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.
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.
This post was made possible by contributions, comments and suggestions from several professionals within the oil industry and the academia.
The invaluable talents and expertise of Enno Peters made it possible to transform the NDIC monthly production data with the formation data into spreadsheet format.
The spreadsheet format allows to sort well data by formation, pool, vintage, company and much more.
NOTE: Actual data used for this analysis are all from North Dakota Industrial Commission (NDIC). Some data are missing for some wells and after discussions, the consensus was that the presented average LTO numbers after the first 12 months should have around 5% added to account for missing data from some wells as well as adjusting for the effects from assuming all wells starts at day one of its reported first month of operation (on average each well flows for half a month during its first month of reported operation).
For wells on confidential list, data on runs was used as a proxy for production.
By adding around 5% of the presented average flows for the first 12 months and around 4% after 36 months numbers should come close to actual.
Production data for Bakken, North Dakota: Monthly Production Report Index
Formation data from: Bakken Horizontal Wells By Producing Zone
Water cut is the ratio of [produced water/(produced water + produced oil)] and expressed as a percentage.
Water cuts for individual wells may swing from 0% to 100%, suggesting a shut in well or data not reported. For the early months of a well’s life the water cut may be influenced from water used for fracking.
The important messages from this analysis are the trends in well productivity, water cut and GOR on an aggregate level and by vintage.
For this presentation wells from two pools in Mountrail (Alger and Van Hook), McKenzie (Banks, Camp) and Williams (Squires, Todd) are presented. Hopefully these pools constitutes a good representation of developments for similar pools.
A growing portion of wells have been/are being targeted the Three Forks formation which may suggest something about remaining attractive targets to drill in the Middle Bakken.
Growth in the Water Cut
It was identified two main causes for the growth in water cut;
- The growth in water cut for newer wells was found to be due to a growing number of wells drilled into formations with lower oil saturation (or higher water saturation).
- The growth in water cut as the wells ages is very likely associated with pressure depletion.
A growing water cut will increase the specific operational costs ($/Bbl) as produced water (brine) needs to be disposed of at dedicated sites that pumps it into a suitable formation.
Gas to Oil Ratio (GOR)
On average Bakken wells has a production Gas to Oil Ratio (GOR) of 1.1 – 1.2 Mcf/Bbl, and this shows considerable variation between pools and individual wells within the same pool. Monitoring the developments in GOR is one paramount task for formation/reservoir/well management.
As (differential) pressure (pressure depletion) is the primary drive mechanism for LTO extraction, a gradual lowering of the down hole well pressure lowers the oil’s ability to hold gas and thus some additional (free) gas gets produced with the oil.
In the shale formation gas is dissolved in the oil and one of the objectives of pressure management of the formation/well is to control the depleting formation pressure relative to the bubble point of the oil. If the pressure in the shale formation falls below the bubble point these risks the formation of unwanted free gas, which affects the flows of liquids (LTO and water).
Normally the lower the bubble point pressure is, the lower the GOR becomes as oil loses its ability to hold dissolved gas.
A general observation from observing the developments for a few Bakken LTO wells showed that when the (produced) GOR suddenly increased the LTO and produced water extraction rapidly fell below trend, refer also figures 09 and 21.
For Alger well productivity has declined with time and 2014 is too early to make a final call on.
In general the productivity of the Three Forks formation in Alger is somewhat poorer than the Middle Bakken formation. For the Van Hook pool the productivity (first 12 months totals) appears to be the same, ref also figure 12.
Water cut of 0% for some wells suggests these were shut in or produced water not reported on the forms where the data was pulled from. The first months flow of produced water may be influenced from water used for fracking the wells.
Note how an increase in the GOR reduces total liquids (LTO and water) flows.
Developments in total LTO extraction from wells in the Van Hook appear to be all over the chart. Note also that wells in Van Hook are generally better than in Alger shown in figure 02.
Well productivity for Van Hook has in general improved in recent years.
For Van Hook the increase in water cut by vintage is considerable.
A general feature of the presented wells for pools in McKenzie and Williams counties is that those with time shows less spread in total LTO.
The initial GOR appear to be fairly constant by vintage and increases at the same rate as the wells age. The same was observed in the Alger pool, refer also figure 08, and Alger had a lower GOR than Banks.
Given the wide range of individual characteristics of pools and individual wells within the same pools, production management appears to be a very demanding task as this involves dealing with a portfolio of wells with individual characteristics and thus bear much resemblance to herding cats.
A little on Light Tight Oil Economics
An alternative approach to break even price is to reverse the equation and solve it for estimates of break even flows (first 12 months totals) against various oil prices.
At a lower oil price a higher flow (well productivity, here defined as first 12 months totals) is needed to break even (meet expected return requirements) and vice versa for a higher oil price.
A LTO well recovers around an estimated 30% of its Estimated Ultimate Revoverable (EUR) during its first 12 months of flow. This makes the well economics sensitive to the price during the wells’ early life.
The break even oil price is for the estimated lifetime of the well. A lower price than the estimated break even reduces the return (profitability) and vice versa.
Cash Flow Positive
The LTO wells will flow as long they are cash flow positive, estimated at an oil price above $10 – $12/Bbl at the wellhead (or roughly $25 WTI).
This should not be confused with what price the wells require to break even, that is; earn a return on their investment.
What a lower Oil Price may lead to
If oil prices remain low ($70/Bbl WTI) I would expect the oil companies to target those areas that have profitable potential at this price level. This will with time, reduce the scale of well manufacturing, but also result in an increase average well productivity.
A sustained lower oil price brings also with it the prospects of lower costs for well manufacturing in the shales as suppliers reduce their prices.
A sustained lower oil price and higher interest rates may bring deleveraging forward in time, that is companies with a heavy debt load will bring this down by using a portion of their lower cash flow. This will affect the company’s capital expenditures for well manufacturing.
According to the Directors Cut for November 2014 there were more than 600 wells awaiting completion in Bakken North Dakota and it takes money to complete these wells and bring them into production.
What remains to be seen is how a sustained lower oil price will affect developments in total LTO extraction from Bakken.