Mill for wellbore milling operations

摘要

A new mill has been invented which has a body, a fluid flow bore therethrough, and apparatus therein for selectively controlling the flow of fluid through the bore. In one aspect the mill is a starting mill connected to a whipstock and controlled flow of fluid through the mill results in setting of an anchor device or anchor packer below the whipstock. In one aspect the mill is initially filled with fluid and apparatus is provided in the mill to permit controlled fluid leakage from within the mill. In another aspect the mill has apparatus thereon for isolating a shear stud from a downward force imposed on the mill, the shear stud releasably connecting the mill to a whipstock.