Methods for determining a position of a droppable object in a wellbore

A method for determining a position of a droppable object inside a casing string, comprising:

• installing the casing string into a liquid-filled borehole, the casing string comprising at least one casing joint installed at a pre-known depth, the at least one casing joint comprising at least three positive upsets, the at least three positive upsets all having a same length, and distances between at least two adjacent pairs of the at least three positive upsets being non-equidistant,
• wherein a minimum magnitude of the at least three positive upsets is at least about 3 mm but smaller than that which would prevent passage of the droppable object through an interior of the casing string;
• installing a pressure data acquisition system at a wellsite;
• installing a pressure transducer at a wellhead at the wellsite;
• placing the droppable object inside the casing string;
• pumping a fluid behind the droppable object, causing the droppable object to travel through the interior of the casing string and pass through the at least one casing joint that comprises the at least three positive upsets, the droppable object encountering and passing by at least three of the at least three positive upsets during its journey through the at least one casing joint, thereby generating pressure pulses that travel to a surface level;
• recording pressure data with the pressure transducer;
• transmitting the pressure data to the pressure data acquisition system;
• and
• mathematically processing the pressure data, the mathematically processing comprising:
• obtaining at least one of:
• the pressure pulse or a pressure pulse reflection;
• and
• determining the position of the droppable object based on the obtained at least one of:
• the pressure pulses or the pressure pulse reflection.

A method for cementing a borehole penetrating a subterranean formation, comprising:

• installing a casing string into the borehole, the borehole being liquid-filled, the casing string comprising at least one casing joint installed at a pre-known depth, the at least one casing joint comprising at least three positive upsets, the at least three positive upsets all having a same length, each of the at least three positive upsets comprising at least one of:
• a screw joint or a weld joint, distances between at least two adjacent pairs of the at least three positive upsets being non-equidistant,
• wherein a minimum magnitude of the at least three positive upsets is at least about 3 mm but smaller than that which would prevent passage of a top cementing plug through an interior of the casing string;
• installing a pressure data acquisition system at a wellsite;
• installing at least one pressure transducer at a wellhead at the wellsite;
• placing the top cementing plug inside the casing string;
• pumping a displacement fluid behind the top cementing plug, causing the top cementing plug to travel through the interior of the casing string and pass through the at least three positive upsets, the top cementing plug encountering and passing by at least three of the at least three positive upsets during its journey through the at least one casing joint, thereby generating pressure pulses that travel to a surface level;
• using the at least one pressure transducer to detect the pressure pulses and transmit pressure data to the pressure data acquisition system, the pressure data comprising:
• pressure pulse propagation velocity;
• and
• reflection time;
• and
• processing the pressure data mathematically, the processing comprising determining a position of the top cementing plug based on the pressure data.