Abstract: In order to further understand the water invasion law of ultra-deep multi-porosity reservoir, the radial unsteady water invasion model for ultra-deep multi-porosity reservoirs was established in dual-porosity reservoirs and tri-porosity reservoirs by assuming that the aquifer was infinite or closed. Mathematical methods such as Laplace transform were used to solve the model, and the cumulative water invasion solution in Laplace space was obtained. Then the cumulative water invasion solution in real space was obtained through numerical inversion. The water invasion curves of infinite aquifer and closed aquifer in multi-porosity reservoirs were programmed and their differences were compared. Then the parameter sensitivity of the water invasion curves in multi-porosity reservoir was analyzed. Finally, the model was verified and analyzed by using the field data of ultra-deep fractured-vuggy reservoir in Tarim Basin combined with the principle of material balance. The results show that the water invasion curve of the infinite aquifer keeps rising, and the water invasion curve of the closed aquifer keeps stable in the later stage and there is a“water invasion step”. Water radius and storativity ratio mainly affect the position of water invasion curve. The inter-porosity flow coefficient mainly affects the time of“water invasion step”. The water invasion model can accurately calculate the amount of cumulative water invasion. The water invasion model established and the water invasion curves drawn can provide theoretical reference for the study of water invasion mechanism in ultra-deep multi-porosity reservoirs.

Key words: ultra-deep reservoirs, multi-porosity reservoirs, unsteady water invasion model, water invasion curve, water invasion step