Petroleum System Analysis On Haitongji Sag Belt In Dongpu Depression

This paper focuses on critical petroleum exploration problems on Haitongji sagbelt, takes petroleum bearing theory as guide and enhances comprehensive analysis onbasic geologic condition. From basic factors and collocation relationship of petroleumsystem to impaction on hydrocarbon generation, according to oil gas shows and oilsource correlation, the paper has also vertically divided Lower Tertiary PetroleumSystem of Haitongji Sag Belt and enclosed planar petroleum system boundary. Afteranalyzing petroleum system formation, further petroleum exploration employmentsuggestion has been made for this sag.Analysis has also been carried out on source rock, reservoir rock, cap rock andsource-reservoir-seal assemblage. Predominant source rock is dark shale, oil shale,limestone, dolomitic shale and calcareous rock of interval ES1 and ES3, among whichES3 source rock is of best quality. Lower Tertiary reservoir is well developed and islithologically siltstone and pebbled sandstone, belonging to fan delta-slump turbiditefan sedimentary system. Each reservoir development area corresponds to a big fanbody source area. Source rock of interval ES3 reached its maximum buried depth atDongying deposition period and all got to its hydrocarbon generation threshold withpart to gas generation period.This paper has analyzes collocation relationship between basic geologic processand geologic factors. After studying thermal evolution and hydrocarbon generationhistory, it is thought that oil and gas of interval ES1 source rock is centrally generatedin Haitongji Sag. Migration mainly happened eastward and southward, secondlywestward and northward and petroleum finally accumulated in Liuzhuang-Mengju.Oil generated of interval ES3 source rock is also centrally in Haitongji Sag. It reachedhydrocarbon threshold when it is buried 2800m deep with Ro 0.5% while it reachedoil generation peak when it is buried 4000m deep with Ro 1.3%. Oil and gas migratedall around to the sag.Using abundant geochemical indexes to do oil source correlation such asproperty of normal paraffin, sedimentary environment, source constitution, maturity,group compositon, characteristics of aromatic hydrocarbon and so on. Crude oil ofES1 derived from ES1 and ES3 source rocks while oil and gas of ES2 and ES3 derivedfrom ES3 source rock. Two petroleum systems were marked off of Haitongji Sag Beltin Dongpu depression, ES1 of Lower Tertiary (!) and ES3-Shahejie (!).From the above, it is considered that Liutun-Haitongji Sag conjunction is afavorable exploration target of inherited palaeohigh, lower S2 of west flank and Wenxiarea.