This paper discusses a stimulation optimization case history in the STACK (Sooner Trend, Anadarko Basin, Canadian, and Kingfisher counties of Oklahoma). This area has been active for a number of years, and operators are still trying to figure out how best to drill and complete the asset. This case history will cover a field trial conducted in the Meramec, the Sycamore and the Woodford, and will compare the completion methods of two offset pads, with one pad serving as the pre-optimization offset.

These field trials consisted of wellbore spacing tests as well as the implementation of certain design and execution changes. The first major design change was the implementation of an algorithm-based, automated controlled breakdown process designed to improve the uniformity and the cluster efficiency of given stimulation treatments. When stimulations are conducted, it has been consistently demonstrated that a disproportionate number of perforation clusters are not effectively treated during any given stimulation treatment. The implementation of a controlled breakdown process not only allows for a better stimulation efficiency, but also allows for consistent treatment operations across stages and wellbores. The second design change was the application of ultra-fine particulates (UFP) during the initial pad stages of stimulation treatments. Unconventional reservoirs contain some level of complexity in the form of microfractures. Conventional proppants are typically too large to prop those microfractures, which limits how much hydrocarbon can be produced from a given reservoir. UFPs are small enough to enter those microfractures. Likewise, UFPs have been shown to reduce near wellbore friction early in stimulation treatments, which improves operational efficiencies. The third design change was the utilization of a wellhead connection system in place of a traditional zipper manifold. This system reduces equipment on location as well as the complexity of operations when stages on two or more wells are being stimulated in sequence.

The operational changes on the post-optimization pad yielded increased efficiencies and reduced costs. The wells also showed a substantial production improvement over the typical curves for the area. The post-optimization wells had a higher rate of return over the pre-optimization pad. The wells where the automated controlled breakdown process was utilized demonstrated a 5 to 15% production increase over comparable offsets on the same pad. The wellhead connection system improved transition times between wellhead swaps during well zipper stimulation operations. The implementation of the breakdown process, the wellhead connection system, and UFPs improved operational efficiencies as well as making treatments more consistent. Observed treating pressures were lower and more consistent when the breakdown process was utilized.

This paper demonstrates how the implementation of a controlled breakdown process, wellhead connection system, and UFPs can help improve well economics. Also, the economic potential for the STACK when utilizing an optimized completion is demonstrated.

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