庙西南凸起馆陶组油气差异成藏规律

针对庙西南凸起馆陶组主要成藏砂体类型与油气富集程度的差异，分析油气运聚条件及其对油气成藏的影响，总结差异成藏规律。研究表明，油田区为多断阶“脊—断”接力式油气运聚模式，油气先沿馆陶组底部区域砂岩输导脊向高部位断阶区横向运移，再由“通脊”断裂将油气分配至浅层聚集成藏。增压应力的分布与强度是影响油气运移与保存的关键，控制主要成藏砂体类型与油气富集程度。增压区利于油气保存而不利于油气运移，以厚砂体成藏为主；弱增压区、亚增压区利于油气运移但不利于油气保存，主要为薄砂体成藏。构造低部位弱增压与高部位增压型断块运移与保存条件最优，油气最为富集。同一断块内部，“脊—断”条件控制不同井区的油气丰度，“通脊”断裂切至输导脊的构造位置越高、在输导脊上累计错动面积越大，该区域的油气丰度也越高。这种油气差异成藏规律有效指导了庙西南凸起馆陶组的高效评价，同时为类似地区的油气勘探提供了重要参考价值。

DIFFERENTIAL ACCUMULATION OF HYDROCARBON IN THE GUANTAO FORMATION OF MIAOXINAN UPLIFT

The differential hydrocarbon accumulation including the differentiation of hydrocarbon enrichment degree in different types of sandbodies on the Miaoxinan Uplift is studied in this paper in a viewpoint of hydrocarbon migration and accumulation. A conceptual model is established as a result for differential accumulation of hydrocarbon. It is found that hydrocarbon movement follows a relaying migration model when it passes through a multiple "ridges-faults system" of a faulted terrace zone as that prevailed on the Miaoxinan Uplift. After moving up to a higher terrace of sandstone ridges of the Lower Guantao Formation, hydrocarbon will move laterally. It will further move along the faults connecting "ridges" to a shallow terrace once it is filled. The distribution and strength of structural compression, driving force to the migration and preservation of oil and gas, control the types of sandy accumulations and the degree of hydrocarbon saturation. High stress area was prone to hydrocarbon preservation. Thicker sandbodies are prioritized. Low stress area is favored to oil and gas migration rather than accumulation, hence thinner sand bodies dominate hydrocarbon accumulations. Fault blocks in the lower position of the low stress area as well as the blocks in higher position of high stress area are the places for optimal migration and preservation of hydrocarbon. Therefore, the regions at higher tectonic position on the transporting ridge with large cumulative dislocation and effective connection to faults will have greater hydrocarbon abundance. Based on the understanding mentioned above, the exploration of hydrocarbon resources on the Miaoxinan Uplift is quite successful.