, Sr. in Journal of Petroleum Technology, June 1979, page 787, discusses the chemistry of commercial scavengers Eor water-based drilling fluids, the parameters that affect the reliability of such materials and the problems affecting scavenger use. On page 796, they point out that "From ~his state of the art review one can see that we believe more research is needed to develop scavengers and tests for scavenger content in muds that match more closely the qualities of an ideal scavenger." U.S. Patent No. 3,706,532 describes a method for determining zinc concentrations in aqueous mediums. A sample medium is acidified, treated with a buffered complexing agent to complex aluminium or iron ions, treated with an organo sulphur compound to co~plex copper ions, then analyzed by adding an indicator the colour intensity of which ls calibrat~d with respect to known concentrations of zinc. U.S.
Patent No. 3,928,211 describes a class of zinc carbonate, basic zinc carbonate and zlnc hydroxlde compounds effective for sulphide scavenging. U.S. Patent No. 4,252,655 describes the :~ removal or ina~tivation of hydrogen sulphide contamination by adding at least one organic zinc chelate.
The present invention relates to a process for determining the amount of unspent zinc-containing sulphide-scavenging material present in an aqueous drilling fluid. A measured volume ;3~
of the drilling fluid is mixed with a significantly larger number of volumes (such as about 6 to 10) of a selective solvent for dissolving zinc ions and establishing within the resulting mixture a pH (such as a pH of from about 4 to 6) at which substantially all of the zinc in the drilling fluid, except for thae combined into zinc sulphide molecules, becomes dissolved in the liquid phase of the mixture. A portion of the resulting liquid solution is separated from the solid components of the drilling fluid and the amount of zinc contained in the solids-free liquid is determined in order to determine the amount of unspent zinc-containing sulphide scavenger in th~ drilling fluid.
In a preferred embodiment of the invention the drilling fluid sample is mixed with about 4 to 10 times its volume of glacial acetic acid, or a selective solvent which is substantially equivalent to glacial acetic acid with respect to selectively dissolving zinc ions which have not combined with sulphide ions. The concentration of zinc in the resulting solution is preferably measured with a portable X-ray fluorescence spectrographic unit which is, or is substantially equivalent to, a Portaspec Model 2501 portable X-ray spectrograph (available from Pitchford Scientiic Instruments Division of the ~ankison Corporation).
In a preferred procedure, for example, in situations in which the proportions found of unspent zinc based scavenger are rela~ively low, an augmentive test for total zinc(including that combined into zinc sulphide molecules) can be performed by (a) an X-ray fluorescence measurement, or equivalent méasurement, of the zinc in the unleached drilling fluid or, (b) using as the solvent for dissolving zinc from the drilling fluid a strong acid, such as hydrochloric acid, as a solvent,~ for combined and non-combined zinc, prior to measuring the concentration of the zinc solution. Such an acid preferably has a normality of from about 1 to 3. The difference between the prior and augmentive 3g tests wiil indicate whether the scavenger concentration was reduced by dilution of the drilling fluid or combination with ~25~i3~i~
sulphide.
Experiments ~ere conducted using samples of an aqueous drilling fluid typical of that used-in drilling operations.
Quadruplicate examples were performed on samples of that mud spiked with proportions of 1 lb. per barrel (ppb) of Sulf-X (a zinc based sulphide scavenger available from Imco Services, a Halliburton Company). The tests employed the following procedures, which are preferred procedures for use in the present invention.
Sample preparation 1. Measure 10 ml of stirred mud into a 10 ml graduated cylinder using a pipet with the end of the pipet cut off to minimize any particle size exclusion.
MEASURING SULPHIDE SCA~ENGER CONTENT OF DRILLING FLUID
The present invention relates to determining the amount of unspent zinc based sulphide scavenger which is present in a water-based drilling fluid. More particularly, the invention relates to a relatively quick and accurate procedure which can be used in field locations.
A state of the art paper entitled "Chemical Scavengers for Sulfides in Water-Based Drllling Fluids" by R.L. Garrett, R.K.
Clark, L.L. Carney and C.K. &rantham, Sr. in Journal of Petroleum Technology, June 1979, page 787, discusses the chemistry of commercial scavengers Eor water-based drilling fluids, the parameters that affect the reliability of such materials and the problems affecting scavenger use. On page 796, they point out that "From ~his state of the art review one can see that we believe more research is needed to develop scavengers and tests for scavenger content in muds that match more closely the qualities of an ideal scavenger." U.S. Patent No. 3,706,532 describes a method for determining zinc concentrations in aqueous mediums. A sample medium is acidified, treated with a buffered complexing agent to complex aluminium or iron ions, treated with an organo sulphur compound to co~plex copper ions, then analyzed by adding an indicator the colour intensity of which ls calibrat~d with respect to known concentrations of zinc. U.S.
Patent No. 3,928,211 describes a class of zinc carbonate, basic zinc carbonate and zlnc hydroxlde compounds effective for sulphide scavenging. U.S. Patent No. 4,252,655 describes the :~ removal or ina~tivation of hydrogen sulphide contamination by adding at least one organic zinc chelate.
The present invention relates to a process for determining the amount of unspent zinc-containing sulphide-scavenging material present in an aqueous drilling fluid. A measured volume ;3~
of the drilling fluid is mixed with a significantly larger number of volumes (such as about 6 to 10) of a selective solvent for dissolving zinc ions and establishing within the resulting mixture a pH (such as a pH of from about 4 to 6) at which substantially all of the zinc in the drilling fluid, except for thae combined into zinc sulphide molecules, becomes dissolved in the liquid phase of the mixture. A portion of the resulting liquid solution is separated from the solid components of the drilling fluid and the amount of zinc contained in the solids-free liquid is determined in order to determine the amount of unspent zinc-containing sulphide scavenger in th~ drilling fluid.
In a preferred embodiment of the invention the drilling fluid sample is mixed with about 4 to 10 times its volume of glacial acetic acid, or a selective solvent which is substantially equivalent to glacial acetic acid with respect to selectively dissolving zinc ions which have not combined with sulphide ions. The concentration of zinc in the resulting solution is preferably measured with a portable X-ray fluorescence spectrographic unit which is, or is substantially equivalent to, a Portaspec Model 2501 portable X-ray spectrograph (available from Pitchford Scientiic Instruments Division of the ~ankison Corporation).
In a preferred procedure, for example, in situations in which the proportions found of unspent zinc based scavenger are rela~ively low, an augmentive test for total zinc(including that combined into zinc sulphide molecules) can be performed by (a) an X-ray fluorescence measurement, or equivalent méasurement, of the zinc in the unleached drilling fluid or, (b) using as the solvent for dissolving zinc from the drilling fluid a strong acid, such as hydrochloric acid, as a solvent,~ for combined and non-combined zinc, prior to measuring the concentration of the zinc solution. Such an acid preferably has a normality of from about 1 to 3. The difference between the prior and augmentive 3g tests wiil indicate whether the scavenger concentration was reduced by dilution of the drilling fluid or combination with ~25~i3~i~
sulphide.
Experiments ~ere conducted using samples of an aqueous drilling fluid typical of that used-in drilling operations.
Quadruplicate examples were performed on samples of that mud spiked with proportions of 1 lb. per barrel (ppb) of Sulf-X (a zinc based sulphide scavenger available from Imco Services, a Halliburton Company). The tests employed the following procedures, which are preferred procedures for use in the present invention.
Sample preparation 1. Measure 10 ml of stirred mud into a 10 ml graduated cylinder using a pipet with the end of the pipet cut off to minimize any particle size exclusion.
2. Transfer to measured mud sample to a 150 ml beaker.
3. Add 60 ml of glacial acetic acid to the mud sample.
4. Heat at about 110C with frequent stirring for 10-15 minutes.
5. Allo~ the solution to cool sufficiently to prevent damage to a plastic centrifuge tube.
0 6. Place a portion of the mud-acetic acid mixture into a plastic 50 ml centrifuge tube.
7. Centrifuge so that all the mud is firmly packed at the bottom of the centrifuge tube.
8. Accurately pipet 10 ml of the centrifuge solution into a Chemplex X-ray fluorescence counting vlal using a 5 ml Finnpipette.
9. Cover the counting vial with polypropylene film, brace the film onto the vial with a small collar, and fix the film onto the vial with a ~ collar. (Note: Position the large collar so that the protruding rim is the first to contact the vial. When fixing the large collar, apply equal pressure to both sides.) Instrumental measurement3 by X-ray fluorescence 1. Position the element selector to Zn using the sidearm lever.
2. Open the sample compartment door.
~25~3~
3. Plug into a llOV outlet and engage "Power" button. Wait for the "ready" light and let warm 10 minutes.
4. Place sample counting vials in the spring-loaded mount.
Insert the mount into the sample chamber with the rounded edge of the stainless mount facing inward. (Note: Make sure no droplets are present on the undersurface of the polypropylene film. These droplets will cause an errant increase in count rate.~
5. Close the sample chamber door and check to see if the "X-rays on" indicator is illuminated. If it is not illuminated, the stainless planchet holder should be reinserted in the other direction.
0 6. Place a portion of the mud-acetic acid mixture into a plastic 50 ml centrifuge tube.
7. Centrifuge so that all the mud is firmly packed at the bottom of the centrifuge tube.
8. Accurately pipet 10 ml of the centrifuge solution into a Chemplex X-ray fluorescence counting vlal using a 5 ml Finnpipette.
9. Cover the counting vial with polypropylene film, brace the film onto the vial with a small collar, and fix the film onto the vial with a ~ collar. (Note: Position the large collar so that the protruding rim is the first to contact the vial. When fixing the large collar, apply equal pressure to both sides.) Instrumental measurement3 by X-ray fluorescence 1. Position the element selector to Zn using the sidearm lever.
2. Open the sample compartment door.
~25~3~
3. Plug into a llOV outlet and engage "Power" button. Wait for the "ready" light and let warm 10 minutes.
4. Place sample counting vials in the spring-loaded mount.
Insert the mount into the sample chamber with the rounded edge of the stainless mount facing inward. (Note: Make sure no droplets are present on the undersurface of the polypropylene film. These droplets will cause an errant increase in count rate.~
5. Close the sample chamber door and check to see if the "X-rays on" indicator is illuminated. If it is not illuminated, the stainless planchet holder should be reinserted in the other direction.
6. With "X-rays on", adjust the current to read 0.5 milliamps.
7. Set the counting scaler on the front panel to 60 seconds.
8. Engage count pushbutton and record the final gross X-ray intensity counts on the digital readout.
(Note: At this point, additional sample measurements simply i~volve changing the vials in the spring-loaded mount and resetting the count pushbutton.
(Note: At this point, additional sample measurements simply i~volve changing the vials in the spring-loaded mount and resetting the count pushbutton.
9. Obtain gross X-ray counts for the glacial acetic acid blank and a calibration standard prepared by the dissolution of ZnO ln glacial acetic acid.
10. To leave instrument in standby position, open the sample compartment door. (Note: Never close sample door without having vials in the counting chamber.)
11~ For longer periods of inactivity, turn down the current, turn off main power and unplug~
Calculations (based on the following conditions) 10 ml mud, 60 ml acetic acid, 10 ml aliquots in counting vial. Calculations are not valid for variations from these amoùnts.
1. Determine net counts for samples and ZnO calibration standard by subtracting the glacial acetic acid blank counts. 0 2. Determine the mg of Zn in 10 ml mud sample by the following ratio:
~25~6~
Net intensity sample mg Zn in 10 ml mud = - x mg Zn Std Net intensitY Std 3. Determine ppb (pounds per barrel) Zn by multipyling the mg Zn in the 10 ml mud sample by 0.035. The factor Q.035 is derived from the following conversion:
lb Zn mg Zn 1000 ml x 3-79 1 x 42 gal x 1 g x 1 lb bbl mud 10 ml mud 1 1 1 gal 1 bbl 1000 mg 454 g 4. Determine ppb Sulf-X by multiplying ppb Zn by 1.67 (Sulf-X
contains 60.0~ Zn).
Test results The tests indicated the following:
Sulf-X was experimentally determined to be present at 0.97 +
0.09 ppb. These results indicate the accuracy and precision of the method to be within the 10 percent relative objective.
Additional experiments were designed to simulate situations where the scavenger containing mud had been totally exhausted by hydrogen sulphide lntrusion. This was accomplished by spiking mud ,with 1 ppb æinc sulphide which is the product from the reaction of the zinc-scavenger with sulphide. Duplicate analyses yielded unspent scavenger concentrations of 0.02 ~ 0.01 ppb indicating that the acetic acid leach is effective at differentiating spent and unspent zinc scavenger.
In a third experiment, unspiked mud was found to have 0.03 ppb unspent zinc scavenger which indicates that potential interferents inherent to the mud are virtually non-existent.
In general, the selective solvent for zinc ions can comprise substantially any buffered liquid having a composition and concentration capable of providing a pH of about 4 to 6 when one part by volume of a drilling fluid having a pH in the range,of from about 9 to 12 i9 mixed with about ~ to 10 parts by volume of ~6~
said liquid. Examples of suitable selective solvent solutions include: glacial acetic acid, 10% formic acid, and 0.0001 M
hydrochloric acid.
In general, the concentra~ion of zinc which becomes dissolved in the selective solvent can be measured by substantially any suitably accurate procedure. Procedures capable of being conducted in field locations are preferred. An example of such a procedure is described in "Colorimetric Determinations of Elements" by G. Charlot, Elsevier Publishing Company, 1964.
Calculations (based on the following conditions) 10 ml mud, 60 ml acetic acid, 10 ml aliquots in counting vial. Calculations are not valid for variations from these amoùnts.
1. Determine net counts for samples and ZnO calibration standard by subtracting the glacial acetic acid blank counts. 0 2. Determine the mg of Zn in 10 ml mud sample by the following ratio:
~25~6~
Net intensity sample mg Zn in 10 ml mud = - x mg Zn Std Net intensitY Std 3. Determine ppb (pounds per barrel) Zn by multipyling the mg Zn in the 10 ml mud sample by 0.035. The factor Q.035 is derived from the following conversion:
lb Zn mg Zn 1000 ml x 3-79 1 x 42 gal x 1 g x 1 lb bbl mud 10 ml mud 1 1 1 gal 1 bbl 1000 mg 454 g 4. Determine ppb Sulf-X by multiplying ppb Zn by 1.67 (Sulf-X
contains 60.0~ Zn).
Test results The tests indicated the following:
Sulf-X was experimentally determined to be present at 0.97 +
0.09 ppb. These results indicate the accuracy and precision of the method to be within the 10 percent relative objective.
Additional experiments were designed to simulate situations where the scavenger containing mud had been totally exhausted by hydrogen sulphide lntrusion. This was accomplished by spiking mud ,with 1 ppb æinc sulphide which is the product from the reaction of the zinc-scavenger with sulphide. Duplicate analyses yielded unspent scavenger concentrations of 0.02 ~ 0.01 ppb indicating that the acetic acid leach is effective at differentiating spent and unspent zinc scavenger.
In a third experiment, unspiked mud was found to have 0.03 ppb unspent zinc scavenger which indicates that potential interferents inherent to the mud are virtually non-existent.
In general, the selective solvent for zinc ions can comprise substantially any buffered liquid having a composition and concentration capable of providing a pH of about 4 to 6 when one part by volume of a drilling fluid having a pH in the range,of from about 9 to 12 i9 mixed with about ~ to 10 parts by volume of ~6~
said liquid. Examples of suitable selective solvent solutions include: glacial acetic acid, 10% formic acid, and 0.0001 M
hydrochloric acid.
In general, the concentra~ion of zinc which becomes dissolved in the selective solvent can be measured by substantially any suitably accurate procedure. Procedures capable of being conducted in field locations are preferred. An example of such a procedure is described in "Colorimetric Determinations of Elements" by G. Charlot, Elsevier Publishing Company, 1964.
Claims (7)
1. A process for determining the amount of unspent zinc-containing sulphide scavenger in an aqueous drilling fluid, comprising:
mixing one part by volume of the drilling fluid with about 4 to 10 parts by volume of a selective solvent for zinc ions, which solvent contains a kind and amount of buffering material such that the mixture has a pH of about 4 to 6 and is capable of dissolving substantially all of the zinc present in the drilling mud which has not been combined into molecules of zinc sulphide;
separating the resulting solution from undissolved solids;
and determining the amount of zinc in the solids-free fluid in order to determine the amount of unspent zinc-containing sulphide scavenger in the drilling fluid.
mixing one part by volume of the drilling fluid with about 4 to 10 parts by volume of a selective solvent for zinc ions, which solvent contains a kind and amount of buffering material such that the mixture has a pH of about 4 to 6 and is capable of dissolving substantially all of the zinc present in the drilling mud which has not been combined into molecules of zinc sulphide;
separating the resulting solution from undissolved solids;
and determining the amount of zinc in the solids-free fluid in order to determine the amount of unspent zinc-containing sulphide scavenger in the drilling fluid.
2. The process of claim 1 in which the amount of zinc in the solution is determined by measuring the amount of X-ray fluorescence exhibited by the solution.
3. The process of claim 1 in which the selective solvent for zinc is glacial acetic acid.
4. The process of claim 1 in which the selective solvent for zinc is glacial acetic acid, the mixture of drilling fluid and selective solvent contains about 1 part by volume of the drilling fluid per 4 to 10 parts by volume of the solvent and the amount of zinc which becomes dissolved in that solution is determined by a measurement of X ray fluorescence.
5. The process of claim 1 in which an additional portion of the same drilling fluid is similarly mixed with a solvent consisting of an aqueous strong acid solution capable of dissolving substantially all combined and non-combined zinc in the drilling fluid, with the amount of zinc in the solution being similarly measured to determine the decrease in scavenger due to drilling fluid dilution and reaction of scavenger with sulphides.
6. The process of claim 5 in which the strong acid is hydrochloric acid having a normality of about 1 to 3.
7. The process of claim 1 in which the amount of zinc dissolved in the selective solvent for zinc ions is determined by colourimetric analyses.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60961184A | 1984-05-14 | 1984-05-14 | |
| US609,611 | 1984-05-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1256361A true CA1256361A (en) | 1989-06-27 |
Family
ID=24441538
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000479639A Expired CA1256361A (en) | 1984-05-14 | 1985-04-19 | Measuring sulphide scavenger content of drilling fluid |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1256361A (en) |
-
1985
- 1985-04-19 CA CA000479639A patent/CA1256361A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |