After successful implementation for more than 6 decades by the oil and gas industry, hydraulic fracturing remains the pioneer well stimulation method to date. Polymers are one of the additives in fracturing fluids that play a significant role. Polymers are used as friction reducers and viscosifiers to provide a transport medium for proppants in fracturing fluids. There are many polymer-based fracturing fluid systems, but choosing the most appropriate type and system depends on the type of application and a wide range of parameters. Currently, there is no complete review study that gives a reference and hence a perspective for researchers on the use of polymers in hydraulic fracturing. This paper summarizes the published literature on polymers used in fracturing fluids and discusses the current research issues, efforts, and trends in the field, aiming to provide an overview of the polymer applications in slick-water and cross-linked gel systems. The mechanism and limitation of polymer use such as polymer degradation, fracture conductivity reduction, and polymer adsorption are also reviewed in this paper. The reviewed literature suggested that polymers are important additives in fracturing fluids not only to provide adequate transportation of proppants but also to determine the width of the fracture whereby higher viscosities yield wider fractures. The development of synthetic polymers and associative polymers in fracturing fluids showed a remarkable potential to improve the stability of fracturing fluids in unconventional reservoirs under reservoir conditions, which makes it an interesting topic for future studies.

Many injection/production wells have been hydraulically fractured to enhance injectivity/productivity. Various engineering models for fracture geometry have been developed, which define the propagation of a fracture with time and wellbore treatment pressure. These models combine with elasticity, fluid flow, material balance, and propagation criterion/in-situ stresses. When this combination describes the fracture dimensions, the fracture-geometry can be of two-dimensional (2D) and three-dimensional (3D), depending on the number of dimensional variables. For design purposes, several 2D and 3D models are already developed. But it is still a concern in the oil industry as to which model is beneficial to design optimum treatment parameters for a particular tight sand, because despite many successes, there have been many wells of poor post-fracture productivity. This article provides a review of 2D and 3D fracture models for prediction of fracture geometry. A P-3D (pseudo) model has been improved by incorporating Carter solution of material balance for the first time and was named P-3D-C model, which has predicted higher fracture conductivity. The improved model is highly potential for repetitive computation in hydraulic fracture design optimization.