--> Differentiating Stacked Tight Gas Reservoirs of the Spirit River Formation in the Deep Basin of Western Canada Using QEMSCAN Analysis on Cuttings

AAPG ACE 2018

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Differentiating Stacked Tight Gas Reservoirs of the Spirit River Formation in the Deep Basin of Western Canada Using QEMSCAN Analysis on Cuttings

Abstract

The Albian Age clastic reservoirs of the Falher and Wilrich Members of the Spirit River Formation account for large volumes of Western Canadian Deep Basin gas production. These reservoirs have been exploited since recognition of their existence in a basin centered gas accumulation (Masters, 1984); and modern advancements in horizontal drilling and completion practices continue to push the economic limits of these plays.

Within the study area a unique stratigraphic geometry exists, namely the juxtaposition of Falher F and Wilrich A arenitic reservoirs. These reservoirs, recently interpreted as a discontinuous depositional succession (Moslow et al., 2017), have subtle but meaningful differences in reservoir characteristics that influence their productive capabilities. The advent of long-reach horizontal drilling, combined with cost cutting measures, has led to a reduction in the amount of reservoir data collected from each lateral. In the absence of core or a conventional suite of downhole geophysical tools, the geoscientist is forced to extract or infer reservoir characteristics from less cost prohibitive methods. The ubiquity of drill cuttings and horizontal gamma ray logs stand out as primary candidates for analysis. As gamma ray to porosity and permeability relationships can be tenuous, the researchers submit that these reservoir parameters may be achieved through analysis of cuttings via the Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) technique.

The following case study presents integrated reservoir quality assessments for two prolific, and unique, Western Canadian tight gas horizons. Utilizing QEMSCAN analysis it is shown that these reservoirs are texturally and mineralogically distinct, providing support to the interpretation of a depositional hiatus or erosion across their stratigraphic contact. Additionally, comparisons of QEMSCAN to conventional core derived grain densities, porosities, and permeabilities are made. These comparative results highlight the promise of the technique, and we propose that it can be usefully employed in determining tight gas reservoir parameters where a paucity of conventional downhole data exists. Finally, we’ll showcase an example where QEMSCAN analysis aided in the business decisions of targeted horizon, downhole drilling characteristics, and production expectations.