Abstract: The method relates to the field of hydraulic fracturing of subsurface formations. A mathematical simulation model of a pressure pulse propagation inside a wellbore and inside a fracture is created. Pressure pulses are sent to the wellbore, and the response of the well to the pressure pulses is registered. Then, a bottom-hole pressure corresponding to each pulse is determined. An average fracture width is derived by using the mathematical simulation model of pressure pulse propagation inside the wellbore and inside the fracture, and a ratio between the simulated average fracture width and the determined bottom-hole pressure is determined. The said ratio is extrapolated to a zero-width point, and the closure pressure is determined as the bottom-hole pressure corresponding to the zero width.

Abstract: The method relates to the field of hydraulic fracturing of subsurface formations. A mathematical simulation model of a pressure pulse propagation inside a wellbore and inside a fracture is created. Pressure pulses are sent to the wellbore, and the response of the well to the pressure pulses is registered. Then, a bottom-hole pressure corresponding to each pulse is determined. An average fracture width is derived by using the mathematical simulation model of pressure pulse propagation inside the wellbore and inside the fracture, and a ratio between the simulated average fracture width and the determined bottom-hole pressure is determined. The said ratio is extrapolated to a zero-width point, and the closure pressure is determined as the bottom-hole pressure corresponding to the zero width.

Abstract: Methods and systems for investigating downhole conditions are described. One method comprises inserting a tubular into a wellbore, the tubular comprising a tubular section having upper and lower fluid injection ports, and having a thermally insulated fiber optic cable section positioned inside the tubular extending to the upper fluid injection port, and a non-insulated fiber optic cable section positioned outside of the tubular section and extending at least between the upper and lower fluid injection ports; positioning the tubular section having upper and lower fluid injection ports near a suspected thief or pay zone; injecting a fluid through the upper fluid injection port; determining a first differential temperature profile between the upper and lower fluid injection ports; injecting a fluid through the lower fluid injection port; and determining a second differential temperature profile at least between the upper and lower fluid injection ports.

Abstract: Methods and systems for investigating downhole conditions are described. One method comprises inserting a tubular into a wellbore, the tubular comprising a tubular section having upper and lower fluid injection ports, and having a thermally insulated fiber optic cable section positioned inside the tubular extending to the upper fluid injection port, and a non-insulated fiber optic cable section positioned outside of the tubular section and extending at least between the upper and lower fluid injection ports; positioning the tubular section having upper and lower fluid injection ports near a suspected thief or pay zone; injecting a fluid through the upper fluid injection port; determining a first differential temperature profile between the upper and lower fluid injection ports; injecting a fluid through the lower fluid injection port; and determining a second differential temperature profile at least between the upper and lower fluid injection ports.

Abstract: Methods and processes are claimed for optimal design of hydraulic fracturing jobs, and in particular, methods and processes for selecting the optimal amount of proppant-carrying fluid to be pumped into the fracture (which is a crucial parameter in hydraulic fracturing) wherein these design parameters are obtained, ultimately from a priori formation/rock parameters, from pressure-decline data obtained during both linear and radial flow regimes, and by analogy with a related problem in heat transfer, in addition the claimed methods and processes also include redundant verification means.