Mill and method for drilling composite bridge plugs

A method for the removal of plugs from a wellbore, the method comprising the steps of:

• (a) running a mill into the wellbore on a downhole motor attached to an end of a coiled tubing, the mill comprising at least three wash ports and a central port being in fluid communication with the coiled tubing;
• (b) pumping fluid down the coiled tubing and through the wash ports and the central port of the mill;
• (c) milling out an upper plug until the upper plug is no longer set within the wellbore;
• (d) pumping fluid through the central port of the mill and directly through an opening in the upper plug, the fluid being pumped through the central port comprising at least 30% of a total amount of fluid being pumped down the coiled tubing;
• (e) circulating proppant located below the upper plug up the wellbore until a lower surface of the upper plug engages a top surface of a lower plug set in the wellbore, a rate at which the proppant circulates away from the lower plug being greater than a rate exhibited if less than 30% of the total amount of fluid is pumped through the central port;
• and
• (f) milling out the lower surface of the upper plug and the lower plug until the lower plug is no longer set in the wellbore.

A method of removing proppant below an unset plug in a wellbore, the method comprising the steps of:

• (a) circulating fluid through a central port in a mill having a bladed cutting structure and circulating fluid through a central opening in the unset plug, the fluid being pumped through the central port in the mill comprising at least 30% of a total amount of fluid being pumped down the wellbore, wherein the central port in the mill is offset from a true center-line of the mill within a degree of offset from the true center-line allowing the fluid circulated through the central port to flow directly through the central opening in the unset plug, the cutting structure extending across the center-line of the mill;
• (b) fluidizing the proppant beneath the unset plug by using the fluid circulated through the central port in the mill that flows directly through the central opening in the unset plug;
• (c) displacing the fluidized proppant up an annular space between the unset plug and the wellbore;
• and
• (d) displacing the fluidized proppant out of the well.