Khuff-B and Khuff-C are the two carbonate reservoirs in the SA-1 field discovered in 1980 with the drilling of exploratory well SA-A. Production from Khuff-B began in December 1983 when a second well was drilled and both were put onstream. The development of Khuff-B was minimal until two years back and only nine stand-alone wells were exclusively completed in this reservoir at that time. Three of these nine wells were actually tied-in to the gas plant. Few other wells were combined Khuff-B/Khuff-C producers. In the commingled producers, Khuff-B’s contribution is significant only in areas where Khuff-C is of relatively poorer quality. The dominant production is generally from Khuff-C reservoir.
A large area is currently within Khuff-B reservoir boundaries with only few producing wells. The development of this vast area is required to meet the increased gas demand. Accurate evaluation of Khuff-B to ascertain reservoir potential and deliverability is of utmost importance. This paper evaluates the Khuff-B reservoir in the SA-1 field and proposes an optimal development plan to effectively deplete its reserves.
Based on detailed analyses, the Khuff-B area has been divided into three regions, namely AREA-1, AREA-2 and AREA-3: The good, moderate, and challenging low quality, tight reservoir. The average production rates from those areas vary between 5 and 50 MMSCFD. The optimal drilling plan in the low quality, low productivity area consists of identifying the productive layer through a slanted pilot hole followed by drilling an extended lateral to attain maximum reservoir contact. A second lateral can also be drilled in special cases where more than one developed layer is encountered in the pilot hole. This development approach also allows placing the production lateral much above the gas-water contact to avoid any future water production or influx. The strategy is promising, has already been implemented in the field, and the results have confirmed a high production, water-free gas rate from the Khuff-B interval.