摘要
在石油、天然气、页岩气和煤层气资源勘探开发方面,镜质体反射率指标被公认是唯一可对比的烃源岩有机质成熟度评价指标。为准确测定窑街矿区海石湾井田油A层腐泥煤的有机质成熟度,采集井田钻孔煤岩样品,开展显微镜下显微成分反射光、荧光光学特征观测。测试发现,油A层腐泥煤中存在2种不同特征镜质组,一种为发荧光的镜质组,反射色低、反射率测值低;另一种为不发荧光镜质体,反射色高、反射率测值相对偏高。油A层沉积环境分层明显,上部为腐泥煤,显微成分以藻类体为主,含有大量的黄铁矿,反映深部沼泽强还原环境;下部显微成分以腐泥基质、基质镜质体、角质体为主,相较于上部,藻类体及黄铁矿含量明显降低,反映出其沉积物源发生变化,藻类等低等生物输入比例降低,高等植物物源比例增高,反映为相对较弱的还原环境。根据井田地层沉积环境、油A层腐泥煤显微组成及其与下部煤二层腐植煤的镜质组成熟度对比分析,认为油A层腐泥煤中不发荧光镜质体的反射率能够反映其真实的成熟度,与下部煤二层处于同一变质阶段。研究认识为开展腐泥煤有机质成熟度分析提供了新的方法、思路,当煤岩层中高等植物含量较少,或者与其相邻地层成熟度差异较大时,建议将局部测试结果与整个煤系各煤/岩层进行比对,同时结合其镜质体荧光特征和沉积环境综合判断分析。
The vitrinite reflectance is recognized as the only comparable evaluation index of organic matter maturity of source rock in the exploration and development of oil and gas, shale gas and coalbed methane resources. Current research was done to determine the organic matter maturity of sapropel coal in oil layer A in Haishiwan mine field more accurately. Coal samples were collected from boreholes and observation of the optical characteristics of reflected light and fluorescence microscopic components were studied under the microscope. It was found that there are two different characteristic vitrinites in sapropel coal in oil layer A. One was fluorescent vitrinite with low reflection color and low determined reflectivity, the other was non-fluorescent vitrinite with measured higher reflection color and relatively higher reflectivity. The sedimentary environment of oil layer A is obviously stratified. The upper part is sapropelic coal. The maceral composition is mainly alginate, containing a large amount of pyrite, reflecting the strong reducing environment of deep swamp;The lower part is mainly composed of sapropelic groundmass, desmocollinite and cutinite. Compared with the upper part, the contents of alginite and pyrite are significantly reduced, reflecting the change of sedimentary source. The proportion of organism like algae decreases,whereas the proportion of plants increases. This reflects a relatively weak reducing environment. According to the sedimentary environment of the mine field, the comparative analysis was carried out between the microscopic composition of the sapropel in oil layer A and the vitrinite composition maturity of the sapropel in its lower coal seam No.2. Major findings were that the reflectivity of the non-fluorescent vitrinite in oil layer A can reflect its true maturity, and that was in the same metamorphic stage as the lower coal seam No. 2. It provides a new method and new thought for the analysis of organic matter maturity of sapropelic coal. When the content of plants in coal seams is relatively low or there is a significant difference with maturity of adjacent strata, it is recommended to compare the test results of specific layers with the whole coal/rock stratum. Then a comprehensive analysis should be made in combination with its vitrinite fluorescence characteristics and sedimentary environments.
作者
宋孝忠
张炳忠
雷莹
宋艳强
SONG Xiaozhong;ZHANG Bingzhong;LEI Ying;SONG Yanqiang(Xi’an Research Institute Co.Ltd.,China Coal Technology and Engineering Group Corp.,Xi’an 710077,China;Yaojie Coal and Power Group Co.Ltd.,Yaojie 730080,China)
出处
《煤田地质与勘探》
CAS
CSCD
北大核心
2021年第6期74-80,共7页
Coal Geology & Exploration
基金
国家自然科学基金项目(41972167)。
关键词
窑街矿区
腐泥煤
有机质成熟度
荧光镜质体
沉积环境
Yaojie mining area
sapropelic coal
maturity of organic matter
fluorescent vitrinite
sedimentary environments