Modeling High-Angle Wells in Laminated Pay Reservoirs

Abstract

Abstract Productivity improvement and acceleration projects have gained substantially from the success of horizontal well drilling technology. Successful placement of near-horizontal wells in difficult reservoir configurations has become routine. However, not all reservoir situations are amenable to horizontal drilling. Specifically, laminated reservoirs such as thinly bedded turbidites in the Gulf of Mexico (GOM) have been perceived as poor targets. Potentially large reserves are locked in these reservoirs. These laminated turbidite systems have near-zero vertical permeability at the Bouma sequence1 scale and extremely small kv/kh ratios (kv/kh≈0) at the full field, reservoir simulation grid-block scale. In general, a low well count helps minimize development costs. Highly deviated wells (80°≤ θw<90°) cutting the entire sand package may make it possible to obtain both high field production rates and low well counts. Slanted wells have been known to improve productivity of wells with kv/kh≈0. However, the slanted well model given by Cinco2,3 does not predict any improvement in well productivity for such wells. This apparent paradox is reconciled in this paper. Bed thickness, well diameter, and well angle determine the geometric pseudoskin of these thin-bedded sequences. For wells that are nearly horizontal, a simple technique is introduced to calculate the geometric skin without complex modeling. The range of validity of this approximation was determined by comparison with fine-grid simulations.