钙质隔夹层特征、成因及分布——以塔里木盆地哈得油田东河砂岩为例

Feature,origin and distribution of calcareous interlayers:A case of Carboniferous Donghe sandstone in Hade Oil Field,Tarim Basin,NW China

综合利用露头、岩心、普通薄片、铸体薄片、扫描电镜、碳氧稳定同位素、常规测井和地层倾角测井等资料,对塔里木盆地哈得油田东河砂岩钙质隔夹层的岩石学特征、测井响应特征、成因模式及分布规律进行系统研究。研究区钙质隔夹层主要为钙质细、粉砂岩,成分成熟度与结构成熟度都较高,钙质成分包括方解石、铁方解石、白云石、铁白云石、硬石膏等。虽然钙质隔夹层一般厚度较薄,但结合常规测井和地层倾角测井资料仍可将其识别。建立了3种钙质隔夹层的成因模式:浅埋藏淡水环境隔夹层、蒸发作用隔夹层和深埋藏期隔夹层。结合沉积相带发育情况,认为钙质隔夹层在临滨、后滨较为发育,容易连片,井间易连续;结合高精度层序地层学特征,认为东河砂岩岩层组界面钙质隔夹层具体产状主要有5种:"上钙下泥"型、"上泥下钙"型、"钙-泥-钙"型、钙质单层界面型和钙泥质界面型。

The petrologic characteristics, well-logging, genetic models and distribution patterns of calcareous inter-layers in Carboniferous Donghe sandstone, Hade Oil Field were investigated systematically by using data such as outcrop, cores, thin sections, stable carbon and oxygen isotopic compositions, conventional logging curves, and dip logging curves. Calcareous inter-layers in the study area are made up of calcareous fine sandstone or calcareous siltstone of high compositional and texatral maturity, in which calcareous components include calcite, ferro-calcite, dolomite, ferro-dolomite and anhydrate. Although the calcareous inter-layers are usually thin, they can be identified by combining conventional logging curves with dip logging curves. Three genetic models of calcareous inter-layers are identified, including shallow burial fresh water, evaporation and deep burial. According to the development of sedimentary facies, it is inferred that calcareous interlayers are well-developed in shore face and backshore sandstones, and likely to join together and show continuity between wells; based on features of high-resolution sequence stratigraphy, it is concluded calcareous inter-layers in Donghe sandstone have five types of occurrence： ＂upper calcareous-lower argillaceous＂ type, ＂upper argillaceous-lower calcareous＂ type, ＂calcareous-argillaceous- calcareous＂ type, purely calcareous type and ＂calcareous-argillaceous complex＂ type.