The Shaunavon Formation

History & Positioning

The Shaunavon Formation is a stratigraphical unit deposited during the mid-Jurassic Era in the Western Canadian Sedimentary Basin. Taking the name from the town of Shaunavon in SW Saskatchewan, it was deposited during the Bathonian age and is approximately 168 million years in age. The 1st well was drilled in 1954 just SW of the town of Shaunavon, the origin of the formations name.

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The Shaunavon is positioned below the Vanguard Group (more specifically the Rierdon Formation) and above the Gravelbourg Formations. Reaching a maximum thickness of approximately 48m the Shaunavon stretches into the Williston Basin in Montana and North Dakota as well as, blending into the shaley facies of the Melita Formation of Manitoba.

Composition

The Shaunavon Formation is composed of two members, an Upper and a Lower member. The Upper Shaunavon consists of a blend of calcareous sandstone, oolitic and argillaceous limestone, shell coquina and interbeds of gray and green shale.

The lower member consists of an oolitic bed overtop a buff microcrystalline limestone. Dolomitization, a process in which dolomite is formed when calcium ions in calcite are replaced by magnesium ions, has been found to occur in both the Upper and Lower Shaunavon members.

Log Characteristics

The complicated and heterogeneous succession of interbedded limestone, multi-colored shale and sandstone of the Shaunavon formations is clearly seen in logs. The Lower Shaunavon limestone displays the most prominent of identification characteristics.

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Production Interest

Crescent Point had dominated the Shaunavon oil play in southwestern Saskatchewan, controlling as much as 90 per cent of the acreage in the play. But now has good competition after Surge Energy Inc. entered the play after buying assets from Cenovus Energy Inc. Initial interest was directed toward the Lower Shaunavon member, however emphasis had shifted by many companies to target the Upper member based on the favorable production recognized.  As well, the opportunity for multi-zone production from both members has also been an incentive for companies targeting the formation.

Going Forward

Using horizontal drilling and multistage-fracturing completion techniques the Upper and Lower Shaunavon reservoirs can be exploited in a much more efficient way. Reservoir investigation using horizontal well evaluations has been shown to improve frac stage effectiveness by targeting specific intervals of the lateral section that are most ideal for frac stimulation. Other sections of the wellbore that are not as ideal (frac energy is not absorbed well) can be avoided, thus reducing the occurrence of wasted/inefficient frac stages.

With Cordax's Logging While Tripping (LWT) system, horizontal open hole logs can be obtained safely, while significantly reducing rig time typically associated with conventional logging operations.