民和盆地侏罗系沉积演化特征及勘探潜力

民和盆地侏罗系为完整的断陷湖泊充填沉积序列,从侏罗纪早期到中晚期沉积范围逐渐扩大。下侏罗统为断陷初始形成期湖泊沉积,具有断陷盆地形成初期"填平补齐"的沉积特征,周缘及低隆起为水下扇相粗碎屑岩沉积,断陷中以滨浅湖沉积为主;中侏罗统为断陷发展期湖泊沉积,经历了两期次级水进旋回,形成冲积扇—半深湖—三角洲沉积序列;上侏罗统为断陷消亡期沉积,形成湿型扇—辫状河—曲流河沉积序列。中侏罗统窑街组形成了欠补偿沉积环境,发育油页岩、暗色泥页岩和煤系地层,侏罗系可形成自生自储的生储盖组合,具有上、中、下三套含油气组合,油气资源量较丰富,勘探前景较广阔。

SEDIMENTARY EVOLUTION AND PROSPECTING POTENTIAL OF JURASSIC IN MINHE BASIN,WEST CHINA

A intact fault subsidence basins sedimentary sequence was formed in Jurassic in Minhe basin. Sedimentary area is gradually spread from early Jurassic to middle-late Jurassic. Lower Jurrassic is early fault subsidence lake sediment, has the characteristics of "fill and level up",existed underwater fan facies coarse clast sedimentary in the basin circumference edge and lower rise and existed shore fleet lacustrine sedimentary in the basin centre. The fault subsidence lake had developed in middle Jurassic, Alluvial fan, sub-deep lacustrine-delta sedimentary sequence was formed and undergone two stage sub-lacustrine transgressive cycle. The fault subsidence lacustrine died out in late-Jurassic and damp type fan, braided stream and meander river sedimentary sequence was formed. Middle Jurassic Yaojie Formation is a lack compensation type sediment and composed of oil shale, dark shale and coal bed. The three autogeny-autoreservoir association were formed in Jurassic. Therefore,oil and gas resource is abundance in this association.