The Part I paper outlined some of the issues and experiences related to the intermediate range of mobility between conventional and unconventional fractured developments. This was expanded upon in Part II by considering the direct transposition of an unconventional development approach to low permeability millidarcy and sub-millidarcy reservoirs. In this paper, the intent is to deepen the consideration into identifying the fundamental underlying factors that influence the selection process and to consider the range of cases where the conventional and unconventional completion designs overlap and could be used in field development. A suite of differing horizontal well development approaches and geometries are considered, over a range of permeabilities. This approach allows for greater insight to be gained into the most effective selection criteria and factors influencing development options for low permeability formations. As part of the selection process, the paper attempts to draw on industry completion experiences, both good and bad, and indicate some of the emerging trends. Finally, economics are considered by assigning typical development costs to each horizontal well approach. This allows the recovery results to be presented as comparative tables of Unit Development Costs (Capital $ spent per BOE recovered) for the differing development approaches as a function of reservoir permeability.

Productivity, recovery, and cost efficiency have been variously presented in a range of graphs; as a function of the reservoir base permeability / mobility. Results indicate that the intermediate range of permeability requires very careful consideration, as the conventional and unconventional production delivery techniques converge. In addition, a number of impactful regionally specific factors are discussed, which may on occasion override, influence and/or directly affect the consideration of the underlying development approach taken and economic results.

With the advent of the development of increasingly tight conventional acreage within existing mature basins, the selection of either conventional or unconventional hydraulic fracturing completion approaches becomes an increasingly important decision. The reported industry experiences have been variable, and it has been the aim of this suite of papers to encourage discourse and generate more detailed and broader publication across such developments. Through the studies presented in this paper the authors provide additional insights which will enhance the industry’s efficiency and economics of future low permeability field developments.