歧口凹陷西南缘湖相碳酸盐岩油气聚集规律浅析

歧口凹陷西南缘湖相碳酸盐岩在古近系沙河街组沙一段下部广泛分布,综合分析认为具备优越的成藏条件,生储盖层空间配置关系良好,沙一段下部分布稳定的油页岩、暗色泥岩与碳酸盐岩储层交互沉积,既是生油层,也是良好区域盖层,有利于碳酸盐岩储层大面积成藏,具有一定的勘探潜力。目前勘探发现的油气主要集中在断裂发育带和褶皱变形区,证明油气成藏与储层岩性和裂缝发育程度密切相关,油藏类型多为构造—岩性油藏。指出下步应在加强工程工艺攻关的基础上,重点围绕断裂发育区、白云岩和砂岩的过渡区域开展勘探工作,在断裂不发育地区,应重点开展碳酸盐岩储层的裂缝平面预测工作。

Elementary Analysis on Hydrocarbon Accumulation of Lacustrine Carbonate Rocks in Southwest Margin of Qikou Sag

Lacustrine carbonate rocks are widely distributed in the lower part of the first member of Shahejie Formation of Palaeogene in southwest margin of Qikou sag. Comprehensive analysis revealed that it had favorable accumulation conditions, good space configuration of source-reservoir-cap rock associations. Oil shale and dark mudstone stably distributed in the lower part deposited with carbonate reservoir interactively, and they were both source bed and favorable regional cap rocks. This was favorable for large-area accumulation of carbonate reservoir and owned certain potential for exploration. Currently, oil and gas discovered through exploration are mainly distributed in fracture development belts and fold deformation zones, which proves that hydrocarbon accumulation is closely related to the degree of fracture development, and reservoir types are mainly structural-lithologic ones. This paper pointed out that exploration should be mainly carried out in the fracture development zone and the transitional zone of dolomite and sandstone, based on strengthening engineering technology research. And plane fracture prediction should be conducted in carbonate reservoirs in these areas without fractures.