潍北凹陷深层致密砂岩气成藏特征

综合研究认为潍北凹陷已具备致密砂岩气成藏条件，即有利于形成致密砂岩气藏的构造条件，气源条件，低孔、低渗储层物性特征及良好的圈闭保存条件。国内外典型致密砂岩气成藏要素对比表明，潍北凹陷致密砂岩气藏具有以下特点:①深部典型的储盖组合，即第三系孔店组二段暗色泥岩、碳质泥页岩及煤层既为致密砂岩气藏提供充足的气源，又使天然气在孔二段的致密砂岩中富集成藏，形成下生上储上盖型和自生自储自盖型两种组合；②致密砂岩普遍含气；③气层具有低压异常。储层物性、构造活动及封闭条件等是影响该区致密砂岩气成藏的地质因素，其中储层非均质性、致密性和良好的封闭条件是最直接因素。

CHARACTERISTICS OF DEEP TIGHT SANDSTONE RESERVOIR FORMATION IN WEIBEI SEG

Through comprehensive research, it was considered that the Weibei Seg is of the conditions beneficial to deep tight sandstone reservoir formation, i.e. the favorable structure, gas source, low porosity and low permeability reservoir, and preservation conditions. In comparison with the formation factors of the typical domestic and foreign tight sandstone reservoirs, it was indicated that the tight sandstone reservoirs in Weibei Seg are characterized by ①there exist the typical source reservoir caprock assemblages in the deep zone, i.e. the dark mudstones, carbonaceous mudstones and shales, and coal beds in Ek2 (second member of Kongdian Formation, Eogene) not only provided plentiful natural gas but also caused the natural gas to be accumulated in the tight sandstones of Ek2 to form gas reservoirs, thus constituting the lower generating, upper storing and upper sealing assemblage and the sulf generating, sulf storing and sulf sealing assemblage; ②the tight gas bearing sandstones are widely distributed; and ③ the abnormal low formation pressures exist in the gas reservoirs. The petrophysical property, structural activity and sealing conditions are the geological factors affecting the tight sandstone gas reservoir formation in the seg, in which the heterogeneity and compactness of reservoir and the favorable sealing conditions are the most important ones.