Numerous case studies substantiate the merit of horizontal drilling, especially in coning situations. Nonetheless, the burning question remains: do horizontal wells assure performance optimization in all cases? This paper explores the effectiveness of horizontal wells in a high-permeability (kh > 3,000 md), high-anisotropy (kv/kh < 0.01) Burgan Third Middle Sand (3MS) reservoir in Kuwait. To do so we built a sector model containing 35 wells to match 50-year history in a strong edge-water-drive system. With the history-matched model, we examined performance of horizontal wells under various scenarios. These scenarios included reservoir and completion considerations, such tubing size, well length, and high-slant configuration. For comparison, we measured the performance of a horizontal well against its vertical counterpart in terms of water-breakthrough time, oil acceleration, and incremental recovery.

Results show that horizontal wells do not appear to offer any decisive advantage over their vertical counterparts in terms of breakthrough time and ultimate recovery. That is because unique reservoir characteristics, such as high-anisotropy (kv/kh) and low-length-to-thickness (L/h) ratios, coupled with high productivity index (PI), all contributed adversely to horizontal wells' performance when compared with vertical wells. Horizontal wells' PI may be higher but the vertical well is equal to the task of delivering desired oil rates, although with a somewhat larger drawdown. In essence, the primary constraint on well performance is the tubing size, not PI. Therefore, a well with large tubing will achieve optimal performance, regardless of its orientation in the 3MS reservoir.

You can access this article if you purchase or spend a download.