从源盖时空匹配关系预测徐家围子断陷的天然气远景

FORECASTING OF GAS PROSPECTING IN XUJIAWEIZI REGION FROM MATCH RELATION BETWEEN SOURCEROCK AND CAPROCKS

在研究徐家围子地区深层天然气源岩发育、地球化学、生气特征和盖层发育、封闭特征的基础上,研究了该区气源岩与盖层之间的时间与空间匹配关系及其对天然气成藏的控制作用。徐家围子地区登二段泥岩盖层与沙河子组—营城组气源岩之间和徐家围子泉一、二段泥岩盖层与沙河子组—营城组气源岩之间时间匹配关系均较好,但前者略好于后者,这是造成该区登二段盖层之下天然气分布多于泉一、二段盖层之下的一个重要原因。徐家围子地区登二段和泉一、二段泥岩盖层与沙河子组—营城组气源岩在空间配置关系上以徐家围子地区中心处登二段源岩和沙河子组—营城组源岩质量为最好,这可能是能在升平、汪家屯和昌德构造多个层位上获得工业气流的重要原因。登二段盖层与沙河子组—营城组泥岩质量空间匹配关系好于泉一、二段盖层与沙河子组—营城组气源岩质量空间匹配关系,这是造成登二段之下天然气聚集多于泉一、二段盖层之下的又一重要原因。认为从盖源时空匹配关系上可以判断徐家围子断陷中心处应是徐家围子地区天然气成藏的有利地区。

Based on studying development, geochemical and generation gas characteristics of sourcerock and development, seal characteristics of caprock of deep strata in Xujiaweizi region. This paper studied the match relation between sourcerock and caprocks in time and space and their controlling to farmation of gas reservoirs in this region. The time match relation between K_(1)d_(2) or K_(1)q_(1+2) mudstone caprocks and (K_(1)sh)+yc sourcerock in Xujiaweizi region is good, but former is better than the latter. It is the important cause that there is more gas distribution under K_(1)d_(2) mudstone caprock than that under K_(1)q_(1+2) mudstone caprock. The space relation between K_(1)d_(2) or K_(1)q_(1+2) mudstone caprock and (K_1sh)+yc sourcerock is best in the centre of Xujiaweizi depression. This is the important cause that gas distributes from basement rock to K_(1)q_(1+2) in the three structures of Shengping, Wangjiatun and Changed in Xujiaweizi depression.The quality matching relation between K_(1)d_(2) caprock and K_(1)sh+yc sourcerock is better than that between K_(1)q_(1+2) caprock and (K_1sh)+yc sourcerock. This is the another important cause that there is more gas distribution under K_(1)d_(2 )caprock than that under K_(1)q_(1+2) caprock. The center of Xujiaweizi depression is the most favorable area for gas to accumulate and form gas reservoirs from the matching relation between caprock and sourcerock.