Shallow Gas determination, prior to drilling, is carried out using 'Engineering Seismic' survey methods. Seismic acquisition data quality is fundamental in achieving this objective as both the data processing methods and interpretation accuracy are subject to the quality of the data obtained. The recent application of workstation based data analysis and interpretation has clearly demonstrated the importance of acquisition data quality on the ability to determine the risks of gas with a high level of confidence. The following pages summarise the 5 primary issues that influence acquisition data QC, suggests future trends and considers their potential impact. The primary issues covered in this paper are: A. Seismic B. Positioning C. QC Data Analysis D. Communications E. Personnel 90 SAFETY IN OFFSHORE DRll.LING FIELD QC ...................... PRIMARY COMPONENTS COMMERCIAL TECHNICAL 1 OPERATIONAL FIGURE 1 HYDROSEARCH The often complex influences of Technical, Commercial and Operational constraints on the acquisition of high quality data require careful management by the QC supervisor in order to achieve a successful seismic survey data set. The following pages only consider the Technical aspects of QC and assume that no Commercial or Operational restrictions are imposed in the achievement of optimum data quality. It is noted however, that such restrictions are frequently responsible for significant compromise in data coverage and quality during routine rig site surveys.

I - Introduction.- 1 Current Drilling Practice and the Occurrence of Shallow Gas.- 2 Shallow Gas and Gas Seepages: A Dynamic Process?.- II - Acquisition.- 3 High Resolution Seismic Source Specifications Applications and Misapplications.- 4 Enhanced Seismic Methods for Marine Hazard Surveys.- 5 Field Quality Control of Marine Data Acquisition - Past, Present, Future.- III - Processing, Analysis and Interpretation.- 6 Processing Procedures for High Resolution Seismic Data.- 7 Shallow Gas Detection Using AVO Processing of High Resolution Seismic Data.- 8 Shallow Gas Reservoirs and Migration Paths over a Central North Sea Diapir.- 9 Philosophy of Advanced Interpretations.- 10 Signature - The Future Approach to Reliable Shallow Gas Detection.- IV - Application of Geophysical Data.- 11 Prediction of Shallow Gas From Seismic Data.- V - Procedures, Regulations and Guidelines.- 12 Quantitative Gas Hazard Analysis: Present Limitations and the Way Forward.- 13 UKOOA Recommended Procedures for Mobile Drilling Rig Site Surveys (Geophysical and Hydrographic) - Shallow Gas Aspects.- Rapporteur's Summary.