Systems and methods for multi-offset seismic profiling

A method for deploying sensors in a wellbore, the method comprising:

• attaching an untethered multi-offset sensor system to a wellbore casing in the wellbore, wherein the untethered multi-offset sensor system includes at least a first sensor element, a second sensor element, and a third sensor element, wherein the first sensor element is connected to the second sensor element by a first cable, and wherein the second sensor element is connected to the third sensor element by a second cable, wherein the first sensor element comprises a first selectably detachable ballast configured to render the first sensor element negatively buoyant in a fluid in the wellbore, wherein the second sensor element comprises a second selectably detachable ballast configured to render the second sensor element negatively buoyant in the fluid in the wellbore, wherein the third sensor element comprises a third selectably detachable ballast configured to render the second sensor element negatively buoyant in the fluid in the wellbore, wherein the first sensor element is attached to the wellbore casing at a first location higher in the wellbore than the second sensor element, wherein the second sensor element is attached to the wellbore casing at a second location higher in the wellbore than the third sensor element;
• selectably detaching the first ballast from the first sensor element rendering the first sensor element positively buoyant in the fluid of the wellbore;
• detaching the first sensor element from the wellbore casing;
• after detaching the first sensor element from the wellbore casing, selectably detaching the second ballast from the second sensor element rendering the second sensor element positively buoyant in the fluid of the wellbore;
• detaching the second sensor element from the wellbore casing;
• after detaching the second sensor element from the wellbore casing, selectably detaching the third ballast from the third sensor element rendering the third sensor element positively buoyant in the fluid of the wellbore;
• detaching the third sensor element from the wellbore casing;
• and
• gathering each of the first sensor element, the second sensor element, and the third sensor element at a surface of the wellbore.

A untethered multi-offset sensor system, the system comprising:

• a first sensor element comprising:
• a first seismic sensor;
• a first detachable ballast;
• a first electromagnet configured to selectably attach the first detachable ballast to the first sensor element;
• a second electromagnet configured to secure the first sensor element to a wellbore casing;
• a second sensor element comprising:
• a second seismic sensor;
• a second detachable ballast;
• a third electromagnet configured to selectably attach the second detachable ballast to the second sensor element;
• a fourth electromagnet configured to secure the second sensor element to the wellbore casing;
• a third sensor element comprising:
• a third seismic sensor;
• a third detachable ballast;
• a fifth electromagnet configured to selectably attach the second detachable ballast to the second sensor element;
• a sixth electromagnet configured to secure the second sensor element to the wellbore casing;
• wherein a combination of the first sensor element with the first ballast attached, the second sensor element with the second ballast attached, and the third sensor element with the third ballast attached is negatively buoyant in a fluid in the wellbore, and wherein upon detaching one or more of the first ballast, the second ballast, or the third ballast, the untethered multi-offset sensor system becomes positively buoyant in the fluid in the wellbore;
• wherein the first sensor element is attached to the second sensor element by a first cable, and wherein a length of the first cable is fixed and defines a deployment location of the first sensor element relative to the second sensor element;
• and
• wherein the second sensor element is attached to the third sensor element by a second cable, and wherein a length of the second cable is fixed and defines a deployment location of the second sensor element relative to the third sensor element.