Provenance And Sedimentary Characteristics Of Sanjianfang Formation In Middle Jurassic In Shengbei-Honglian,Tuha Basin

The oil and gas resources in medium-shallow reservoir in shengbei-honglian of Tuha basin have drawn researchers' attention, but the whole exploring extent is still low, and we have not made significant oil and gas exploration breakthrough. So, The research of Sanjianfang Formation has theoretical and practical significance.On the basis of previous studies, taking Sedimentology, petroleum geology, and so on knowledge as a guide, Based on the comprehensive analysis of drilling core, well logging data, seismic data and sample test data, the provenance direction, sedimentary facies types and characteristics, depositional model and lithofacies palaeogeographic characteristics were studied systematically.Comprehensive use of detrital component, sandstone distribution characteristics, characteristics of heavy minerals, ZTR index and seismic interpretation data, it is concluded that there are two provenances from the southern margin in the study area during the period of Sanjianfang deposition. The provenance of Shengbei area mainly comes from southwest in Lukeqin area, the source of Honglian mainly comes from the southern of Yingyeer slope.Based on the the comprehensive analysis of petrology, sedimentary structure, paleontology and logging facies marks, in the study area we have identified out braided river delta plain, front and shore-shallow lake subfacies, and we have identified multiple deposition micro facies, such as underwater distributary channel, underwater distributary Bay, mouth bar and sheet bar. Lacustrine facies mainly deposit mudstone, siltstone and shallow lake sub facies. The delta plain in shengbei area mainly deposit the micro facies of distributary channel, but Honglian area is dominated by the micro facies of plain swamp.Based on the analysis of the provenance and sedimentary characteristics, combine with the distribution of sand body, we have revealed the distribution characteristics of lithofacies palaeogeographic of Sanjianfang Formation in three layers. The sedimentary facies controlled the distribution of sand bodies in three layers, the sands thickness in Honglian area is thinner than the sands thickness in Shengbei area. In space,the sandstone is spread from the south to the north. From the plane,the delta lobe in Shengbei area is much stronger and further than the delta lobe in Honglian area.