A Novel Multi-Density Dynamic Well Killing Method for Ultra-Deep Wells and the Simulation System

Abstract Tremendous amounts of oil and gas reservoir are located in ultra-deep formations, such as Shunbei and Shuntuo block in Tarim basin of China, some reservoirs buried deeper than 8000m and which are major exploration areas of SINOPEC. The reservoirs in these areas are full of fractures and cavities which resulting in a series of drilling problems, especially well control safety problems. Therefore, the novel well killing method for ultra-deep wells is very important. Firstly, in order to reduce the well head pressure (WHP) and balance the formation pressure of ultra-deep well quickly in the killing well process, a novel multi-density dynamic well killing method was established, through which we can use two different killing fluids to kill well and one of them is high density fluid. A comprehensive multi-density killing fluids design method was proposed based on the theoretical analysis, through which the optimal density and volume of different fluids can be obtained easily. And based on the optimal killing fluid parameters, we can not only balance formation pressure quickly but also avoid fracturing formation. Secondly, according to the density contrast of operating fluids, a vacuum (U-Tube effect) will appear at the inlet in the well killing process without dynamic controlling of killing parameters, an integrated U-Tube effect analytical model was established based on the Euler equation. For preventing result into a vacuum phenomenon, a real-time calculation model for killing parameters dynamic adjusting was proposed, in which the multiphase flow model was take into account. Based on this model the real-time stand pipe pressure (SPP), WHP and pump flow rate in different stages of well killing can be obtained easily. Moreover, a series of system software for parameters calculating and simulating of multi-density dynamic killing well was developed, through which we can accurate calculating dynamic parameters and hydraulics. The proposed model has been applied in ultra-deep well kick control in SINOPEC Northwest oil filed, the simulating result show that the proposed method and software system can give precisely killing parameters design and simulation. Based on the proposed killing well method, we can quickly reduce operating risk and improve the success rate of killing well. This paper established a novel multi-density dynamic well killing method and the corresponding software, which has been verified with field data and applied in ultra-deep well killing simulating. Through the application, the results show that it can provide technical support to reduce operating risk, and the novel method can improve the success rate of killing well and reduce the drilling cost.