The Applied Research Of Seismic Pre-stack Imaging Technique On Medium-deep Glutenite Body

Since 2005, many exploration wells such as Che66, Fengshen1, Yan22, Lishen1 and etc. in Shengli Oil Field have made major breakthrough in drilling and production test, which shows that the fan-shaped glutenite reservoir near the abrupt slope area in Jiyang Depression has great exploration potential. Early understanding of the glutenite depositional features were as follows: The glutenite body controlled by single boundary faulting became narrow in the lateral distribution due to the impact of the slope, and the conglomerate body was difficult to develop to the lake side, resulting in relatively low degree of prospecting. Now we have new understanding of the glutenite depositional features: With strong structural activities, adequate sources and bigger vertical thickness, the glutenite body was easy to be developed from the delta front slump. The reservoir space has been effectively improved, and the better physical properties make it easy to form a reservoir.Through forward modeling technique, we understood the seismic reflection characteristics of the medium-deep Glutenite body as follows: the internal reflection was disorderly and constantly changing, strong continuous or discontinuous reflection occurred on the top, the end and the front of Glutenite Body; The frequency is low and can be changeable with bad frequency stratification; Most of the glutenite accumulated under salt dome showed the reflection features of massive size, weak amplitude. Some of the continuous reflection is related to the depositional sand body from different times.In this paper, a dual-domain wave equation pre-stack depth migration method for solving inverse problems is based on commonly used perturbation theory. By using of this method, the wave field alternatively extends between space and wave number domain automatically in term of the non-uniformity of velocity field. This method combines Fourier transform method and finite difference method with their respective advantages, and can be adaptive to the complexity of medium. Wave travels freely in the wave number domain through a uniform medium with some sort of reference velocity. The reference velocity can change with depth with maximum angle up to90 o.The interaction between wave and the non-uniform medium in the space domain is carried out by modifying wave front. The method using dual-domain can greatly reduce the grid dispersion caused by numerical dispersion, and the calculation work in time - space domain is less compared with the finite difference migration technique. This method will significantly increase the adaptability to lateral velocity variation.In this paper, geologic and seismic data analysis especially for glutenite rock in the medium-deep zone has been conducted, and typical through-well cross sections have been selected for forward modeling. Based on this, specific processing study work has been carried out. Meanwhile, 3D seismic data processing technique has been used in around Fengshen1 well area. The application of the technique has further enhanced the imaging precision and resolution of the glutenite body in the medium-deep, and met the need of the glutenite reservoir description near the abrupt slope area in JiYang Depression.