Micro-proppant placement in hydraulic and natural fracture stimulation in unconventional reservoirs: A review

Tight hydrocarbon reservoirs require stimulation to improve the recovery of oil and gas resources. Hydraulic fracturing is a technique extensively employed in the oil and gas industry to generate fractures including primary and secondary fractures. To keep these fractures open, proppants are used. However, some of these ractures are very narrow for conventional proppants to penetrate and prop, hence smaller proppants called micro-proppants are required. These micro-proppants can improve the hydraulic conductivity of both, the primary fractures and the untouched microfractures, leading to enhanced oil and gas recovery. This paper presents a critical review on the progress of current micro-proppants models, technologies and field applications (sub 100mesh proppants) with a particular attention to micro-proppants placement in hydraulic and natural fractures. The impact of various factors on micro-proppant placement in the fractures is analyzed. These factors include proppant concentration (i.e., volume fraction of solid proppant), proppant size, fracturing fluid chemistry, and confining stress (causing proppant deformation and proppant embedment into the rock). This review concludes that using micro-proppants can improve the efficiency of the hydraulic fracturing treatment, leading to enhanced oil and gas production. (C) 2021 The Authors. Published by Elsevier Ltd.