Wellhead flow block and flow control mechanisms

A unitary wellhead flow block, comprising:

• a flow block body configured to be attached to an outflow pipe or a master valve of a wellhead;
• a main passageway that extends through a central portion of the flow block body from a bottom of the flow block body to an upper portion of the flow block body;
• a return passageway that extends along a side portion of the flow block body from the upper portion of the flow block body to a lower portion of the flow block body;
• a borehole in the flow block body located above the return passageway;
• an upper passageway that extends between and joins the main passageway to the return passageway;
• and
• a flow restrictor plug that is configured to restrict flow between the upper passageway and the return passageway, the flow restrictor plug comprising:
• a cylindrical body that is mounted in the borehole of the flow block body, wherein a circular groove is provided on an exterior of the cylindrical body;
• and
• a circular seal mounted in the circular groove, wherein the circular seal is configured to form a seal between the cylindrical body and an interior of the borehole;
• wherein a length of the cylindrical body is such that when a head of the cylindrical body is mounted in an entrance to the borehole, a bottom of the cylindrical body is located in and at least partially blocks a junction between the upper passageway and the return passageway to thereby limit flow between the upper and return passageways.

A method of altering a flow through a passageway of a wellhead flow block, wherein the wellhead flow block includes a flow block body, a first passageway that extends through the flow block body, a borehole located above the first passageway and a second passageway that extends through the flow block body and that joins the first passageway at a junction between the first and second passageways, the method comprising:

• removing a first flow restrictor plug from the borehole, the first flow restrictor plug having a cylindrical body having a first length, a head and a bottom, wherein the first flow restrictor plug was originally mounted within the borehole such that a head of the cylindrical body was positioned in an entrance to the borehole;
• and
• installing a second flow restrictor plug in the borehole in the flow block body, the second flow restrictor plug having a cylindrical body with a second length that is different from the first length, a head and a bottom, wherein the second flow restrictor plug is installed in the borehole such that the head of the second flow restrictor plug is positioned in the entrance to the borehole;
• wherein because the first length of the cylindrical body of the first flow restrictor plug is different from the second length of the cylindrical body of the second flow restrictor plug the bottom of one of the first and second flow restrictor plugs extends further into the junction between the first and second passageways than the bottom of the other of the first and second flow restrictor plugs such that the second flow restrictor plug provides a different amount of flow restriction between the first and second passageways than the first flow restrictor plug.