Changes

The geometry of the field is defined by a series of structure contour maps of key reservoir horizons ([[:Image:Drive-mechanisms-and-recovery_fig3.png|Figure 6a]]). The maps, showing several levels through the prospect or reservoir, are generated from well elevations of reference beds or depth-converted seismic sections (see [[Subsurface maps]]). Workstations for three-dimensional [[seismic interpretation]] considerably aid the process because the shapes of the structure contours and the faults are readily observable on horizontal seiscrop sections generated by the workstation (Brown, 1986). Contour maps can be quickly generated from stacked seiscrop sections.

The geometry of the field is defined by a series of structure contour maps of key reservoir horizons ([[:Image:Drive-mechanisms-and-recovery_fig3.png|Figure 6a]]). The maps, showing several levels through the prospect or reservoir, are generated from well elevations of reference beds or depth-converted seismic sections (see [[Subsurface maps]]). Workstations for three-dimensional [[seismic interpretation]] considerably aid the process because the shapes of the structure contours and the faults are readily observable on horizontal seiscrop sections generated by the workstation (Brown, 1986). Contour maps can be quickly generated from stacked seiscrop sections.

[[File:Drive-mechanisms-and-recovery fig3.png|thumbnail|'''Figure 6.''']]

[[File:Drive-mechanisms-and-recovery fig3.png|thumbnail|'''Figure 6.''' a) Structure map and b) restored structure map showing fault gaps removed. Remaining gaps and overlaps in the restored faults represent geometric incompatibilities in the interpretation. (From Galloway et al., 1983.)]]

Faults must be located in wellbores by omission (extension fault) or repetition (reverse fault) of stratigraphic section. These are defined on the electric logs by repetition or omission of parts of the SP and gamma ray signatures compared to a reference well that is believed to show an unfaulted section. Fault map trends and dip direction can also be defined by SCAT dipmeter analysis or on the stacked three-dimensional seiscrop sections. Generally, fault cuts have to be correlated from well to well to define the dip and curvature of the fault. Once these are estimated, fault contour maps can be generated by contouring the subsurface elevations of the fault cuts or, more directly, on the seismic workstation by stacking the seiscrop sections (Brown, 1986). The faults will offset the reference beds, and the amount of offset in section and map view must be estimated. Once the separation is known, a separatin surface can be projected along the fault retaining the same trend, but adjusted in value by an amount appropriate for the offset on the fault (see [[:Image:Drive-mechanisms-and-recovery_fig3.png|Figure 6a]]).

Faults must be located in wellbores by omission (extension fault) or repetition (reverse fault) of stratigraphic section. These are defined on the electric logs by repetition or omission of parts of the SP and gamma ray signatures compared to a reference well that is believed to show an unfaulted section. Fault map trends and dip direction can also be defined by SCAT dipmeter analysis or on the stacked three-dimensional seiscrop sections. Generally, fault cuts have to be correlated from well to well to define the dip and curvature of the fault. Once these are estimated, fault contour maps can be generated by contouring the subsurface elevations of the fault cuts or, more directly, on the seismic workstation by stacking the seiscrop sections (Brown, 1986). The faults will offset the reference beds, and the amount of offset in section and map view must be estimated. Once the separation is known, a separatin surface can be projected along the fault retaining the same trend, but adjusted in value by an amount appropriate for the offset on the fault (see [[:Image:Drive-mechanisms-and-recovery_fig3.png|Figure 6a]]).