岩心分段密封及逸散轻烃采集测定技术与初步应用

Segmented sealing of cores and collection and test of escaped light hydrocarbons and its preliminary application

含油气岩心轻烃逸散具有普遍性,岩心出筒后轻烃收集及其逸散差异性的表征技术和方法尚有提升空间。以专利"一种岩心分段式密封装置及其使用方法(2013101681829)"技术为核心,研究设计了岩心分段密封装置及轻烃采集测定方法。装置具有筒状结构,内置数个环状密封圈,能够将置入其中的岩心进行非破坏式的分段密封,形成数个互不连通的密闭空间以存储岩心逸散的轻烃;装置配套了气体采样泵、便携式甲烷检测仪以及气相色谱仪等辅助设备,用于对不同密闭空间中的轻烃进行采样以及逸散轻烃浓度和组分测定,建立了密闭空间中逸散轻烃浓度转换为逸散量的方法。初步实验应用表明,利用该装置及方法能够获取岩心出筒后逸散的轻烃,进而表征岩心轴向不同部位轻烃逸散量及其组分的差异性,结合岩性及物性等资料,为页岩油气层系非均质性评价及其主控因素研究提供依据。

Light hydrocarbons easily escape from hydrocarbon-bearing cores when they are recovered from wellbores, which makes it necessary to improve the methods for collecting light hydrocarbons from cores and characterizing the differences of hydrocarbon losses. A new method for the segmented sealing of cores and the collection and test of light hydrocarbons was developed based on the patent "a segmented sealing device for cores and its instructions(2013101681829)". The device has a cylindrical structure with several annular seals built in, which can non-destructively seal the core inserted therein to form several closed spaces that are not interconnected to store light hydrocarbons escaping from the core. The device is matched with auxiliary equipment such as gas sampling pumps, portable methane detectors, and gas chromatographs, which are used to sample light hydrocarbons in different confined spaces to determine the concentration and composition of mobile light hydrocarbons. The concentration of escaped light hydrocarbons in confined spaces can be converted to escape quantity. Preliminary applications show that the device and method can be used to obtain light hydrocarbons that escape after the cores are recovered from the wellbores, and then to characterize the differences in the amount and components of light hydrocarbons escaping from different parts of the core in an axial direction. Combined with lithology and physical properties, it provides a basis for the evaluation of shale oil and gas formation heterogeneity and its main controlling factors.