Method and apparatus for measuring carbon dioxide dissolved in solution and wellbore monitoring systems based thereon

摘要

A sensing apparatus (and corresponding method) for monitoring carbon dioxide dissolved in a liquid solution employs a crystal surrounded in part by a sample chamber such that, in use, the liquid solution is in direct contact with the crystal.

主权项

1. A downhole sensor for monitoring carbon dioxide dissolved in a liquid solution within a reservoir or an aquifer, the sensor comprising:
a housing that defines a cavity; a cover; a crystal that comprises:
a non-planar section having at least three surfaces for internally reflecting infrared radiation; anda base section having a bottom surface and a top surface; a sample chamber that surrounds at least part of the crystal, wherein the sample chamber is adapted such that, in use, the liquid solution under pressure characteristic of reservoir conditions is in direct contact with the at least three surfaces of the crystal and the at least three surfaces form an interface between the crystal and the liquid solution; a washer located between the cover and the top surface of the base section of the crystal, wherein the washer provides a seal between the cover and the crystal to isolate the sample chamber from the cavity defined by the housing; an infrared light source that directs at least one beam of infrared radiation into the crystal through the bottom surface of the base section so that the beam undergoes an attenuated internal reflection at each of the at least three surfaces of the crystal and then passes out of the bottom surface of the base section of the crystal, wherein the infrared light source is located within the cavity defined by the housing; an infrared detector that detects attenuated reflected infrared radiation produced by the crystal and that passes out of the base section of the crystal, wherein the infrared detector is located within the cavity defined by the housing; a signal processor, operably coupled to the infrared detector, that measures intensity of the attenuated reflected infrared radiation detected by the infrared detector; and a data processor, operably coupled to the signal processor, that determines concentration of carbon dioxide dissolved in the liquid solution from the intensity of the attenuated reflected infrared radiation measured by the signal processor.