Abstract: A direction adjustment tool for a downhole drilling apparatus is disclosed. The tool has a tubular housing adapted to be incorporated into a downhole drilling apparatus, and steering blades mounted to the housing. A drive shaft transmits drive to a drill bit of a drilling apparatus, wherein the shaft defines a passage for transmitting drilling fluid to the drill bit. A first pressure chamber is defined between the housing and the shaft and communicates with the passage, wherein the steering blades are moved from retracted positions to extended positions thereof as a result of increase of fluid pressure the first pressure chamber. A pendulum member is pivotably mounted to extend in a vertical orientation when the shaft is not rotating relative to the housing, and pistons prevent movement of at least one steering blade to the extended position thereof as a result of the angle between a longitudinal axis of the shaft and the longitudinal axis of the pendulum member exceeding a predetermined amount.

Abstract: The present invention relates to a method of evaluating the hydraulic potential of a porous stratum defined between two depths zlow and zhigh, the method consisting in generating periodic modulation in the rate of flow from the well, in lowering down the well and in activating for a few periods at the depth zlow a measuring PLT sonde, in extracting from the resulting measurements the amplitude ?Qlow of the sinusoidal component of the flow rate modulation relating to one of the imposed periods T, the amplitude ?Plow of the sinusoidal component of the pressure modulation relating to the same period T, and the phase delay of the pressure sinewave relative to the flow rate sinewave ?low, in determining the response R low = ? ? ? P low ? ? ? Q low ? ? - ?? low in raising the sonde to depth zhigh, and in determining the complex response R high = ? ? ? P high ? ? ? Q low ? ? - ? ? ? ? high in calculating the complex response