Broadband Ultra-high Resolution Seismic Technology And Characteristics Of Channel Sand Bodies In Sartu Oilfield, Songliao Basin
Authors: Zishun Li , Xuebin Guo , Hao Li , Xingcai Fan , Li Bao , Chaonian Si , Shunguo Cheng , Haibo Mao , Long Pan , Guo Li 
Published: February 2025

The Daqing Sartu Oilfield in China has entered a high water cut development stage, with a structural area of 500 square kilometers and remaining oil reserves of 1.5 billion tons. The sandstone reservoir in Sartu Oilfield is thin, with a general single-layer thickness of 2-3m and a maximum single-layer thickness of 12m. It is difficult to identify and predict sandstones and compare small layers between wells using low frequency seismic data.

For conventional low-frequency seismic high pass filtering analysis, it was found that high-frequency signals above 200Hz have a high signal-to-noise ratio. For shallow small-scale VSP data analysis, it is believed that high-frequency attenuation of seismic waves mainly occurs in the shallow layers. Applying a broadband high-resolution seismic method with invention patents, extracting high-frequency attenuation parameters of seismic waves from direct waves of shallow small-scale VSP data, deconvoluting ground seismic data, restoring high-frequency attenuation of seismic waves, and obtaining broadband high-resolution seismic data. Calculate the thickness of thicker channel sand bodies using the time difference method.

The main frequency of the surface broadband ultra-high resolution seismic in the Sartu Oilfield is 170Hz, with the resolution increase of over 300%. The main frequency of the surface broadband ultra-high resolution seismic in Sichun basin is about 300Hz, with the resolution increase of over 800%. The standard for broadband ultra-high resolution seismic is sedimentary lens imaging, which means that the thickness changes of small layers or small layer groups are clear. For the first time, the lens like structure characteristics of the thick channel sand body in the Sartu oil layer and the reflection wave characteristics of the riverbed have been discovered. The riverbed is a major geological event similar to a fault, and it is particularly important for small layer comparison. The seismic reflection waves inside the river sand body are intermittent, with strong and weak, reflecting the changes in the interlayers in the sandstone. For the first time, a typical highlight feature of channel sand oil and gas reservoirs in the Sartu oil layer was discovered - strong reflection of dipole phase waveforms. Consistent with the typical bright spots of marine thick oil and gas reservoirs abroad. This achievement has broad guiding significance for the exploration and development of high-quality thin layer reservoirs with low acoustic impedance and bright spots. For the first time, the time difference method was used to calculate the thickness of thicker channel sand bodies. The thickness chart shows that the planar characteristics of the channel sand bodies in the Sartu oilfield are strip-shaped and lumpy. The ultra-high resolution seismic provides an important basis for the comparison of small layers in oil fields, and is of great significance for the study of remaining oil distribution in oil fields.