官寨井田沉积环境与聚煤规律

Guanzhai Minefield Depositional Environment and Coal-Accumulating Pattern

以井田大量钻孔地质资料为基础,从岩性特征,层理特征、古生物、含煤性、煤质等方面对官寨井田二叠系上统龙潭组含煤地层沉积环境、聚煤作用进行分析,得出本区沉积环境为过渡相,地势北东低南西高,海水由北东向南西推进,根据海水进退规律可分为三个成煤期:早期为泻湖—潮坪环境,总体处在海平面上升期,属退积型。因海水进退频繁,不利于成煤,形成的煤层多为薄层,煤层局部可采;中期为潮控三角洲环境,是海平面下降期,属进积型,此时地壳运动相对稳定,形成了井田中主要可采煤层4号、9号煤,属中厚层,连续性好;晚期为泻湖—潮坪环境,该期总体为海平面上升期,属退积型,海水进退较频繁,在垂向上旋回多而小,完整性差,形成了不可采的1、3号煤层及全区大部分可采的2号煤。在横向上区内北东部较南西部聚煤条件好,从西—东,二叠系沉积厚度增大,煤层含煤系数增大,可采系数变大。

Based on large amount borehole geological data, analyzed Upper Permian Longtan Formation coal-bearing strata depositional environment, coal-accumulating process from aspects of lithologic and bedding features, paleontology, coal-bearing property and coal quality, worked out the depositional environment in the area belongs to transitional facies, the relief was low in northeast, high in southwest, sea water advanced from northeast to southwest, three coal-forming stages were divided according to marine progression and regression pattern： early stage was lagoon-tidal flat environment, stood in a sea level rising stage as a whole, belongs to retrogradation type, because of frequent transgression and regression went against coal forming, so coal seam formed in this stage are usually thin and only local mineable; middle stage was tidal delta environment, stood in a sea level lowering stage, belongs to progradation type, crustal movement was relatively stable, main mineable Nos.4 and 9 coal seams were formed, belong to medium thick coal seams and good continuity; late stage was lagoon-tidal flat stage environment, stood in a sea level rising stage as a whole, belongs to retrogradation type, because of frequent transgression and regression, many sedimentary circles vertically but smaller, with poor integrity, non-mineable Nos.1 and 3 coal seams and mineable for the greater part No.2 coal seam were formed. Transversely, northeastern part has better coal-forming condition than southwestern part, Permian sedimentary thickness, coal- bearing coefficient and mineable coefficient are increasing from west to east.