Study On The Sedimentary Facies And Sand Body Distribution In Upper Es4Formation Of Paleocene In Lijin Sag

Beach bar sand bodies, one of the most important reservoirs, have been attractingincreasing attention recently. Beach bar sand body was widely distributed in the upper Es4formation of Paleocene in Dongying Depression and is regarded as one of the potential oiland gas reservoirs. In this paper, the stratigraphy and plane distribution of the upper Es4formation was studied based on the theories of high resolution sequence stratigraphy andsedimentology. The high-resolution sequence stratigraphic framework of the upper Es4formation of Paleocene in Lijin Sag was established by study on combination with numerouscore observations, seismic data, well logging data and well tests. The upper Es4formation is athird-order sequence, composed of a lowstand systems tract, a transgressive systems tract anda highstand systems tract respectively, and can be future divided into7parasequence sets.Based on core observation and seismic data, well logging, and well test analysis, fourdepositional systems, fan delta, beach bar, storm beach bar and semi-deep lacustrine, areidentified in the study area. On the basis of cores, well logging and seismic response to theappropriate Core facies–Logging facies-Seismic facies plate is formulated and used to helpfurther identify the depositional systems in nearby area. In this paper, we distinguish the stormbeach bar from beach bar according to the different hydrodynamic conditions and thedifferent sedimentary structures. Storm beach bar is characterized by the sedimentarystructures of scour surfaces, hummocky cross-bedding, cutting structure, flush cross-bedding,wave ripple bedding and wavy cross-bedding on the core. Four main depositional systemswere indentified from the response of seismic data. Fan delta exhibits wedge external andforest structure internal. Beach bar and storm beach bar show similar seismic features,showing strong reflection of the sheeted in the amplitude, continuous, short axis like acontinuous phase axis as distribution. Semi-deep lacustrine demonstrated as sheeted external,the upper and lower interfaces are parallel, internal parallel, sub-parallel or chaotic reflectionconfiguration.In addition, the sand body distribution of the upper Es4formation of Paleocene in LijinSag was characterized in the study area by single well facies analysis and multi-well crosssections analysis. Fan delta facies are well developed near the Binxian Uplift in the wholesequence, and lowstand systems tract is the period fan delta prevailed. Beach bar systemdistributed principally in front of the fan delta or near provenance, mainly developed in thelowstand systems tract. While storm beach bar system mainly developed in relatively deepwater and are mostly found in the third parasequence sets of lowstand systems tract and fewfound in transgressive systems tract. Storm beach bar is distributed close to the fan delta frontand the beach bar sand body.