Groups of multi layer wells – Results for selected cases

 

September 2016

This article has been updated with official production data until July 2016.

Pad drilling and down spacing has become the norm in 2013-2014. Several companies have talked about extending drilling to several layers in the same space unit as a way of placing  more wells in the already rather densely drilled sweet spot areas.

At the end of 2013 and in 2014, Continetal Ressources made several tests with very tight spaced wells. The productivity of 5 groups of such tight spaced wells (Hawkinson, Tangsrud,  Wahpeton, Rollefstad, Mack), totaling 56 wells, have been analyzed .  Each group was drilled within a group-specific space unit of 1×2 sqm, often not fully using the width of the space unit. Because of investments of up to $100 Million per group, it’s likely that CR choose locations expected to have above average potential.

Besides IP30, the decline curves of these wells are analyzed.

The wells of a group often didn’t reach IP30 the same months. It was often stretched over 2 to 3 months, sometimes more. For the calculation of averages, the well production profiles  have been aligned on their IP30 month.

Summary results

The Hawkinson wells represent the oldest group of tight spaced multilayer wells. Their performance was presented by CLR in 2014 as example that the concept of tight spaced multi layer wells works and that the capacity of the Bakken play can be extended profitably through infill drilling and by significantly reducing spacing between wells.

Indeed, the Hawkinson wells have shown an outstanding performance.  The average IP30 was 15% above the average 2014 Bakken well while first and second year decline rates were equal or less than those of the average Bakken well. But the Hawkinson wells are the exception.

The Rollefsted wells did also OK, with average performance 5 to 10% below the average 2014 Bakken well. No previous well existed on the drilling area.

But the average IP30 of the 30 new wells belonging to the 3 other groups was an abysmal 262 b/d. Their average decline rate was also very steep. After one year, production was down to 17% of IP30. After two years, that number was 10%. These wells did certainly not recover their investments on a full cost basis, even at $100/b WTI.

Hawkinson wells

The Hawkinson wells are best known among the 5 groups analyzed. The group consists of 13 wells, drilled in the Bakken and Three Forks layers of the Oakdale field on a typical 2*1 miles space unit. Mason Inman did an analysis of the layer structure of those wells (see here).

Ten wells were completed in the 4th quarter of 2013 and added to 3 wells already producing since 2010 and 2011 in the space unit.

These older wells had shown an outstanding productivity. Until the production start of the new wells in the last months of 2013, the existing wells had produced nearly 1.1 Mb of oil. The oldest and most productive well (file nr 18275) had produced without interference until the arrival of the new wells. For the 3 months Nov 2013 to Jan 2014, that 4 years old well was still producing an average of 328 b/d. After the addition of the 10 new wells at the end of 2013, production of that older well fell faster than normal for wells of its age. In the past year, its production averaged 50-60 b/d.

The average IP30 of all the new wells was a remarkable 642 b/d. Average production one year later was 165 /d, or 25.7% of peak production, corresponding to the average 2014 Bakken well decline rate. After 2 years, production was down to 120 b/d, or 18.7% of peak production.

Tangsrud wells

The Tangsrud wells consist of a group of 14 wells drilled in the Mid-Bakken and Three Forks layers of the Hayland field in one space unit. Two existing wells, producing since the beginning of 2010 (nr 17649) and the beginning of 2011 (nr 19107) were integrated. The new wells were completed in October/November of 2013 and started production in early 2014.

The average IP30 of the 12 new wells was only 209 b/d.

The two-month average productions of the older wells were 50b/d and 86b/d at the end of 2013. Their production fell unusually fast after the new wells were added. One of the older wells  ceased production in April 2015 and the other has produced between 2.5 and 3b/d in the past year.

The decline rate of the new wells was steep. Production was at 16.5% of peak after one year and 9.5% of peak after two years.

Wahpeton wells

The Wahpeton wells consist of a group of 14 wells drilled in one spacing unit in the Middle Bakken and Three Forks layers of the Banks field.

One older well (Nr 19540) was producing there since 2012. The 13 new wells were drilled between March and August 2013 but were only completed in May 2014.

One well (Nr 24838) was apparently a failure and was abandoned after having produced only 350b. Although that well had been completed and had probably cost as much as the other wells, it has been excluded from the calculated averages (which makes them look somewhat better than they really are). The Mid Bakken wells were more productive than the Three Forks wells.

IP30 of the 12 retained new wells was 328 b/d. The production decline was steep: only 17% after the first year and 10.9%  (data for 9 of 12 wells)  at the end of the second year.

 Rollefstad Wells

The group consists of 8 wells in the Middle Bakken and Three Forks layers, covering an area of  0.5×2 miles in the Antelope field. The wells were completed in the first quarter of 2014. There was no previous well in the space covered by the wells.  The different performance profiles of the wells are quite remarkable. Apparently there has been a lot of experimentation in the ramp up production phase of those wells..

The average IP30 of all wells was 541b/d, which is quite good. After one year, production was down to 22% of peak, 10% worse than the average 2014 Bakken well, and 14.8% after two years, in line with the average Bakken well.

 Mack wells

That group consists of 9 wells drilled within the half width of a spacing unit (0.5*2 sqm).

 It´s the group with the shortest history. Three wells existed on the plot since 2009/2011. Two of them seem to have been revitalized for a couple of months with or trough the completion of the new wells. Six wells were added and completed in August/September 2014.

Performance of the new wells was very poor. IP30 was only 230 b/d and after one year, production was down to 18% of peak. Well production at the end of the second year isn’t available yet, but at production months 20 and 21, production was below 10% of IP30.

Advertisements