井间地震观测系统设计——以垦71区块为例

Crosswell seismic observation system design

垦71区块存在低序级断层组合关系不明、剩余油分布不清、油水关系复杂及储层较薄且多等问题,并且纵、横向变化大,为此,利用井间地震技术研究该地区的低序级断层及储层特征。首先根据实施井间地震工区的地质模型建立速度模型,然后依据设计的观测系统进行正演模拟,模拟的波场反映了井间地震的主要波场特征,反射波成像剖面反映了地质模型的地质特征。依据设计的观测系统进行野外作业,实际资料的反射波成像剖面分辨率较高,落实了井间的低序级断层以及薄储层特征。通过对正演模型模拟数据以及垦71区块实际资料的处理分析,对井间地震的观测系统设计有以下认识:①炮点距及检波点距应满足两井之间纵、横向分辨率的要求,3m左右为宜;②反射角度的范围根据该地区的地质特点以及采集仪器的特点确定;③根据目的层段的深度范围确定覆盖次数。

The Ken 71 Block has unknown low-order fault complex relation, unknown remaining oil distribution, complex oil-water relation, thin and multiple reservoirs and varies greatly in horizontal and vertical direction. Therefore, the low-order fault complex and reservoir characteristics in the area are researched by crosswell technology. Firstly, the velocity model is established by the geological model of the crosswell seismic working area. Secondly, the forward modeling is done according to by the designed observation system. The modeled wave field reflected the main wave field characteristics of the crosswell seismic, the reflected wave imaging profile reflected geologic characteristic of geologic model. The field operation was done based on the designed observation system, the resolution of the reflected wave imaging profile of the real data is high, and the characteristics of the low order fault complex and the thin reservoirs cross wells were ascertained. By the processing and analysis of the forward model modeling data and the real data from Ken 71 faults, the conclusions for the observation system design of the crosswell seismic are： 1） The shooting distance and geophone interval should meet the requirements of the horizontal and vertical resolution between the two wells, 3m is suitable. 2） The range of the reflected angle should be ascertained based on the areal geology and acquisition instrument features. 3） The fold should be ascertained according to the depth interval of the intended interval.