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Above: P&A activities to DH 1 & 2

Photo by: Geir Ove Titlestad

Well DH5R was shut in and had 25 bar gas pressure on the surface. A down-hole sensor was installed in the well in 
2012. This sensor was re-programmed and reinstalled in the well at 643 m for monitoring the pressure and tempera-
ture during the test. The sample frequency for the down-hole sensor was 1 sampling per minute.

In order to connect the pump line to the well for the step rate testing the gas was bled off in a controlled manner. 
There was no pressure in the annulus (the space between two or more pipe/tubing) between the NQ and HQ string. 

The pump line was connected to the well and pressure tested before opening the well. No pressure drop or leakage 
was observed at this point. 

When the well was opened up the gas pressure rose to 22 bars in less than 2 hours. The surface pressure decreased 
when the well was filled with water. Pump pressure was observed at 1400 liter where by step rate injection into the 
formation began.  The last step rate was planned at 200 liter/min to be injected into the formation for 48 hours be-
fore the well was shut in. The injection rate increased slowly from 209 l/min to 223 l/min over the 48 hours period that 
the test lasted. 

The well was shut in from August 13th to September 17th – for 35 days. Both the pressure at surface and the down-
hole pressure were recorded during these 35 days. When the well was reopened September 17th the surface pressure 
was 6,7 bar. The pressure was bleed and a small amount of gas came from the well.

Wells Plugged in 2014

DH1 and DH2

DH1 and DH2 are located at Hotellneset along the side of the main road to the airport, and were drilled to core the 
caprock and reservoir succession. DH1 is the first well that was drilled in the Longyearbyen CO2 project in September 
2007. Well DH2 was drilled immediately after DH1 with only 15 meters distance between them. 

• DH1 proved equally difficult to drill with collapsing of the hole in the fault area at 400 – 450 m. Equipment was 

lost and drilling was aborted. 

• DH2; At 517,8 m the drill-bit broke and the diamonds from the bit were lost in the well. During the work to recover 

these diamonds the hole partially collapsed. The drilling operation was recovered and successfully drilled pasted 
the obstruction reaching a depth of 870m.

Both wells have stayed open since 2007. During an inspection in 2012 the wells were found to be stabile with no leak-
age of gas or water. Coal was found at this location from 165 m to 180 m. The rock had good drill ability but a fault was 
detected at 400 m. The fault is unstable and accountable as the cause for the collapse of the drill holes. During the 
plugging of DH1 and 2 Store Norske mining company requested to log the temperature in the well to compare it with 
the temperature logs from 2007. 

DH1; 1200 liter of G cement slurry (G cement is Portland G class cement – the most commonly used cement in the 
North sea oil industry) was pumped through a WL46 (46 mm with the smallest dimension) work string at a maximum 
pump pressure of 60 bars until cement was visible in the return at the surface. The well was tight and a balanced 
cement plug employed (see figure on Blanced cement plug). It was not possible to verify the cement plug by pressure 
testing due to an open area around 9m – 160m. After some days a cement core was taken; this was sufficient to verify 
a good plug.

Dh2 was open to 435 m. Some bobbles with gas were visible but the amount was too small to record with a portable 
gas detector. The original work string was removed and 1200L of cement slurry based on G cement was pumped at a 
pressure of 10 bars rising to 30 bars into the well. It is believed that some cement could have been injected into the 
open formation; therefore the expected top of cement is believed to be a little lower than originally planned. Like DH1 
there was an open section in the well making pressure testing of the cement plug out of the question. A good drill core 
of the cement was drilled to verify the plug.

Injection test DH5R – August 2014

DH5R has never been injection tested; its primary purpose was for observation. The main function of the well was to 
observe any communication during injection tests in DH7a which lies 94 m south of DH5R. DH5R have an open section 
from 645 m to 701. At 670 M there is a sandstone formation –potential good for CO2 storage.

It was decided to do a step rate injection test in well DH5R just before P&A of the well. In August 2014 the test was 
performed. To gain conclusive results geophones were temporary installed in well DH4 for monitoring of any mi-
cro-seismic activity caused by the injection test. A cable with 5 geophones was installed in Dh4 and hooked up to the 
data acquisition for monitoring of the seismic activities prior to the testing.