四川盆地侏罗系大安寨段致密油多尺度差异化富集及主控因素

Differentiation accumulation in multiple scales of tight oil and its main controlling factors of Jurassic Da′anzhai member in Sichuan Basin

致密油的分布呈现大面积低丰度含油背景下局部富集的特征,亦只有在富集区内才能获得可观的商业油流。因此,甜点区的优选是致密油地质研究的重点。为分析致密油的富集规律,服务致密油甜点评价,以四川盆地侏罗系大安寨段为例,依托油田详实的生产数据,运用成藏物理模拟实验、显微薄片、场发射扫描电镜资料,并结合综合地质成图,对致密油的富集主控因素进行了研究。结果表明,研究区致密油的富集具有强烈的非均质性,占总井数22.5%的高产井产出了84.4%的油气,致密油富集程度的差异在盆地和区带尺度的分布上持续存在,并分别受不同因素的差异化控制。在盆地尺度下,受二次运移的影响,烃源岩只能控制致密油的分布外边界,在有利烃源岩区内部无法严格约束甜点区分布。在区带尺度下,有利沉积相带控制了致密油富集区带的分布。致密油富集甜点受有利成岩相和裂缝的控制。基于上述认识,建立了一套致密油富集甜点评价参数体系,为致密油甜点选区提供支持。

The tight oil is characterized by large scale distribution with low abundance,and accumulating in local areas.Only in enrichment regions,commercial oil production can be acquired.Thus,the evaluation of sweet spot is the key work of geological research of tight oil.Da′anzhai member in Sichuan Basin was taken as an example to study the accumulation pattern of tight oil,to serve the sweet spot evaluation of tight oil.Based on the large amount of production data from the oil field,accumulation physical analog experiment,thin sections,and Field Emission Scanning Electron Microscope(FESEM)were utilized to research the main controlling factors on tight oil accumulation,combined with the geologic mapping.According to the study,the accumulation and distribution pattern of tight oil shows a severe heterogeneity in the study area.High production wells,22.5%of all wells,produced 84.4%hydrocarbon in all production of the study area.This heterogeneity continuously exists both in basin and play scales.In different scales,the accumulation was controlled by different factors.In basin scale,due to the secondary migration,source rock could only control the distribution boundary of tight oil,and was unable to control the distribution of favorable play within the source rock area.In play scale,favorable sedimentary facies controlled the distribution of tight oil accumulation area.The final tight oil accumulation sweet spots were controlled by the favorable diagenesis facies and fractures.Based on the study,a set of evaluation parameters for the tight oil accumulation sweet spot was established to support the profitable area evaluation.