中国大型致密砂岩含气区展望

PROSPECTS FOR THE LARGE SIZED TIGHT SANDSTONE GAS BEARING REGIONS IN CHINA

中国常规储层油气藏数量有限，今后将较多地面临致密深层油气藏。通过对致密砂岩含气区、砂岩致密化的影响因素以及致密砂岩气藏的特征进行分析研究，认为低孔渗砂岩级别以上储层，必须有局部圈闭才能成藏；向斜凹部“深盆气”只能在致密砂岩级别中形成；超致密砂岩只有裂缝发育条件下方可成藏。中国致密砂岩含气领域广阔，可慨括为四大类型：①活动性超致密砂岩含气区（如四川西部）；②“深盆气”区（ 如鄂尔多斯盆地）；③断陷盆地致密砂岩含气区（如松辽Ｊ３ —Ｋ１ 断陷） ；④非常深埋高丰度致密砂岩含气区（如准噶尔盆地南部） 。以川西含气致密砂岩为例，建立了中国含气致密砂岩成藏模式。阶段Ⅰ：原生常规储层油气聚集；阶段Ⅱ：“深盆气”；阶段Ⅲ：超致密化；阶段Ⅳ：裂缝重组气藏；阶段Ⅳ′：次生浅层气藏。

In China,the conventional reservoirs are limited in number,so the deep tight reservoirs will be more uncountered in the future.Through analyzing and studying the factors of influencing compactification of the sandstones in tight sandstone gas bearing regions and the characteristics of tight sandstone gas reservoirs,it is considered that only by relying on the local trap,can the gas reservoir be formed in the reservoir bed which petrophysical property is better than the low porosity and low permeability sandstone;the “deep basin gas” in the concave part of a depression can be formed in the tight sandstone;and the gas reservoir in supertight sandstone can be formed only under fracture developed condition.The tight sandstone gas bearing areas are widely distributed over China,being roughly generalized as four categories:①active supertight sandstone gas bearing areas (as West Sichuan Basin);②“deep basin gas” areas (as E'erduosi Basin);③rift depression basin tight sandstone gas bearing areas (as the J 3 K 1 rift depression in Songliao Basin);and ④ superdeep high abundance tight sandstone gas bearing areas (as the south part of Zhunge'er Basin).A reservoir formation model of gas bearing tight sandstones in China is set up by taking the gas bearing sandstones in West Sichuan Basin as an example.There are four stages:Stage Ⅰ is the oil and gas accumulation in original conventional reservoir;Stage Ⅱ “deep basin gas”;Stage Ⅲ super compactification;Stage Ⅳ fracture recomposed gas reservoir;and Stage Ⅳ′ secondary shallow gas reservoir.