GB1493890A - Hydraulic fracturing process using reverse flow - Google Patents

Abstract

1493890 Fracturing formations O M KIEL 28 Oct 1975 [27 Jan 1975] 44380/75 Addition to 1460647 Heading E1F A method of hydraulically fracturing an underground formation comprises a double cycle including injecting fluid into the formation at a pressure sufficient to fracture the formation, maintaining the pressure for at least three minutes, discontinuing the fluid injection, allowing at least one period of reverse flow from the formation for a period of time to allow a pressure drop in the fluid, resuming injection of the fluid into the formation, and discontinuing the latter injection of fluid. The period of reverse flow may be from 30 seconds to five minutes and may be sufficient to return 0.25 to 1.00% by volume of the fluid injected into the formation. The method may include two or three double cycles, the well not being produced between double cycles. The injection pressure during each double cycle subsequent to the first double cycle is at least 10% greater than during the first double cycle and the periods of discontinuance of injection, other than the last one, are such that the pressure does not fall to less than <SP>1</SP>/ 3 of the amount of increase in pressure during the previous injection. Each period for discontinuing injecting fluid, except the last period, lasts from 5 to 60 minutes. Sand may be injected with the. fluid to limit the vertical conductive extent of the fracturing and to act as a fluid loss control agent.