川西中浅层高效成藏模式研究

RESEARCH ON THE HIGH EFFICIENT RESERVOIR-FORMING PATTERN FOR THE SHALLOW LAYER IN THE WESTERN SICHUAN

川西坳陷中浅层河道砂岩气藏的成藏模式众多,但不同成藏模式控制下的成藏区域或层系的开发效益存在明显差异。本文通过解剖川西坳陷中浅层河道砂岩气藏高效开发层系或区域的成藏地质条件,明确该区中浅层高效成藏模式为"香肠式"成藏,该成藏模式包括两个重要环节,即"香肠式"充注和"香肠式"圈闭。研究表明"香肠式"成藏必须同时具备以下几个基本条件:(1)条带状外形的河道砂体;(2)河道砂体一端存在明显的岩性尖灭;(3)河道砂体另一端延伸至中浅层源岩断层发育区内;(4)河道砂体一端直接相接的源岩断层的倾角小;(5)单斜背景下的岩性圈闭。通过后期钻井测试、试采证实,具备"香肠式"成藏条件的区域或层系,单井产能高,稳产时间长,且无水产出。类比分析,在地质条件相当的其他地区河道砂岩气藏的勘探开发中,该成藏模式可作为一种高效成藏模式来进行推广运用。

There are various reservoir-forming models for the shallow layer channel sandstones in the west of Sichuan,but the efficient development and benefit for different reservoir region or layer system with various accumulation models are obvious different. The study of shallow layer channel sandstones in the west Sichuan indicates that reservoir formation is characterized by ＂sausage＂ reservoir-forming model, including ＂intestinal＂ infilling and ＂intestinal＂ trap. It shows that the formation of ＂intestinal type＂ reservoir have several basic conditions： （1） The channel sand body have a strip shape; （2） Pinchout occurs at one end of the channel sand body; （3） The other end of sand body extends to the shallow source rocks in the fault development zone; （4） The dip angle of the fault contacted by the sandstone is small; （5） Lithological trap under the background of monocline. Test drilling confirmed region and layer with ＂sausage type＂ reservoir forming conditions reveals that the single well productivity is high, with stable productivity for a long time and without output of water. In the channel sandstones with similar geological conditions, this reservoir-forming model can be used as an efficient reservoir model for the exploration and development of oil and gas.