Downhole tool for determining laterals

Abstract

The present invention relates to a downhole tool ( 1 ) for determining laterals in a borehole wall ( 3 ) or a borehole casing ( 4 ), comprising a tool housing ( 5 ) extending along a longitudinal axis ( 6 ) and having a circumference perpendicular to the longitudinal axis and adapted to be lowered into a well, and a plurality of sonic transceivers ( 7 ), each sonic transceiver transmitting sonic signals ( 8 ) from the housing and receiving sonic signals reflected from the borehole wall or borehole casing in a pre-defined angular segment ( 9 ), wherein the plurality of sonic transceivers are arranged along the circumference of the tool housing having a mutual distance and are capable of transmitting 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, one sonic transceiver, during a pulse time, transmits a sonic signal in the predefined angular segment of that sonic transmitter, and wherein one sonic transceiver, during a subsequent echo time, receives a reflected sonic signal from the borehole wall or borehole casing, and wherein an absence of the received reflected sonic signal, during the subsequent echo time, indicates a lateral. Furthermore, the invention relates to a downhole system and a method of determining a position of a lateral.

1 . A downhole tool ( 1 ) for determining laterals in a borehole wall ( 3 ) or a borehole casing ( 4 ), comprising:
 a tool housing ( 5 ) extending along a longitudinal axis ( 6 ) and having a circumference perpendicular to the longitudinal axis and adapted to be lowered into a well, and   a plurality of sonic transceivers ( 7 ), each sonic transceiver transmitting sonic signals from the housing and receiving sonic signals ( 8 ) reflected from the borehole wall or borehole casing in a predefined angular segment ( 9 ),   
       wherein the plurality of sonic transceivers are arranged along the circumference of the tool housing having a mutual distance and are capable of transmitting 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, one sonic transceiver, during a pulse time, transmits a sonic signal in the predefined angular segment of that sonic transmitter, and wherein one sonic transceiver, during a subsequent echo time, receives a reflected sonic signal from the borehole wall or borehole casing, and wherein an absence of the received reflected sonic signal, during the subsequent echo time, indicates a lateral, and wherein the downhole tool further comprises a magnetic profiler for measuring a magnetic profile of the borehole casing. 
     
     
         2 . A downhole tool according to  claim 1 , wherein the magnetic profiler is capable of applying a magnetic field and measuring a change in the magnetic field. 
     
     
         3 . A downhole tool according to  claim 2 , wherein the change in the magnetic field is measured as a function of an interaction between the borehole casing and the magnetic field. 
     
     
         4 . A downhole tool according to  claim 1 , wherein the sonic transceivers are arranged equidistantly along the circumference of the tool housing, having a fixed mutual distance. 
     
     
         5 . A downhole tool according to  claim 1 , wherein the sonic transceivers are arranged along the circumference of the tool housing in a regular pattern. 
     
     
         6 . A downhole tool according to  claim 1 , wherein more than one transceiver are receiving during the echo time. 
     
     
         7 . A downhole tool according to  claim 1 , wherein more than one transceiver are transmitting during the pulse time. 
     
     
         8 . A downhole tool according to  claim 1  wherein the downhole tool comprises at least four sonic transceivers, each transceiver being capable of transmitting sonic signals covering at least one forth of the entire central angle such as at least eight sonic transceivers, each transceiver being capable of transmitting sonic signals covering at least one eighth of the entire central angle. 
     
     
         9 . A downhole tool according to  claim 1 , wherein the downhole tool comprises an array of sonic transceivers capable of transmitting sonic signals covering the entire central angle. 
     
     
         10 . A downhole tool according to  claim 1 , wherein a plurality of sonic signals can be transmitted during the pulse time in different predefined angular segments. 
     
     
         11 . A downhole tool according to  claim 1 , wherein the sonic transceivers are capable of transmitting sonic signals having different predefined amplitudes and phases. 
     
     
         12 . A downhole tool according to  claim 1 , further comprising a plurality of second sonic transceivers ( 10 ) arranged at a longitudinal distance away from the plurality of sonic transceivers and arranged along the circumference of the tool housing having a mutual distance and being capable of transmitting sonic signals radially away from the tool housing in an entire central angle of 360 degrees towards the borehole wall or borehole. 
     
     
         13 . A downhole system ( 200 ) comprising:
 a wireline ( 14 ),   a tool string ( 100 ),   a driving unit ( 11 ),   a lateral locator ( 12 ), and   an operational tool ( 13 ) for operating in a lateral,   
       wherein the system further comprises a downhole tool for determining laterals according to  claim 1 . 
     
     
         14 . A downhole system according to  claim 13 , further comprising a magnetic profiler. 
     
     
         15 . A downhole system according to  claim 13  the operational tool is a logging tool, a key tool, a milling tool or a drilling tool. 
     
     
         16 . A downhole system according to  claim 13 , further comprising a positioning tool (not shown), such as a casing collar locator. 
     
     
         17 . A method of determining a position of a lateral comprising the steps of:
 moving the downhole tool according to  claim 1  to a first position in the borehole,   conducting a series of pulse/echo measurements comprising:
 transmitting a sonic signal by a sonic transceiver in a first angular segment during a first pulse time, 
   recording if a reflected sonic signal is received by a sonic transceiver during a first echo time,
 transmitting a sonic signal by a neighbouring sonic transceiver in a second angular segment during a second pulse time, and 
 recording if a reflected sonic signal is received by a sonic transceiver during a second echo time, 
   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,   determining the position of the lateral from the absence of received reflected sonic signals in a subset of the measurements, indicating the position of the lateral, and   recording a magnetic profile for each recording by the sonic transceiver.   
     
     
         18 . A method according to  claim 17 , further comprising the step of performing a plurality of measurements using the method according to  claim 17  and subsequently combining several recordings by the sonic transceiver having matching recorded magnetic profiles. 
     
     
         19 . A method according to  claims 17 , further comprising the step of inserting an operational tool into the lateral. 
     
     
         20 . A method according to  claim 17 , further comprising a step of forcing the downhole tool into the lateral with a lateral locator tool.