渭河盆地圈闭特征研究及勘探展望

Characteristics of Trap Development and Exploration Prospects, Weihe Basin

圈闭研究是油气地质研究的重要组成部分,能够划分油气藏类型,反映油气藏的成因,是评价含油气盆地勘探潜力的重要指标。为了进一步认识渭河盆地油气资源特征,借鉴东部断陷盆地圈闭研究经验,在前人勘探认识的基础上,结合盆地构造、沉积发育史和地热井钻测井等资料,分析认为渭河盆地发育有众多圈闭类型,包括构造圈闭、岩性圈闭、地层圈闭以及复合圈闭等4种主要圈闭类型。构造圈闭主要发育背斜圈闭和断层圈闭,岩性圈闭发育上倾尖灭型岩性圈闭和砂岩透镜体岩性圈闭,地层圈闭仅发育地层超覆圈闭,复合圈闭发育构造—岩性复合圈闭和构造—地层复合圈闭,各圈闭类型分布在不同的区域和层位。深层高成熟度裂解甲烷气与氦气圈闭勘探重点位于盆地南部陡坡区,发育的主要圈闭类型为断层圈闭及其复合圈闭;浅层生物气圈闭勘探的重点应在固市凹陷北部斜坡区,该区域主要发育岩性圈闭。

To study trap is a significant component of making petroleum geology clear. Types of oil and gas reservoirs can be classified by means of trap features. Meanwhile, different features can reflect various origins to form these reservoirs. So, trap elements are the important index to evaluate an exploration potential for a lot of oil and gas basins. In order to further understand the characteristics of oil and gas resources in Weihe Basin, the basin structure, sedimentary history, and many data from drilling and well logging in some geothermal wells were analyzed on the basis of previous achievements. Results show that(1) there are different trap types developed, including structural traps(anticline and fault traps),lithological traps(lithologic updip pinch- out traps and sand lens lithologic traps), stratigraphic traps(only stratigraphic overlapping traps), and compound traps(structural-lithological compound traps and structural-stratigraphic compound traps); and(2) different trap types are located at different zones or strata. Some deep and highmaturity pyrolysis CH_4 and He traps are located at steep slope area of southern basin; and the main types are fault traps and their compound traps. In addition, shallow biogas traps are mainly situated at the steep slope area of northern Gushi depression, and the main type is lithological trap.