鄂尔多斯盆地北部上古生界致密砂岩储层特征及其成因探讨

Characteristics and genesis of the Upper Paleozoic tight sandstone reservoirs in the northern Ordos basin

鄂尔多斯盆地北部上古生界致密砂岩储层具有:1)低孔、低渗、小孔隙、细喉道和渗透率对压力敏感;2)束缚水饱和度高、气水关系复杂;3)储集空间以溶孔和微孔为主、裂缝相对发育的特点。分析认为,上古生界砂岩储层致密的主要原因为古埋藏深度大、热演化程度高、晚成岩阶段的破坏性成岩作用强,热液活动进一步使储层致密化。

The Upper Paleozoic tight sandstone reservoirs in the northern Ordos basin have the following three characteristics： 1 ）low porosity and low permeability （sensitive to pressure changes ）, small pores, and slim throats;2） high irreducible water saturation and complex gas-water relationship; and 3 ）reservoir space being dominated by dissolved pores and micropores and fractures being relatively well developed. Analysis of these reservoirs suggests that the tightness of the Upper Paleozoic sandstone reservoirs is mainly caused by large palaeoburial depth, high thermal evolution, strong destructive diagenesis during its late phase, and further compaction of reservoirs evoked by hydrothermal activities.