Complex Mountainous Area Of ​​china's Western Piedmont Zone Of Seismic Exploration Technology Research,

In the recent years, the improvement of equipment has expedited the development of seismic exploration technologies, enhanced the abilities to attack difficult exploration problems and accelerated the exploration pace. The prospecting has been extending into complex mountain areas. The discovery of Kela-2 and Dina-2 oil & gas fields in Chuche basin west China indicates that there is great potential in complex mountain areas.However, there are two main issues that hinder the seismic exploration. The first one is the complex surface conditions, for instance the rugged landforms, rapid lithology variations, outcrops with conflicting dip angles, or thick gravel layers. The second one is the complexity of the subsurface structures, say, deeply faulted or steeply dipping overthrusts, especially in Chuche basin. All these complicate the seismic wave fields, cause strong coherent noises and weaken reflections, and thus, make the seismic exploration a very difficult task. This paper presents key techniques related to the three most crucial factors that influence seismic data quality, namely, reflection energy absorption and decay, statics and coherent noises.The first part is about how to get sufficiently strong reflections in data acquisition. In the shooting aspect, the various factors related to excited energy, such as explosion mechanism, shooting lithology, shot depth etc., are studied. In the recording aspect, focusing on how to record as much as possible reflected energy and reasonably avoid the "seismic barrier', acquisition geometries including spread pattern, group interval and fold coverage are studied and with the help of a physical model, a reasonable and optimum acquisition geometry for a steeply dipping overthrust is designed. The second part is on the research of static correction methods. A reasonable near-surface model to solve long-wavelength statics problem is first built, then refracted first arrivals are used to compute relative statics to solve the field statics problem. We also developed a priory information constrain method and a 'scanning-style' priory information constrain method in tomographic statics inversion. These two methods give higher convergence speed and inversion precision and therefore, solved the problems in conventional tomographic statics inversion. The third part is the research on coherent noise attenuation. According to the variety of strong coherent noises in the data of west China, a 2-D data is processed as a special 3-D data. A 'point-by-point' auto-adaptive noise discrimination method was used to attenuate coherent noises in pre-stack 2D and 3D data. Real data examples are finally shown. The obvious effects show that the research results of this paper can effectively solve the crucial problems in the seismic exploration in complex mountain areas of west China.