元坝气田长兴组礁滩相气藏复杂气水关系成因

摘要

元坝气田以上二叠统长兴组礁滩隐蔽性岩性气藏为主。元坝西北部整体含气性较好，气产量高，但东部和南部气水关系复杂，多个圈闭见水，气产量多为中低产。不同岩性的气藏，其气水界面与气藏高度变化较大。通过地质、测井、物探的联合分析认为，优质储层的形成分布特征、成藏富集的规律特点、裂缝与构造的良好匹配是控制复杂气水关系的主要因素。分析表明，元坝西北部的礁带是最有利的勘探区。这一分析结果与高产富集带的预测、含气性的检测及测试结果具有高度的吻合性。%Upper Permian Changxing subtle reef-shoal facies gas reservoirs are developed in Yuanba Gas Field, Sichuan Basin. High-yield wells are concentrated in the northwestern part of Yuanba area where pure gas is preponderant but water areas are present in many gas traps in the eastern and the southern parts of Yuanba where middle-to low-yield gas wells are common. Different lithologic gas reservoirs are characterized by different gas-water interfaces and heights. Based on geological, logging and geophysical analysis, it is shown that the features of high-quality reservoirs, the enrichment regularity of gas accumulation and the well-matched fractures with structures are the main factors controlling the complicated gas-water relation. It is pointed out that the reef belt in the northwestern Yuanba probably is the most favorable area for exploration. This analysis result well coincides with the past predication of gas-enriching areas and gas potential zones.