深部热储层弱地震信号采集技术研究

A Study on the Acquisition Technology for Weak Seismic Signals from Deep Geothermal Reservoirs

摘要: 我国地热资源丰富，分布范围广泛，经过多年持续勘探开发，浅部地热资源大多已探查完毕，目前探查目标以深部地热资源为主。在众多地球物理勘探方法中，地震勘探是地热资源勘探开发最有效的手段。受深部热储层地震地质条件影响，地震反射信号弱，信噪比低，热储层成像效果差，制约了深部地热资源的开发利用。本文通过对热储层地球物理特征的分析，认为热储层与盖层间强波阻抗界面的屏蔽作用、热储层内部较小的反射系数以及热储层中的热液、蒸汽等高温流体对地震波严重的吸收衰减是造成深部热储层地震反射信号弱的主要原因。提出了一套以高精度可控震源低频激发、高灵敏度检波器长排列接收、小面元高覆盖等技术为主的地震资料采集技术，应用到青海共和盆地干热岩地震采集中，取得了很好的应用效果。

Abstract: There are rich geothermal resources widely distributed in China. After years of continuous exploration and production, most of the shallow geothermal resources have been explored. At present, the exploration mainly focuses on deep geothermal resources. Among many geophysical exploration methods, seismic exploration is the most effective means of geothermal resource exploration and development. The weak seismic reflection signal, low S/N ratio and poor imaging of thermal reservoirs due to their seismic geological conditions restrict the production and utilization of deep geothermal resources. Based on the analysis of the geophysical characteristics of the thermal reservoir, it is concluded that the main reasons for the weak seismic reflection signal of deep thermal reservoir are the shielding effect of the strong wave impedance interface between the thermal reservoir and the cap, the small reflection coefficient in the thermal reservoir and the serious absorption and attenuation of the seismic wave by the high temperature fluids such as hydrothermal fluid and steam in the thermal reservoir. A set of seismic data acquisition techniques based on high precision vibroseis, low frequency excitation, high sensitivity geophone, long array receiving, small surface element, high coverage and other technologies are put forward, which has been applied to the dry hot rock seismic acquisition in Gonghe Basin, Qinghai Province, and achieved good application results.