The Prestack Seismic Prediction Of Tight Hydrocarbon-bearing Sandstone Reservoir

Tight hydrocarbon-bearing sandstone reservoir accounts of more and more proportion in China's proved reserves of crude oil and natural gas year by year. Tight sandstone reservoir with low porosity and low permeability also distributes in the major oil and gas blocks in China. Therefore, it is one of the most promising and important fields for exploration in the 21st century.For the weak relative changes in geophysical characteristics to different porosity and hydrocarbon saturation, effective prediction and hydrocarbon detection are very difficult for tight sandstone reservoirs. This paper bases on predecessors' work and the objective reservoir characteristics of Xujiahe group formation, carries out the processing system to maintain seismic data amplitude and seismic rock physics analysis, analyses hydrocarbon-bearing reservoir 's geophysical response characteristics, optimizes the effective elastic sensitive parameters, and then researches pre-stack inversion method by improved inversion algorithm and their application on tight sandstone reservoir prediction and hydrocarbon detection. Thesis main includes the following contents:1) The formation of Xujiahe group has the characteristics of thin layer and poor reservoir properties with secondary dissolution porosity. Effective prediction and hydrocarbon detection are very difficult for tight sandstone reservoirs. So, the paper pursuits the overall description and no longer rigidly adheres to the views of single thin layer identification accuracy.2) Based on the actual seismic data processing, this thesis detailed analyses the main factors which impact the seismic data fidelity, and put the new de-noising method according to the AVO attribution. The paper also forms a set of seismic data fidelity treatment system and key technology for maintaining amplitude accuracy.3) Thesis first time analyses hydrocarbon-bearing reservoir's geophysical response characteristics of tight sandstone reservoir, and launches forward modeling studies of tight sandstone reservoir based on logging data in site to explore the general laws of seismic response in different frequency bands. These laws are affected by different layer thickness, porosity and fluid saturation. That is to say, the paper researches the feasibility to predict effective reservoir and detect hydrocarbon in theoretical by using seismic data.4) Thesis first time establishes a set of seismic rock physics sensitivity parameters analysis system for tight hydrocarbon-bearing sandstone reservoir of the formation of Xujiahe group. It provides a technical basis for the rapid inversion of massive pre-stack seismic data.5) Thesis picks out the effective reservoir prediction technology of tight sandstone, such as lithology impedance-Vs impedance prediction technique, elastic impedance prediction technique. Thesis also picks out the effective hydrocarbon detection technology, such as elastic impedance prediction technique,λρinversion technique.6) Thesis first time creates a seismic rock physics board using the in suit logging data, and carries out the hydrocarbon saturation prediction. It should to be noted that the forecast result matches the characteristics of structure-lithology gas reservoir in whole.