Abstract: A system and method for monitoring fluid flow in a downhole reservoir, characterized by at least one energy source (1), which simultaneously sends two or more utility pulses. The pulse can be a fast propagating and flow-independent acoustic pulse, a somewhat slower propagating and flow-dependent pressure pulse, a slow propagating heat pulse or a slow-propagating tracer pulse. The energy sources are connected via said pulses, without cable, and at least an upper heat source (1?) is connected to equipment on the surface via a cable (4).

Abstract: A method and system of monitoring fluid flow in a wellbore. One or more space-distributed temperature input pulses are induced into at least a portion of a fluid in a housing in the wellbore. The housing has at least one cavity and one or more flow ports. A temperature response pulse, caused by the temperature input pulses, are sensed at one or more locations downstream of the cavity and a flow rate of the fluid through the cavity is determined. The flow rate may be determined based on one or more characteristics of the temperature response pulse, and a Retention Time Distribution (RTD) of the cavity.

Abstract: A method and system of monitoring fluid flow in a wellbore (16). One or more space-distributed temperature input pulses (6a,b; 6?; 6?) are induced into at least a portion of the fluid in a housing (15; 15a,b; 15?; 15?) in the wellbore, The housing has at least one cavity (14; 14a,b) and one or more flow ports (4; 4?. 5; 5?; 5a?,b?). A temperature response pulse, caused by said temperature input pulses, are sensed at one or more locations (2) downstream of said cavity (14; 14a,b) and a flow rate of said fluid through said cavity (14) is determined. The flow rate may be determined based on one or more characteristics of said temperature response pulse, and the Retention Time Distribution (RTD) of said cavity.