A Novel Slow-Release Rheology Modifier for Well Treatment Fluids

摘要

Fluids with high viscosity are needed during hydraulic fracturing to convey the high pressure to create fractures in the rock formation, and to carry the proppant downhole to hold these fractures open after the treatment. A number of oxidative breakers, live and/or encapsulated, are usually mixed into the fluids upon pumping downhole to break the fluids after the treatment to flow back fluids and minimize the damage to the formation. It is not always easy to control the breaking rate of these breakers. If they break the fluids too early in the treatment, the fracturing fluids may not effectively create fractures, and screenout may occur. Well treatment fluids for other oilfield applications may also require controllable slow-release rheology modifiers. A novel rheology modifier has been identified recently and successfully used in a number of well treatment fluid systems. In one example, the rheology modifier can be used to break crosslinked fracturing fluids at desired rates. By adding the rheology modifier into the fracturing fluids prepared with the crosslinked polysaccharides, the fully controllable breaking of the fluids has been realized in our laboratory tests. In another example, the rheology modifier can be used to create a temporary plug that gradually self-breaks at a controllable rate. Low-residue and salt-tolerant hydroxyethyl cellulose (HEC) solution can be crosslinked into a viscous gel and used as a temporary gel plug. By including the rheology modifier at selected concentrations in the gel, the originally thick temporary plug can be gradually thinned to flowable fluid after the preset period of time. This way, the temporary plug can be easily removed from the wellbore after it has served its purpose. The performance of the rheology modifier in the selected well treatment fluid systems will be discussed.