Research And Application Of Cross Well Seismic

The cross well seismic technology have been applied to ignite and receive inside the well, therefore, it overcame the effects of low weathering layers and increased the resolution by the scale of 10-100 times. This technique is capable of delineate the minimum sedimentary unit of the oil-bearing body and resolve the issues like: reservoir interconnection, dynamic monitoring and micro-structural description etc. In addition, it also provides the fine geological model for reservoir modeling and scientific evidence for the oilfield development plan designing. In this paper, the author explains the cross well technology series that suits for the Bohai Bay Area that combines oilfield production with cross well seismic acquisition, processing and result analysis, therefore, a key technical method was provided for oilfield development in EOR and determination of residual oil distribution.The precondition for processing cross-well seismic data is that to perform the original data analysis thoroughly and determine the various waveforms and wave field as well as using the effective way to boost the direct arrival and reflection and suppress the disturbances and other noises.Basically, the cross-well seismic data processing has two steps: traveltime velocity inversion tomography for direct arrival and seismic reflection stack image. The SIRT inversion operator can be applied to solve the large-scale sparse linear equation and velocity tomographic inversion can be performed based on direct arrival traveltime and accuracy could be 3 meters. The least square conjugate gradient and odd values decomposition method also can be used to perform tomographic inversion. The least traveltime ray tracing method can greatly reduce the amount of calculation for tomographic inversion and increase the accuracy for ray tracing. The important method to do the cross well seismic reflection image is XSP-CDP algorithm. The key to enhance the image quality is to separate the reflection that has high signal to noise ratio and the scope of stack can defined optimally by common-angle gathers. The processing results of velocity tomographic section and image section of reflection in depth domain has provided encouraging geological results in the areas of Shengli Caoqiao, Yong An, Luo Jia, Wen Liu of Zhongyuan Oilfield and Ba Mian He of Jiang Han Oilfield.The cross-well seismic forward modeling program can be applied to geologicalmodel that has different velocities and dips to calculate cross-well seismic synthetics for given sources and receivers by ray tracing the least traveltime or four order differential wave equation. In doing so, we will not only have the correct understanding of reflection in real seismic data but also they can be used to guide the design for cross-well seismic field data acquisition.We have imported some state-of-the-art equipments such as: high-frequency Vibroseis and multi-level geophones for field data acquisition. By doing so, we have acquired high-quality seismic data with high sample rate, high signal to noise ratio and high frequency content.In the area of interpretation, it is important to fully understand the characters of kinematics and dynamics for various wavefields for cross-well seismic data and to perform fine resolution calibration on cross-well seismic sections as well as complete synthetic logs in depth domain. Then, we have defined the geological meanings to each reflection sets and a preliminary interpretation method has been set up.