高含硫储层硫沉积微观特性

Microscopic characteristics of sulfur depositions in high-sulfur-content reservoirs

四川盆地川东北地区相继发现了一大批高含硫碳酸盐岩气藏,其储量占四川盆地天然气储量的一半以上。然而,硫沉积一直是制约高含硫气藏高效开发的一大难题。结合微米CT扫描、扫描电镜、能谱分析和气相色谱分析等实验手段,运用储层高含硫气体完成了碳酸盐岩岩样的硫沉积实验,获得了实验前后岩样微观孔隙结构和气体组分的定量变化,首次实现了储层岩石中硫沉积的三维可视化。硫沉积实验结果显示,高含硫气体中总硫含量减小12.58%,有机硫组分减小9.07%;硫微粒主要沉积在半径小于500μm的岩石孔隙中,导致岩石渗透率降低34.40%~67.80%,孔隙度减小3.77%~7.69%。研究结果进一步提升了对硫沉积微观特性的认识,为高含硫气藏增产措施的制定提供了支撑。

A large number of high-sulfur-content carbonate gas reservoirs have been discovered in the northeastern part of the Sichuan Basin, and their reserve accounts for more than half of the total natural gas reserves in the basin. However, sulfur deposition has been a major problem for a long period which is restricting for the efficient development of high-sulfur-content gas reservoirs. In this paper, sulfur deposition experiments in carbonate rock samples were carried out with high-sulfur-content natural gas by the means of micro-CT scanning, scanning electron microscopy, gas chromatograph and energy spectrum analysis. The changes of the microscopic pore structure of the samples and gas composition before and after the experiments were quantitatively obtained, and the 3D visualization of sulfur deposition in reservoir rocks was achieved for the first time. Results show that after sulfur deposition experiment, the total sulfur content in high-sulfur-content gas decreased by 12.58%, and the organic sulfur component decreased by 9.07%. Sulfur particles were mainly deposited in rock pores with a radius of less than 500 μm, resulting in decreases in rock permeability and porosity by 34.40%-67.80% and 3.77%-7.69%, respectively. This study further improved the understanding of the microscopic characteristics of sulfur deposition and provided support for the formulation of production enhancement measures for high-sulfur-content gas reservoirs.