鄂尔多斯华池地区三叠系延长组长8油层组沉积相特征

Sedimentary Facies Characteristics of Triassic Yanchang Formation Chang 8 Oil Layer in Huachi Area,Ordos Basin

鄂尔多斯盆地华池地区三叠系延长组长8油层组勘探潜力巨大,但由于对沉积特征缺乏系统的认识,可能会影响后期的油气勘探开发。基于岩心观察、粒度分析和常规测井相分析,对华池地区三叠系延长组长8油层组进行了系统研究。结果表明:(1)沉积相类型是辫状河三角洲,属于辫状河三角洲前缘亚相,发育有水下分流河道、分流间湾、河口坝、远砂坝和席状砂5种沉积微相。(2)纵向上长81河道砂体发育情况好于长82,横向上南西—北东方向上的河道砂体发育情况和横向连片性均好于西北—东南方向上的河道砂体。(3)在平面上发育南西—北东向的水下分流河道,长82—长81沉积微相的变化反映了物源持续推进,水下分流河道范围继续拓宽,且分布范围变广的物源进积过程。(4)基于不同微相物性对比和沉积相纵向、横向、平面研究,得出优势相为水下分流河道和分流间湾。

The Chang 8 oil-bearing formation of Triassic Yanchang Formation in Huachi area of Ordos Basin has great exploration potential,lack of systematic understanding of sedimentary characteristics,which may affect the later oil and gas exploration and development.Based on core observation,particle size analysis and conventional logging facies analysis,the Chang 8 reservoir group of Triassic Yanchang Formation in Huachi area was systematically studied.The results show that:①The sedimentary facies type is braided river delta,which belongs to the braided river delta front subfacies.There are five sedimentary microfacies:underwater distributary channel,interdistributary bay,estuary dam,distal bar and sheet sand.②Vertically,the development of channel sand bodies in Chang 81 is better than that in Chang 82.Horizontally,the development of channel sand bodies and lateral connectivity in the southwest-northeast direction are better than those in the northwest-southeast direction.③On the plane,the underwater distributary channel in the southwest-northeast direction is developed.The change of sedimentary microfacies of Chang 82-Chang 81 reflects the continuous advancement of provenance,the scope of underwater distributary channel continues to widen,and the distribution range becomes wider.④Based on the comparison of physical properties of different microfacies and the vertical,horizontal and plane study of sedimentary facies,the dominant facies are the underwater distributary channel and the interdistributary bay.