Gallic Energy Ltd., Calgary, temporarily suspended completion operations at its Ossun-2D reentry well on the Ger permit in the Aquitaine basin in southern France.
Gallic, with 100% interest, drilled to a total depth of 3,050 m and set production casing after open-hole logs indicated characteristics of hydrocarbon-bearing formations in both the Upper Cretaceous Flysch carbonate and the Dano-Paleocene. Wellbore information confirmed the 200 m thickness, porosity, resistivity, and calculated hydrocarbon saturation of the Upper Cretaceous Flysch carbonate zone as the primary zone of interest.
Formation imaging logs identified fracturing in the target limestone zone, including a 17-m thick interval with perpendicular, intersecting fracture sets. The presence of natural fracture permeability was further confirmed when 9.1 cu m of drilling mud were lost into the Upper Cretaceous.
After perforating a 64-m interval in the upper 130 m of the Flysch carbonate, an extrapolated pressure response of 27 to 28 MPa was evident in the Upper Flysch formation, which is encouraging with no formation water seen. Post perforating, the well encountered what Gallic believes are correctible problems that restricted the permeability of the formation, i.e. mud and-or cement losses into the formation while running casing.
As a result, before resuming any further completion or testing, Gallic will analyze all data gathered to understand the inconsistency between the lack of permeability seen post casing and the previous formation data observed. Furthermore, the formation pressure is believed to be near hydrostatic gradient.
The pressure on the formation was 1.36 times hydrostatic when circulating mud around the 7-in. production casing at TD. This is believed to have driven mud into the fractures, effectively sealing them. The pressure on the formation was 1.41 times hydrostatic while cement was being pumped around the production casing, possibly filling any remaining open fractures with cement.
Gallic plans to either successfully resume completion at Ossun-2 and-or to drill future horizontal wells. The majority of fractures seen on formation imaging logs dip 40-70° from horizontal. Therefore a horizontal wellbore is expected to intersect many more of these fractures than can a vertical wellbore.
The Hagolle-2 well is Gallic’s next drilling target on its Ledeuix permit in the Aquitaine basin. The company has recently completed its submission for a permit to drill the prospective well and expects to commence operations in Q3 2012. Hagolle-2 well will target a shallow gas zone previously drilled in the 1980s at Hagolle-1 and is defined on 3D seismic as a thrusted anticlinal structure.
Hagolle-1 demonstrated a gas-charged limestone of Upper Cretaceous age at 1,100 m and extending to 1,800 m. Hagolle-2 is positioned to be updip on the same structure. The limestone reservoir is believed to be extensively fractured from the uplift and folding of the thrusted anticline by tectonic forces.