致密岩性气藏储量评价和计算方法问题与对策——以鄂尔多斯盆地大牛地气田上古生界气藏为例

Problem and countermeasure of reserve estimation and calculation of tight lithologic gas reservoir:A case study in Upper Paleozoic gas reservoir in Daniudi Gas Field of Ordos Basin

大牛地气田位于鄂尔多斯盆地北部,上古生界地层为1套完整的海相潮坪—近海三角洲—陆相辨状河碎屑岩沉积。在较强的成岩作用和上石盒子组区域盖层的封盖作用下,该气田在上古生界形成了由多层大型致密岩性气藏叠合的箱型气藏,具有"三低"的特点,多层合采提高了单井产能,达到了单层储量动用的目的及气田开发的经济效益。根据大牛地气田上古生界气藏地质和生产特征,提出以纵向叠合、平面连片的气层组(砂层组)为计算单元的储量评价、计算思路和方法以及纵向合层、平面碾平经济评价方案,解决了该气田单层产量低、经济评价效益低的问题,为类似致密岩性气藏储量评价和计算提供了思路和方法。

In the Daniudi Gas Field which locates in the north of the Ordos Basin,a set of complete marine tidal flat-inshore delta-terrestrial braided channel sediments has been found in the Upper Paleozoic.Influenced by severe diagenetic effects and sealed by regional cap rocks in the Upper Shihezi Formation,box-shaped gas reservoirs which were composed of multi-layered large-scale tight lithologic gas reserves were formed in the Upper Paleozoic.Production in multiple layers has enhanced single well productivity and improved economic benefit.In view of the geologic and productive features of the Upper Paleozoic gas reservoirs in the Daniudi Gas Field,an estimation method of longitudinal superposition and crosswise connection as well as an economic evaluation plan of longitudinal multiple zone production and crosswise flatten were proposed.The questions of low yielding rate and low economic benefit were solved,providing ways for the estimation and calculation of tight lithologic gas reserves.