Equipment QC approaches in land seismic acquisition

Steve Wilcox analyses the capabilities of the most popular land acquisition systems available today in terms of their ability to provide the observer with QC data. Since the introduction around 2003 of the first modern wireless land acquisition systems (see Panel 1), the market has seen a variety of different systems introduced with a blend of different features. Over the same time, the land seismic market in North America has also undergone a remarkable transformation, whereby the traditional telemetry cable-based systems have lost their dominant position, having been overhauled by the combination of various wireless solutions. In traditional cabled systems, the observer had a clear view of his task controlling the operation of the system. The status of the entire system was available to him in real-time, with QC data being transmitted from the field equipment via telemetry cable. He could see the condition of the batteries, and direct the crew to replace them as required; he could see with a high degree of confidence what wind or environmental noise the sensors were picking up; and above all he could immediately detect if sensors were out of specification or cables were damaged. Thus, he had all the information necessary to acquire good quality seismic data. The Achilles’ heel of the operations, of course, was the susceptibility of the telemetry cables to damage during operations and an alternative to these was long sought. The introduction of wireless systems removed the issues around cable-damage, and their success – reflected in their increasing dominance in the North American market – clearly shows that seismic contractors using them experience operational benefits in doing so. Figure 1 gives an illustration of the change in relative market share from 2007 to 2011, and indications are that wireless systems have further increased their market share since. There are, however, a number of differences in the capabilities of the different systems available, most especially regarding their provision of QC data to the system observer. Additionally, some systems have been developed to offer some of the advantages of both cabled and wireless systems, and it is the intention in this paper to address systems according to their capabilities rather than their data transmission medium.