Sequence Stratigraphy And Lithologic Trap Predication In The Lunpola Basin

Tibetan Plateau is located in the eastern part of Tethys and has potential for oil andgas exploration. In recent years, as one of the strategic replacement bases of energy inChina, it has been receiving much attention. Cenozoic continental basins, containingLunpola, Nima, Dongcuo and Tuotuohe basin, have been proved with hydrocarbongenatation conditions. Lunpola basin in central Tibet covers an area of some3600km2and is the highest petroliferous basins in the world with average elevation ofabout4600meters. This article is based on the petroleum exploration practice ofLunpola basin. Under the research of basin tectonic framework, through establishedthe sequence stratigraphic framework of the area, sequence structure and sedimentarysystem distribution and evolution were analyzed. Distribution and prediction model ofsedimentary sand bodies were built. Petroleum geology was also researched. We alsopredicted good hydrocarbon accumulation area. It is importance of next oilexploration in Lunpola basin.This paper takes the latest development of sequence stratigraphy as researchmethods. According to the comprehensive materials of seismic、drilling、logging、cores and paleontology in the Lunpola basin, also used on the characteristics ofsequence boundary, two second-order sequence and five third-order sequence wereidentified. We also summarized the genetic type of sequence boundary and sequencestratigraphic framework characteristics of the Lunpola basin. On the base ofisochronous stratigraphic framework, we had determined five sedimentary systems, asalluvial fan, fan delta, braided river delta, sublacustrine fan, lake. We alsoreconstructed the process of sedimentary evolution.Structural features and tectonic evolution were analyzised systemly. Lunpolabasin experienced four stages including the initial rift, rift expension, rift contractionand basin transformation period.Both normal and thrust fractures exist in the Lunpola basin. Thrust fracturesmainly develop in northern part of the basin. Normal fractures mainly exist in thecenter of the basin. Due to these fractures, Lunpola basin was divided into three partsfrom north to south including overthrusting area, central depression and uplift zone.On the base of sequence stratigraphic analysis, we studied hydrocarbonaccumulation condition characteristics of Lunpola basin 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 inhydrocarbon accumulation process, analyzedthe controlling factors of hydrocarbon distribution pattern and enrichment, built thehydrocarbon accumulation model. We predicted two favorable hydrocarbonexploration zones: Jiangriacuo to Jiangjiacuo zone in the central depresssin and thearea between well N-4and L-5. We had determined two concrete exploration targetsincluding fan delta front facies and turbidite face.