湘中涟源凹陷泥盆系佘田桥组海相致密泥灰岩气藏特征

近期，湘新页1 井在中扬子湘中地区涟源坳陷泥盆系海相致密泥灰岩试气中获工业气流，取得了该地区油气勘查的重要发现。本文基于地层划分与对比、岩石矿物组分、烃源岩评价、含气性分析及与国内外泥灰岩油气藏的对比，对涟源凹陷泥盆系海相致密泥灰岩气藏形成条件进行了深入解剖，以期为湘中地区该类型油气资源勘查与潜力评价提供依据。结果表明，湘中涟源凹陷泥盆系佘田桥组分段特征明显，厚度稳定，可对比性强，含气层集中在下部泥灰岩段，含气段厚度大于150 m；泥灰岩矿物组分以碳酸盐矿物为主，脆性矿物平均含量达到79.4%，有利于后期压裂成缝；泥灰岩有机质类型主要为Ⅱ1、Ⅱ2型，有机质成熟度处于过成熟阶段；岩心中构造成因的裂缝以中、高角度缝为主，低角度缝较少；泥灰岩段气测全烃曲线饱满，垂向气水分异作用不明显，为典型致密气藏特征。与渤海湾盆地沙河街组和墨西哥湾盆地鹰滩组相比，涟源凹陷泥盆系泥灰岩气藏具有埋藏浅、厚度大、地物指标好等特征，具有良好的勘探开发潜力。

Characteristics of Devonian Marine Tight Marl Gas Reservoir in Lianyuan Sag

Recently, industrial gas flow has been obtained from the XXY1 well in the pilot gas test of the Devonian marine tight marl, and an important discovery has been made for oil and gas exploration in central Hunan of the Yangtze region. In order to reveal the basic reservoir-forming characteristics of this type of gas reservoir, this study is based on stratigraphic division and correlation, rock and mineral composition, source rock evaluation, gas-bearing analysis and comparison with marl oil and gas reservoirs at home and abroad, the formation conditions of Devonian marine tight marl gas reservoirs in the Lianyuan Sag are deeply dissected, which provides an important basis for oil and gas resource exploration and potential evaluation in the central part of Hunan Province. The results show that the segmented characteristics of the Shetianqiao Formation Devonian in the Lianyuan Sag of central Hunan are obvious, with stable stratigraphic thickness and strong comparability. The gas bearing layer is concentrated in the lower mudstone section, the thickness of which is more than 150 m. The main mineral composition of Marl is carbonate mineral, and the average brittle mineral content is 79.4% , which is favorable for fracture formation in the later stage of fracturing. The organic matter type of the marl is mainly II1 and II2, and the maturity of the organic matter is in the over-mature stage. In the core, there are mainly middle and high angle cracks with relatively less low angle cracks among the tectonic cracks. Full gas log hydrocarbon curve and no obvious vertical gas-water differentiation are typical characteristics of tight gas reservoir. Compared with the Shahejie Formation in Bohai Bay Basin and Yingtan Formation in Gulf of Mexico Basin, the Devonian marl gas reservoir in Lianyuan Sag has the characteristics of shallow burial, large thickness and good geological features, which show good exploration and development potential.