Study On The Hydrocarbon Accumulation Characteristics Of The Lower Cretaceous In The Southern Sag Of The Wuliyaistai Depression,Erlian Basin

In this paper,based on the full investigation of the geological structure background of the southern sag of the Wuliyasitai depression,combined with geochemical analysis test data,logging,logging,oil testing,lithology observation,formation temperature and pressure test data,production dynamic data,mercury intrusion test analysis Data and other data,using oil and gas geochemistry,molecular geochemistry,petroleum geology,organic petrology and other disciplines as theoretical guidance,comprehensive and detailed research on the oil and gas accumulation characteristics of the Lower Cretaceous in the southern sag,and on this basis,further analysis of oil and gas accumulation mode and main controlling factors.The formation temperature and pressure field is characterized by the atmospheric high pressure gradient.Reservoir porosity type is mainly ultra-low porosity and low porosity,permeability is mainly ultra-low permeability and ultra-low permeability,secondary pores are mainly developed,and the separation is poor,the overall evaluation of reservoir properties is poor,effective storage The lower limit of layer physical property and depth decrease exponentially.Organic matter is mainly in the immature to mature stage,with the characteristics of unimodal hydrocarbon generation.The biomarker maturity parameter is not recommended for use in the study area;due to the original productivity,the organic matter abundance is high,and the redox degree of the deposition environment It also has a greater impact on it;organic matter type?is the main type,biomarkers have the characteristics of higher plant input from terrestrial sources,the original sedimentary environment is partial freshwater partial oxidation,and crude oil is mainly characterized by light and high wax content,and does not have two consecutive The characteristics of the crude oil density of other depressions in the basin decrease with depth.The crude oil group components are mainly saturated hydrocarbons,followed by aromatic hydrocarbons.The biomarker maturity parameters are generally large,which reflects that the crude oil in the south depression is mainly mature crude oil.The carbon isotope of whole oil and the characteristics of biomarkers indicate that crude oil is mainly contributed by higher plants.Accumulation power is mainly atmospheric system,which can be divided into two types:self-source atmospheric pressure and other source atmospheric pressure accumulation system.The oil and gas reservoirs in the K1ba Formation may be continuous two-stage filling and accumulation,while the K1bt~1 oil and gas reservoir may be mainly one-stage filling and accumulation.The hydrocarbon accumulation model mainly includes the following three types:the lithology of oil and gas migrating along the sand body or the fault-sand body laterally,the structure-lithology trap accumulation model;the stratigraphic trap formation with the lateral migration of unconformity surface Reservoir model;the hydrocarbon migration trap formation model of the sandstone lens in the source.The main controlling factors of oil and gas accumulation in the study area:the vertical and horizontal distribution areas of effective source rocks determine the distribution range of oil and gas;different transmission systems determine the distribution positions of different types of oil and gas reservoirs;Distribution;favorable sedimentary facies to control the formation and distribution of oil and gas-rich areas.