Analysis Of Formation Conditions Of Stratigraphic Architecture And Non-structural Traps Of Silurian In Tarim Basin

Analysis of outcrop sections, cores, well logs and seismic data, applying the theory and methods of sequence stratigraphy, and modern sedimentology, the sequence stratigraphy and depositional system of the Silurian in the Tarim basin were systematically researched and analyzed. The main results and understandings are as follows:Analysis of sequence boundary, combined with the contact between the upper and lower of the key seismic stratigraphic sequence boundary, integrated by the filling evolution and the palaeo-geomorphic research of the basin, the three level sequence stratigraphic framework of Paleozoic Silurian in Tarim Basin was established. The Silurian is divided into two second-order sequences, four third-order sequences and eight system tracts, in where three types of sequence boundary were identified. In the third-order sequence stratigraphic framework, the stacking patterns, and distribution area of stratigraphy were analyzed, the sequence stratigraphic patterns of the tidal flat, coastal and brainded rive delta were constructed, and the spatial distribution law and evolution of different systems tracts were discussed. It is concluded that there are three sequences constitutes including rising base-level transgressive, stable base-level aggradational and downing base-level progradational parasequence sets. According to the comparison and analysis of features of the sequence stratigraphic framework of the study area, it is summarized that formation and development of sequence stratigraphy are controlled by the three elements: tectonic subsidence, changes of lake level, and paleoclimate.According to the causes of sedimentary facies and identification marks, four depositional systems were identified in Paleozoic Silurian Tarim Basin, which were tidal flat, coastal, braided-river delta and shallow shelf, etc. Within the sequence stratigraphic framework, further summary for the evolution of various types of sand body was set up. It is shown that sq1 is mainly coastal depositional systems and a little tidal flat depositional systems in centre of Tarim, tidal flat depositional systems in Bacu, coastal depositional systems and shallow shelf in north part of Tarim, coastal depositional systems and brainded rive delta depositional systems in east part of Tarim, sq2 is mainly shallow shelf in north part of Tarim, shallow shelf and tidal flat depositional systems in centre of Tarim to Bacu, sq3 is mainly shallow shelf and tidal flat depositional systems, and a little coastal depositional systems in east and north part of Tarim, sq4 is mainly coastal depositional systems, and a little tidal flat depositional systems and brainded rive delta depositional systems somewhere, and there does not lie in north part of Tarim, there lies in coastal depositional systems and brainded rive delta depositional systems in east part of Tarim, totally. The transgressive systems tract were the coastal depositional systems, which mainly developed retrogradation accompanied by aggradation of Silurian in Tarim Basin. The high system tract were mainly the tidal flat depositional systems, which developed progradation accompanied by aggradation and erosion of Silurian in Tarim Basin.Palaeogeomorphology, sequence stratigraphy and sedimentary facies were analyzed, and the control of the Palaeogeomorphology, different A/S, and sedimentary facies to the depositional systems development were identified. Summarizing the controlling mechanism of sand body by sequence and facies, and the controlling model of Palaeogeomorphology on the deposition systems. It is found that there lied in two slope in south and north part of Tarim, and divide into up and down slope, and gradual slope mainly developed tidal depositional systems and sand-body distributed widely and thin in centre of Tarim, and steep slope mainly developed coastal depositional systems and sand-body distributed little and thickly in north part of Tarim, sand-body distributed widely and thickly in southeast part of Tarim. TST is maily coastal depositional systems and HST is tidal flat depositional systems.Analysis of sedimentary of sequence and palaeogeomorphology and depositional systems, formation conditions and the type of non-structural traps are founded including stratigraphic overlap trap, stratigraphic unconformity trap, updip pinchout trap and igneous traps,.On the basis of comprehensive research on the sequence stratigraphy, the distribution of depositional systems and hydrocarbon accumulation conditions, favorable reservoir distribution of Silurian in Tarim Basin was defined, and the favorable exploration area is focus on the depression such as Manjiaer and Awat rift, especially along Suntuoguole nose hump.