Experimental study on waterflood development in large–scale karst structures.

Abstract On the basis of the seismic data volume of a certain well group unit of the Tahe fracture–vuggy reservoirs, the similarity theory is adopted, and a numerical model with geometric, kinematic, dynamic, and fracture–cavity characteristic parameter similarities is designed. Moreover, a large–scale three–dimensional physical karst cave model is built with the carving technology. The model is used in the experimental study of two–phase flow of oil/water during waterflood development and in the analysis of relevant influencing factors. Results show that the displacement efficiency of low–high mode is obviously superior to the case of high–low mode. A high crude oil viscosity is found to equate to a low ultimate recovery. High–velocity water flooding improves ultimate recovery but results earlier water breakthrough. Well shutdown improves recovery factor and well shutdown during middle water cut stage achieves optimum effects. Bottom water energy benefits oil reservoir exploitation to some degree. Highlights • A large–scale three–dimensional physical karst cave model is built to study the two–phase flow of oil/water. • Displacement efficiency of low–high mode is obviously superior to the case of high–low mode. • A high crude oil viscosity is found to equate to a low ultimate recovery. • High–velocity water flooding improves ultimate recovery but results earlier water breakthrough. • Well shutdown during middle water cut stage achieves optimum effects. [ABSTRACT FROM AUTHOR]