Geosteering control framework

1 . A method comprising:

receiving resistivity data acquired by a downhole tool of a drillstring disposed in a borehole in a subsurface environment, wherein the borehole comprises a downhole end, the borehole defines a borehole axis, and the resistivity data is collected uphole of the downhole end of the borehole;

generating, using at least a portion of the resistivity data, synthetic resistivity data for a region of the subsurface environment beyond the downhole end of the borehole;

receiving seismic data for the subsurface environment, wherein the seismic data comprise spatial locations;

applying a joint inversion to at least a portion of the resistivity data uphole of the downhole end of the borehole, at least a portion of the synthetic resistivity data downhole of the downhole end of the borehole, and at least a portion of the seismic data to estimate values for physical properties of a portion of the subsurface environment that includes at least a portion of the region of the subsurface environment beyond the downhole end of the borehole;

based on the physical properties beyond the downhole end of the borehole, identifying an adjustment to a wellbore trajectory to stay within a target area of the subsurface environment beyond the downhole end of the borehole; and

actuating one or more geosteering actuators to adjust a tool trajectory of the downhole tool according to the adjustment to follow the wellbore trajectory and stay within the target area.

2 . The method of claim 1 , wherein the seismic data comprise surface seismic data of the subsurface environment.

3 . The method of claim 1 , wherein the seismic data comprise borehole seismic data.

4 . The method of claim 1 , wherein the seismic data comprise acoustic impedance data.

5 . The method of claim 1 , wherein the physical properties comprise porosity.

6 . The method of claim 1 , wherein the physical properties comprise water saturation.

7 . The method of claim 1 , wherein the physical properties comprise volume of clay.

8 . The method of claim 1 , wherein the physical properties comprise porosity and one or more of water saturation and volume of clay.

9 . The method of claim 1 , wherein the physical properties comprise volume of shale.

10 . The method of claim 1 , wherein applying the joint inversion includes generating uncertainty metrics for the physical properties.

11 . The method of claim 1 , wherein identifying the adjustment to the wellbore trajectory includes identifying the wellbore trajectory in real-time responsive to the receiving of the resistivity data.

12 . The method of claim 1 , wherein the resistivity data comprise vertical resistivity data and horizontal resistivity data.

13 . The method of claim 1 , wherein applying the joint inversion includes applying the joint inversion using one or more rock physics models for one or more lithologies of the subsurface environment.

14 . The method of claim 13 , comprising segmenting at least a portion of the subsurface environment into zones, wherein each of the zones comprises one of the one or more lithologies.

15 . The method of claim 1 , wherein identifying the adjustment to the wellbore trajectory to stay within the target area includes optimizing reservoir contact between the borehole and a reservoir formation of the subsurface environment.

16 . The method of claim 1 , wherein receiving the resistivity data comprises receiving the resistivity data from a downhole logging while drilling tool via mud-pulse telemetry or wired-drill-pipe telemetry and further comprising transmitting the adjustment to one or more downhole tools using the mud-pulse telemetry or the wired-drill-pipe telemetry.

17 . The method of claim 1 , wherein applying the joint inversion includes applying the joint inversion simultaneously to the resistivity data, the synthetic resistivity data, and the seismic data.

18 . The method of claim 1 , wherein there is no distinct spatial division between effects of the resistivity data and the synthetic resistivity data.

19 . A system comprising:

a processor;

memory accessible to the processor; and

processor-executable instructions stored in the memory and executable by the processor to instruct the system to:

receive resistivity data acquired by a downhole tool of a drillstring disposed in a borehole in a subsurface environment, wherein the borehole comprises a downhole end, the borehole defines a borehole axis, and the resistivity data is collected uphole of the downhole end of the borehole;

generate, using at least a portion of the resistivity data, synthetic resistivity data for a region of the subsurface environment beyond the downhole end of the borehole;

receive seismic data for the subsurface environment, wherein the seismic data comprise spatial locations;

apply a joint inversion to at least a portion of the resistivity data uphole of the downhole end of the borehole, at least a portion of the synthetic resistivity data downhole of the downhole end of the borehole, and at least a portion of the seismic data to estimate values for physical properties of a portion of the subsurface environment that includes at least a portion of the region of the subsurface environment beyond the downhole end of the borehole;

based on the physical properties beyond the downhole end of the borehole, identify an adjustment to a wellbore trajectory to stay within a target area of the subsurface environment beyond the downhole end of the borehole; and

actuate one or more geosteering actuators to adjust a tool trajectory of the downhole tool according to the adjustment to follow the wellbore trajectory and stay within the target area.

20 . One or more non-transitory computer-readable storage media comprising processor-executable instructions executable to instruct a processor to:

receive resistivity data acquired by a downhole tool of a drillstring disposed in a borehole in a subsurface environment, wherein the borehole comprises a downhole end, the borehole defines a borehole axis, and the resistivity data is collected uphole of the downhole end of the borehole;

generate, using at least a portion of the resistivity data, synthetic resistivity data for a region of the subsurface environment beyond the downhole end of the borehole;

receive seismic data for the subsurface environment, wherein the seismic data comprise spatial locations;

apply a joint inversion to at least a portion of the resistivity data uphole of the downhole end of the borehole, at least a portion of the synthetic resistivity data downhole of the downhole end of the borehole, and at least a portion of the seismic data to estimate values for physical properties of a portion of the subsurface environment that includes at least a portion of the region of the subsurface environment beyond the downhole end of the borehole;

based on the physical properties beyond the downhole end of the borehole, identify an adjustment to a wellbore trajectory to stay within a target area of the subsurface environment beyond the downhole end of the borehole; and

actuate one or more geosteering actuators to adjust a tool trajectory of the downhole tool according to the adjustment to follow the wellbore trajectory and stay within the target area.