Analysis Of Salt Lake Basin Depositional System

The evaporite resources of Jiangling Depression is extremely rich. Since the drilling brine layer from the Sha4well and Lu9well, especially Jia Gang1well, there are multiple wells have been drilled evaporates and brine, Further confirmed the evaporite resources in jiangling depression is rich. Shashi formation are main reservoir of evaporite in jiangling Depression, By studying the salt lake sedimentary system of the Shashi formation in Jiangling Depression. We are able to fully understand the salt formation of growth characteristics and the plane distribution rule, the further promote the rational development of evaporites especially potassium salt.The study target of the article is the Jianghan formation in the Jiangling Depression in the Paleogene. Taking the principal theory of sequence stratigraphy and depositional systems as a basis, Through a comprehensive analysis of the regional geological data, core data, logging data, it is found that4sedimentary facies which included Salt lake facies, fluvial facies, delta facies and lake facies,9depositional sub-facies and9sedimentary micro-facies developed in the Shashi formation of Jiangling depression. Base on the recognition of sedimentary facies, Combined with seismic data and geochemical analysis of sequence, analyzed he recognition marks of cores, log and seismic boundary surface of various hierarchy, summary freshwater and salt formation stacking patterns, precise analyzed comparison and classification of stratigraphic sequence, divided thePaleogene of shashi formation into4third order sequences, From bottom to top, respectively SQsl, SQs2, SQs3, SQs4, to establish isochronous stratigraphic framework, and then analysis of the sedimentary system in the study area.Based on the analysis of the jiangling depression in shashi group of each on the basis of sedimentary system. This thesis focuses on shashi formation salt lake sedimentary system, The Paleogene in jiangling depression of shashi group, mainly consisted of clastic rock and mingled with thin beds of carbonatite, gyprock and salt rock, is a typical depositional framework of Salt lake basin. Comprehensive Study of Shashi Saline types, causes, sedimentary characteristics and controlling factors, the following results were obtained and understanding.(1) Classified by the chemical composition of the brine water, salt lake can be divided into carbonate type, type of sulfate and chloride type. The Jiangling Depression in the Paleogene is the chloride Salt Lake.(2) Salt Lake genetic model can be divided into two type:A Playa mode:At the end of the lake development, Water continuously enriched, the area decreases, water body becomes shallow, finally dried up into a salt. B Deep basin mode:In the period of the development of lake, at the same time, concentrated or salinity increasing, the area of the basin does not shrink or even larger, the water is not shallow and even deepen, due to the high salinity increase proportion of sinking, saline in the layer of salt precipitation, precipitation, into salt. Cause of the Salt Lake of the Jiangling Depression in the Paleogene belongs to the latter.(3) The Salt Lake salt-forming characteristics of Jiangling Depression:Vertically, the evaporite sedimentary strata with a clear rhythm, Identified the basic salt rhythm of the9types, Include sand-shale—salt rock, mudstone—containing gypsum salt rock, mudstone—containing mirabilite gypsum, mudstone—containing gypsum mudstone, mudstone—containing mudstone gypsum, mudstone—containing salt rock gypsum, mudstone—gypsum quality mudstone, marl—containing gypsum mudstone and mudstone—gypsum bed.Look from the plane by a center on the edge of a basin, development in turn carbonate, glauber’s salt, gypsum, evaporation from sub-sag edge to the center of rhythm has the obvious regularity, rock salt paste content increased, Mudstone, including cream mudstone and mudstone content decreased. Evaporite population distribution is widespread, characterized by southwest, eastern thickness thin, large area in north-central thickness. Shashi formation depositional period has multiple into the center of salt, the same as the pattern of sedimentary structure of wide basin depression in Jiangling.(4) Combined with Jiangling Depression geological background and sedimentary characteristics, We can conclude that the Salt Lake basin of Shashi formation in Jiangling Depression controlling factors:Paleoclimate, ancient landform and datum changes. Finally, based on the study of the jiangling depression salt lake control factors, We can concluded the Salt-forming mode of the Salt Lake Basin in Jiangling Depression.