I am in Western Oregon as well. Oregon white oak trees that are only 8-12" dbh will not yield much usable lumber. The core of the log (the center) is full of juvenile wood which is not stable and will twist and split when dried. So, with 8-12 inch diameter logs there is very little left to make into lumber after boxing around the core. You need 18-24" dbh logs to make lumber.
Another possible market for the small logs is as nurse logs used in shiitake mushroom production. Shiitake mushroom spawn is pressed into holes drilled into these nurse logs and the logs are kept damp and dark in an insulated hoop house. The fungus grows in the wood and produces mushrooms that grow out the sides of the nurse logs.
Regardless, I would strongly suggest that you contact your county small woodlands Oregon State University Extension Agent. I have attached the web link to OSU below. OSU is recognized as the best Forestry school in the world, so are a great resource.
The agent can help with both finding a market for your thinning operation and offer expertise on managing your forest property.
Best of luck.
Go Beavs!!!