Modelling Complex Well Behaviour in the Field Using a Transient Multiphase Flow Simulator

摘要

The objective of the paper is to present the application of a transient multiphase flow simulator for the purpose of modelling and improving understanding of complex well behaviour which is not possible with a steady-state solution.The outcome was optimizing well production performance of problematic wells in terms of slugging flow and water loading at high network pressure in a gas condensate and oil field.Continuous reservoir pressure decline,increasing gas-oil-ratio(GOR)and water cut have led several wells in the field to exhibit slugging flow.Different intervention trials in the subject wells failed to bring the well online in continuous flow.The methodology employed was to construct the well model in a transient multiphase flow simulator using the available data;well completion schematic,compositional PVT fluid properties,and well test data.The fluid was characterised using the PVT package.The well model was built,and its performance was matched to dynamic natural slugging flow,shut-in conditions,clean-up operations,and artificial lifting case where nitrogen was injected via coiled tubing to lighten the wellbore fluid density.The modelling results of the well performance analysis have explored crossflow between reservoir zones and water loading phenomena on long sub-horizontal oil producers,at high operating well head pressures,as the cause of flow instability.The multi-stage completion and multiple reservoir intervals,with differing reservoir properties,were captured during construction of the well model.The static fluid gradient survey analysis verified the simulator outcomes,and this in turn proved its applicability for the complex fluids.The well model provided deep understanding of fluid flow in the wellbore for flowing and static conditions.The model was used to evaluate well intervention scenarios to establish a stable flow regime.These studies highlighted the possibility to achieve optimal operating well head pressures to avoid aggravating water loading and stable production process.Various multiphase stable flow optimization methods were examined along with an economic assessment.The dynamic multiphase flow simulator has been found useful in reproducing complex flow behaviour observed in problematic wells and improve stable production.The approach of using a transient multiphase flow simulator on wells with water loading issues and also with crossflowing intervals is vital,and this first time application has proved beneficial for the Karachaganak gas condensate and oil field.