The 9C-3D Acquisition Technology and Its Application in Sanhu Area

Abstract

AbstractThere is great potential for natural gas exploration in the Sanhu area, Qaidam Basin, so several rounds of P-P wave and P-SV wave survey have been carryout out there, but no substantial breakthroughs were made for imaging difficulties of low-relief structures due to the presence of gas. The first P- and SH-wave joint high-density wide-line 2D survey was carried out in the area in 2017, when high-quality broadband SH-wave data was obtained. After the performance of shear wave vibrators improved and upgraded in 2019, The P-, SH- and SV-wave joint 9C-3D acquisition test was carried out and its technical feasibility is further explored in the area. In the project, the following key techniques are used: 1) The P-wave, SH-wave and SV-wave joint excitation technology is to improve the S/N ratio of the raw single shot record in the gas-bearing “Gas Cloud Area”; 2) the small group interval and high density uniform sampling 3-D geometry design is used to increase the spatial sampling density in the lateral direction of the target layer and improve the imaging S/N ratio of the target layer; 3) we researched and developed source azimuth inspection and recording device on account of navigation system, and the device is used to accurately record the shear wave vibrator excitation angle which provides reliable basic data for the subsequent polarity correction processing of shear-wave raw shot records. Through the implementation of the 9C-3D acquisition technology, high-quality P-wave, SH-wave and SV-wave seismic datum are obtained in Sanhu Area. The SH-wave and SV-wave datum eliminate the influence of gas clouds. Its imaging have an absolute advantage over P-wave in truly reflecting the low-relief structure feature of the target layer.KeywordsSanhu area9C-3DHigh density 3DP waveSH waveSV wave