渤海湾盆地南北两侧奥陶系古风壳储层的不同发育模式

Different Genetic Models of Ordoviclan Carbonate Weathered Crust Reservoirs and Petroleum Exploration Trend in the Bohai Bay Basin

根据渤海湾盆地北缘河北唐山赵各庄及盆地南缘山东新泰汶南两奥陶系古风化壳剖面较系统的研究,表明赵各庄剖面属于“潜山型”古风化壳,顶部垂直渗流带和水平潜流带总厚近200m,构成了古风化壳储层的主要层段;而南部汶南剖面则发育顺层“台地型”古风化壳,层间厚380余米的古岩溶带成为主要储层类型。认为构造作用强度、断裂发育、古地形、岩溶作用时间的差异是造成不同类型岩溶带的主要原因。两剖面古风化壳储层均以碳酸盐岩溶洞、溶孔和裂隙形成的复合储层类型为主。在储层预测上,“台地型”较“潜山型”更容易预测。建议渤海湾盆地进行奥陶系古风化壳岩性地层油气藏的勘探时,关注”潜山型”、“台地型”这两种不同类型的古风化壳储层。两种不同类型的古风化壳储层发育形式为渤海湾盆地奥陶系碳酸盐岩油气勘探提供了直观的对比模式。

The characteristics of Ordovician carbonate weathered crust reservoirs （Megakarst） were studied at two localities： the Zhaogezhuang section, Tangshan, Hebei province and the Wennan section, Xintai, Shandong province. They are located in the northern and southern margin of Bohai Bay basin, respectively. The former is of buried-hill type, and the major reservoir is composed of vertical vadose （ infiltration ＆ percolation zone） about 200 m thick and horizontal phreatic （saturation） zone. The latter is of plateau type, and the major reservoir is an interlayer paleokarst about 380 m thick. The reservoir space is carbonate solution cave, pore, fracture and their combination in both sections. These different genetic patterns provide a direct and visual model for the petroleum exploration of Ordovician carbonate in the basin. As to the petroleum exploration potential of ancient weathered crust reservoirs, it is usually determined by direct overlying source rock strata with high quality. The plateau paleokarst type is easier than the buried-hill type to be predicted.