二连盆地温压系统特征

Characteristic of Geotherm-Geopressure System in Erlian Basin

二连盆地腾格尔组地温梯度较高,而在浅层和深层地温梯度相对偏低。平面上凹陷中心或生油洼槽区古地温梯度较低,而隆起区或斜坡区古地温梯度较高,并且古地温高于今地温,在不同凹陷地温异常发育特征各异,受地温场制约,生油门限深度从凹陷中心向边缘逐渐变浅。地层压力系数都小于1.0,具明显的异常低压系统。在不同的凹陷异常低压出现的深度略有不同,阿南凹陷最浅,乌里雅斯太凹陷最深。各凹陷纵向上发育单一型温压系统,平面上以常温常压区分布最广。流体动力特征都决定了本地区油气的运移方向和聚集部位,油藏主要分布在能量相对较低的断阶带和构造带。

Tengge'er formation in Erlian basin is of higher geothermal gradient on the whole, but at shallow and deep strata of the basin, it is relatively low. In plane, such a lower paleogeothermal gradient occurs in the center of the sag or source area, while higher one in the uplift or slope area. Also, the paleotemperature is higher than the present temperature; in different sags, there exist different characteristics of geothermal field-dependent geothermal anomalies; the depth of oil threshold is becoming shallower gradually from the sag center toward the sag edges. The formation pressure coefficients are measured to be less than 1.0, showing its abnormally low pressure system. In different sags, somewhat different abnormally low pressure occurs in different depths, for instance, the shallowest is in Anan sag, the deepest in Wuliyastai sag. Vertically, individual geotherm-geopressure system appears for different sags; laterally, normal temperature and normal pressure distribute broadly. According to the fluid dynamic characteristics in this area, the petroleum migration direction and accumulation location could be determined, showing that the reservoirs will mainly be found in fault terrace belt and structural belt with relatively low energy.