Fracturing Fluid Systems State Of The Art

Since 1949 when the first fracturing treatment was conducted using a Naplam gel and a very small quantity of sand, significant advances have been made in the state of the art concerning fluids to be used in carrying proppants into fracture systems. Up until the late 1960's, the basic fracturing fluids went through a transition stage from the Napalm type gel to crude oils, condensates, and then to water based fluids. Eventually, the aqueous fluids were viscosified using starch, then finally to guar gum and cellulose derivatives. Viscous diesel and crude oils were also used. Crude oils and diesel fuel were thickened using fatty acids and caustic; creating a soap like material which adequately carried proppants. There was some use of oil external emulsions but these were limited due to high friction pressures. The only real variation in the type of fluids related to concentration of viscosifying agents which subsequently controlled proppant transport and viscosity of the fluids in the fracture systems. Some advances were made in degrading agents; i.e., internal breakers during these periods. But basically the fluids used up until that time were simply thickened fluids used to pump proppants back into the fracture systems which were controllably degraded and released. Some of the more obvious disadvantages of these fracturing fluids were: (1) High friction pressure required to pump these fluids (2) Low temperature stability (3) Vunerability to shear (4) Downhole viscosity dependent upon surface viscosity If high viscosity was required downhole at elevated temperatures, an extremely viscous fluid was needed on the surface. This could cause serious problems in regards to hydraulic horsepower requirements and pressure limitations on the surface. There were significant improvements during these years on the types and quality of thickeners, friction reducers, etc. However, basically nothing new in the art; i.e.breakthroughs yielding more temperature stability downhole or more efficient use of hydraulic horsepower were present.