Horizontal wells optimize production in a super K sandstone reservoir Minagish Field, West Kuwait. 9th Middle East Geosciences Conference, GEO 2010.

Abstract

The Burgan reservoirs in the Minagish Field are clastic sandstone reservoirs with super-K permeability. The upper reservoir layer consists of fluvial sandstones with grain sizes ranging between medium to coarse. The average porosity is about 28 to 35% and the average permeability varies between 0.7 to 10 Darcy. This reservoir has been a production challenge due to early water breakthrough resulting from coning. We present a case study in which horizontal well technology has been used to mitigate risk of water coning besides enhancing productivity. At the early stages six vertical wells were completed in the Burgan reservoirs with low production rates. Water coning was a major problem because of the homogeneous massive nature of the sand bodies that probably have vertical to horizontal ratios (Kv/Kh) close to 1. The high ratio between the oil viscosity and the water viscosity is also a major reason for coning. Although the first horizontal well drilled in 2005 (with 950 feet of net pay) achieved unprecedented production rates, its production life was short. Water coning and early water breakthrough was due to several factors: (1) low stand-off with the oil/water contact (OWC); (2) high off-take rates; and (3) the presence of a fault acting as a conduit. The second horizontal well was completed at the uppermost part of the reservoir where the facies grade from marine siltstones and shales to fluvial clean sand package. Only 300 ft of the heel out of 1,000 ft horizontal section has been penetrated. Based on the study sweet spots were defined by taking into account: (1) control on production rates; (2) stand-off from the overlying marine shale; (3) level of the oil/water contact; and (4) absence of significant faulting. Five horizontal wells were drilled and successfully completed in targeted sweet spots, achieving a dry oil production and minimizing the possibility of water coning.