湘西碳酸岩山区页岩气地震勘探采集技术研究

Study on Shale Gas Seismic Prospecting Data Acquisition Technology in Western Hunan Carbonate Rock Mountainous Region

湖南湘西碳酸盐岩山区不同时期灰岩出露,岩性变化较大,且受风化、淋滤、剥蚀作用,溶洞、裂缝十分发育,导致地震波能量衰减严重,且地震波传播路径和地震波场的复杂,地震原始资料信噪比较低。针对上述问题,采用单/双井微测井相结合的精细浅表层结构调查方法,结合药柱长度和爆炸理论计算出的爆炸半径,动态设计井深激发方式。通过室内模拟计算,研究低频检波器多串、线性等组合接收方式在区内压制面波、折射波、多次折射及侧面波等多波干扰的效果,最终选择2串24个检波器等灵敏度组合及小道距、高覆盖观测等关键采集技术。实践表明,该区选择的观测系统较好的克服了南方岩溶地区地震勘探信噪比低的问题,具有极强的推广价值。

The outcropped limestone of various periods in carbonate rock mountainous region, western Hunan, their lithology varies greatly. Because of weathering, leaching and denudation, bring on karst caves and fissures well developed, thus result in serious attenu- ation of seismic wave energy, as well as complex wave propagation path, rather low original data signal to noise ratio. In allusion to above issues, using single/double well micro-logging adjoined precise near-surface structure examination combined with seismic charge column length and explosion theory calculated explosion radius, dynamically designed well depth and shot mode. Through in- door simulation, studied low-frequency geophone multiple strings, linear array receiving and the like modes to suppress multi-wave in- terferences from ground roll, refraction, repeated refraction and lateral wave in the area, finally selected key acquisition technologies of 2 strings, 24 geophones equal sensitivity array and small group interval, muhifold observation etc. Practices have demonstrated that field setup selected for the area has overcome low signal to noise ratio in seismic prospecting in southern karst regions better, so it is in possession of strong popularization value.