Apparatus and method for orienting a downhole tool in a horizontal or deviated well

A tool for use in a horizontal or deviated well, comprising

• a housing having a longitudinal axis;
• and
• a rotatable structure within said housing having a ballast chamber containing a flowable ballast material offset from said axis to contribute to rotation of the structure with respect to said housing about said axis under gravitational forces, the ballast chamber being formed of a material having a first density and the ballast material having a second density greater than the first density.

A method of orienting a tool in a horizontal or highly deviated well, comprising

• filling a ballast chamber with a flowable ballast material,
• placing said ballast chamber into a swivelable tool housing having a longitudinal axis, with the gravitational center of said filled chamber effectively offset from said axis, and
• lowering said housing into said well, enabling said housing to rotate under gravitational forces acting upon said offset gravitational center of said filled chamber.

A downhole gun for use in a horizontal or deviated well, comprising:

• a housing having a longitudinal axis;
• and
• a loading tube containing at least a first and a second cavity shaped to carry perforating charges, the first cavity containing a perforating charge and the second cavity containing a ballast weight, the perforating charge and ballast weight positioned so that the gravitational center of the perforating charge and ballast weight is offset from the longitudinal axis of the housing to contribute to the rotation of the loading tube.

A system for use in a horizontal or deviated well, comprising:

• a rotatable downhole structure having a longitudinal axis;
• and
• an internal ballast in the structure having a flowable material with a density greater than about 500 pounds per cubic foot, the ballast being effectively offset to the axis to enable the ballast to contribute to rotation of the structure about the axis due to gravitational forces, to align the structure in a desired orientation in the horizontal or deviated well.