S油田高89区块基于AVO属性的CO_2驱油波及范围地震监测

Seismic detection of the CO_2 flooding extent based on the AVO attributes in the G89 area in S oilfield,China

以S油田高89区块中、深层注气层段为研究对象,研究了基于AVO属性的CO_2驱油波及范围地震监测方法,将注入的CO_2看作是储层中的人造气藏,利用注气后采集的三维地震资料开展AVO属性特征研究,主要是利用敏感属性反演气藏分布,进而预测CO_2驱油波及范围。基于理论模型的研究表明,CO_2的注入可引起注气层段Ⅰ类AVO异常,梯度属性对孔隙压力及CO_2饱和度的变化最敏感;实际工区注气层段具有明显的Ⅰ类AVO特征,而非注气层段的储层和盖层均无明显的AVO异常。AVO异常与注气量或产气量存在一定的量化关系,这表明利用梯度属性可较好地反映中、深层注气层段CO_2驱油波及范围。高89区块注气层段中CO_2封存效果好,包含3个放射状CO_2波及环带,且与注气史具有良好的对应关系。

Based on AVO theory,the method of CO2 flooding extent detection has been studied taking the middle and deep beds in G89 of S oilfield as the research region.The injected CO2 can be regarded as an artificial gas reservoir formed in the reservoir.AVO attribute characteristics are studied using 3D seismic data collected after gas injection.The distribution of gas reservoir is retrieved by sensitive attributes,and then the range of CO2 gas flooding is predicted.The theoretical forward model proved that the injection in the reservoir can cause the class I AVO anomaly,and the attributes gradient of AVO is more sensitive to the changes of pore pressure and CO2 concentration.In the G89 area the reservoir with injected CO2 has the obvious I class AVO characteristics,while the reservoir with no injected CO2 and the caprock do not have the AVO anomaly.There is certain quantitative relationship be tween the CO2 injection and the AVO anomaly,which showed that using gradient attribute can better reflect the CO2 flooding extent in the middle and deep reservoirs.The resutt of the CO2 sequestration in G89 area is satisfactory,and there are 3 concentric circular ripple effects which has a good corresponding relationship with the history of the CO2 injection.