If anything, Russia's petro exports to China are going down, not up. The wells and pipelines that supply (mostly) China are in Siberia. It's quite a challenging environment for both wells and pipelines, mostly due to permafrost. Shortly after the February invasion of Ukraine many Western companies exited Russia. That included the petro 'majors' that Rosneft had partnered with on the Siberian wells. Russia does not appear to have home-team talent to replace the staff of the now-exited majors. On top of that, equipment needed for (eventual) maintenance and drilling new wells are on the sanctions list. It's looking as though those wells will need to be 'shut in'. The only eventual repair would be re-drilling.

The western wells have, as you mention, pipelines that go to Europe with few terminal points in warm-water ports. Of those, the ones in the Black sea would need tanker transport that transits the Bosporus, the one that goes to St. Petersburg is hampered by both seasonal ice-in, and there being insufficient depth for even-normal-sized oil tankers - and the Baltic has turned into a NATO internal sea, so any transfer would have to be done off of unfriendly shores.

Also one pipeline to (and potentially through) Turkey to the Med, and a couple that go to the Caspian (not useful for shipping to China.

Then there's the whole insurance thing. Maritime insurance is almost entirely Anglo/American - and they're refusing to insure any shipping with Russian cargo. Russia can provide insurance themselves (sovereign) but what happens if a NATO power holds a tanker for violating sanctions in their waters? Russia might be able to indemnify on one or maybe two but probably no more. And just the thought that this might happen is making Russian insurance unattractive to shippers.