Lithofacies controlled geostatistical inversion of tight carbonate reservoirs in deep formation

Research Tasks:
The carbonate reservoirs in the study area are deeply buried. The reservoir heterogeneity is strong and it is difficult to accurately predict the reservoirs by interpreting conventional seismic properties, which seriously restricts the research work such as well replacement and follow-up drilling. The purpose of this project is to finely characterize the carbonate reservoirs in the study area through fine reservoir inversion technology.

Technological innovation points:
Key Technology 1 - Geostatistical inversion after removal of mud + lithofacies controlled poststack geostatistical inversion to improve the accuracy of reservoir prediction
Firstly, the results of post-stack inversion were combined with the fine adjustment of the formation tops on the well, combined with the characteristics of the resistance curve of the argillaceous limestone and with the clay content map, the attribute control was obtained. In addition, the background acoustic impedance of the whole region of the slurry response was obtained, and the acoustic impedance was used as a facies control condition to participate in the geostatistical inversion.
Key technology 2 - multi-seismic data prestack, poststack inversion, joint optimization of reservoirs
The inverted Vp/Vs ratio in this area display with good predictability compared with high-quality reservoirs. After multi-well statistics on production and oil test data, the pre-stack Vp/Vs ratio of the reservoir is generally high-yield layer when it is lower than a certain value, and vice versa. In this way, on the basis of the post-stacked acoustic impedance identified reservoir, the distribution range of high-quality reservoirs can be further identified by the pre-stack Vp/Vs ratio, which effectively guides the research work of well placement.

Results achieved: the results of the inversion before and after the mud removal of more than 90 wells in the whole region were counted in four strata sections and the reservoir coincidence rate reached 90%.