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Geosteering—Are We There Yet?



In the last 36 months, 34,070 horizontal wells have been completed in the U.S. This represents about 12% of all horizontal wells drilled, and since the last three years have seen a big uptick in both activity and technology improvement in unconventional play development, I thought it was a good time to dig into geosteering data to get some perspective on this critical piece of the unconventional puzzle.

Of the horizontals completed in the last three years, nearly 14,000 have been analyzed in our Play Assessments application for characteristics, such as percentage of well bore in landing zone, toe in landing zone, and footage in landing zone.

How good of a job have we done getting our horizontals into their targeted landing zones to maximize the productive potential of our unconventional resource play acreage?

Using our highly quality controlled DI Play Assessments data, we can start taking a look at these 14,000 wells to see where operators landed their wells.

Since wells with a relatively high percentage of out-of-zone drilling within targeted landing zones will negatively affect play economics, I thought I’d look at wells, by basin, in Play Assessments with 25% or more of lateral length out of zone. The graph below shows the percentage (displayed logarithmically) of wells, by basin, that had less than 75% of their wellbore positioned in the intended landing zone.

Note that the DJ, Gulf Coast, and Williston were the most likely basins to see wells out of zone (DJ 35%, Gulf Coast 13%, Williston 21%).

In contrast, the basins that showed the highest percentages of wells 90% or greater in zone were the Central Basin Platform at 94%, Mid-Continent at 91%, and Midland Basin at 90%. What accounts for the differences?

Operators in the three Permian sub basins—Delaware, Central Basin Platform, and Midland—are doing a great job of landing their wells in zone and keeping them there.

But what’s going on the Williston and DJ in particular?

These are the most targeted landing zones by basin (source: DI Play Assessments).


For the 23 operators that have completed any wells in the last three years with at least 25% of the wellbore out of Middle Bakken landing zone, nearly one quarter of them account for almost 45% of the out-of-landing-zone wells.

Since the percentage of total wells completed with more than 25% of lateral out of zone in the Middle Bakken in the last three years is about 16%, is this operator dependent or geologically driven (high faulting, rapid lithologic changes, challenges of staying in zone in high dip areas)?


Since the out-of-zone wells are not concentrated in one part of the basin, this implies that geology, faulting, or steep dip complications are not the drivers of out-of-zone performance.

Most of the large operators have done a good to excellent job of keeping their wellbores in their landing zones.


If we look in DI Play Assessments at the 10 operators in the DJ that account for 93% of the wells landed in the Niobrara B, their in-zone landing performance is also quite variable.

Plotting these on a map also shows spatial variability in the position of these wells, again implying that the out-of-zone performance in the DJ is most likely operator driven and not tied to geologic complexity.


In Part 2, I’ll look at identifying the most problematical landing zones.

Please send me an email at [email protected] if you have any observations on or comments about geosteering challenges.

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Mark Nibbelink

Mark Nibbelink is co-founder and director of university outreach at Enverus. Before co-founding Enverus (formerly Drillinginfo) in 1999, Mark had a long career as a prospect geologist at Gulf Oil before beginning work as an independent geologist. Mark is responsible for quality control and data integrity. He received his Bachelor of Arts in geology and his master’s in geology and geophysics from Dartmouth College.