摘要
大牛地气田位于鄂尔多斯盆地东北部、伊陕斜坡之上,上古生界构造较为平缓,断裂不发育,属于强非均质性的致密砂岩气藏,油气近源聚集。大28井区位于大牛地气田北部,二叠系下石盒子组一段盒1-1亚段为主力开发层系之一,辫状河沉积特征明显。为了厘清该井区主力开发层系的沉积特征,以盒1-1亚段沉积微相为研究对象,分析了露头、岩心、测井资料,识别出辫状河道、心滩、泛滥平原共3种主力沉积微相。研究结果表明:①盒1-1亚段可细分为盒1-1-1、盒1-1-2两个小层,共发育4期河道,垂向、侧向叠加均表现出正韵律特征,单期砂体保存完整,剥蚀不明显,河道多次冲刷导致厚层泥质沉积较少,局部发育细粒薄夹层,为高能辫状河道沉积;②砂体沿物源向南连片推进,主河道位置不变,具有中部厚、两侧薄的特征,北部砂体更为发育,以粗粒沉积为主。结论认为:①盒1-1亚段砂体叠置规律复杂,厚度与含气性存在明显差异,心滩有效砂体厚度超过6.5 m,辫状河道有效砂体厚度小于4.0 m;②气层在心滩与辫状河道沉积微相中均可发育,尤其是在二者演变区域,受水流冲刷影响,砂质更纯,泥质含量低于15%,自然伽马值介于45~70 API,砂体物性更好,含气程度更高,可以作为后期开发、措施井位部署的参考依据。
Daniudi gasfield is located at Yishan slope in northeastern Ordos Basin,where the Upper Paleozoic structure is relatively gentle and no faults are developed.It is a tight sandstone gas reservoir featured by strong heterogeneity and proximal oil and gas accumulation.Da 28 well area just lies in northern gasfield,in which He 1-1 submember of the Permian Lower Shihezi 1 Member is one of the principal development reservoirs and presents obvious sedimentary characteristics of braided river.In order to clarify the sedimentary characteristics of the principal development reservoirs in this well area,the sedimentary microfacies of He 1-1 submember was taken as objectives to analyze outcrop,core,and logging data.And three principal microfacies were identified,in⁃cluding braided channel,point bar,and flood plain.Results show that(1)this submember can be subdivided in⁃to He 1-1-1 and He 1-1-2.There is four-phase channel developed,and vertical and lateral superposition repre⁃sents the nature of positive rhythm.Single-phase sandbody is preserved completely without obvious denudation.Frequent channel scouring leads to a few thick argillaceous sediments with some thin fine-grained interbed,which belong to high-energy braided channel deposits;and(2)the sandbody advances continuously southward along provenance,and the main channel stays in the same place,presenting the characteristics of thick in the middle and thin on both sides.The sandbody in the north is more developed and dominated by coarse sedi⁃ments.In conclusion,the sandbody of He 1-1 submember is characterized by complex superposition and clear difference between thickness and gas content.The effective sandbody thicknesses of point bar and braided chan⁃nel are 6.5 m and less than 4.0 m,respectively.what's more,gas layers are developed in the microfacies of point bar and braided channel,especially in their evolution zones,where sand is purer due to the effect of cur⁃rent scouring.Shale content is less than 15%,Gamma-ray value ranges from 45 API to 70 API,the sandbody's physical property is better and gas content is higher,which can be used as reference and basis for the late de⁃velopment and measured well deployment.
作者
刘嘉
LIU Jia(No.1 Gas Production Plant,Sinopec North China E&P Company,Zhengzhou,Henan 450006,China)
出处
《天然气技术与经济》
2022年第3期11-18,共8页
Natural Gas Technology and Economy
