Apparatus and method for a wireless sensor to monitor barrier system integrity
This invention describes an apparatus and a method for integrity monitoring of a borehole and the seal integrity of a caprock suitable for sequestration of greenhouse gases. The apparatus includes plural neutrally buoyant sensors for placement outside of a casing, placement including distribution within at least mud filter cake, cement, and proppant. This invention also includes a method for monitoring integrity of a borehole suitable for sequestration of greenhouse gases or other types of well using the described apparatus.
1. A method of sequestration of greenhouse gases, the method comprising:
drilling a borehole through a caprock and into a formation beneath the caprock;
distributing a plurality of neutrally buoyant sensors within mud filter cake around the borehole;
casing the borehole with the sensors outside of the casing;
filling an annulus with cement, the cement comprising a plurality of distributed neutrally buoyant sensors;
injecting a greenhouse gas into the formation; and
monitoring an integrity of the borehole by powering and interrogating the sensors with a wireline tool movable inside the casing.
2. The method of claim 1 , wherein the sensors measure or detect geomechanical properties, geochemical properties, porosity, permeability, conductivity, presence or migration of carbon dioxide or hydrocarbon(s).
3. The method of claim 1 , wherein the sensors exclude data storage and power storage.
4. The method of claim 1 , wherein the sensors have a service life of at least 30 years.
5. The method of claim 1 , wherein the distributing a plurality of sensors comprises placement in or along a caprock or other non-productive interval.
6. The method of claim 1 , the method further comprising:
powering the plurality of sensors by acoustic energy, radio frequency energy, or electrical induction.
7. The method of claim 1 , wherein the interrogating the plurality of sensors comprises the wireline tool sending a radio frequency signal and the sensors transmitting a radio frequency signal.
8. The method of claim 1 , the method further comprising:
determining a depth and an azimuth of the sensors with respect to the borehole.
9. The method of claim 1 , wherein distributing the sensors comprises:
circulating drilling mud down the borehole;
forming a mud filter cake; and
embedding sensors in the mud filter cake.
10. The method of claim 1 , further comprising locating a plurality of sensors on a centralizer.
11. The method of claim 1 , wherein monitoring the integrity of the borehole comprises measuring or detecting pH, carbon dioxide, hydrocarbon, or conductivity.