Seismic Data Acquisition Theory And Practice In Complex Mountain Region

Mountain area, deep structure and carbonate lithology are three challenging but important targets for domestic and international oil and gas exploration. The studied areas in this thesis is from the middle uplift of Guizhou and the north-east of Sichuan basin. These are extremely difficult areas for oil exploration because they contain complex mountain regions, deep targets and carbonates at the same time.To meet the challenges in this region involves efforts in data acquisition, processing and integrated studies. This thesis focuses on data acquisition. The first step is to improve the quality of data acquisition. By improving the source and receiver conditions, we improve the resolution of seismic data and increase signal-to-noise ratio. A number of special techniques are developed through a great amount of theoretical studies and field tests. These techniques provide a great support for the discovery of Puguang gas field.Some of the theoretical and technical advances of this thesis include:1. The saturat exploding theory based on rock mechenics and rock physics. This theory is developed by studying the relationship between characteristics of seismic wavelet and the amount of dynamite and rock's elastic parameters. The theory is tested on both lab measurements and field experiments.The key points of the saturat exploding theory are: (1) The amplitude of seismic impulse is related to the strain of the nearby rock, and the amount of dynamite controls the stress of media. (2) The saturat exploding is the state that the media achieves maximum strain. (3) At saturat exploding state, the relation is linear and addition can be made.(4) At saturat exploding state, seismic impulse has the wide frequency bandwith and high S/N ratio.The saturat exploding theory has following impacts on high fidelity data acquisition: (1) The saturat exploding theory provides some guidelines for choosing optimal source parameters and matching group. (2) At saturat exploding state,the impulse has more high frequency and better S/N ratio. (3) It solves a theoretical issue about whether small amount of or large amount of dynamite should be used for high resolution seismic.2. Acquisition of high frequency seismic by putting sources and receivers in carbonate outcrops. This method is based on The saturat exploding and rock physics. The method has a great success in the middle uplift of Guizhou. A good image is obstained from the the middle uplift of Guizhou reflector. Overall, high quality interpretable seismic data are obstained in the region with carbonate outcrops by using this technique.3. Acquistion of high resolution and high S/N ratio seismic in complex mountain region based on the saturat exploding theory. The main frequency of the new seismic data is 50 Hz - a big improvement comparing with 30 Hz for the old data. Combining with high frequency processing, the main frequency can reach as high as 70 Hz at 2000 ms (about 6000 meter in depth).4.The prominent achievement of 3D seismic survey in city region was obtained by using the variational survey method combining regular with irregular survey. We compensated for excitation by increasing sources outside of city in order to increase the fold coverage and obtain...