INDUCTION LOGGING SONDE INCLUDING A FOLDED ARRAY APPARATUS HAVING A PLURALITY OF COWOUND RECEIVER COILS AND BUCKING COILS

摘要

A new induction logging tool has a toolstring length that is shorter than the toolstring length of theinduction logging tool of the prior art. The new induction logging tool includes a new induction arraywhich appears to be folded about an axis that coincides with the transmitter of the induction array of theprior art induction logging tool. The new folded induction array including a transmitter coil, located atan end of the new folded induction array, and a plurality of "cowound" receiver coils and bucking coils,a further plurality of individual receiver coils, and at least one further bucking coil located adjacent toand on one side of the transmitter coil of the new folded induction array. In the new folded inductionarray, each of the plurality of cowound receiver coils and bucking coils include a receiver coil (N-1) anda bucking coil (N), associated with another receiver coil (N), which are cowound together about thesame bobbin, the receiver coil (N-1) and the bucking coil (N) being positioned at approximately thesame distance from the transmitter coil. Each of the plurality of cowound receiver coils and buckingcoils are formed by winding both the bucking coil (N) and the receiver coil (N-1 ) in a bifilar way on thesame ceramic bobbin starting from the center of the bobbin and winding the receiver coil (N-1) and thebucking coil (N) in opposite outward directions.