Production Characteristics and Importance of Uncertain Parameters of Water Huff-n-Puff for Volume Stimulation Horizontal Wells in Tight Oil Reservoirs

Water huff-n-puff is considered to be an available method to exploit unconventional oil reservoirs, which can significantly promote the reservoir pressure and facilitate water-oil exchange under the imbibition effect. To explore the production characteristics and well performance during water huff-n-puff in the Huanjiang oil field that is a tight oil reservoir, field tests were carried out and production characteristics and well performances were investigated. Moreover, reservoir simulation works were conducted to study the various factors that influence the water huff-n-puff performance. Furthermore, sensitivity analysis for various factors was carried out with the tornado diagram method and the importance of different influencing factors was ranked quantitatively. The results demonstrate that water huff-n-puff has great significance to effectively replenish reservoir pressure as well as promote oil production. Field tests demonstrate that the average liquid rate as well as the oil rate of the horizontal wells increased by 5.94 and 1.18 m3/day, respectively. Considering the different oil production characteristics, the oil production process can be classified into three different stages. The levels importance of different influencing factors were ranked as rock wettability, water huff-n-puff cycles, water injection volume, hydraulic fracturing sections, well position, and soaking time.