深水稀井区天然气藏储盖组合定量预测方法研究:以琼东南盆地陵水凹陷为例

Quantitative Forecast Method of Reservoir-seal Assemblage for Gas in Deep-water Area with Sparse Wells: A Case Study of Lingshui Depression,Qiongdongnan Basin

南海北部油气勘探表明天然气是本地区主要的资源类型。与石油相比,天然气藏的形成对盖层要求更为严格,因此开展天然气藏储盖组合研究对油气勘探具有重要意义。通过统计和调研的方法,将砂岩储层孔隙度12%定义为琼东南盆地天然气有效储层评价的下限参数,将泥岩排替压力1 MPa定义为天然气有效泥岩盖层评价的下限参数。利用测井资料开展了单井天然气藏储盖组合窗口定量预测,得出陵水凹陷W22-1井发育单个天然气藏储盖组合窗口。在此基础上,针对稀井或无井区,提出了基于地震反演速度剖面的天然气藏储盖组合定量预测方法,以琼东南盆地陵水凹陷主洼过井测线为例,开展了天然气藏储盖组合窗口地震预测,确定出该凹陷主洼发育单个天然气藏储盖组合窗口,大体上包括陵水组-莺歌海组上部多套地层,拓宽了陵水凹陷天然气勘探层系。这种方法对其它深水区和低勘探新区均有借鉴意义。

Recent exploration shows that hydrocarbon resources in northern South China Sea are dominated by gas. Compared to oil,the requirement of cap rocks for gas reservoirs is stricter. Therefore,research on the reservoir-seal assemblage for gas is important for hydrocarbon exploration. Using statistics and geoscientific investigation,sandstone reservoir porosity of 12% is defined as the lower limit for the gas effective reservoir in the Qiongdongnan Basin,and the mudstone displacement pressure of 1 MPa was defined as the lower limit for thegas effective cap rock. Based on logging data,we conducted quantitative window forecasting for the reservoirseal assemblage for gas in a single well,and the results show that one reservoir-seal assemblage window is developed in the well W22-1（ Lingshui Depression）. We proposed a new quantitative prediction method for reservoirseal assemblage in the areas with very few or no wells,based on the velocity inversion section. Taking the Lingshui Depression of the Qiongdongnan Basin as an example,we predicted that there is one reservoir-seal assemblage window developed in the depression,which includes the Lingshui-Yinggehai formations. Results of this study broaden the natural gas exploration layers in the Lingshui Depression,and may also be applicable to other deep-water area and underexplored area.