Fishbones Drilling installation in tight sandstone formation
Location: Offshore, Norway
In July 2015, Fishbones Drilling technology was successfully installed in a new, horizontal well in a sandstone formation in the Norwegian Sea.
Dual-lateral well drilled from a semi-submersible drilling rig targeting a 30m thick oil bearing tight sand formation above a depleted gas reservoir. Horizontal barriers exist within the sand formation which limit vertical flow. Due to the low permeability, the reserves were previously regarded as non-economical to develop. The horizontal well length is 2012m (6600ft).
A solution to vertically connect the reservoir without the risk for fracturing into the gas reservoir below was called for.
A 5.5” Fishbones Drilling completion with 48 ea. Fishbones subs and 7 ea. Backbone open hole anchors was installed in the 8.5” open hole in the main borehole, spaced out across selected zones targeted for stimulation. Each sub contained three ea. needles with 120 degrees phasing and each needle equipped with a drill bit and a turbine to effect drilling of 144 laterals. The needles were equipped with a positive identification feature that allowed for indication of fully extended needles. The liner system was run in hole equipped with a circulation valve to address well control requirement and a liner running tool with disconnect feature allowing for another liner to be installed above to meet adjacent well objectives.
Fishbones Drilling was developed through a Joint Industry Project (JIP) with Statoil, Lundin, Eni and Innovation Norway, and is also supported by the Research Council of Norway.
The Fishbones Drilling completion was run to TD at 6545mMD/3,853mTVD (21,473ftMD/12,641ft TVD) as planned. The circulation sub was closed prior to the drilling of the Fishbones laterals. Low solids OBM was then circulated for 6 hours utilizing mud pumps. Pressure responses during drilling operation indicated full extension of needles into the formation.
Interpretation of inflow tracer data (October 2015) concludes that the main bore (w/Fishbones Drilling lower completion) produces with a higher rate than the lateral (with predrilled liner). The data also indicate higher productivity in zones where Fishbones Drilling is installed compared to zones completed with pre-drilled liner.
Statoil interpretation of production log (September 2017) concludes that ~2/3 of the production is originating from the main bore
After completion of Fishbones laterals drilling operations, the liner running tool was released. That operation included setting down weight on the liner confirming that the Backbone anchors had been set. A second 8.5” lateral was then drilled, the well was completed and put on production.
Statement from Statoil on using Fishbones Drilling in this well: click here
Summary of achievements:
Production from thin, tight sandstone formation previously considered uneconomical
The Fishbones liner was run to TD as per plan
The equipment was safely and practically installed in a well, at an acceptable operational risk level
Full (11m/36ft) deployment of the needles confirmed from mud pump pressure chart reading
The Backbone anchors set
Production log run September 2017 confirms the Fishbones branch contributes ~double the rates compared to the lateral with pre-drilled liner