Measuring an adsorbing chemical in downhole fluids
Interaction of adsorbing chemicals with a downhole tool presents inaccuracies in the adsorbing chemical measurement and analysis. The principles of the present disclosure provide a method and system of sampling fluids including an adsorbing chemical in a subterranean reservoir. One method may include modeling an interaction between the adsorbing chemical and a downhole tool, applying the model to a measurement of the adsorbing chemical, and adjusting the measurement in response to applying the model.
1. A method to detect a chemical in a subterranean reservoir comprising: simulating behavior of a chemical as the chemical moves from a reservoir to a location within a downhole tool;
based on the simulation, using mathematical fitting to generate a model of the behavior; using the downhole tool, sampling a downhole fluid containing the chemical; characterizing a response of the downhole tool to the chemical using the model, wherein characterizing includes defining a characteristic that corresponds to at least one of an adsorption and desorption interaction between the downhole fluid and downhole tool; and
operating the downhole tool in response to the characterization.
2. The method as defined in claim 1 , wherein:
the model is matched to downhole test data;
the model is comprised of a gaussian model, exponential model, or double exponential model;
the model is derived from an approximation; or
the model comprises an error function.
3. The method as defined in claim 1 , wherein the downhole tool is a formation tester, a fluid identification or contamination section of a downhole tool or a nuclear magnetic resonance (“NMR”) section of a downhole tool.
4. The method as defined in claim 1 , wherein:
the simulation is a numeric simulation or finite element simulation; or
the simulation is performed as part of a pre-job operation.
5. The method as defined in claim 1 , wherein:
the model is adjusted while the downhole tool is downhole; or
the model is used to determine a concentration of the chemical in the downhole fluid.
6. The method as defined in claim 1 , wherein:
the chemical is at least one of H2S, mercury, CO2, tracer, water scaling chemical, sulfur containing species, a mercaptan, filtrate tracer, a radioactive tracer, Tritium, a bromide compound, an iodide compound, a fatty acid or Nitrate anion; or
the chemical is a corrosive or adsorbing chemical.
7. The method as defined in claim 1 , wherein:
the chemical is detected optically, electrically or chemically; or
the chemical is detected using a Gas Chromatograph, sulfur detector or nuclear magnetic resonance (“NMR”) device.
8. The method as defined in claim 1 , wherein operating the downhole tool comprises predicting, planning or adjusting in real-time a sampling job in response to the characterization.
9. The method as defined in claim 1 , wherein:
the simulation uses at least one of a composition, temperature, pressure, fluid flow rate or formation tester configuration; or
the simulation is a steady state model.
10. A tool for sampling fluids including a chemical in a subterranean reservoir, comprising: a formation tester having a sampling chamber; and a processor coupled to the formation tester to perform operations comprising: simulating behavior of a chemical as the chemical moves from a reservoir to the sampling chamber; based on the simulation, using mathematical fitting to generate a model of the behavior; using the formation tester, sampling a downhole fluid containing the chemical; characterizing a response of the formation tester to the chemical using the model, wherein characterizing includes defining a characteristic that corresponds to at least one of an adsorption and desorption interaction between the downhole fluid and downhole tool; and operating the formation tester in response to the characterization.
11. The tool as defined in claim 10 , wherein:
the model is matched to downhole test data;
the model is comprised of a gaussian model, exponential model, or double exponential model;
the model is derived from an approximation; or the model comprises an error function.
12. The tool as defined in claim 10 , wherein:
the simulation is a numeric simulation or finite element simulation; or
the simulation is performed as part of a pre-job operation.
13. The tool as defined in claim 10 , wherein the model is adjusted while the downhole tool is downhole.
14. The tool as defined in claim 10 , wherein:
the chemical is at least one of H2S, mercury, CO2, tracer, water scaling chemical, sulfur containing species, a mercaptan, filtrate tracer, a radioactive tracer, Tritium, a bromide compound, an iodide compound, a fatty acid or Nitrate anion; or
the chemical is a corrosive or adsorbing chemical.
15. The tool as defined in claim 10 , wherein the chemical is detected optically, electrically or chemically.
16. The tool as defined in claim 10 , wherein:
a detector for detecting the chemical is located proximal to the sampling chamber;
the detector is a Gas Chromatograph, sulfur detector or nuclear magnetic resonance (“NMR”) detector.
17. The tool as defined in claim 10 , wherein operating the downhole tool comprises predicting, planning or adjusting in real-time a sampling job in response to the characterization.
18. The tool as defined in claim 10 , wherein the model is used to determine a concentration of the chemical in the downhole fluid.
19. The tool as defined in claim 10 , wherein the simulation uses at least one of a composition, temperature, pressure, fluid flow rate or formation tester configuration.
20. The tool as defined in claim 10 , wherein the simulation is a steady state model.