Abstract

A requirement for appraisal of unconventional resource plays is the development of type wells: predictions of production results for future wells drilled within geologic subsets (areas with relatively homogeneous reservoir properties). Unfortunately, evaluators typically have a limited sample of wells available, so while the subset may be considered relatively homogeneous, the full range of reservoir properties may not have been sampled. Unconventional plays also have gradational changes in reservoir properties, so defining a "homogeneous" geologic subset implies an averaging of these gradients. This paper presents a workflow to deal with these issues. In this workflow, type wells are modified to account for the expected productivity difference between a sampled region and an unexplored region of a given area of interest. Since well productivity and key inputs (e.g. completion design, reservoir quality) are not perfectly correlated, statistical relationships are used to modify type wells while accounting for uncertainty. Combined with an economic model and mapped variability in geologic/reservoir properties, a regional map of break-even oil price is generated. This technique translates the gradational variation of multiple subsurface parameters into a continuous map of relative economic value, which can then be used to discuss a multitude of appraisal and development issues.

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