鄂尔多斯盆地三叠系延长组低渗透石油资源评价方法

Low-Permeability Petroleum Resource Assessment Methods of Triassic Yanchang Formation in Ordos Basin

摘要: 鄂尔多斯盆地三叠系延长组90%以上的油藏属于低渗透油藏。近年来盆地三叠系延长组相继提出了长7优质烃源岩成烃机理、湖盆中部三角洲前缘牵引流及重力流复合成因砂体、多层系复合成藏规律、连续性油藏分布规律等地质新认识，对石油勘探生产作用显著，也为进一步认识盆地石油资源潜力奠定了基础。低渗透油藏与常规油藏在成藏机理、赋存状态、分布规律等方面有较大差异，其资源评价思路及方法也有所不同。针对鄂尔多斯盆地三叠系延长组低渗透油藏大面积分布的特点，详细分析了烃源岩、储集层等成藏地质条件，明确了以地质评价为主、统计分析为辅的评价思路。在开展地质风险分析、有效烃源岩评价、精细油藏解剖的基础上优选了类比法、成因法、统计法共三大类五种较为适用的评价方法，并详细介绍了各种方法的关键步骤。上述评价方法涉及了地质分析、数理统计、勘探生产实践各个方面，开展多方法综合评价是客观评价低渗透石油资源的基础。

Abstract: More than 90% of the reservoirs are low-permeability in the Triassic Yanchang formation. Some newly geological understandings, such as hydrocarbon forming mechanism of quality hydrocarbon source rock of Chang 7 formation, traction flow and gravity flow genetic composite sand body of delta front in central of lake basin, the mechanism of multi-layers multiply forming poll rules, continuity of reservoir distribution law and so on, are produced in recent years, which has played significant role in oil exploration and production, and also laid the foundation for the further understanding of the potential of the oil resources of the basin. The low-permeability reservoir was different from the conventional reservoir in the aspects of accumulation mechanism, occurrence and distribution, which result in the different methods of hydrocarbon resource assessment. Because the wide-spread characteristic of the low-permeability reservoir of Triassic Yanchang formation in Ordos Basin, the detailed research about geologic conditions of hydrocarbon accumulation was made, which formed the evaluation reason of mainly the geologic analysis and secondly statistic analysis. Based on the geologic risk analysis, evaluation of efficient source rocks and fine reservoir analysis, the analogy method, genetic method and statistic method were selected to evaluate the low-permeability petroleum resource of Ordos basin, and the strategic steps of various methods were introduced. All the above evaluation methods included various aspects of the practice, such as geological analysis, mathematical statistics, exploration and production. Comprehensive assessment using multiple methods is the basis for objectively evaluating the low-permeability oil resources.