A more plausible explanation is that an oil/gas expulsion front followed by a gas expulsion front has moved slowly and sporadically updip toward the perimeter of the basin near the present oil and gas fields.

• 较为可信的解释是一个油气排出前缘及其之后的排气前缘缓慢地和零星地向上倾方向向盆地周边的目前的油气田所在地推进。