民和盆地永登凹陷油气成藏地质特征

Hydrocarbon Accumulation Geology Features of Yongdeng Sag in Minghe Basin

民和盆地勘探主体包括巴州凹陷和永登凹陷。永登凹陷勘探程度较低,为盆地沉积和生烃主体。通过对盆地构造演化、露头资料、地震解释、巴州凹陷探井资料分析对比、周围煤田钻孔资料的研究,确定自盆地中燕山回返以来,永登凹陷长期处于构造高部位,处于古地温场低值区,主要目的长期埋浅,滨浅湖相发育宽广,储层主要为扇三角洲砂体、滩坝砂体,物性较好,属中孔中渗-中孔低渗型,发育了断背斜、背斜等有利圈闭,并在凹陷东斜坡坡折带区发育构造-地层复合圈闭。油源断层发育,喜山期对圈闭改造作用弱,圈闭保存条件好,具备长期捕获油气能力。

The main exploration bodies of Minhe basin is consisted of Bazhou and Yongdeng sag. Exploration degree for Yongdeng sag is lower, which is main body of deposition and hydrocarbon source. Through a series of researches on the evolution of basin structure, field outcrop, the seismic interpretation, the analysis and contrast of exploration well information in Bazhou sag and the study on drill hole data in the peripheral coal fields, it is obvious that since Minhe basin returned at the Middle yanshanian stage, Yongdeng sag is located in the high spot of structure for a long time and in the lower temperature field ; the main stratums buried shallowly for a long time, offshore shallow lake facies developed broad, the reservoirs are dominated by fan deltaic sands body and the beach dam sands body and so on. The physical properties are better, which belong to middle porosity and mid - low permeabil- ity. It grew advantageous traps which included fault - anticline, anticline and so on. Especially in the east slope of the sag, it grew structure - stratum combination trap on slope belt area. Faults grew in the source rock, which were helpful for oil and gas moving. During Xishanian stage, the structure movement affected weakly to the traps, the traps＇ preservative condition was good, which had the long- term ability to capture oil gas.