DETERMINATION OF DOWNHOLE PRESSURE WHILE PUMPING

摘要

Tubewaves are used to transmit an indication of the depth at which a cond ition is detected in a well. In particular, the depth is calculated based on the difference in arrival time at the surface of a first tubewave which pro pagates directly upward in the borehole and a second tubewave which initiall y travels downward and is then reflected upward. The tubewaves may be genera ted by a canister designed to implode at a certain pressure. After being int roduced into the flowline at an above ground inlet, the canister is carried downhole by gravity and the fluid being pumped. When the canister reaches a depth at which its pressure tolerance is exceeded, it implodes and generates the tubewaves. An analyzer at the surface detects the tubewaves with a hydr ophone array and generates a pressure versus depth profile of the well, i.e. , one data point for each implosion. Canisters may be acoustically tagged by controlling volume and orifice size in order to generate tubewaves having p articular frequency and amplitude characteristics. Canisters may also be con figured to produce multiple implosions, e.g., one implosion at each of a sel ection of different pressures. Canisters may also be equipped with triggerin g and arming mechanisms, and may generate tubewaves in response to condition s other than a particular pressure.