Sequence Stratigrapgy And Hydrocarbon Reservoir Forming Characteristics Research In Cretaceous Of Huhehu Depression

Huhehu depression is a secondary structural unit in the Hailaer-Tamucage Basin, The recent exploration shows that, Huhehu depression has good exploration potential and it is a new substitute field for hydrocarbon resources in Hailaer-Tamucage Basin. Recently,the hydrocarbon exploration in Huhehu depression gets more and more attention.This article is stand on the petroleum exploration practice of Huhehu depression. Under the study of basin tectonic framework, through established the sequence stratigraphic framework of the study area, sequence structure and sedimentary system distribution and evolution were analyzed. distribution and prediction model of sedimentary sand bodies were built , also connected with hydrocarbon accumulation condition,exploration achievements and the hydrocarbon reservoirs distribution rule shows by it, the hydrocarbon accumulation model were built.that the hydrocarbon exploration favorable areas were predicted. This has some practical significance to the next hydrocarbon exploration of Huhehu depression,also has theoretical and production significance to continental fault basin sequence stratigraphyand sequence stratigraphy applied in hydrocarbon exploration and other filed.This article takes latest development of sequence stratigraphy as theoretical basis.On the comprehensive research of seismic,drilling,logging,cores and paleontology in the whole of depression, also based on the characteristics of sequence boundary,we could divided cretaceous of Huhehu depression into three first-order sequence,five second-order sequence and eight third-order sequence.We had summarized the genetic type of sequence boundary and sequence stratigraphic framework characteristics of lake basin's different parts in this areas.On the base of isochronous stratigraphic framework,we had determined the study area main development five sedimentary systems,as alluvial fan,fan delta,braided river delta,sublacustrine fan,lake and so on,also had contrasted and analyzed the characteristics of typical sand body,and comprehensive application information of sandbody,heavy minerals,paleogeomorphic,seismic foreset reflection characteristics and so on,detailed study the deposit source of depression in different angles and different levels.We had system researched the space time distribution rule of sedimentary system,built the stabilized development model, intuitionistic reconstruction the process of sedimentary evolution.The characteristics and evolution of tectonic were analyzed in this article. Huhehu depression has three tectonic movements. From down to up separately is early extensional faulted depression stage, middle post-fault thermal subsidence fault sag stage, late depression stage. Two sets of fault system are developed in longitudinal direction: lower extensional faulted system mainly is NEE, NE and NNE; upper strike-slip fault system mainly is NNE and NNW. Multi-stages tectonic movement determines more structural style coexistent, the different fracture feature and combination form of this two fault system shows that the formation period's stress characteristic had obvious differences.The results show that contemporaneous sedimentary faulting has many assemble pattern in Huhehu depression, contains parallel fault terrace type,broom type,forked type and fault accommodation zone ect fault system,this bring up complicated tectonic paleogeomorphic and slope-break system of lake basin,and the model of sedimentary and accumulation of sandbody dispersion system in the depression were strictly controlled by their. This revealed that contemporaneous sedimentary faulting had controlled the sedimentary system distribution and sandbody dispersion style,also discussed the relationship between sandbody controlled by codeposition faulted slope fold belt and hydrocarbon reservoir enrichment.On the base of structure background, Huhehu depression was decided into fault controlled steep slope zone, gentle slope fault terrace zone and depression zone. On this way, different tectonic units established different sequence architecture patterns and sedimentary system composing model. and this special types of sequence architecture patterns also decided that different tectonic units had oil-gas formation model.On the base of sequence stratigraphic analysis,we studied hydrocarbon accumulation condition characteristics of Huhehu depression by petroleum geology theory, contains source rock characteristics,reservoir characteristics,source reservoir cap assemblage characteristics,hydrocarbon migration and aggregation characteristics,trapping characteristics and other field in hydrocarbon accumulation process, analyzed the controlling factors of hydrocarbon distribution pattern and enrichment,built the hydrocarbon accumulation model. predicted three favorable hydrocarbon exploration zone: northwest gentle slope zone,southern depression zone and southeast steep slope zone.We had determined three concrete exploration target.