Wellbore Flow Behavior and Natural Flow Cessation Prediction in Ultra‐Deep Wells: A Case Study of Shunbei Oilfield

ABSTRACT With continuous attenuation of reservoir pressure, an increasing number of self‐flowing wells in deep and ultra‐deep reservoirs will face flow cessation. Accurately predicting wellbore pressure drop and bottom‐hole flow pressure is key to determining flow cessation time. Existing commonly used pressure models in engineering exhibit poor prediction performance due to the limitation of high‐temperature and high‐pressure conditions in deep and ultra‐deep wellbores. This study first considers the effect of wellbore temperature and pressure on fluid properties, and corrects the crude oil high‐pressure physical parameters based on the measured results of high‐pressure PVT parameter. Second, a new liquid holdup model is established by fitting the fluid holdup derived from the back‐calculation of actual temperature and pressure from production wells. The new model is validated by an example well in Shunbei Oilfield to be significantly superior to other commonly used engineering models in predicting wellbore flow pressure. Finally, a prediction method for self‐flowing well cessation is established using nodal system analysis. Further validation using wells that experienced natural flow cessation in Shunbei Oilfield confirms < 3% error in predicting cessation reservoir pressure.