Study On Sequence Stratigraphy And Sedimentary Facies Of Carboniferous-permian Sequence In The Central And Southern Part Of Huanghua Depression

Huanghua Depression is a relatively prospective oil-gas depression in the Bohai Bay Basin.It is rich in resources,but due to the complexity of geological conditions,it has a big impact on exploration.In order to explore deep-seated oil and gas storage conditions,The study of the depression began deep into the Carboniferous-Permian strata and the study area was in the central and southern depressions.The first step is to analyze the sequence stratigraphy of the study area,analyze and determine the sedimentary types and their distribution characteristics in the sequence stratigraphic framework,and then combine with conditions for oil and gas accumulation,predictions of favorable areas will be provided to provide a basis for deep oil and gas exploration.Combining the characteristics of structural evolution and sedimentary characteristics within the depression,the sequence stratigraphic theory was applied to the study of the Huanghua depression.By identifying the sequence boundary,the sequence stratigraphy in the study area was accurately divided.The study area is divided into six third-order sequences,Sq1 includes the Carboniferous Benxi Formation and the lower Taiyuan Formation,Sq2 includes the upper Taiyuan Formation,Sq3 includes the entire Shanxi Formation,Sq4 corresponds to the Lower Shihezi Formation,Sq5 includes the Upper Shihezi Formation,and Sq6 corresponds to the Shiqianfeng Formation,and establish a sequence stratigraphic framework in the study area.According to the established sequence stratigraphic framework,the types of sedimentary facies and their distribution characteristics were judged.The following three types of sedimentary systems are mainly present in the region: lagoon-barrier sedimentary systems,delta depositional systems,and river sedimentary system.Among them,the Sq1 and Sq2 mainly develop the lagoon-barrier sedimentary system;the Sq3,Sq4 and Sq5 mainly develop the delta sedimentary system;the Sq6 mainly develops fluvial sedimentary system.Integrated single well and joint well sedimentary facies analysis,make a plan view of the sedimentary facies of the Carboniferous-Permian in the central and southern Huanghua Depression.Using the sedimentary facies types and their distribution characteristics analyzed within the sequence stratigraphic framework,the sedimentary reservoirs are associated with oil and gas distributions.Combined with the results of previous studies on neighboring regions,it is believed that the delta plain subfacies has the closest relationship with the oil and gas distribution.Based on this,the favorable reservoir facies belts of the Carboniferous-Permian in the middle and southern Huanghua Depression are predicted.