东营凹陷沙三段沉积期湖泊古生产力研究

生产力是生物在单位面积、单位时间内所产生的有机质的量。陆相古湖泊古生产力值高的地区一般能形成较好的烃源岩，古生产力值较低且不利于有机质保存的地区则相反。借用古海洋学推导古生产力计算公式的方法，利用云南滇池、洱海和抚仙湖的沉积学和生物学资料，用18个采样点的数据推导了用有机碳法计算湖泊古生产力的公式。用此公式计算东营凹陷沙三段数百口井的古生产力值，绘制了东营凹陷沙三段沉积各时期的古生产力平面分布图，半深湖相或者半深湖与深湖相交界处古生产力值较高，湖盆边缘(三角洲相或滨浅湖相)古生产力值较低。图2表1参11

Lacustrine palaeo-productivity in the Third Member of the Shahejie Formation in Dongying Sag

Productivity is the quantity of organic matter produced by organisms per unit area and unit time. Hydrocarbon source rocks can be usually formed in the regions where palaeo productivity values are large in a paleo lake, and it is contrary in the regions where palaeo productivity values are small and preservation conditions are poor. By using the method of calculating palaeo productivity derived from paleo oceanography, the sedimentary and biological data from Dianchi, Erhai and Fuxian Lakes in Yunnan, the formula that palaeo productivity in a lake can be calculated is obtained from the data of 18 sampling positions. Then, the values of palaeo productivity for hundreds of wells drilled into the Third Member of the Shahejie Formation of Dongying Sag were calculated by this formula, and the plan views of contour lines were drawn. The results show that the palaeo productivity values of semi deep lacustrine facies or facies between semi deep lacustrine and deep lacustrine are high, while those of the lake margins (delta facies or lacustrine offshore facies) are much less than the values for lacustrine facies.