Abstract:

As Tahe fractured-vuggy carbonate reservoir has many fractured-vuggy units, pressure systems and seepage units, its oil-water relation is complex and the water body energy distribution is unbalanced. Therefore, studies on the water intrusion process before water seepage is conducted for the elastic drive unit oil wells in single fracture and single hole reservoir with closed bottom water. There exists a connected water body. The fluid expands elastically in the dissolved hole. As time goes on, the water intrusion is inevitable due to the pressure decay of the reservoir during the mining process and begins at some point. Based on the characteristics of the fracture-cavity reservoir, the intrusion water is considered as the bottom water, and the elastic water flooding continues to supply the insufficient of the formation energy. According to the Poiseuille’s equation, the pressure of the karst cave before water breakthrough and the incremental rate of the cumulative oil production in the dissolved pores both decrease exponentially with time, following the rules of rapid in the early stage and slow down in the later stage. Meanwhile, combining the improved material balance method of reservoir engineering to calculate the water influx during the elastic driving period before water breakthrough. Taking well-TH12523 as an example, water intrusion occurs during its elastic mining stage, and the elasticity and the water body drive together. The actual measured incremental rate of the measured oil production and the karst pressure varied with in the whole mining process are consistent with the dynamic prediction results of the reservoir .

Key words: fractured-vuggy carbonate rock, elastic mining, cumulative oil production, water influx, cavern pressure