The group that initiated the blockade, which also includes Egypt, the UAE, and Bahrain, accused Qatar of supporting terrorist groups and being too close to Iran... Qatar has denied the accusations and launched counter-accusations against the leader, Saudi Arabia, of trying for a regime change in the Gulf state.
However Qatar is the smallest producer in Opec and didn’t have much say in how things went with Opec anyway.
Below data covers 2017:
Value of exports (million $) 84,906
Value of petroleum exports (million $) 35,496
Current account balance (million $) 6,408
Proven crude oil reserves (million barrels) 25,244
Proven natural gas reserves (billion cu. m.) 23,861
Crude oil production (1,000 b/d) 600.0
Marketed production of natural gas (million cu. m.) 163,598.6
Refinery capacity (1,000 b/cd) 433
Output of petroleum products (1,000 b/d) 699
Oil demand (1,000 b/d) 339.0
Crude oil exports (1,000 b/d) 466.0
Exports of petroleum products (1,000 b/d) 639.4
Natural gas exports (million cu. m.) 128,645.3
https://www.opec.org/opec_web/en/about_us/168.htm