Publications

The Kuat oil field produces from the Lower Pematang formation at 6900 ft. The sandstone reservoir has porosity of 8-15% and a permeability of 2-5 mD. The reservoir is normally pressured around 2000-2200 psi , it has a high temperature of 3200F. The reservoir drive mechanism is a weak solution-gas drive, so the reservoir pressure surrounding well declines quickly, around 245 psi/year. The completion paradigm has changed several times since the first well was drilled in 2004, evolving from cased-and-perforated vertical wellsto highly deviated open-hole wells with slotted liners, and finally to hydraulic-fracture-stimulation of cased vertical and deviated wells. From 2007–2011, seven wells were drilled and hydraulic fracture-stimulated. These wells gave initial oil rates and oil recoveries up to four times higher than the best un-stimulated well, with an average initial rate of 359 BOPD and an ultimate oil recovery of 264 MSTB. So fracture-stimulation has been the most successful technique tried so far to maximize the oil rate and recovery per well, although one of the seven wells failed to flow due to well integrity problems and surface facility limits. Despite frac operations now being fairly smooth, based on improvements from our experience in earlier frac campaigns, our fracced wells are yet to yield consistently high oil rates and recoveries. So to understand why, we have turned our attention to variable reservoir and rock properties as a major influence on frac results. We decided to map frac results against various parameters to look for patterns, which would hopefully lead to a workflow to select candidate frac sands with reliable results. For our fracced sands, we looked for trends between input parameters such as reservoir properties (pressure and permeability), rock properties (frac gradient and in-situ stress), frac properties (frac half length and conductivity), and outputs parameters such as oil production profile and economic metrics. We did find relationships between our economically successful wells and several reservoir parameters. This has led us to change the proposed drilling locations for our next campaign of drilling and fraccing. Keywords: Pematang, Low Permeability, High Temperature, Hydraulic Fracturing, Malacca Strait