A method of well planning for obtaining hydrocarbons comprising: obtaining a three dimensional Earth model (100; 130; 300; 400; 600; 620; 640; 660; 700; 720; 730) representing a subsurface region; determining one or more reservoir targets (107a, 107b, 109a, 109b, 111a, 111b, 113a, 113b; 137a, 137b, 139a, 139b, 141a, 141b, 143a, 143b; 306, 307, 314, 315) within the 3D Earth model; creating a well plan to provide a fluid flow path from the one or more reservoir targets to a well pad (402; 702; 722); CHARACTERISED BY: defining one or more reservoir segments (106, 108, 110, 112; 136, 138, 140, 142; 305, 313; 405,407,409,411; 606, 608,610, 612; 626, 628, 630, 632) in the 3D Earth model, wherein each of the reservoir segments pass through at least a portion of one of the target reservoirs; evaluating the reservoir segments; and creating the well plan based on the reservoir segments to provide the fluid flow path from the one or more reservoir targets to a well pad (402; 702; 722) through the one or more of the reservoir segments, wherein evaluating the reservoir segments comprises: obtaining one or more of geographic data, geological data and seismic data (642, 644) associated with the subsurface region; comparing the one or more of geographic data, geological data and seismic data associated with the subsurface region with the reservoir segments to verify the reservoir segments; calculating a cost function for the reservoir segments; determining whether the calculated cost function is within a threshold; and updating the reservoir segments if the cost function does not satisfy the threshold. obtaining a three dimensional Earth model (100; 130; 300; 400; 600; 620; 640; 660; 700; 720; 730) representing a subsurface region; determining one or more reservoir targets (107a, 107b, 109a, 109b, 111a, 111b, 113a, 113b; 137a, 137b, 139a, 139b, 141a, 141b, 143a, 143b; 306, 307, 314, 315) within the 3D Earth model; creating a well plan to provide a fluid flow path from the one or more reservoir targets to a well pad (402; 702; 722); CHARACTERISED BY: defining one or more reservoir segments (106, 108, 110, 112; 136, 138, 140, 142; 305, 313; 405,407,409,411; 606, 608,610, 612; 626, 628, 630, 632) in the 3D Earth model, wherein each of the reservoir segments pass through at least a portion of one of the target reservoirs; evaluating the reservoir segments; and creating the well plan based on the reservoir segments to provide the fluid flow path from the one or more reservoir targets to a well pad (402; 702; 722) through the one or more of the reservoir segments, wherein evaluating the reservoir segments comprises: obtaining one or more of geographic data, geological data and seismic data (642, 644) associated with the subsurface region; comparing the one or more of geographic data, geological data and seismic data associated with the subsurface region with the reservoir segments to verify the reservoir segments; calculating a cost function for the reservoir segments; determining whether the calculated cost function is within a threshold; and updating the reservoir segments if the cost function does not satisfy the threshold. defining one or more reservoir segments (106, 108, 110, 112; 136, 138, 140, 142; 305, 313; 405,407,409,411; 606, 608,610, 612; 626, 628, 630, 632) in the 3D Earth model, wherein each of the reservoir segments pass through at least a portion of one of the target reservoirs; evaluating the reservoir segments; and creating the well plan based on the reservoir segments to provide the fluid flow path from the one or more reservoir targets to a well pad (402; 702; 722) through the one or more of the reservoir segments, wherein evaluating the reservoir segments comprises: obtaining one or more of geographic data, geological data and seismic data (642, 644) associated with the subsurface region; comparing the one or more of geographic data, geological data and seismic data associated with the subsurface region with the reservoir segments to verify the reservoir segments; calculating a cost function for the reservoir segments; determining whether the calculated cost function is within a threshold; and updating the reservoir segments if the cost function does not satisfy the threshold. obtaining one or more of geographic data, geological data and seismic data (642, 644) associated with the subsurface region; comparing the one or more of geographic data, geological data and seismic data associated with the subsurface region with the reservoir segments to verify the reservoir segments; calculating a cost function for the reservoir segments; determining whether the calculated cost function is within a threshold; and updating the reservoir segments if the cost function does not satisfy the threshold.