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在日本石油公司柏崎试验区与 TRC-RW2井相距 200m的观测井中,利用井下三分量系统探测 TRC-RW2井的随钻地震信号。随钻探测到信号的信噪比约为 3dB左右。对这些三分量信号进行了移动主分量分析(MPCA),并估算了主震源的位置和地震信号的类型。MPCA的分析结果表明:主震源就是钻头,它持续激发纵、横波。三分量钻头震源 VSP(TAD-VSP)法已用于这些信号的处理,并对该区的地下构造进行解释。应用纵波推断的地下构造与TRC-RW2井的声波测井结果基本一致,并且也与日本石油公司所做的 SWD(随钻地震测量)结果相吻合,它揭示了在相对松软的地层中TAD-VSP法是可行的。
In the observation well at Nippon Oil Company’s Kashiwazaki test area and at a distance of 200 m from the TRC-RW2 well, the downhole three-component system is used to detect the seismic signals while drilling in the TRC-RW2 well. Signal-to-noise ratio of the signal detected while drilling is about 3dB. The principal component analysis (MPCA) of these three-component signals was performed and the location of the mainshock and the type of seismic signal were estimated. MPCA analysis shows that the main source is the drill bit, which continuously excites the longitudinal and transverse waves. The three-component bit vibroseis VSP (TAD-VSP) method has been used for the processing of these signals and the subsurface structure of this area has been explained. The underground structure inferred using P-wave is basically consistent with that of the TRC-RW2 well and also coincides with the results of the SWD (seismic-while-drilling) measurements performed by Nippon Oil Corporation, revealing that in relatively soft formations the TAD- VSP method is feasible.