黄骅坳陷非油型天然气成因与聚集条件

Genesis and accumulation of non-oil-type natural gases in Huanghua Depression, Dagang Oilfield

除常规油型气外,黄骅坳陷还发现了多种其他类型的天然气。板桥凹陷中大量发现的凝析气是陆源有机质经过微生物(主要是细菌)强烈改造,使腐殖型为主的有机质产生“腐泥化”,并在有机质的成熟阶段产生大量凝析油气。发现于千米桥潜山的“重烃具异常重碳同位素”天然气,是以古近系沙三段偏腐殖型有机质为母源,在较高成熟演化阶段产生的天然气。孔南地区石炭二叠系含煤地层中的腐殖型有机质,以有效生烃组分含量高为特点,目前已在乌马营构造奥陶系发现工业性煤成气藏。上述类型天然气在聚集上有一个共同特征,圈闭形成条件均与挤压应力有关。这表明在总体拉张背景下,既要注重天然气成因研究,拓展勘探领域;又要注重压性构造研究,拓宽勘探目标,这是发展断陷盆地天然气勘探的重要方法。

Besides the conventional oil-type gases, many other types of gases have been found in Huanghua Depression. The rich condensate oils and gases found in Banqiao Sag are generated from terrigenous organic matters that have been strongly reformed and changed by microorganism. The natural gases in Qianmiqiao buried hill are heavy hydrocarbons with abnormal heavy carbon isotopic composition, which were generated from trimellitic-humic organic matters during the highly-matured stage in the 3rd Member of Paleogene Shahejie Formation. The humic organic matters in Carboniferous-Permian coal-bearing strata in the Kongnan area are rich in effective hydrocarbon generating macerals, and coal derived gas reservoirs have been found in the Ordovician Wumaying structure. The collective character of the gases accumulation is that their entrapment is all related to extrusion stress. Both the gas genesis and local compression structure should be studied.