Conventional and Unconventional Developments Part I: What Applies, Where and Why ?
Authors: Rylance M. , Pearson M. , Fowler G. , McClure M. 
Published: January 2025

Successful integration of hydraulic fracturing and horizontal wells is now very well established within the industry, commencing as a technique in good quality conventional reservoirs and more recently and much more extensively in unconventionals. However, there has actually been very little application of this combination within 'tight’ permeability, with many of the lower permeability onshore fields within North America (NA) having been originally developed with conventional fractured verticals. Therefore, as the Rest of World (RoW) begins to develop their tight-resources, an oft asked question is when does conventional fracturing transition into unconventional, and when can conventional viscous fluid high-density proppant-pack be replaced by slickwater placed partial "proppant" coverage ?

While there is a tendency to conveniently partition into Conventional and Unconventional fracturing; the reality is that for the lower-perm ‘tight’ environment, that we need to understand the nuanced transition and multiple drivers for selecting the most effective approach. This selection process needs to include all aspects of the completion, fracture design and deployment. This includes tangible aspects such as staging, connectivity, fluids, flush, materials, conductivity and placement. As well as those less tangible, such as logistics, infrastructure, access and capability. While economic drivers are largely reservoir, reserves and recovery driven; the cost, time and economic realities of the process (particularly in an offshore or remote environment) begin to play an increasingly magnified role as the fracturing intensity increases.

The more recent drive to developing ‘tight’ conventional reservoirs, across the RoW, has begun to set new challenges for hydraulic fracturing. While the standard unconventional approaches are very well developed, staging, clusters, fluids, materials, fracture placement, conductivity and geometries; these are targeted at micro- to nano- Darcy environments. Whereas in the case of conventional horizontal well fracturing, perforating, staging and isolation can be cost/time impactful as fracture count increases, with complex logistics and with the associated reward reducing. Settled bank fracturing creates a very different effective flow environment than conventional planar fracturing and the provision and sustainability of sufficient conductivity is the underlying challenge. The paper will demonstrate those approaches that appear to be gaining momentum in this area; such as sliding-sleeve staging, the use of HVFR where appropriate and fit for purpose proppant placement. The Part I paper will both investigate and report on the historic, emerging trends and potential direction that this specific application of fracturing is taking.

The emergence of an area of opportunity, in fracturing capability, has developed between the very well understood higher/medium permeability, extensive conductivity conventional fracturing approach and the well-established unconventional range. This transitional area requires detailed consideration as to where the adoption of appropriate techniques are key in ensuring cost-effective delivery; and line of sight to economic development. With treatment/stage count, time and cost playing an increasingly impactful role as the conventional fracturing stage count increases. For fracturing to develop the tight potential that exists, it will be imperative that this hybrid application continues to develop and is further optimised.