Yanpeng Li

A New Method For Converted Wave Statics Correction

Summary A new simple and effective shear wave static method is introduced, which is based on the time difference between the X component and Z component first break at same receiver. This time difference approximately is the time difference between P-wave and S-wave traveled in the weathering, and in combination with P-wave near surface model it can be used to remove the effect of weathering. Theoretical analysis has proved this method is feasible. Field data processing has given a perfect result.

Walkaway-VSP survey using distributed optical fiber in China oilfield

Distributed acoustic sensing (DAS) is a new type of replacement technology for geophysical geophone. DAS system is similar to high-density surface seismic geophone array. In the stage of acquisition, DAS can obtain the full well data with one shot. And it can provide enhanced vertical seismic profile (VSP) imaging and monitor fluids and pressures changes in the hydrocarbon production reservoir. Walkaway VSP data acquired over a former producing well in north eastern China provided a rich set of very high quality data. A standard VSP data pre-processing workflow was applied, followed by pre-stack Kirchhoff time migration. In the DAS pre-processing step we were faced with additional and special challenges: strong coherent noise due to cable slapping and ringing along the borehole casing. The single well DAS Walkaway VSP images provide a good result with higher vertical and lateral resolution than the surface seismic in the objective area. This paper reports on lessons learned in the handling of the wireline cable and subsequent special DAS data processing steps developed to remediate some of the practical wireline deployment issues. Optical wireline cable as a conveyance of fiber optic cables for VSP in vertical wells will open the use of the DAS system to much wider applications.

Robust three‐term AVO analysis and elastic parameters inversion

Amplitude versus offset (AVO) interpretation can be facilitated by cross-plot of AVO intercept (A), gradient (B), and curvature (C). It is theoretically possible to obtain the all attributes exactly. However, the method had a little success in practice because the high order coefficient C dominates the process as the critical angle is approached and has a poor S/N ratio (Swan, 1993). An alterative approach, which uses c to substitute and its high-order terms can make the reflection coefficients be controlled by the three new attributes simultaneously no matter in small angles, intermediate angles, or large angles (Sun, 2004a; 2004b). In this paper we investigate the rationality of the three attributes AVO as an indicator of the gas saturation in a reservoir. First, we discuss the relationships between the modified attributes and the characters of cross-plots for Castagna and Smiths (1994) worldwide examples. Consequently, by analyzing the 2D & 3D cross-plots of inverted AVO attributes for a real well log data, we highlight the advantages in robust three parameters inversion as well as in construction multiple cross-plots. The result also shows that the presented method would be more stable and less ambiguous in both fluid content detection and lithology discrimination than the traditional AVO cross-plots. os2i 2 sin i