Tang Donglei

A Wide Line Acquisition Case for Overthrust Nappe Structure of Kulong Mountain in Jiuquan Basin

Summary It is difficult to acquire an interpretable seismic data from the overthrust nappe structure of the Kulong Mountain, Jiuquan basin in western China, the main reason is the static problem from the complicacy of the topography and the near surface geology, ray distortion caused by the overthrust nappe and the weak reflection energy from the targets. But for the field acquisition, the side wave interference is the main reason of low S/N ratio. To overcome this difficulty, in 2001, we used wide line acquisition technique to suppress the side wave and accomplished huge success. Excellent data obtained prove the effectiveness for using the wide line acquisition technique in such complex area as Kulong Mountain, Jiuquan Basin.

Experiments using fan‐spread to determine limitation of geophone‐array elevation difference and applications

In the complex mountainous areas, there is severe scattered interference, so the seismic data have very poor S/N ratio. In order to suppress scattered wave in field, the geophone array with long array length is needed. In theory the limit of elevation difference within an array can be calculated , but in practice the velocity needed is difficult to be determined when calculating, so the accurate limitation cannot be determined. In this paper, a spread pattern by test and calculation method is proposed, and finally the practical limitation value is determined and a reference method for receiver’s array in complex mountainous areas is provided.

The Q-correlation Technique for Vibrator Acquisition Data

Summary In conventional vibrator data acquisition, correlation data is obtained by correlating the vibrating signal with the reference signal. This correlating method has difficulty with the propagation characteristics if sweep signal is not considered during the process of correlation. Because the filter effect of earth, sweep signal changes with propagation distance. Therefore a changing sweep signal instead of a vibrator reference signal is needed to perform the correlation with vibrator data. Earth absorption a 2D problem, so the absorption needs to compensate for two variables, time and frequency. The Q-correlation method proposed in this paper is for computing the amount of attenuation and generating a time-varying sweep signal according to the quality factor, Q, and then determines the vibrator correlation with the ability to compensate for absorption. When compared with conventional correlation, the Q-correlation arithmetic has obvious merits. Because the attenuation of earth is compensated for in the Qcorrelation method in the process of correlation and 2D is finished in time domain only, the data resolution is greatly improved, especially for weak signals with high frequency

The estimation of noise suppression of 3D recording geometry and its application

*Summary Using 3-D recording geometry can attenuate noise. Different geometries have different effects on noise suppression. At present, the popular estimation method for the noise suppression of 3-D recording geometry is qualitative analysis. The qualitative analysis can cause errors in a 3-D seismic survey design. In this paper, we present a quantitative parameter analysis method. First we compute the common midpoint (CMP) stack response of noise from the residual traveltime difference of the noise, and then average the CMP-stack response. Finally we estimate the noise suppression of the 3D recording geometry. According to the estimation of quantitative parameters, designers can make an appropriate choice from several 3D recording geometries. It is an efficient method for the optimization of 3D seismic survey design.