阿姆河盆地右岸地区膏盐岩分布及其对盐下礁滩成藏的影响分析

近年来,含盐盆地油气勘探成为研究热点,并取得了重要进展。以阿姆河盆地右岸地区为例,自中石油2007年进入以来,在中上侏罗统卡洛夫-牛津阶内部相继探明和发现了一系列的礁滩气藏,其上直接为上侏罗统基末利阶巨厚的膏盐岩覆盖,天然气地质储量丰富,展示了盐下碳酸盐岩良好的油气勘探前景。以阿姆河盆地右岸地区上侏罗统膏盐岩为主要研究目标,重点分析了膏盐岩空间展布特征及其对盐下礁滩成藏的影响。研究表明,基末利阶膏盐岩纵向上为"3膏+2盐"的地层组合,自西向东厚度呈先增大再减小的特征。膏盐岩对礁滩成藏具有重要影响,中东部地区下盐段发育的盐丘与礁滩体具有较好的空间配置关系,盐丘之间下伏卡洛夫-牛津阶往往有礁滩体发育,为右岸地区最重要的钻探目标;膏盐岩引起的硫酸盐热还原反应(TSR)所形成的次生溶蚀孔洞是礁滩体重要的储集空间;膏盐岩对油气的运移及富集具有明显控制作用,西部地区受牛津阶上部多层石膏限制,形成层状台内滩气藏,纵向上发育多套气水系统。中东部地区受盐丘侧向封堵,形成各自独立的构造-岩性复合礁滩气藏,气水特征复杂,具有"一礁(滩)一藏"的特征。

Distribution Characteristics of Saline Deposits and Influences on Subsalt Reef-beach Hydrocarbon Accumulations in the Right Rank Area ofAmu Darya Basin

In recent years, the hydrocarbon exploration of salt-bearing basins has become a hotspot and major progress has been achieved. Taking the right bank area of Amu Darya Basin as an example, a series of reef-beach gas reservoirs have been discovered and proved in the middle-upper Jurassic Callovian-Oxfordian since the access of CNPC in 2007, which are directly covered by hugely thick saline deposits, the geological reserves is very abundant and shows a good exploration prospect. Based on the case study of saline deposits of upper Jurassic Kimmeridgian in the right bank area of Amu Darya Basin, the spatial distribution characteristics and influences on the subsalt reef-beach hydrocarbon accumulations are emphatically analyzed. The results show that the stratum assemblage of Kimmeridgian is 3 layers anhydrite and 2 layers halite in vertical and the total thickness increased first and then decreased from the northwest to the southeast. The saline deposits have important influences on the subsalt reef-beach hydrocarbon accumulations, there is a better space allocating relation among the Callovian-Oxfordian reef-beach bodies and lower salt layer salt domes, it is often the case that the reef-beach bodies developed between two salt domes and become the most important drilling targets in the central and east areas; the secondary solution pores formed by the thermochemical sulphate reduction (TSR) become important reservoir space; the migration and enrichment of hydrocarbon are obviously controlled by the anhydrite and halite, because of the strictly restriction of the multiple layers anhydrite of the upper part of Oxfordian, the gas reservoir type is layered intraplatform shoal reservoirs in the west of the right bank area and multiple gas-water systems developed in vertical. While the separate structural lithologic reservoirs developed in the central and east are controlled by the lateral blockage of salt domes, the gas-water systems are complex, every single reef or beach has its own gas-water system.