SEISMIC METHODS 915 



6. If field shutdowns are frequent, determine cause and take steps to remedy 

 situation. 



7. Examine records frequently for quality. Carefully examine all sections for 

 conformation of dips. 



8. If records are poor, consult with party chief and supervisor to determine 

 reason. If not the result of poor equipment, improper technique, weathering 

 or surface conditions, poor records are very significant because tliey usually 

 have geologic reason. A no-record (NR) hole or a lack of continuity in 

 records may be of utmost importance if due to some geological condition, such 

 as a fault zone, etc. 



9. Discuss method of weathering and elevation corrections. Determine whether 

 corrections are being made to sufficient depth. Estimate the limit of error in 

 work. 



10. Determine whether all possible reflections or refractions are being obtained, 

 by judicious use of filtering, etc. 



11. Assist in securing velocity surveys from wells in the area. 



12. Remember that there are very few areas in which there has been much explo- 

 ration activity where the roads have not been thoroughly worked by numerous 

 crews. Therefore, if you expect to find anything new, get off the roads unless 

 you are in areas of difficult transportation. 



IV. Integration (after reports are submitted by the geophysicists) 



1. Recontour the maps, using all available geologic data. Apply data to beds 

 above and below. Velocities may be ofif. Reflections have no labels. Carefully 

 examine all maps made on phantoms. 



2. Construct isopach maps of all critical intervals, particularly from the shallow- 

 est to deepest reflections, to avoid anomalies resulting from weathering. The 

 use of uncorrected time values often is preferable. Such maps may suggest 

 areas for further work or erroneous structural interpretations. 



3. Carefully examine cross sections for continuity and to see where dips fail to 

 conform. If dips do not conform, possible explanations should be considered. 

 Be certain dips have been migrated in steep dip areas. 



4. Read the geophysical report carefully. Look for qualifications therein. Keep 

 an open mind because your preconceived ideas of the subsurface might be 

 wrong. Be willing to accept new, unique, and unconventional ideas. 



5. Appraise the reliability of the work; analyze the results carefully to deter- 

 mine whether or not more work is necessary. Then assign the geophysical 

 records their value in the overall geologic setting. Be certain all useful data 

 on records have been utilized. 



6. Make a recommendation for future exploration based on a careful integrated 

 analysis of the geology and the geophysical work. 



7. Select areas of interest in which additional work may be desirable. 



V. Review 



1. If prospect has been drilled, review the geophysical work in light of informa- 

 tion furnished by drilling of the test well, whether productive or dry. If there 

 are discrepancies, attempt to reconcile them in order to clarify the geologic 

 picture. 



2. Request review of seismic data if such action appears desirable. 



3. Post all current well data and geology on the geophysical maps. If reinterpre- 

 tation of the geophysical data appears desirable, request the necessary geo- 

 physical assistance. All data should be reviewed whenever new information 

 becomes available. 



4. The construction of a composite map showing the geophysical profiles or con- 

 tours and the geology as developed by wells, etc., may be of considerable 

 benefit. 



