Reservoir Modelling in the Shale Gas Reservoirs Based on Horizontal Wells and Seismic Inversion

Abstract

The seismic vertical resolution is too low to identify the vertical boundary and petrophysical properties of the thin shale layers inside the target precisely. This study focuses on structural and petrophysical modeling of shale reservoirs based on horizontal wells and seismic inversion. Combined seismic trend surface with the well tops on horizontal wells, we calculated the top and bottom surface of the target formation, and obtained the structural surface of each small layer according to the thickness percentage of each layer from few vertical wells. Ultimately, the structural model is made. The horizontal trend of the petrophysical properties can be controlled by the seismic inversion results. The vertical trend of the petrophysical properties can be controlled by well logs. Constricted by the linear combination weighting of the horizontal and vertical trend, the petrophysical model is established. The results show that the trajectory of the horizontal well in the target layer is accurate, and the layers are not intersected. The thickness of each layer is relatively even in plane, which is basically the same as that of the vertical well, indicating the characteristics of shale stable deposition. The discrepancy between the thickness of each layer in the model and those of the vertical wells is very small, especially in the main production layer 1, less than 0.1m. With the linear combination weighting, petrophysical properties show the bimodal distribution in vertical trend, which is in accordance with the regularities of petrophysical distributions from vertical wells, making up for the seismic low resolution in vertical direction. The research shows the fine structural and petrophysical modeling of the thin shale reservoirs, which provide the credible spatial distribution network and petrophysical properties for further modeling.