Sedimentary Characteristics Study On Wulanhua Sag, Erlian Basin

Wulanhua is a newly discovered sag in Jining area,Erlian Basin, an area of 600km2,the maximum depth of 3000 m.It is a relatively independent sag which is located on Wenduermiao uplift,southern of Erlian Basin At early stage(during the deposition of A-4 episode),sedimentary characteristics are very different between Wulanhua sag and other areas of Erlian basin,especially in the central and northern.In particular, Aershan Formation can be divided into four episodes, among them,A-4 episode is a set of thick layer coarse debris sediments,and only A-4 episode is developed in Wulanhua sag, locally developed thin glutenite,mainly thick mudstone, Industrial oil flow is found in Aershan Formation and Tenggeer Formation of Wulanhua sag, but the degree of enrichment of low reservoir with complex forming conditions,requiring further study on stratigraphic features, sedimentary distribution of Wulanhua sag.This study longitudinal research on all of sedimentary strata above the sag substrate, specific studies are:(1)Research of stratigraphic sequence and development characteristics: Make full use of three-dimensional seismic and well data, application of sequence stratigraphy、sedimentology and other petroleum geological theory,carry out work of stratigraphic sequence division and correlation profile of area isochronous sequence stratigraphic framework, In isochronous framework of sequence analysis sequence characteristics of different zones,find out the sequence structure characteristics and relationship between layers.(2) Seismic facies: using existing three-dimensional seismic data,carry out seismic facies identification, and to establish the relationship between the conversion of seismic facies and sedimentary facies,make study on plane distribution of typical seismic facies, prepared by plan of seismic facies.(3) Sedimentary facies: Use of existing data, establish sedimentary facies model in this area, identify sedimentary facies mark,divide types of seismic facies,make clear of sedimentary facies distribution characteristics. Combined with reservoir characteristics and hydrocarbon distribution has been found, summarize the oil-bearing of different sedimentary microfacies.(4) Prediction of favorable phase: Combined with seismic facies and sedimentary facies of the correspondence between,make prediction of favorable sedimentary facies, reservoir facies on the main oil-bearing strata, highlight the feature of identification and distribution among different causes of reservoir.Study found in the A-4 episode,the sedimentary strata of Wulanhua sag was thick northern and southern thin, depocentre in northern sag.And in the Tengger Formation sedimentary, Wulanhua sag overall settlement, the north and the south depression layer thickness are basically the same.Considering the variety of geological background Wulanhua recessed provenance, tectonic setting and climate,Make full use of core, logging and seismic facies analysis, etc,On the A-4 episode ~ Teng-1 episode sedimentary facies were studied,finally found that the A-4 episode ~ Teng-1 episode developmental fan delta, nearshore subaqueous fan, lake fan, braided river delta, lake five sedimentary type,,And A-4 episode provenance direction diverse, rich sedimentary types, developmental four kinds of depositional system :ditch fan, fan delta, Valley fans, slots fan;and Teng-1 episode provenance direction and sedimentary facies types are relatively simple, provenance mainly from the south, fan delta development.In general,on the A-4 episode ~ Teng-1 episode of Wulanhua sag,water became shallow from the bottom up,sediment Increased and bacame thicker,Sediment source from multiple directions to a single direction. Finally through the sand body distribution, sedimentary environment, tectonic characteristics came to the conclusion that central of southern sag is the favorable phase.