Scales of lateral petrophysical heterogeneity in dolomite lithofacies as determined from outcrop analogs: Implications for 3-D reservoir modeling

摘要

Petrophysical data from dolomite outcrops of the Mississippian Madison Formation at Sheep Canyon, Wyoming, exhibit three scales of lateral variability in single rock fabric units. These include a near-random component (nugget effect), a short-range structure, and a long-range cyclic trend (hole effect). The nugget effect is high and accounts for 31–39 and 48–50% of the variance in porosity and permeability, respectively. Short-range lateral variability is reflected by correlation lengths of 6.5–16 ft (2–5.5 m). Laterally, long-range periodicities are equivalent to approximately 10% of the petrophysical variance and have wavelengths of 31 and 140 ft (9.5 and 42.6 m) for porosity and permeability (55 ft [16.8 m] for log₁₀ permeability), respectively.