Finding drilling locations with the best production potential in an extensive shale play holding is key to achieving production profile expectations and good economic metrics. Shale plays have been described as statistical plays. However, it becomes increasingly unacceptable to drill disappointing, underperforming wells as the operator and partners move from the exploration and appraisal life cycle stages into the field development stage.

This study demonstrates a methodology for evaluation of key shale properties and the development of a multidimensional (in property and space) geostatistical representation of shale quality (i.e., sweet spot identification). The analysis applies data collected from a 36-mile2 (92-km2) unit of a maturing play to quantify key properties using detailed logging and core analysis from 16 wells penetrating the shale. The analysis demonstrates the utility of multivariate geostatistical property mapping for high-grading drilling locations in the unit. The relative categorizations of 160-acre quarter-sections within the study area are validated by production histories.

The methodology has applicability in maturing shale plays in North America and in evolving shale play exploration and appraisal efforts around the world.


Exploitation of shales (source rock reservoirs) is well into its second decade in the United States. Thousands of wells have been drilled, targeting both gas- and oil-bearing shales, resulting in a remarkable impact on daily domestic production rates. Much has been learned about shales themselves. Drilling and stimulation best practice learning curves have compressed with each new shale development. However, the spatial variability of shale properties confounds operators' production and estimated ultimate recovery (EUR) forecasting. Offset wells' production performance can vary dramatically, despite keeping the drilling and stimulation designs constant. Figure 1 shows the statistical variability of 100 horizontal wells drilled by one operator in one portion (20 – 22 miles) of the Barnett shale core area during a two-year period, after stimulation best practices had been by and large resolved. Initial month production rates (per 100 feet of lateral length) vary by a factor of more than 10. Four-year cumulative production (per 100 feet of lateral length) varies by a factor of 22. Drilling program and capital expenditure (CAPEX) optimization remains a serious challenge to operators, even in high-quality shale areas.

URTeC 1580188

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