柴达木盆地渐新统红层的成因特征及石油地质意义

柴达木盆地渐新统下部的红层,是半干旱气候条件下,内陆湖盆中湖水间歇性涨缩及河湖两种营力交替作用形成的河湖交互相红层。勘探实践表明,这种红层具备形成油气藏的良好条件。岩石矿物分析鉴定表明,该组红层并非碎屑成因,而是同沉积作用和成岩作用的产物。红色染色素含量的多寡及其在岩石中的分布形式是决定岩石能否呈现红色及红色色调深浅的主要因素。

GENETIC CHARACTERISTICS OF THE OLIGOCENE RED BEDS IN CHAIDAMU BASIN AND THEIR SIGNIFICANCE IN PETROLEUM GEOLOGY

The discovery of the red beds reservoir of Lower Oligocene in Chaidamu basin illustrates that red beds, in addition to their capacity of being oil and gas reservoir, may be regarded as one type of strata of exploration. This red sedimentary formation includes red beds of both fluvial facies and lacustrine facies. They are the result of intermittent expanding and shrinking of lake water under semiarid climate. Repeated alternation of fluvial agent and lacustrine agent resulted in the formation of the corresponding alternating facies. According to core observation, mineral assemblage and chemical composition analysis,red beds of Lower Oligocene in Chaidamu ba-sin are not so much the product of terrigenous sedimentation as that of synsedimentation and diagenesis. The content and distribution of red hematite pigment in rock, which depend on the oxidizing-reduction condition of synsedimentary water and diagenetic water, are the main factors that determine the formation of red colour and its tone