FRACTIONAL FLOW

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Archive for August 2016

The Bakken, a little about EUR and R/P

In this post I present some of the methods I have used to get estimates based on actual NDIC data on the Estimated Ultimate Recovery (EUR) for wells in the Bakken North Dakota.

The Bakken is here being treated as one big entity. As the Bakken shales [for geological reasons] are not ubiquitous there will be differences amongst pools, formations and companies.

One metric to evaluate the efficiency of a Light Tight Oil (LTO) well and a large population of wells are looking at developments in the Reserves over Production (R/P) ratio.

The R/P ratio is a snapshot that gives a theoretical duration, normally expressed in years, the production level for one particular year can be sustained at with the reserves in production at the end of that year.

Further, as LTO wells decline steeply and a big portion of the total extraction has come/comes from wells started less than 2 years ago, this dominates the Reserves/Production (R/P) ratio. The flow from a big population of high flowing wells in steep decline results in a low R/P ratio (and vice versa).

The R/P metric says nothing about extraction in absolute terms, which is another metric that needs to be brought into consideration in order to obtain a more complete picture of expected developments.

Development in Well Totals by Categories

Figure 1: In the chart above the about 10,000 wells with 12 months of flow or more [started as of Jan-08 - Jul-15] has been split into 5 categories [ref the legend] and the average monthly flow versus total [for the average] has been plotted for each category. Cut off has been made after 72 months (6 years) as the declining number of wells over time makes the calculations susceptible to noise like from refracking in the tail and because of a declining well population. This method makes it possible to identify the EUR trajectories for each category of wells. The average well in the Bakken now follows a trajectory 2-4% below the green line [wells above 75 kbo and less than 100 kbo after the first 12 months of flow]. The colored dotted lines [sloping upwards to the right] connects each category after the first 12, 24, 36, etc months of flow.

Figure 1: In the chart above the about 10,000 wells with 12 months of flow or more [started as of Jan-08 – Jul-15] has been split into 5 categories [ref the legend] and the average monthly flow versus total [for the average] has been plotted for each category. Cut off has been made after 72 months (6 years) as the declining number of wells over time makes the calculations susceptible to noise like from refracking in the tail and because of a declining well population.
This method makes it possible to identify the EUR trajectories for each category of wells. The average well in the Bakken now follows a trajectory 2-4% below the green line [wells above 75 kbo and less than 100 kbo after the first 12 months of flow].
The colored dotted lines [sloping upwards to the right] connects each category after the first 12, 24, 36, etc months of flow.

The average Bakken well is now estimated to reach a EUR of 320 kbo [kbo; kilo barrels oil = 1,000 bo]. Based on this, the average well has an R/P of 2.7 after its first year of flow, which suggests that about 27% of its EUR is recovered during its first year of flow.

Estimates done by others based on actual NDIC data puts now the EUR for the average Bakken well slightly below 300 kbo.

As from what point the wells reach the end of their economic life, educated guesses now spans from 10 bo/d (0.3 kbo/Month) to 25 bo/d (0.75 kbo/Month).

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Written by Rune Likvern

Sunday, 21 August, 2016 at 20:13

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