China holds strategic petroleum reserves and does not publish their level. It has occasionally disclosed figures for particular sites or at particular moments, but there is no regular series, and the split between strategic and commercial inventory is not reported.
The market therefore infers reserve accumulation as a residual. Take crude imports plus domestic production, subtract refinery runs, and whatever is left has gone into stock somewhere. That surplus-to-runs calculation is the standard approach and it is genuinely informative, but every term carries error and the residual accumulates all of it.
The behavioural pattern that does seem robust is price-responsive accumulation: buying has tended to increase when prices are low and slow when prices are high. That is rational for a strategic buyer with a long horizon and no obligation to accumulate at any particular moment, and it makes reserve buying a partial stabiliser on the downside. It also means reserve demand is not a reliable source of support at higher prices.
The distinction from a commercial stockpile matters for the same reason it matters for the US reserve: strategic stocks do not respond to curve structure and do not drain in backwardation. Adding an inferred strategic build to commercial inventory produces an aggregate with two different response functions in it.