Microgravity Monitoring in Fractured-Vuggy Carbonate Reservoirs

Abstract

With the development of Tahe Oilfield entering the high water cut stage, gas channeling occurs in fractured-vuggy system during nitrogen injection, resulting in some inefficient wells. To improve the development effect of gas flooding, how to define the distribution of fracture, vuggy, and remaining oil has become one of the urgent problems to be solved at present. Microgravity monitoring technology uses high-quality data, the residual gravity anomaly of the target layer is obtained by depth recursion processing, the density distribution of the target layer is obtained by layer density inversion, and the fractured-vuggy distribution is depicted by edge detection. The results show that the lower part of the fractured-vuggy system in the north is connected to the middle, while the fractured-vuggy system in the south is directly connected to the middle, which leads to different effects of injected nitrogen. The early injected nitrogen in the SX area is mainly distributed in the north. Nitrogen injection in the north needs to reach a certain amount of gas before the middle can be effective. Nitrogen is injected in the south, and the central part is effective quickly. The research results provide a basis for adjusting injection-production scheme and improving reservoir development effect. Compared with the production performance and seismic interpretation results, it verifies the accuracy of ultradeep microgravity monitoring in depicting the development of fractured-vuggy system, which provides a new technology and idea for characterizing fractured-vuggy carbonate reservoirs.