GB1148201A - Hydraulic fracturing of subsurface earth formations - Google Patents

Abstract

1,148,201. Wells &c. ESSO PRODUCTION RESEARCH CO. 12 July, 1966, No. 31198/66. Heading E1F. A method of fracturing or increasing a fracture in a formation surrounding a well comprises feeding a fracturing fluid down the well with a less viscous fluid so that the less viscous fluid forms a film or layer between the well and the fracturing fluid. The ratio of viscosities of the fluids ranges from 10:1 to 100:1 at 70‹-80‹F. The less viscous fluid may have a viscosity of 0.5-100 cps at 70‹- 80‹F, and the fracturing fluid may have a viscosity of 100-10 million cps at 70‹-80 and carry 0.5 1b/gall-201b/gall of sand. The fluids may be introduced into the well as an emulsion and an agent added to facilitate separation of the fluids in the well. The fluids may be introduced into the well as a loose admixture containing a de-emulsifier but preferable the less viscous fluid which may contain a wetting agent is introduced as an annulus surrounding a core of the fluids, which may contain a propping agent, a surfactant, or deemulsifier. The fracturing fluid may be a water in oil emulsion, and the less viscous fluid may be water. For water wells the fracturing fluid may be thickened water, and the less viscous fluid may be a light oil. The fluids may be injected in a space between tubing and casing, the fracturing fluid being located between annulii of less viscous fluid. The fluids may be heated prior to injection in the well or the formation may be cooled before fracturing. When the fracture is formed the fluids may be removed by a solvent. The fluids may be followed by a sand free fluid to clear the well. The fluids may be preceded by a fluid having a small viscosity.