FRACTIONAL FLOW

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Archive for December 2014

Will the Bakken Red Queen Outrun Growth in Water Cut?

This post presents a closer examination of actual data on Light Tight Oil (LTO) extraction, developments in water cut and Gas Oil Ratio (GOR) for some pools and individual wells in the Middle Bakken and Three Forks formations in North Dakota.

LTO extraction’s primary drive mechanism is (differential) pressure and there are some noticeable trends for LTO extraction from Bakken:

  • LTO productivity (measured as average totals by vintage) in 2014 have increased, most notably from the Middle Bakken formation which has better well productivity than Three Forks.
    There are differences to LTO productivity developments amongst the pools.
  • Water cut; generally increases as the wells ages.
    An indicator for depletion.
  • Water cut; generally increases for newer wells.
    This suggests that the areas with the highest oil saturation has been developed.
  • Gas Oil Ratio (GOR, produced and expressed as Mcf/Bbl); generally increases as the well ages. 
  • What appears to characterize a Bakken sweet spot is the presence of natural fractures (favorable geology), high oil saturation and a pressure above hydrostatic pressure.

Further, this post also has a brief look into well economics and describes how well manufacturing is likely to be affected by the decline in the oil price and what this may entail if a lower oil price ($70/Bbl, WTI) is sustained.

Figure 01: The chart above shows development in the water cut [water cut = [water/(water + LTO)] for the “average” wells by vintage in North  Dakota. Produced water (brine) is transported to dedicated disposal sites. Chart by Enno Peters.

Figure 01: The chart above shows development in the water cut [water cut = [water/(water + LTO)] for the “average” wells by vintage in North Dakota. Produced water (brine) is transported to dedicated disposal sites.
Chart by Enno Peters.

What is fascinating about LTO wells in Bakken is that the individual wells appear to have their own “personality” when it comes to productivity, surrounding rock properties, water/oil saturation and GOR which makes well management (of close to 9,000 “personalities”) a paramount task.

This post contains in total 30 charts that hopefully are self explanatory.

Read the rest of this entry »

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