Wells producing 20-40 bbls water per MMCF were found to have reduced apparent lengths of ~150 ft, versus designed lengths of 700-1000 ft. Fracs were redesigned to achieve more width and conductivity. Higher conductivity fractures provided improved apparent lengths of 600 ft. Figure 16 shows that high conductivity fractures provided twice the initial rate, and sustained benefit in production over the three year study period.
This manuscript will outline the stimulation design criteria for wells in the Lobo Trend in south Texas and fracture design changes based on post fracture production analysis using commercial software.
Production data will be modeled with the corresponding fracture geometry. Model results will be used as the benchmark to discuss fracture design changes and the effect on well performance. Case histories will focus on tight gas sands with reservoir quality ranging from 0.05 to 1.5 md with some pressure depletion. Multiphase flow effects in areas with higher water production will be investigated. Some discussion will focus on the details of calibrating fracture model inputs using open hole logs, radioactive surveys, sonic logs, production logging tools and mini-frac analysis.
Results comparing post fracture well production, utilizing a pseudo 3D fracture design model and industry available production matching models, will show the effects of permeability, pressure depletion and multiphase flow effects on well performance. Understanding this information will allow the stimulation design engineer to better predict how geometry and fracture conductivity will alter well performance under varying reservoir conditions. With this knowledge, the engineer can better design ‘fit for purpose’ treatments, including those that may require extreme design changes in order to improve gas reserve recovery.
Author(s): S.D. Larkin, E.K. Brown, L.W. Bazan, G.W. Manuel, J.L. Becnel, Conoco Inc.
Paper Number: SPE 74361