Is the effect of lateral heterogeneity on horizontal shale production well known?

• “Many papers and production logging studies illustrate that on average in horizontal multiple-cluster unconventional resource wells, only 50% to 60% of the wells’ perforation clusters contribute significantly to production.”

– JPT 6059-technology-update-2-4, Methods Improve Stimulation Efficiency of Perforation Clusters in Completions; Stephen R. Ingram, Matthew Lahman, and Stephen Persac,