Detection of gas reservoirs by the joint use of P- and PS-waves: A case study on the Ordos basin, China

• 来源期刊: 地震学报（英文版）
• 学科: 地球科学
• 年，卷（期）: 2009,（3）
• 页码范围: 307-313
• 页数: 7页
• 分类号: P315.63
• 语种: 英文
• DOI: 10.1007/s11589-009-0307-8

摘要

We present an example of using converted-waves for characterizing onshore gas reservoirs in the Ordos basin in Northwest China. The Ordos basin is the largest gas province in China. The main gas reservoirs (about 3 300 m in depth) are in upper Paleozoic sandstone that has low or reversed P-wave impedance and is immediately above a coal seam. This makes it very difficult to image the gas reservoirs using conventional P-wave data. Analysis of core, log and VSP data shows a weak PP reflection but a relatively strong PS-converted wave reflection, or both strong PP- and PS-reflections but with opposite polarity from the gas bearing sands, which indicates the potential of using PS-waves to image the gas reservoirs in the Ordos basin. Subsequently, thirteen seismic lines were acquired, processed and interpreted to verify the PP- and PS-responses, and two corresponding attributes (PP- and PS- amplitude ratio and polarity ratio) are used to map the reservoirs through joint PP and PS analysis.