Sedimentary Characteristics And Oil And Gas Prospect For The Mesozoic And Cenozoic In Northern South Yellow Sea Basin

The northern depression of South Yellow Sea Basin lies in 34°50′~37°00 ′ofnorth latitude , 120°30′~125°30′of east longitudes, making Qianliyan Uplift as theboundary in the north. Its southern stratum onlaps the middle uplift of South Yellow SeaBasin, and on the whole it downfaullts to north and onlaps to the south, with area about51,000 km2. It took shape in late Mesozoic Era. The basement is the metamorphic rock at Siniansystem or Pre- Sinian system and has deposited the stratum from Triassic Period to QuaternaryPeriod. It included six minus structural units (Northeast concave, north concave, middle concave,west concave, south concave, east concave) and three plus structural units (north protruding,west protruding, south protruding). Since well Huang 2 was drilled in 1975 in the northern depression of South YellowSea Basin, it has been almost 30 years already and about 11,000km seismic surveying line hasbeen finished, and also made corresponding regional exploring in gravity and magnetic force .Atpresent, there are 12 drilling wells in this district of which 6 belong to our country, with a totalfootage of13840. 72 meters; Korea has 6drilling wells in the east of the basin, with a totalfootage of 15680 meters. Among them, our country has found liquid crude oil in the crack ofcoring of well zhucheng 1-2-1of Taizhou formation in north concave, and Korea has found gasmanifest in its 2 wells, but neither of the two countries get commercial oil and gas current. On the basis of forefathers and the latest materials, this text is to analyze single well faciesand seismic facies characteristic of the north sea area of South Yellow Sea Basin, to draw thedepositional characteristic of the basin, and then appraise the oil and gas potentiality of the basin;make every effort to have a more exhaustive understanding to depositional characteristic of theMesozoic and cenozoic of South Yellow Sea Basin,in order to offer the stratum basis for theoil and gas exploring in the South Yellow Sea Basin. Single well facies analyzing is core and its main content includes color, type, originaldepositional construction, paleospecies, the form of well logging curve and its associationcharacteristic. Its core is combining geology facies with well logging facies, studying theresponse characteristics of rock and well logging curve of different depositing microfacies, thensetting up the mode of depositional facies. During this research, the authors selected such 3 wellsas well huang 7,well city zhu 7-2-1 and well zhucheng 1-2-1 of the northern depression ofSouth Yellow Sea Basin to analyze single well facies. Three types of depositional faciesare divided namely fluvial facies , lake , fan-delta. And seven kinds of subfacies: are flood plain,fan-delta plain, fan delta front, pro-fan delta, shallow lake and the half deep lake. Meanwhile, the 75摘要author has analyzed the horizontal and vertical characteristic of sedimentary facies according tosingle well characteristic. For the vertical change of depositional facies, the well huang 7 waschosed, combined with all-around well logging materials. Seismic facies is the comprehensive reflection of different characteristics of the seismicreflectional section of depositional body. According to the difference of these characteristics,seismic facies district can be divided out with different characters in plane and profile. Purposeof analyzing seismic facies is to resume environment of depositional and confirm rockcharacteristic of strata in the basin through the division and discernment of every seismic faciesunit in the strata, then dividing seismic section into seismic facies district of differentcharacteristic. It can be used as the foundation to analyze the depositional environment andpaleogeography of stratum, to reconstruct the history of depositional and constructing of thebasin, then to predict source rock and reservoir, stratigraphic or lithol...