Page 140 - Acquisition and Processing of Marine Seismic Data

2.6 QC IN DATA ACQUISITION 131

interpretation zone, which typically covers the implementations intend to remove the effects or
target structure in the subsurface. The whole any agents that may cause QC issues in the prod-
3D area is planned by the field geophysicists uct and to take the necessary precautions.
who actually design the complete survey and The quality control term in seismic surveys
determines the acquisition parameters, depend- comprises procedures and applications for anal-
ing on the requirements of the survey. Full-fold ysis and evaluation of the seismic data quality in
zone is handled by seismic processors to prop- each specific step, from data acquisition to inter-
erly migrate the data that involves the target pretation, to ensure the quality of the seismic
structure. Finally, the data in the target zone is data. It is classified as QC in data acquisition
ready for interpreters. and in data processing, and comprises a compre-
hensive documentation and reporting proce-
dure. QC analyses of seismic data acquisition
2.6 QC IN DATA ACQUISITION can be done in real-time and offline following
the acquisition. In this section, offline quality
By its general definition, quality control (QC)is control applications used on the seismic data
the process that defines how well the solution of a after it is acquired as well as documentation
problem is known, or how well the methodology and reporting in QC processes are discussed.
used to solve the problem is applied. QC work is QC assessments in seismic data acquisition
often pronounced with quality assurance (QA) comprise not only the analysis of the seismic data
implementations, which include a documented itself but also the navigation data, as well as the
and certificated management system of the sys- evaluation/analysis/recalibration of mobilized
tematic control process to prevent faults and instruments and seismic source performance
mistakesduringproduction andtocheckwhether tests, and periodic reporting of the QC analyses
the product meets the specified requirements and results (Fig. 2.82). The main purpose of the
of the work. As a general approach, QC applica- QC implementations in seismic data acquisition
tions aim to detect and eliminate the errors and is to evaluate the data quality onboard during
defects in the final product or data, while QA the acquisition, even in real-time if possible, to

FIG. 2.82 Responsibilities of onboard seismic survey crew in terms of QC applications for data acquisition.