Detecting wellbore leaks

1 . A method, comprising:

selecting, as a function of a density of an annulus fluid disposed within an annulus that is defined between a wellbore string and a wall of a wellbore, a number of weights to be positioned within a weight compartment of a microbead to adjust a weight of the microbead to allow the microbead to descend along the annulus at a predetermined speed;

adjusting, as a function of a density of the fluid, a weight of the microbead to allow the microbead to descend along the annulus at a speed of between 5 and 15 meters per second;

deploying the microbead into the annulus, the microbead comprising one or more sensors comprising a pressure sensor and a temperature sensor disposed within a housing of the microbead, the microbead further comprising a microchip electrically coupled to the pressure sensor and temperature sensor;

receiving, from the one or more sensors, sensor feedback comprising at least one of pressure information or temperature information of the annulus, the receiving comprising receiving, from the microchip, pressure information and temperature information gathered by the pressure sensor and temperature sensor;

determining, as a function of the sensor feedback, a location of a fluid leak within the annulus; and

controlling, based on the location of the fluid leak, at least one of a valve or a pump to regulate a fluid flow within the wellbore.

2 . The method of claim 1 , further comprising, before determining the location of the fluid leak:

determining a change in pressure of the fluid;

determining a location of the change in pressure of the fluid; and

comparing the change in pressure to a threshold;

wherein determining the location of the fluid leak comprises determining, as a function of determining that the change in pressure satisfies the threshold, the location of the fluid leak.

3 . The method of claim 2 , wherein the receiving comprises receiving pressure values associated with timestamps, and determining the location of the change in pressure comprises determining, as a function of (i) a time at which the one or more sensors were deployed, (ii) a falling speed of the one or more sensors, and (iii) the timestamps, a depth of the change in pressure.

4 . The method of claim 1 , wherein deploying the one or more sensors comprises delivering the one or more sensors into the annulus through a lubricator residing at a terranean surface of the wellbore.

5 . The method of claim 4 , wherein the lubricator is part of a wellhead fluidly coupled to the wellbore string, the lubricator coupled to at least one of a tubing head spool or a casing spool of the wellhead.

6 . The method of claim 1 , wherein the determining comprises determining, by the microchip, as a function of the sensor feedback, a falling speed of the microbead, and a time of deployment, the location of the fluid leak.

7 . The method of claim 1 , wherein the microbead further comprises a memory configured to store a log of pressure values and temperature values at different timestamps along the wellbore as the microbead falls within the annulus, and the determining comprises determining, as a function of the pressure values and temperature values, the location of the fluid leak.

8 . The method of claim 1 , wherein the receiving comprises continuously receiving pressure information or temperature information from the microchip as the microbead travels within an annulus fluid along the annuls in a downhole direction.

9 . The method of claim 1 , wherein receiving the sensor feedback comprises receiving sensor feedback continuously or at time intervals as the one or more sensors descend within the annulus.

10 . The method of claim 1 , further comprising, before deploying the one or more sensors, pre-installing the one or more sensors within a wellhead, and the deploying comprises deploying the one or more sensors using a lubricator attached to the wellhead.

11 . The method of claim 1 , wherein the wellbore string comprises an aperture through which fluid leaks into or out of the wellbore string, and determining the location of the fluid leak comprises detect a location of the aperture.

12 . A method, comprising:

receiving, by a system comprising one or more computers in one or more locations, sensor feedback from one or more sensors of a microbead, the sensor feedback comprising at least one parameter of an annulus defined between an external surface of a wellbore string and a wall of a wellbore, the parameter gathered while the one or more sensors fall downhole within the annulus, the microbead comprising a number of weights positioned within a weight compartment of a microbead to adjust a weight of the microbead to allow the microbead to descend along the annulus at a predetermined speed, the number of weights selected as a function of a density of an annulus fluid disposed within the annulus to allow the microbead to descend along the annulus at a speed of between 5 and 15 meters per second, the one or more sensors comprising a pressure sensor and a temperature sensor disposed within a housing of the microbead, the microbead further comprising a microchip electrically coupled to the pressure sensor and temperature, the receiving comprising receiving, from the microchip, pressure information and temperature information gathered by the pressure sensor and temperature sensor;

determining, by the system and as a function of (i) the sensor feedback and (ii) a falling speed of the one or more sensors, a location of a fluid leak within the annuls; and

controlling, based on the location of the fluid leak, at least one of a valve or a pump to regulate a fluid flow within the wellbore.

13 . The method of claim 12 , further comprising, after the determining, providing, by the system and to a receiver, the location of the fluid leak.

14 . The method of claim 12 , wherein the determining comprises:

comparing, by the system, the parameter to at least one threshold;

determining, by the system and as a function of the comparison, that the parameter satisfies the at least one threshold.

15 . The method of claim 12 , further comprising, before determining the location of the fluid leak:

determining a change in pressure of the fluid;

determining a location of the change in pressure of the fluid; and

comparing the change in pressure to a threshold;

wherein determining the location of the fluid leak comprises determining, as a function of determining that the change in pressure satisfies the threshold, the location of the fluid leak.

16 . A system, comprising:

one or more hardware processors; and

a computer storage medium communicatively coupled to the one or more hardware processors, the computer storage medium comprising instructions that, when executed by the one or more hardware processors, cause the one or more hardware processors to perform operations comprising:

receiving, from one or more sensors of a microbead, sensor feedback comprising at least one of pressure information or temperature information of an annulus defined between an outer surface of a wellbore string and a wall of the wellbore, the microbead comprising a number of weights positioned within a weight compartment of a microbead to adjust a weight of the microbead to allow the microbead to descend along the annulus at a predetermined speed, the number of weights selected as a function of a density of an annulus fluid disposed within the annulus to allow the microbead to descend along the annulus at a speed of between 5 and 15 meters per second, the one or more sensors comprising a pressure sensor and a temperature sensor disposed within a housing of the microbead, the microbead further comprising a microchip electrically coupled to the pressure sensor and temperature, the receiving comprising receiving, from the microchip, pressure information and temperature information gathered by the pressure sensor and temperature sensor;

determining, as a function of the sensor feedback, a location of a fluid leak within the annulus; and

controlling, based on the location of the fluid leak, at least one of a valve or a pump to regulate a fluid flow within the wellbore.

17 . The system of claim 16 , wherein the receiving the sensor feedback comprises receiving, from the microchip, the pressure information of the annulus and temperature information of the annulus gathered by the one or more sensors as the microchips falls within the annulus.

18 . A method, comprising:

selecting, as a function of a density of an annulus fluid disposed within an annulus that is defined between a wellbore string an a wall of a wellbore, a number of weights to be positioned within a weight compartment of a microbead to adjust a weight of the microbead to allow the microbead to descend along the annulus at a predetermined speed;

adjusting, as a function of a density of the fluid, a weight of the microbead to allow the microbead to descend along the annulus at a predetermined speed;

deploying the microbead into the annulus, the microbead comprising one or more sensors comprising a pressure sensor and a temperature sensor disposed within a housing of the microbead, the microbead further comprising a microchip electrically coupled to the pressure sensor and temperature sensor, the deploying comprising inserting the microbead through a lubricator residing at a terranean surface of the wellbore, and then dropping the microbead into the annulus;

receiving, from the one or more sensors, sensor feedback comprising at least one of pressure information or temperature information of the annulus, the receiving comprising receiving, from the microchip, pressure information and temperature information gathered by the pressure sensor and temperature sensor; and

determining, as a function of the sensor feedback, a location of a fluid leak within the annulus.

19 . The method of claim 18 , further comprising controlling, based on the location of the fluid leak, at least one of a valve or a pump to regulate a fluid flow within the wellbore.

20 . The method of claim 18 , wherein the lubricator is part of a wellhead fluidly coupled to the wellbore string, the lubricator coupled to at least one of a tubing head spool or a casing spool of the wellhead, and the deploying comprises inserting the microbead through the lubricator until the microbead reaches the annulus, and then dropping the microbead into the annulus.