Research On Key Technologies Of High-precision Seismic Exploration In Liaohe Oilfield Land-water Transition Zone

Land-water transition zone includs paralic zone and onshore transition zone (water network area). This paper studies the key technologies of high-precision seismic exploration in land-water transition zone in the Liaohe Basin. In field seismic data acquisition, as a result of complex surface structure, different stimulating lithology and different geophone characteristics, the seismic wavelets from the land, marshes and water are different, and the data has different qualities and inconsistent phase, and in the transition zone because of profiles with the poor continuity of event, low signal to noise ratio, low resolution, imaging difficulties and changed structural shape, the dynamic characteristics of reflection wave field can not be used directly in reservoir inversion and hydrocarbon prediction. Conventional surface structure investigation techniques can not be carried out in the water network area, resulting in lack of clear understanding of the surface structure, making static correction inaccurate and residual static correction difficult to achieve. Second, the conventional wavelet approach can not correct the differences brought by excitation and reception, or even creates a false impression, which will lower the resolution. At the same time, the complex characteristics of underground structure make conventional stack and post-stack migration methods can not accurately imaging.Based on the geological and geophysical characteristics of complex land-water transition zone of Liaohe oilfield, this paper systematically carries out research on key technology of high-precision seismic acquisition and data processing, and a set of technology suitable for the land-water transtion zone is formed.(1) Research on fine survey methods of complex near-surface characteristics. With the conventional investigation methods of the surface structure is limited, the underground structure can not be learned more about. In the investigation of complex surface structure, the one-time molding cables are used for micro-logging surveying, and the well depth is designed point by point, and the results are explained by the software. So the surface rocks partition can be divided in details, and the tomographic imaging techniques are used to solve the near-surface model structure, which provids detailed information for the fine static correction. And the statics is calculated using a database-based refraction method to static correction on 3-D shot point and detection point, residual statics is acquired according to velocity analysis iterations to do residual static correction.(2) Technology of high-precision seismic acquisition. For the special surface conditions of land-water transition zone, the optimal excitation lithology, depth combined excitation have been researched, according to the near-surface survey data. By studying the special surface structure of transition zone, different types of geophones are used to receive. For difference of data caused by different geophones, the anti-combined filtering is studyed to reduce this difference and improve the resolution.(3) Research on surface consistent processing technology. Surface consistent processing usually refers to the consistency processing of the amplitude, frequency, phase and so on, which includes surface consistent phase correction, surface consistent amplitude compensation, surface consistent amplitude correction, surface consistent wavelet processing techniques. Due to the large lateral changes of the complex surface, the energy and frequency between sources and traces in different parts vary much, and consistency is terrible. Using surface consistent amplitude compensation processing technology on the one hand can eliminate this difference, on the other hand, may also have significant suppression effects to wild value. Application of surface consistent deconvolution (common source points,common receiving points) technology is able to compress the wavelet and eliminate the surface factors impact on the amplitude, wavelet, and improve the quality of profiles. In the complex surface areas, the results of single-channel deconvolution (such as pulse, predictive deconvolution) are unsatisfactory usually, mainly because in the auto-correlation time window, each trace contains different proportions of interference (such as wild value, surface wave, etc.), resulting different auto-correlation function and different deconvolution operators among traces, as a result, the results of deconvolution filtering vary considerably. Surface consistent deconvolution processing can compensate for the deficiencies of this single-channel deconvolution and get better processing effect.(4) Research on high-fidelity noise suppression technology. The very complex surface conditions in land-water transitional zone area, underground fracture, and the development of small structure, make the seismic data have low signal to noise ratio and low resolution features. By studying the characteristics of various de-noising methods, and analyzing the processing results of actual data, and selecting the appropriate method of noise suppression, we can achieve the suppression and attenuation of high-fidelity random noise, regular noise, and improve the signal to noise ratio of seismic data in land-water transition zone.(5) Research on high-precision seismic wave imaging technology. As the regional structure is complicated and the longitudinal and lateral velocity change rapidly, the pre-stack time and depth migration is very difficulty to be applied. In response to these characteristics, the research based on the curved-ray amplitude-preserved pre-stack imaging technology is proposed. Through the actual processing analysis and study, a suit of modeling methods suitable for complex structures areas is obtained, that is "time domain interpretation-depth domain model-depth domain explanation " double domains interface cyclical iteration, and the initial velocity-depth model is established, so that pre-stack migration imaging achieves good results.Based on the above research results, high-prcision acquisition and processing is carried out in water network area of Liaohe Oilfield, as a result,the quality of data in land-water transition zone is proved and the imaging precision is raised, Only in the Damin tun area 67 new traps is found, the total area of traps is 213.6km2.More than one hundred tons of oil has been reserved in many drilling, such as shen 625, shen 229, shen 629, shen 262.etc.The outturn of crude oil is maintain the leave of 1.26x 106t. The better economic and society benefit has bee got.