AI-assisted stratigraphic modeling and geosteering utilizing gamma ray measurements

A method for steering a first tool of a first drill string traversing a subsurface region, comprising:

• drilling of at least one reference well into a subsurface region;
• initializing a first stratigraphic model of the subsurface region at a control system, the first stratigraphic model of the subsurface region showing a representation of a plurality of layers of the subsurface region mapped with respect to total vertical depth (TVD) and total horizontal length (THL);
• initializing a first gamma ray model at the control system, the first gamma ray model comprising reference gamma ray values indexed over the THL, wherein the reference gamma ray values are obtained during the drilling of the at least one reference well into the subsurface region;
• receiving, in real time, first gamma ray measurements at the control system from a gamma ray sensor coupled to a first tool of a first drill string traversing the subsurface region during drilling of an additional well, wherein the control system indexes the received first gamma ray measurements over a first portion of the THL;
• determining that a first difference between the reference gamma ray values indexed over the first portion of the THL and the received first gamma ray measurements indexed over the first portion of the THL exceeds a first error threshold with the control system;
• updating the first stratigraphic model based on the first difference to create a first updated first stratigraphic model comprising an updated representation of a position of the plurality of layers of the subsurface region;
• updating the first gamma ray model to create a first updated first gamma ray model comprising first updated gamma ray values;
• sending, in real time during the drilling of the additional well, at least one control signal from the control system to a steering module of the first drill string based on the first updated first stratigraphic model and the first updated first gamma ray model, wherein the at least one control signal is generated based on a comparison between the first updated first gamma ray model and the received first gamma ray measurements;
• and
• steering, via the steering module and the at least one control signal, the first tool of the first drill string in a trajectory to a hydrocarbon-bearing target layer.

A non-transitory computer-readable medium comprising instructions stored thereon that when executed by one or more processors cause a control system to control a first drill string to target at least one target layer of a subsurface region, the controlling comprising:

• drilling of at least one reference well;
• initializing a first stratigraphic model of the subsurface region at a control system, the first stratigraphic model of the subsurface region showing a representation of a plurality of layers of the subsurface region mapped with respect to total vertical depth (TVD) and total horizontal length (THL);
• initializing a first gamma ray model at the control system, the first gamma ray model comprising reference gamma ray values indexed over the THL, wherein the reference gamma ray values are obtained during the drilling of the at least one reference well into the subsurface region;
• receiving, in real time, first gamma ray measurements at the control system from a gamma ray sensor coupled to a first tool of a first drill string traversing the subsurface region during drilling of an additional well, wherein the control system indexes the received first gamma ray measurements over a first portion of the THL;
• determining that a first difference between the reference gamma ray values indexed over the first portion of the THL and the received first gamma ray measurements indexed over the first portion of the THL exceeds a first error threshold with the control system;
• updating the first stratigraphic model based on the first difference to create a first updated first stratigraphic model comprising an updated representation of a position of the plurality of layers of the subsurface region;
• updating the first gamma ray model to create a first updated first gamma ray model comprising first updated gamma ray values;
• sending, in real time during the drilling of the additional well, at least one control signal from the control system to a steering module of the first drill string based on the first updated first stratigraphic model and the first updated first gamma ray model, wherein the at least one control signal is generated based on a comparison between the first updated first gamma ray model and the received first gamma ray measurements;
• and
• steering, via the steering module and the at least one control signal, the first tool of the first drill string to a hydrocarbon-bearing target layer.