PP and PS response from volcanic gas reservoirs

Nowadays multi-component seismic has gained more acceptance from the hydrocarbon industry than was the case several years ago. Nevertheless, the anticipated breakthrough into a mainstream technology is still to be realized. One of the bottlenecks is the lack of convincing data examples that demonstrate the full benefit of the technology. This is particularly true for land multi-component seismic. As a step towards filling this gap, we present a case study of using land PP and PS converted-waves for characterizing volcanic gas reservoirs in the Daqing oilfield, Northeast China. The Daqing oilfield is the largest producing oilfield in China and has been in production for more than 40 years. Shallow targets at depth of less than 2 km have largely been exhausted and the current focus is on exploring deep targets buried at depths ranging from 2800 m to 3600 m, which provide a good potential for reserve growth. These deep targets are mostly volcanic gas reservoirs, and often give rise to an incoherent P-wave response. Past multi-componentt seismic experiments reveal some potential to use PS convertedwaves to image these targets, but the results have been limited due to data quality issues. Recent advances in digital MEMS (micro-electro-mechanic-systems) sensors have rekindled interests in using converted-wave data to delineate the volcanic reservoirs in this area. Compared with conventional geophones, the MEMS sensors often have a lower dynamic range and wider bandwidth, giving rise to improved data quality. For this, a multi-component experiment was set up in 2005, and the results are presented in this paper.