zhè / kǒu / jǐng / zuān dào / yī dìng / shēn dù / hòu / zhōng yú / fā xiàn / le / wěn dìng / de / yóu céng

这口井钻到一定深度后，终于发现了稳定的油层。

After this well was drilled to a certain depth, a stable oil layer was finally discovered.