271 wells producing exclusively from the Nikanassin and equivalent
formations in a very large area of more than 15,000 km2 in the
Western Canada Sedimentary basin (WCSB), Alberta and British Columbia, Canada,
have been evaluated with a view to determine the distribution of cumulative gas
production and the possibilities of intensive infill drilling.
The Upper Jurassic to Lower Cretaceous Nikanassin formation is generally
characterized as a tight gas formation with low values of permeability
(typically a fraction of millidarcy) and low porosities (usually less than 6%).
It is likely that natural microfractures and slot pores dominate the
productivity of the formation. The study area was divided into six smaller
narrow areas (A through F) approximately parallel to the
northwest/southeast-trending thrust belt of the Canadian Rocky Mountains. Area
A is located to the west of the deformation edge, Area B is on the deformation
edge, and Areas C through F are located to the east. Area C is the deepest and
closest to the thrust belt, whereas Area F is the shallowest and farthest from
the thrust belt.
Cumulative production characteristics within each area were evaluated with a
variability distribution model (VDM) developed recently for naturally fractured
reservoirs. The evaluation of each one of the six areas (271 wells) resulted in
coefficients of determination, R2 greater than 0.99 in all cases.
The results indicate that the gas cumulative production distribution per well
is more homogeneous along the deformation edge (Area B), in which 80% of the
wells contribute approximately 50% of the cumulative production. The highest
heterogeneity was found in Area F (the shallowest), with 80% of the wells
contributing only 25% of the cumulative gas production. Areas A, C, D, and E
have more or less the same distribution with 80% of the wells contributing
between 35 and 45% of the cumulative gas production. In preliminary terms,
there is an association between the cumulative-production distribution and
lateral variations of borehole breakouts in the Nikanassin formation on a
transect perpendicular to the deformation belt of the WCSB.
Analysis of the distributions leads to the conclusion that the Nikanassin is
a very heterogeneous formation and that there is significant potential for
massive drilling to efficiently drain the formation. The possibilities of
horizontal wells and multistage hydraulic-fracturing jobs are being
investigated at this time.
© 2011. Society of Petroleum Engineers
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- Original manuscript received:
15 April 2010
- Meeting paper published:
28 June 2010
- Revised manuscript received:
12 November 2010
- Manuscript approved:
17 December 2010
- Published online:
16 May 2011
- Version of record:
7 June 2011