Geophysics Presentation Summary the Process

Geophysics Presentation Summary

The process of working up a prospect generated from seismic data collected entails six principal elements: (1) Acreage lease amount, (2) Acreage price, (3) Drilling location, (4) Platform erection cost-benefit analysis, (5) Platform location, and (6) the number and location of individual wells.

Identifying prospects from seismic lines is typically a matter determined by the apparent presence of bright spots, structural highs, fault or salt traps, nearby well control, prior experience in the same area, and geological knowledge. In prior eras, creating a seismic map was executed by picking a seismic line location on a base map, viewing the seismic line, and zooming in. Then, the interpreter must decide what to map based on bright spots, nearby well control, knowledge of local geology, and continuity and relative ease of mapping. That traditional method relied on event tracing using colored pencils. More specifically, whether by pencil or modern computer mouse, the interpreter perpendicular identifies seismic lines, extending those picks as far as possible in both directions, monitoring progress by a map view, and picking every tenth line while taking care to maintain consistency. Holes must be filled by one of three possible methods: (1) Picking every line, (2) Grid, and (3) Auto-track. Gridding is an algorithmic method based on estimating missing picks according to the known value of actual picks. Among the potential complications are ambiguous data, poor data, and phantom horizons.

Identifying seismic prospects the modern way involves the volume interpretation processes based on computer-based 3-D displays. The primary tool in those processes is auto-tracking, based on one or more initial interpreter picks. The computer extends those picks as far as possible. The cleaner the data, the fewer picks necessary. Cross-correlation allows us to determine whether adjoining traces are sufficiently similar to calculate accurate picks. Traces are first converted to number arrays and neighboring traces are compared according to gated sections. The addition of sample-by-sample multiplication generates a single number plotted at the gate center. The same process is repeated for successive gates. The cumulative process allows the generation of a cross-correlation. Time shift is determined by the largest positive value, which also corresponds to the numerical similarity of any two traces.

That process is followed by determining the maximum advisable price. That figure is generated by the total hydrocarbon value minus their total development cost multiplied by the probability of success. A first well (Well a) must be drilled to determine the presence of hydrocarbons. If Well a yields hydrocarbons, a second well (Well B) is drilled to determine the downdip limits of the reservoir and provides both volumetric estimates and the presence or absence of an oil rim.