鄂尔多斯盆地东部奥陶系盐下储层预测

鄂尔多斯盆地奥陶系的膏盐岩沉积面积达5×104km2,天然气的勘探程度很低。为此,利用测井技术和地震反演技术对盐下储层进行了预测。首先,通过对盐下沉积特征的综合分析,对盐下储集层段的发育层位和主要储集岩类型进行了描述;然后,采用ELAN测井技术对盐下储层的物性进行了分析,认为盐下储层的物性在普遍较差的背景上存在相对发育的层段和区带;最后,利用全局优化多道地震反演技术,对岩下储层进行了预测,认为盐下存在的局部隆起是圈闭和储层发育的有利区带。

Prediction for under-salt reservoir of Ordovician in East Ordos basin

Now, the exploration for natural gas in Ordovician system mainly concentrates on the top of weathered crust. So to find the new strata to carry out the exploration for natural gas is the key to enlarge the exploration area and increase the reserve. Through analyzing the evolution of Ordovician sedimentary facies, it is found that Ma1, Ma3, Ma5 member of Majiagou stage, Ordovician, is the prosperous period for evaporite deposition, with the area of gypsum/salt rock being 5×104km² and the gypsum/salt lake sediment and tidal flat sediment alternatively appearing in the vertical sequence, making the dolomite and gypsum/salt rock be interlay-ered, which laid a good foundation for forming the under-salt hydrocarbon reservoir. The result of core analysis as well as logging analysis shows that there still exist some well-developed zones on a background of poor under-salt reservoir property. Based on the characteristic of easy flowing and deforming of the salt rock, the seismic inversion technique is used to forecast those zones favorable for forming the upheaval and fault structure, providing guidance for natural gas exploration in under-salt reservoir.