The Source And Filling History Of Oil And Gas Of Mid-Shallow Layer In Bal-Tang-Ma Coastland, Off-Shore Area Of Dagang

Bai-Tang-Ma coastland, off-shore area of Dagang, lies north from Lujuriver,south to Mapengkou area, west from shoreline,passing by surface and sea wall, eastto about 2m deep surface of marine chart. According to structure position,Bai-Tang-Ma coastland lies to east slope of north Dagang burial hill structure zone.It includes such four local structures as Baishuitou, Tangjiariver,Madong-Madongdong and Mapengkou and the total area is about 300km2.Mid-shallow layer in off-shore area consists of all stratum which is above 3500mdeep. As for the Bai-Tang-Ma coastland, the mid-shallow layer includes Nm,Ng ofthe upper Tertiary, Ed and part of upper Es1 of the lower Tertiary. TakingTangjiariver oil field for example, the author researched thoroughly the source andfilling history of oil and gas of mid-shallow layer in Bai-Tang-Ma coastland,off-shore area of Dagang. The aim of the paper is to clarify the source of oil and gasof main oil layers of mid-shallow layer in Bai-Tang-Ma coastland and to discuss themigrating and filling stage and time of the oil and gas of the main oil layers. Thesewill offer geochemistry evidence for establishing filling modes of mid-shallow layerreservoirs in exploration area. In this paper, many methods and techniques are utilized, such geochemicalmeasuring and testing techniques as carbon isotope, color spectrum (CS), colorspectrum-mass spectrum (CS-MS). In addition, normal slice identification, scanningelectron microscopic observation (SEM) and energy spectrum analysis, casting sliceanalysis, transmission polarization observation, fluorescence microscope analysisand cooling-heating platform, etc. are involved in this research. According to geochemical analysis such as carbon isotope, CS, CS-MS of oiland source rock, δ13C and such biological marks as G/ C30H,O/ C30H,Ts/Tm,ααR C27/C29,ααR C28/C29,C3122S/(S+R),C2920S/(S+R) are chosen to compareoil with source rock. It is indicated that the oil of mid-shallow layer doesn't originatefrom source rock of Es1 and Ed, but from deep source rock of Es3 and Es2.IV大港滩海白唐马沿岸带中浅层油气来源及成藏历史分析Considering the limited thickness and ability of producing petroleum of source rockof Es2, it is deemed that source rock of Es3 is the main source of oil and gas inTangjiahe area, but the Es2 still has possibility of offering oil. Based on normal slice identification, SEM, energy spectrum analysis andcasting slice analysis are adopted to investigate diagenesis sequence and fluidevolvement of sandstone. It is believed that three stages are classified according tocements and authigenic minerals assemblage and sequence. The first is the stage ofalkali fluid with such cements or authigenic minerals as early microcrystallinecalcite and smectite. The second is the stage of acid fluid during which feldspar andcalcite is dissolved, overgrowths of quartz or feldspar, authigenic quartz andkaolinite are formed or filled in the sandstone. The third is the stage of alkali fluidduring which iron pyrites, chlorite and late calcite and dolomite formed. By means of transmission polarization observation, fluorescence microscopeanalysis the author studied fluorescence characteristic and development degree oforganic inclusions in the micro-fracture of quartz grains and the overgrowth ofclastic quartz. Combining diagenesis sequences of reservoir, the author alsoconfirms filling stages and time of the oil and gas as well as main filling stage. It isindicated that there are at least three times oil and gas injecting in this area in whichboth of the first and the third stage are the main filling stages. The first stagehappened before overgrowth of quartz had grown during which hydrocarboninclusions mainly exist within the micro-fractures of debris. Mostly these fracturesdidn't break through overgrowth and the content of the inclusions is rather high. Thesecond oil and gas filling stage happened during overgrowth deve...