六盘山盆地石油地质条件及评价

PETROLEUM GEOLOGY OF THE LIUPANSHAN BASIN AND ITS EVALUATION

六盘山盆地是白垩系—第三系沉积盆地。盆地内构造发育,生油层系多,目的层不仅有白垩系,而且还有侏罗系及古生界,并且储层条件优越。近年来,通过有机地化指标分析及深层地震勘探,发现下白垩系生油层成熟度低,以白垩系为目的层钻探浅层局部构造是不合适的。然而,在大断裂附近由于断裂活动有可能促使地温增高,而使有机质“先熟”。因此,断裂带及逆冲推覆构造下盘是油气藏形成的有利地带。本文提出在断裂带及深层找油的必要性及可能性。

Liupanshan basin is a Cretaceous-Tertiary depositional hasin with deve- loped structures and various formation sequences.The objective interval are Cretaceous,Jurassic and Paleozoic,and reservoir formations are also favou- rable. In recent years,through an analysis of organic geochemical index and seismic prospecting,it is concluded that the maturity of source rock of Lo- wer Cretaceous,so the drilling of shallow Cretaceous formations is not sat- isfactory.However,the fractring activities near fracturing zone may cause an increase in the geothermal gradient which results in an“early-maturi- ng”of the organic matter.Thus,the frauturing zone and footwall of the ov- erthrust are faovurable for oil and gas generation.This paper suggests a po ssibility and necessity for oil and gas exploration in fracturing zone and at deeper horizons.