Maximizing Return-On-Fracturing-Investment by Using Ultra-Lightweight Proppants to Optimize Effective Fracture Area: Can Less Be More?

Abstract

Abstract Hydraulic fracture deliverability is largely defined by the fracture area exhibiting sufficient conductivity contrast within the productive reservoir interval. Increasing effective fracture area has typically been addressed by employing larger treatments and proppant volumes, resulting in increased stimulation treatment costs, which unless accompanied by similar increase in the value of the incremental well productivity, has negative implications on ROFI. The introduction of ultra-lightweight proppants having superior proppant transportability relative to conventional proppants and sufficient strength to withstand the harsh environments has spurred renewed interest in the application of proppant partial monolayers (PMLs). A properly placed partial monolayer exhibits conductivity equivalent to packed fractures having greater than ten proppant layers. The enhanced transportability of the ULW proppants allows for distribution over a much greater portion of the created fracture area. Thus, ULW proppant partial monolayers equate to a high conductivity fracture with much reduced volumes of proppant distributed across a larger area than can be achieved with conventional proppants. Case histories of PML fracturing treatments have consistently illustrated stimulated production increases well beyond expectations, effectively validating the productivity benefits of the process. This paper compares effective fracture area, fracture conductivity, and resultant production simulations for ULW proppants partial monolayer fracturing treatment designs with those of conventional proppant packed fractures. Normalized stimulation costs of the respective treatment designs are subsequently compared with the stimulated fracture deliverability to assess the respective Return-On-Fracture-Investment. Introduction Successful well stimulation requires the created fracture pathways to provide permeability orders of magnitude greater than the reservoir matrix permeability. Proppant is placed to increase the conductivity of the fractures, providing a highway for flow of hydrocarbons between the reservoir and the producing wellbore. Thus, proper placement of the proppant is perhaps the most critical facet of a fracture stimulation as it largely defines the ultimate deliverability. Effective fracture area is that portion of created fracture area which exhibits sufficient conductivity contrast within the productive reservoir interval to promote accelerated drainage of reservoir. The effective fracture area is characterized by the conductive fracture height and length, and is often compromised by the inability to place the proppant throughout the created fracture area. It is well accepted that stimulation of well performance may be accomplished by optimizing the fracture area for efficient drainage of the reservoir. Fracture conductivity is a measure of the flow capacity of an area within a fracture, and is defined as the areal fracture permeability multiplied by the fracture width. Attention needs to be given to the conductivity of this flow path in order to optimize the production rate and recovery. Fracture conductivity improvement efforts have typically focused on the physical characteristics of the propping agents, increasing the propped fracture width (or proppant volume), and minimizing damage to the propped fracture.