萍乐拗陷龙潭组海相泥页岩勘探潜力

Exploration potential of the Permian Longtan Formation marine mud shale in the Pingle Depression,China

为评价中国东南地区上古生界富有机质泥页岩勘探前景,基于区域地质背景、露头观察和地球化学测试,通过对萍乐拗陷二叠系龙潭组岩相古地理、富有机质泥页岩的有机地球化学特征及平面分布差异的系统分析,探讨富有机质泥页岩控制因素。萍乐拗陷龙潭组时期为整体海退背景下的海陆过渡潮坪沉积环境;龙潭组富有机质泥页岩厚度在平面上表现为西厚东薄;有机碳质量分数为0.06%～12.32%,高值区位于萍乡一带,表现出西高东低的特点;有机质类型主要为Ⅲ型干酪根,总体以生气为主;R_o值为0.5%～5.45%,呈现自东向西成熟度逐渐增高的趋势。萍乐拗陷龙潭组富有机质泥页岩整体质量西高东低,沉积环境、埋藏史及热事件是形成该现象的主要控制因素。对萍乐拗陷西部地区而言,埋藏和热事件影响较大;而中东部地区则主要受埋藏作用的影响。中部丰城地区具备较好的非常规油气勘探前景。

Based on the regional geological background, outcrop observation and analysis of geochemical data, the lithofacies paleogeography, organic geochemical characteristics and distribution discrepancy of the Permian Longtan Formation organic matter-rich mud shale in Pingle Depression are studied and the controlling factors of the mud shale are discussed in order to evaluate the exploration prospects of the Upper Paleozoic organic matter-rich mud shale in southeast China. Research shows that the Longtan Formation is deposited in a sedimentary environment of sea-land transition tidal flat under an overall regressive background. In the Pingle Depression, the Longtan Formation organic matter-rich shale is thick in the west and thin in the east. The distribution range of TOC of the mud shale is 0.06%~12.32% and the highest TOC value occurs in the Pingxiang area, and generally, the TOC value in the west is higher than that in the east. Organic matter types of the mud shale are mainly gas-produced Ⅲ kerogen, with a R o distribution range of 0.5%~5.45%, and its maturity increases from east to west and the overall quality of the Longtan Formation organic matter-rich shale in the Pingle Depression is also high in the west and low in the east. It is revealed that the sedimentary environments, burial history and thermal events are the main controlling factors for the enrichment characteristics of organic materials. Of the controlling factors, burial and thermal events play an important role in the accumulation of organic materials in the western Pingle Depression, while buried history is the main controlling factor in the central and eastern regions. It is proposed that the Fengcheng area in the central Pingle Depression has a good prospect for unconventional oil and gas exploration.