Patio natural gas fireplace with 1/2" pipe
You want a 150,000 BTU firepit? That's like a gas bonfire! Most gas fire pits I've seen are in the 30-50k BTU range, a few are 100k.

1/2" pipe run 55ft is good for about 70 cu. ft. / hour, assuming 2 PSI or less supply. At 1100 BTU per cu. ft., that will get you 77,000 BTUs, somewhere in the upper end of what I've seen for fire pits.

For 150,000 BTUs, you are going to need about 136 cu. ft. / hr so for 55ft you would need a 3/4" pipe, all the way back to your trunk line (I'm not counting your total demand on that trunk line)..