Downhole tool for determining laterals

A downhole system comprising:

• a wireline;
• a tool string;
• a driving unit;
• a lateral locator;
• an operational tool for operating in a lateral;
• and
• a downhole tool for determining laterals in a borehole wall or a borehole casing, the downhole tool comprising:
• a tool housing extending along a longitudinal axis and having a circumference perpendicular to the longitudinal axis and adapted to be lowered into a well, and
• a plurality of sonic transceivers, each sonic transceiver configured to transmit sonic signals from the tool housing and to receive sonic signals reflected from the borehole wall or borehole casing in a predefined angular segment that is different from the predefined angular segments corresponding to the other sonic transceivers of the plurality of sonic transceivers,
• wherein the plurality of sonic transceivers are arranged along the circumference of the tool housing having a mutual distance and are configured to transmit sonic signals radially away from the tool housing in an entire central angle of 360 degrees towards the borehole wall or borehole casing and wherein, during use, only one first sonic transceiver of the plurality of sonic transceivers transmits, during a first pulse time, sonic signals, and each of the plurality of sonic transceivers are configured to receive, during a pre-set first echo time period subsequent to the first pulse time, the reflected sonic signals from the borehole wall or borehole casing, and wherein only one second sonic transceiver of the plurality of sonic transceivers neighbouring the first sonic transceiver transmits during a second pulse time subsequent to the pre-set first echo time period, sonic signals and each of the plurality of sonic transceivers are configured to receive, during a pre-set second echo time period subsequent to the second pulse time, the reflected sonic signals from the borehole wall or borehole casing, and wherein an absence of the received reflected sonic signal, during the pre-set first echo time period or the pre-set second echo time period, indicates a lateral.

A method of determining a position of a lateral in a borehole wall or a borehole casing using a downhole tool comprising (1) a tool housing extending along a longitudinal axis and having a circumference perpendicular to the longitudinal axis and adapted to be lowered into a well, and (2) a plurality of sonic transceivers arranged along the circumference of the tool housing having a mutual distance and configured to transmit sonic signals radially away from the tool housing in an entire central angle of 360 degrees towards the borehole wall or borehole casing, each sonic transceiver configured to transmit sonic signals from the tool housing and to receive sonic signals reflected from the borehole wall or borehole casing in a predefined angular segment that is different from the predefined angular segments corresponding to the other sonic transceivers of the plurality of sonic transceivers, the method comprising:

• moving the downhole tool according to a first position in the borehole,
• at the first position in the borehole, conducting a series of pulse/echo measurements comprising:
• transmitting a sonic signal in a first angular segment by only one first sonic transceiver of the plurality of sonic transceivers during a first pulse time,
• receiving reflected sonic signals by each of the plurality of sonic transceivers during a pre-set first echo time period subsequent to the first pulse time,
• transmitting a sonic signal in a second angular segment by only one second sonic transceiver of the plurality of sonic transceivers neighbouring the first sonic transceiver during a second pulse time subsequent to the pre-set first echo time period,
• receiving reflected sonic signals by each of the plurality of sonic transceivers during a pre-set second echo time period subsequent to the second pulse time, and
• continuing the series of pulse/echo measurements at the first position until all angular segments along the entire circumference of the tool housing has been investigated using the plurality of sonic transceivers,
• moving the downhole tool to a second position in the borehole,
• conducting a second series of pulse/echo measurements at the second position in the borehole, and
• determining the position of the lateral from an absence of received reflected sonic signals in the pre-set first echo time period or the pre-set second echo time period, indicating the position of the lateral.