System instability prediction is essential when designing a production system and/or providing operational adjustment to maintain a stable production. The conventional system Nodal Analysis articulates that the system is unstable to the left of the minimum of the Outflow Performance Relationship (OPR) curve where the well loads up. However, recent data shows that there are stable production points on the left of the minimum of the OPR curve, especially for low permeability shale plays. In this work, a new practical model is presented for both conventional and unconventional wells using Nodal Analysis with a novel approach.
The new approach is based on the derivative analysis of the inflow performance relationship (IPR) and OPR at a nodal point of the bottom hole. Perturbation analysis is used to facilitate the explanation of the new model. It shows that the system is stable when the absolute value of slopes or derivatives of the IPR is greater than that of OPR. To evaluate this concept, transient numerical simulations were conducted using a commercial transient simulator at various IPR conditions, including different permeabilities, for both vertical and horizontal wells. Meanwhile, the concept is also compared with available experimental and field data.
The transient simulation and the available data presented in this study demonstrate that there are stable production operating points on the left of the minimum of the OPR curve. The system stability also depends on the reservoir permeability, i.e., the flow rate corresponding to the onset of instability decreases with decreasing permeability. The new approach predicts this trend well. Overall, the new model matches well with observation from the experiments, field data, and the transient numerical simulations.
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Brill, J. P. and Beggs, H. D. 1988. Two-phase flow in Pipes. 6th Ed.
Lee, J. F.,Nickens, H.V.,Wells, M. R. 2008. Gas Well Deliquification. Gulf Professional Publishing.
Lewis, A., and Hughes, R. G. 2008. Production Data Analysis of Shale Gas Reservoirs. SPE Annual Technical Conference and Exhibition. Denver, Colorado, 21-24 September.
Uzunoglu, H. 2018. Gas Lift Studies at Constant Pressure Boundary Conditions. MS thesis. The University of Tulsa. Tulsa, OK.
van Wijhe, A., and Belfroid, S. P. C. 2017. Unstable Well Behavior in Gas Well Liquid Loading – Stability Tests. 18th International Conference on Multiphase Production Technology, 7-9 June, Cannes, France. BHR-2017-145.
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