Predicting the onset of liquid loading and selecting the appropriate artificial lift technology for mitigation is an industry-wide challenge. Well performance and recoverable reserves are impaired when liquids drop out and load up the wellbore, creating a back-pressure effect on the reservoir. In the absence of a managed pressure drawdown strategy, as well as a timely cost-effective deployment of an appropriate artificial lifting technology, the technical reserves life index of the well can be greatly reduced.
Tackling this challenge first requires a proper understanding of liquid loading dynamics in wet horizontal wells. The current Turner & Coleman liquid loading models are not appropriate for horizontal wells because the governing physics is based on upward movement of liquid droplets and film. On the other hand, adopting transient flow models widely used for pipelines simulations in combination with shale gas reservoir models provides insight into the flow dynamics in long, undulating and multiple source (perforations) horizontal wellbores.
A case study was performed to prove this concept on the Utica\Point Pleasant formation, a wet-gas play typically developed with long, hydraulically fractured undulating horizontal wells with varying trajectories (toe-up\toe-down), where wells experience within a year multiphase flow after experiencing a drawdown below saturation pressure. Analytical reservoir models and wellbore transient modeling were integrated to develop a fit-for purpose, quick-look workflow for investigating the onset of liquid loading, assess the key parameters controlling it, and characterize its impact on well performance and technical reserve life index. Results show that reaching the technical well life will require proper drawdown management strategy and the early deployment of an appropriate artificial lift technology.
This simple yet robust workflow provides a platform usable by all wet shale gas plays to predict liquid loading onset, quantify the impact of well trajectory and draw down on performance, and select the appropriate technical life. The application of this technique has a direct impact on the reliability of production profiles and is a potential source of value creation in wet gas fields.