Performances of Openhole Completed and Cased Horizontal/Undulating Wells in Thin-Bedded, Tight Sand Gas Reservoirs

With the recent advancements in drilling technology, drilling undulating wells, which specifically target various zones in a reservoir, has become a rather routine application. In accordance, drilling engineers are able to steer the well to coincide with pre-established sinusoidal trajectories. This advancement in drilling practices calls for the enhancement of our understanding of the production characteristics of undulating wells. This paper provides an in-depth comparative analysis of production performances of open-hole completed and cased horizontal/sinusoidal wells. Horizontal wells offer great advantages in thin-layered, tight sand gas reservoirs as they increase the productivity through a larger contact area with formations. In this study, a comprehensive performance comparison of open-hole vs. perforated horizontal wells in thin, tight sand gas reservoirs is presented. This is accomplished using a 3-D, single-phase flow model, which is capable of accommodating vertical, horizontal, undulating, perforated, and fractured wells. Effects of drilling damage and crushed zones are considered in the simulations. The parametric study presented in this paper includes various phase angles, shot densities, perforation lengths, and number of fractures. Additionally, the study considers effects of uneven perforation lengths on the topology of the flow fields generated around the perforations. The flow performance comparison is further extended to undulating wells in thin-layered, tight sand gas reservoirs with shale streaks. In the presence of shale streaks, it is observed that undulating wells, which penetrate individual isolated layers, perform more effectively than horizontal wells.