When a well is being fractured, the high pressures cause a network of openings, aka “fractures”, throughout the formation allowing channels for the hydrocarbons to be produced. After this pressure is released these channels must remain open in order to keep the hydrocarbon production flowing. Fracture Proppants are used to take the stress from the surrounding formation, holding the fractures open, as well as allow the hydrocarbons to pass through their mesh like structure makeup.
Proppant Attributes
Proppants are typically made up of a solid material, sand or ceramic. It is added to the fracture fluid, mainly slickwater, which has become the popular choice since 2012. As shown below there are different sizes or proppants used, each having their own pros and cons.
Typical Issues when using Proppants
Formation Stresses
High stresses from the formations take a toll on the Fracture Proppants, especially in circumstances when a well is shut in and awaiting production. During this time Proppants can break down and create “fines” which cause blockage in the channels. Coulter & Wells (Journal of Petroleum Technology, June 1972) has done research stating “that just 5% fines can decrease fracture flow capacity by as much as 60%”.
Proppant flowback
Pressures from the formation while hydrocarbons are being produced may cause the proppants to “flowback” into the borehole. If the flowback is great enough this may cause the channels to close up and loss of complete production from that network.
Coated Proppants
To increase the strength of the larger sized proppants, and to ensure less “Fines” are being created, the sands can be coated with resin. This resin allows the larger sized proppants to be used, making the channels bigger in the formation, and also allowing the hydrocarbons to still pass through the resin covered proppant. Also, the resin on the coated proppants allows them to form a bond in order to minimize the amount of proppant flowback from the channels.
As studies continue on the best practices for completions of a well, there are many components including breakdown pressures, fracture fluids and proppants used can affect the production. Parameters such as breakdown pressures can be adjusted using petrophysics analysis of open hole logs. Cordax's Logging While Tripping technique allows open hole data into the lateral in a much safe, cost effective method.
