柴西地区地温-地压系统特征及其与油气分布的关系

Characteristics of geotemperature-geopressure system in western Qaidam basin and their relationship with oil and gas distribution

李鹤永 刘震 党玉琪 李潍莲 梁全胜 张永庶

Li Heyong Liu Zhen Dang Yuqi Li Weilian Liang Quansheng Zhang Yongshu

柴西地区地温梯度分布范围为每百米2.0-4.5℃,平均值约为每百米3.1℃。在2300 m深处开始发育异常高压, 压力系数最高可达2.0。按照地层压力系数及地温异常的分布区间,柴西地区温压系统在平面上划分为高温高压等9个分区,在纵向上分为上部常压型温压系统及下部超压型温压系统。上、下两套温压系统流体能量差较大,油气垂向运聚能力较强,易于在温压系统分界面附近聚集成藏。平面上,油气藏基本位于流体能量相对较低的分区内,高流体能量区也有油气藏分布,但大多为封闭保存条件好的岩性及构造-岩性等原生油气藏。现今温压系统特征表明,深层高压型温压系统油气封闭条件好,赋存有大部分油气资源,是今后油气勘探的重要领域。

Geothermal gradients range between 2.0℃ and 4.5℃ per hundred meters in western Qaidam basin, with an average value of 3.0℃ per hundred meters. Abnormally high pressure can occur at a depth of 2 300 m and over, and the pressure coefficient can be as high as 2.0. Laterally, the temperature-pressure systems in western Qaidam basin can be divided into 9 subareas such as HPHT, according to the formation pressure coefficients and the distribution intervals of the abnormal geotemperatures. Vertically, they can be divided into the upper static pressure type and the lower overpressure type. The upper and lower temperature-pressure systems have quite different fluid energies, thus hydrocarbons are highly capable of migrating vertically and are prone to accumulate around the boundaries of temperature-pressure systems. Laterally, oil and gas pools are basically distributed in the subareas with relatively low fluid energy; there are also oil and gas pools occurring in the sub-areas with high fluid energy, but most of them are primary oil and gas reservoirs with good sealing and preservation conditions, such as lithologic and structural-lithologic reservoirs. Characteristics of present temperature-pressure systems show that the deep temperature-pressure systems of high pressure type have good sealing conditions and contain most of the oil and gas reserves, thus they would be the main targets of future petroleum exploration.

10.11743/ogg20060107