![]() ![]() Well velocity survey provides more accurate velocities, but available only at the limited number of well locations. Obtained from well velocity surveys, or VSPįunctions used in the NMO-correction that was applied in the processing stage. There are two main sources for the velocity data for the surveyed area. Interval changes may indicate true thickness changes or velocity changes, which both can give significant geologic information. The produced time-interval contour maps correspond to the depth interval (or isopach) contour map. Another set of contour maps are also drawn for the iso-time intervals (time-interval between two adjacent reflectors). Is drawn to produce the isochron map which expresses the structural behavior of the reflector. ![]() The picked reflection values are posted onto the seismic lines at regular intervals, and then a contour map This problem, which may be due to anisotropy or other causes, needs special treatment to make the horizons at the intersections, to tie perfectly at intersections. In the process of tying horizons picked at intersecting sections, reflection times may not coincide. A common difficulty, met with, is the mistie-phenomenon. Care is needed to be taken when the reflectors are affected by faults. The process is carried out for the same horizon in all of the sections in the area. Reflection times of the reflection horizon are read (manually or electronically) by a process called (reflection picking This phenomenon (called phase difference) is taken into consideration when doing the stratigraphic calibration. This is due to the differences in the way the two types of data were recorded and processed. Sometimes it is found that there is some difference in time between the synthetic seismogram and the seismic section. To attach stratigraphic definitions to seismic reflection events, a synthetic seismogramįrom a near-by well, is computed. Reflection horizons are chosen based on their continuity and amplitude This is the initial stage in any seismic interpretation project. The standard sequence normally followed in seismic structural interpretation The standard sequence involves four main steps: reflection identificationĬomputations. In a procedure similar to that normally followed in the seismic data processing, interpretation is carried out by a sequence of steps, the interpretation sequence. The resulting maps (called isopach maps) are used in the studies of sedimentary environments, in sediment-source zones, and other geologic changes. Reflection time-intervals between two adjacent reflectors are computed and converted into thicknesses using the corresponding interval velocity ![]() In addition to geometrical shape of reflectors, another set of maps showing changes of formation thicknesses are calculated. (the time- and the depth-maps) are expected to show some dissimilarity. ![]() Due to the velocity vertical and lateral variations, the two contour maps ) which can be converted into depth structural map using the appropriate velocity field of the area. The interpreter usually produces a time-map (called time structural map, or isochron map The end result is presented in the form of a time (or depth) contour-map. For each reflector of the studied area, the three-dimensional structural picture is established. ), and plotting the values, relative to a defined datum level, along the seismic line. Essentially, this involves measuring the two-way vertical time at the CMPs of the stack This approach represents the conventional way of interpreting seismic reflection data that has been followed by most interpreters since the establishment of the seismic reflection method in the 1930s. ![]()
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