The Bakken formation ranks as one of the largest oil developments in North America in the past 40 years. Various estimates place the total resources (recoverable and non-recoverable) with today's technology, from 2 to up to 24 billion barrels of oil (BBO). According to the North Dakota Industrial Commission (NDIC) there were 6,884 horizontal wells by end of 2012 in North Dakota with majority of these wells completed in the Bakken formation. The main target for exploitation has been the middle Bakken siltstone member which is sandwiched between Upper Bakken Shale and Lower Bakken Shale. However, targets below Lower Bakken Shale have shown commercial production notably from the Three Forks benches and sporadically occurring Pronghorn member. The close proximity of these targets coupled with the need for hydraulic fracturing, introduces uncertainty in the "source" of oil production in wells and hence in technically recoverable resource forecasts.

In this paper, we discuss models built to replicate well performance under various completion configuration and depletion pattern to demonstrate the challenges in estimating technically recoverable resource early in to the life of a well or group of wells. These challenges may arise from the stimulated reservoir volume (SRV) not contained within a single reservoir but straddling more than one reservoir at a time. Connectivity between multiple reservoirs and the wellbore may vary with time due to change in stress contrast related to fluid production or by hydraulic fracture conductivity degradation; such varying connectivity can further complicate production allocation from multiple reservoirs. A lack of understanding of SRV distribution and subsequent drainage from multiple reservoirs may lead to significant uncertainty in technically recoverable resource estimation - especially when using short-term production data.

This paper also highlights the effects of completion interference between a well and its infill offsets on uncertainty in estimating technically recoverable resource. We intend to emphasize the issues previously mentioned to the broader audience with the intention to promote further technical discussion on the role that well completion plays in resource evaluation of unconventional plays such as the Bakken Shale.

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