SPECTROSCOPIC pH MEASUREMENT AT HIGH-TEMPERATURE AND/OR HIGH-PRESSURE

Abstract

Methods and apparatuses for high-temperature and high-pressure measurement of pH and/or alkalinity of a fluid is described.

1 . An apparatus for high-temperature and high-pressure measurement of pH of a fluid, the apparatus comprising:
 a fluid sample chamber to receive a fluid sample at a measurement pressure in operable communication with a first pressure regulating means, wherein said first pressure regulating means is configured to ensure that the pressure does not drop below the measurement pressure;   a dye chamber in fluid communication with the fluid sample chamber, and in operable communication with a second pressure regulating means, wherein said second pressure regulating means is configured to ensure that the pressure does not drop below the measurement pressure;   a light source and a detector in optical communication with the interior of the fluid sample chamber; and   a spectral analyzer, wherein the spectral analyzer is configured to analyze the optical density of a mixture of the fluid sample and dye.   
   
   
       2 . The apparatus of  claim 1 , wherein at least one of the first pressure regulating means or the second pressure regulating means is a piston. 
   
   
       3 . The apparatus of  claim 1 , wherein the measurement pressure is greater than about 1 bar. 
   
   
       4 . The apparatus of  claim 1 , wherein the fluid sample chamber, the first pressure regulating means, the dye chamber, and the second pressure regulating means are located in a heating device. 
   
   
       5 . The apparatus of  claim 4 , wherein the heating device is configured to maintain the apparatus at a measurement temperature. 
   
   
       6 . The apparatus of  claim 5 , wherein the measurement temperature is greater than about 323° K. 
   
   
       7 . The apparatus of  claim 1 , wherein the fluid sample chamber contains a mixer configured to mix the contents of the fluid sample chamber. 
   
   
       8 . An apparatus for high-temperature and high-pressure measurement of pH of a fluid, the apparatus comprising:
 a container capable of withstanding high-pressure and high-temperature;   a light source and a detector in optical communication with the interior of the high-pressure, high-temperature container;   a first pressure regulator having a first volume chamber in fluid communication with the high-pressure, high-temperature container, wherein the first pressure regulator is configured to ensure that the first volume chamber does not drop below a measurement pressure;   a second pressure regulator having a second volume chamber in fluid communication with the high-pressure, high-temperature container, wherein the second pressure regulator is configured to ensure that the second volume chamber does not drop below said measurement pressure;   a fluid sample container capable of withstanding high-pressure and high-temperature in fluid communication with the first volume chamber;   a dye reservoir in fluid communication with the second volume chamber; and   a spectral analyzer to receive data gathered by the detector wherein the spectral analyzer is configured to analyze the optical density of a mixture of a fluid sample and a dye.   
   
   
       9 . The apparatus of  claim 8 , further comprising:
 a water reservoir in fluid communication with the first volume chamber.   
   
   
       10 . The apparatus of  claim 8 , wherein at least one of the first pressure regulator and the second pressure regulator is a positive displacement pump. 
   
   
       11 . The apparatus of  claim 8 , wherein at least one of the first pressure regulator and the second pressure regulator is a syringe pump. 
   
   
       12 . The apparatus of  claim 8 , further comprising:
 a first actuator in operable communication with the first pressure regulator;   a second actuator in operable communication with the second pressure regulator;   a pressure transducer in fluid communication with the high-pressure high-temperature container; and   a controller in signal communication with the first actuator, second actuator, pressure transducer, and spectral analyzer.   
   
   
       13 . The apparatus of  claim 8 , wherein the measurement pressure is greater than about 1 bar. 
   
   
       14 . The apparatus of  claim 8 , wherein an oven is used to maintain the temperature equal to a measurement temperature. 
   
   
       15 . The apparatus of  claim 14 , wherein the temperature is greater than 323° K. 
   
   
       16 . A method to obtain total alkalinity of a fluid sample comprising:
 a. inputting an acid-dye solution into a dye chamber;   b. inputting water into a fluid sample chamber, wherein the fluid sample chamber is at a measurement pressure and temperature;   c. measuring the spectrum of the water;   d. displacing the water with a fluid sample, while maintaining measurement pressure;   e. measuring the spectrum of fluid sample;   f. inputting an amount of the acid-dye solution into the fluid sample chamber, while maintaining measurement pressure;   g. measuring a spectrum of the dye solution and fluid sample mixture;   h. determining the pH of the fluid sample;   i. repeating (e), (f), (g), and (h) one or more times to develop a relationship between pH and acid-volume added to the fluid sample; and   j. determining the alkalinity of the fluid sample from said relationship.   
   
   
       17 . An apparatus for high temperature, high pressure measurement of pH of a fluid, the apparatus comprising:
 a flowline to receive a fluid sample in fluid communication with a process line, wherein the flowline is configured so that it may be isolated from the process line;   a dye injector in fluid communication with the flowline, wherein the flowline, process line and dye injector are maintained at or above a measurement pressure;   a light source located downstream of the dye injector and in optical communication with the interior of the flowline; and   a spectral analyzer in communication with the detector.   
   
   
       18 . The apparatus of  claim 17 , wherein the measurement pressure is greater than about 1 bar. 
   
   
       19 . The apparatus of  claim 17 , wherein the dye injector is configured to inject a dye into the flowing fluid sample. 
   
   
       20 . The apparatus of  claim 17 , wherein the flowline, process line, and dye injector are maintained at a measurement temperature. 
   
   
       21 . The apparatus of  claim 20 , wherein the measurement temperature is greater than about 323° K.