鄂南地区中生界浅层油气藏特征

为发现和更好地开发利用鄂尔多斯盆地南部中生界浅层油气资源，探索油气复合成藏规律，依据盆地南部几个浅层油气藏的勘探开发实例，结合实验分析及试采成果等，对鄂南中生界延长组浅层油气藏地质特征进行了分析研究。分析认为：延长组浅层油气藏与构造及岩性圈闭密切相关；适度的埋深和一定的构造匹配以及良好的封盖条件是其成藏的关键，岩性-构造（低幅度）复合油气藏的发育具有更为普遍的意义；其砂岩储层均具特低-低渗透特征；平面油气水自内向外常呈环带状及半环带状分布；纵向油气分异较好，油水分异较差，含油饱和度低，开发效果差；中高电阻率、高声波时差及显著的电性差异是识别浅层油气藏的重要标志。进而得出结论：浅层油气藏是鄂南中生界油气成藏的一种重要形式；延长组浅层油气藏埋深浅，发育条件广泛，油气性质优良，地质储量可观，勘探开发潜力较大；其次，稳油控水、油气并举是提高浅层油气藏采收率的关键。

CHARACTERISTICS OF SHALLOW MESOZOIC OIL AND GAS RESERVOIRS IN SOUTH ORDOS BASIN

In addition to the Mesozoic oil reservoirs and large middle oilfields, shallow Mesozoic oil and gas reservoirs also occur in the southern Ordos Basin. Based on a study of the geologic features and an analysis of the preliminary development effects and in combination with the exploration and development practices, a systematic study is performed on the shallow Mesozoic oil and gas reservoirs in the southern Ordos Basin. The results show that the shallow oil and gas reservoirs are closely related with structural traps, appropriate burial depth and rational structural combination are important conditions for their formation, and the low amplitude structures are more important. The shallow oil and gas reservoirs are characterized by ultra low permeability, circular and semi circular areal distribution of oil/gas/water, relatively good vertical differentiation of oil/gas but poor differentiation of oil/water, generally low oil saturation, high resistivity, high interval transit time, and remarkable difference of electric properties. The shallow oil/gas reservoirs have the advantages of small burial depth, good oil/gas quality, large reserves, relatively large potentials of exploration and development. Moreover, the water cut is relatively high and changes rapidly, and development effects of gas cap are good. Therefore, the key for enhancing the recovery factors of the shallow oil/gas reservoirs is stabilizing oil production and controlling water and concurrent development of oil and gas.