Assessing a solids deposit in an oilfield pipe

A method for determining type of a solids deposit inside a long fluid-filled pipe, comprising:

• transmitting a first acoustic tube wave along said pipe to produce two deposit-modified acoustic tube waves, including a perturbed acoustic tube wave and a reflected acoustic tube wave, following encounter of said first acoustic tube wave with a solids deposit;
• receiving the perturbed acoustic tube wave at a pair of spaced-apart first and second receivers to produce first and second acoustic signals;
• digitizing said first and second acoustic signals to produce time-based digital data;
• performing FFT on said time-based digital data to produce frequency-based digital data;
• subtracting phase associated with said second acoustic signal from phase associated with said first acoustic signal to produce a phase difference for each of a plurality of frequencies;
• multiplying each phase difference by its associated frequency;
• and
• dividing the result by the distance between said first and second receivers to produce slowness spectrum data, indicative of type of a solids deposit.

A method for determining slowness of a solids deposit inside a long fluid-filled pipe, comprising:

• transmitting a first acoustic tube wave along said pipe to produce two deposit-modified acoustic tube waves, including a perturbed acoustic tube wave and a reflected acoustic tube wave, following encounter of said first acoustic tube wave with a solids deposit;
• receiving a perturbed acoustic tube wave at spaced-apart first and second receivers to produce first and second acoustic signals;
• and
• determining the value of a selected characteristic of said at least one acoustic signal indicative of a solids deposit in said pipe;
• wherein determining the value of a selected characteristic includes subtracting time of arrival of said first acoustic signal from time of arrival of said second acoustic signal to determine slowness.

A permanent-sensor flow assurance measurement system for detecting a solids deposit inside a long fluid-filled pipe, said system comprising:

• a long instrumented pipe including:
• a long pipe;
• an acoustic tube wave transmitter attached to said pipe positioned to transmit a first acoustic tube wave along said pipe;
• and
• an array of acoustic tube wave receivers, said array aligned with said pipe, said receivers attached to said pipe, said array spaced apart from said transmitter, each of said receivers adapted to receive a perturbed acoustic tube wave propagating along said pipe and to produce from the perturbed acoustic tube wave an acoustic signal;
• and
• means for processing acoustic signals to determine the value of a selected characteristic of an acoustic tube wave indicative of a solids deposit in a the long fluid-filled pipe.

A long instrumented pipe for use in a permanent-sensor flow assurance measurement system for detecting a solids deposit inside a long fluid-filled pipe, said instrumented pipe comprising:

• a long pipe;
• an acoustic tube wave transmitter attached to said pipe positioned to transmit a first acoustic tube wave along said pipe;
• and
• an array of acoustic tube wave receivers, said array aligned with said pipe, said receivers attached to said pipe, said array spaced apart from said transmitter, each of said receivers positioned to receive a perturbed acoustic tube wave propagating along said pipes and to produce from the perturbed acoustic tube wave an acoustic signal indicative of a solids deposit in the long fluid-filled pipe.

A permanent-sensor flow assurance measurement system for detecting a solids deposit inside a long fluid-filled pipe, said system comprising:

• a long instrumented pipe including:
• a long pipe and an array of acoustic tube wave transmitter/receivers, said array aligned with said pipe, each transmitter/receiver attached to said pipe, each transmitter/receiver having a transmitter function and a receiver function, each transmitter/receiver positioned to transmit a first acoustic tube wave along said pipe to produce a reflected acoustic tube wave when said first acoustic tube wave encounters a solids deposit in said fluid-filled pipe, each transmitter/receiver positioned to receive a reflected acoustic tube wave produced from its first acoustic tube wave, and adapted to produce therefrom an acoustic signal;
• and
• means for processing acoustic signals to determine the value of a selected characteristic of an acoustic tube wave indicative of a solids deposit in a the long fluid-filled pipe.

A method for assessing a solids deposit inside a long fluid-filled pipe, comprising:

• transmitting a first acoustic tube wave along said pipe to produce two deposit-modified acoustic tube waves, including a perturbed acoustic tube wave and a reflected acoustic tube wave, following encounter of said first acoustic tube wave with a solids deposit;
• receiving a deposit-modified acoustic tube wave to produce at least one acoustic signal;
• and
• determining the value of a selected characteristic of said at least one acoustic signal indicative of a solids deposit in said pipe.