Research On Sedimentary Facies Of Shahezi Formation And Prediction Of Favorable Areas In Yingshan Fault Depression In Songliao Basin

Yingshan fault depression is a double break graben fault depression controlled by the Sizhan and Linjiang fault,which locates in the southeast of Daqing exploration area in northern Songliao Basin.The main part for double break,local to a single fault at both ends in north to the south.The target formation of this paper is Shahezi formation.Deep natural gas exploration in Yingshan fault depression has made some breakthroughs,also has some cognition.The research results obtained are given priority to volcanics of Huoshiling formation and Yingcheng formation,the lack of Shahezi formation of sedimentary facies system research and understanding of distribution law of hydrocarbon source rock.At present,hydrocarbon main fault trough of Yingshan fault depression is not implemented and the next step exploration direction is not clear.In order to predict exploration prospect of Shahezi formation in Yingshan fault depression,the paper is based on logging,seismic,outcrop and other relevant information and guided by the theory of sedimentology,structural geology and sequence stratigraphy.Firstly,make seismic data interpretation by the hierarchical scheme of the latest drilling and logging,seismic data in the interest of making clear the structure of fault depression,the distribution range of Shahezi formation and the development position of hydrocarbon main fault trough;Secondly,sedimentary facies of Shahezi formation are studied by the seismic facies analysis,single well facies and even well facies analysis,together with the technology of seismic attribute;Finally,the favorable areas are predicted based on the research above.Studies have shown that Yingshan fault depression is SN-NNE trending on the whole.It is divided into four tectonic units:Taipingchuan trough district to the north,Sizhan tectonie inversion zone to the south,then south to Xingshan trough district,the southermmost part for Linjiang uplift belt.The research on sedimentary facies of Shahezi formation in Yingshan fault depression find that it developes four types of sedimentary facies in the main.The sedimentary facies are lake facies,fan-delta faeies,braided river delta facies and alluvial fan facies.Based on the characteristics of seismic reflection,the seismic facies of Yingshan fault depression of Shahezi formation divided into three types:the seismic response of parallel,middle and low amplitude,continuous represents sedimentary environment of the deep and semi deep lake;the seismic response of quasi parallel,middle and low amplitude,middle and low continuous represents sedimentary environment of shore-shallow lake and fan delta;the seismic response of random reflection,middle and low amplitude,intermittent represents sedimentary environment of alluvial fan and braided river delta.On the plane,the favorable exploration area in Yingshan fault depression is the transitional zone between the main fault trough at moment and the main fault trough of Shahezi phase;In profile,the favorable exploration zone is close to the boundary of development zone of 'fan delta,finger interaction to hydrocarbon source rocks of lake facies,which becomes geological conditions of tight gas reservoir.