Monitoring a Geological Formation
First Claim
1. A method of monitoring a geological formation subjected to steam injection, the method comprising:
- performing distributed fibre optic sensing on a first optical fibre deployed in a borehole running through the geological formation to acquire a first set of measurement signals being indicative of disturbances acting on each of a plurality of longitudinal sensing portions of the first optical fibre;
wherein at least part of the first optical fibre is disposed adjacent to at least a first electrode spaced apart from a second electrode, with a gas between the first and second electrodes and wherein the potential difference between the first and second electrodes is such that an ionisation event within the gas results in an avalanche multiplication;
the method further comprising analysing the first set of measurement signals to determine a spatial distribution of radioactive sources throughout the geological formation.
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Accused Products
Abstract
This application relates to methods and apparatus for monitoring a geological formation that is or has been subjected to steam injection using a distributed fibre optic sensor apparatus to perform distributed fibre optic sensing on an optical fibre deployed in a borehole running through the geological formation to acquire a first set of measurement signals being indicative of disturbances acting on each of a plurality of longitudinal sensing portions of the first optical fibre where at least part of the optical fibre is disposed adjacent to at least a first electrode spaced apart from a second electrode and the first and second electrode are separated by a void that is filled with a gas and an electrical source applies a potential difference to the first and second electrodes such that an ionisation event within the gas results in an avalanche multiplication.
18 Citations
22 Claims
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1. A method of monitoring a geological formation subjected to steam injection, the method comprising:
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performing distributed fibre optic sensing on a first optical fibre deployed in a borehole running through the geological formation to acquire a first set of measurement signals being indicative of disturbances acting on each of a plurality of longitudinal sensing portions of the first optical fibre; wherein at least part of the first optical fibre is disposed adjacent to at least a first electrode spaced apart from a second electrode, with a gas between the first and second electrodes and wherein the potential difference between the first and second electrodes is such that an ionisation event within the gas results in an avalanche multiplication; the method further comprising analysing the first set of measurement signals to determine a spatial distribution of radioactive sources throughout the geological formation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for monitoring a geological formation subjected to steam injection, the apparatus comprising:
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a fibre optic cable structure comprising a first optical fibre disposed adjacent first and second electrodes, the first and second electrodes being separated by a gas; a distributed fibre optic sensor interrogator unit configured to, in use, perform distributed fibre optic sensing on the first optical fibre when the fibre optic cable structure is deployed in a borehole running through the geological formation to acquire a first set of measurement signals being indicative of disturbances acting on each of a plurality of longitudinal sensing portions of the first optical fibre; an electrical source for generating a potential difference between the first and second electrodes such that an ionisation event within the gas results in an avalanche multiplication; and a processor configured to analyse the first set of measurement signals to determine a spatial distribution of radioactive sources throughout the geological formation. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of determining information about a geological formation subjected to steam injection, the method comprising:
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accessing a first set of measurement signals, the first set of measurement signals having been acquired by performing distributed fibre optic sensing on a first optical fibre deployed in a borehole running through the geological formation and being indicative of disturbances acting on each of a plurality of longitudinal sensing portions of the first optical fibre; wherein at least part of the first optical fibre was disposed adjacent to at least a first electrode spaced apart from a second electrode, with a gas between the first and second electrodes and wherein the potential difference between the first and second electrodes is such that an ionisation event within the gas results in an avalanche multiplication; the method further comprising analysing the first set of measurement signals to determine a spatial distribution of radioactive sources throughout the geological formation.
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Specification