宽频激发技术在苏里格地区采集中的应用

Application of Broadband Excitation to Seismic Data Acquisition in Sulige Area

苏里格气田以低压、低渗透、低丰度为特征,是以河流砂体为主体的岩性气藏,其储层分布面积广,构造平缓(倾角小于1°),断层不发育,适合宽频激发技术应用。苏里格北部地区表层结构横向变化较大,试验证明该区单炮能量、频率、信噪比与是否在潜水面以下激发有直接的联系。近年通过加强对该区表层结构与潜水面关系的研究,在激发井深设计时不再单独依靠高速层顶来确定井深,而是根据潜水面与降速层顶、高速层顶的关系以及表层速度来确定激发井深,获得了能量、频率一致性较强、频带较宽的原始资料,取得了较好的地震、地质效果。

Sulige gas field is characterized by low pressure, low permeability, and low abundance. It is a lithologic reservoir dominated by fluvial sand bodies, with widely pool distribution, flat structure (the dip angle is less than 1°), but no development of faults. So it is suitable for the application of broadband excitation techniques. Surface structure of the northern area of the gas field varies a lot horizontally. Test shows that single shot energy, frequency, signal-to-noise ratio of the northern area is directly related to whether they are excited below the free surface. Based on reinforcing study on the correlation between the surface structure and free surface of the area in recent years, to design the excitation depth no longer relies on the high-speed layer top, but on the correlation between the free surface and the spin-down layer top and high-speed layer top, and the surface speed. Raw data featuring in high consistency of energy with frequency and broad band are obtained, and better seismic and geologic results are acquired.