海拉尔盆地伊敏凹陷煤层气成藏条件及成藏模式

Accumulation condition and reservoir formation model of coalbed methane in Yimin Sag,Hailaer Basin

为明确海拉尔盆地伊敏凹陷中低煤阶煤层气成藏富集条件,研究主力煤组的煤岩煤质、厚度、埋深、煤储层物性、含气性、顶板封盖性,以及水文地质条件,类比国内外中低煤阶成熟勘探区成藏地质条件,综合构造、煤储层分布、含气性、保存条件和水文地质条件,建立煤层气成藏模式,提出勘探选区建议。结果表明:伊敏凹陷西南部和中南部主力煤组(16号煤组、27号煤组)煤层厚度大,埋深适中,储层物性较好,顶板封闭性强,水文地质条件处于缓流区,适合煤层气富集成藏;研究区成藏条件与国内外中低煤阶成熟勘探区对比具有一定相似性,具备良好煤层气富集成藏基础,建立断层-地层封盖型热成因气和缓坡带晚期生物气型或混合型两种成藏模式,且前者优于后者;五牧场等地埋藏较深的大磨拐河组为煤层气勘探首选目标区,西南部埋藏较浅的大磨拐河组和伊敏组为煤层气勘探的第二选择。

In order to define the conditions of coalbed methane accumulation and enrichment of medium and low rank of Yimin Sag in Hailaer Basin,a systematic study was conducted on the proximate analysis and maceral of the coal and rock,thickness,gas content,reservoir property,roof sealing and hydrology geological conditions of major seams in the area.Domestic and overseas reservoir conditions were compared with mature exploration areas of medium and low rank.Based on the comprehensive structure,coal reservoir distribution,gas bearing property,preservation conditions and hydrogeological conditions,CBM accumulation models were established,and suggestions for exploration selection were put forward.The results show southwest and central southern area of the main coal groups(No.16 and No.27)have large coal seam thickness,moderate burial depth,good reservoir physical properties,strong roof sealing,and hydrogeological conditions in the slow flow region,which is suitable for coalbed methane accumulation and enrichment.The conditions of coalbed methane accumulation and enrichment in Yimin Sag are similar to the mature exploration areas of medium and low rank at home and abroad,and the study area have excellent foundation of coalbed methane reservoir.Two coalbed methane enrichment models with thermogenic fault-stratigraphic sealing type and late stage biogas or mixed type in gentle slope were provided,the former was superior to the latter.Damoguaihe Formation with deep burial in Wumuchang and other places are the first choice for CBM exploration,while Damoguaihe Formation with shallow burial in southwest and Yimin Formation are the second choice.