Study On Stratigraphy Framework And Sedimentary Facies To Yingshan Formation In The Central Uplift Zone, Tarim Basin

Tarim basin is the inland superimposed petroliferous basin in China, which is a key area ofoil and gas exploration, especially the Central Uplift Zone because of its huge explorationpotential. However, to make sure the progress of oil and gas exploration and research, determiningsequence division and sedimentary facies distribution is essential. This study selected the CentralUplift Zone in Tarim Basin as the research area, focus on YingShan Formation of the LowerOrdovician. We carried out a study on detailed sequence stratigraphy and sedimentary facies,seeking to provide new ideas of the next exploration.According to previous study,this paper studied on sequence division and sedimentary faciesdistribution of YingShan Carbonate Formation by comprising the characters such as drilling cores,logging, seismic and geochemical data, etc., based on comprehensive application on Geology,Geochemistry, Geophysics, and other related principles and methods. These research couldprovide the basis for prediction of advantageous reservoirs in the future.Using the classic sequence stratigraphy method combined with the situation in the CentralUplift Zone, this paper established the sequence stratigraphic division scheme through the in-depthanalysis of the YingShan Carbonate Formation. YingShan Formation was divided into43rd-sequences and94th-sequences. In addition, on the basis of sequence stratigraphic frameworkestablished on YingShan Formation, the study carried out a study on sedimentary facies of twokey blocks in Bachu and Tazhong area, pointed out the sedimentary characteristics of the CentralUplift Zone in different periods. After the research on56wells, we believe the study area mainlydeveloped a set of marine carbonate rocks with the main sedimentary facies tapes as Continentalshelf facies, Platform margin slope facies, Slope edge facies, Open platform facies and Restrictedplatform facies, distributed as platform to shelf from west to east. The study found the sedimentaryfacies distribution under the influence of tectonic stress and ancient ancient landforms showed adirectional distribution, generally spread nearly N-S. By a combination of extensional stress andextruding stress, Platform shoal subfacies and lagoon subfacies of Restricted platform facies in theCentral Uplift Zone distributed near NE-SW interleaved high and low relief. During SQ1-3periodwhich was transgression stage as a whole, the northeastern and Southern of the study area had progradation by Continental shelf facies, Platform margin slope facies, Slope edge facies of gray,dark gray mudstone and mud-limestone. In the central of the study area, Restricted platform faciesconcentrated was developed as gray and gray-white dolomite which was significantly reducedfrom SQ3period. There was a large-scale regressive happened on SQ4period. Not onlyContinental shelf facies in the northeast and southwest area showed a trend of out-migration,Restricted platform facies in central area had a significant improvement in content and distributionof gray and gray-whit dolomite.In general, the Central Uplift Zone of Tarim Basion basically inherited the ancient geographyof the late Cambrian during the early Ordovician sedimentary with some large change in someregion, of which the platform expanded obviously. Sea level rendering the cyclical change led tothe migration of facies. This paper established the sedimentary mode of YingShan Formation inthe Central Uplift Zone through the research on sedimentary facies evolution. This modesufficiently showed the sedimentary characteristics in the study area, reflecting the distributionand migration of YingShan Formation on plane.