四川盆地页岩气储层含气量的测井评价方法

含气量是页岩气储层评价的一项重要参数指标,其值的高低直接影响着页岩气区块是否具有工业开采价值。而页岩气含气量主要由吸附气和游离气组成,其影响因素较多,包括孔隙度、含气饱和度、地层压力、地层温度、总有机碳含量等。为此,针对四川盆地蜀南地区下志留统龙马溪组页岩气储层开展综合研究,形成了一套系统的页岩气储层含气量测井评价方法 :(1)通过页岩岩心等温吸附实验,建立了兰格缪尔方程关键参数计算模型,并对吸附气含量主要影响因素地层温度、地层压力、有机碳含量进行分析及校正,提高了吸附气含量计算精度;(2)开展页岩储层孔隙度和含水饱和度精细评价,为精确计算游离气含量奠定了基础;(3)由于吸附态甲烷占据一定孔隙空间,扣除吸附气体积影响后,总含气量计算精度较高,与岩心分析数据具有较好的一致性。通过实验与理论的结合,所形成的四川盆地页岩气储层含气量评价方法在该区块具有较好的适应性,为现场试油层位的优选和区块资源潜力评价提供有效的技术支撑。

A logging evaluation method for gas content of shale gas reservoirs in the Sichuan Basin

Gas content, as an important indicator for shale gas reservoir evaluation, directly determines whether a shale gas block is ofindustrial production value. Gas content is mainly composed of free gas and adsorbed gas, and is impacted by many factors, includingporosity, gas saturation, formation pressure, formation temperature and total organic carbon content (TOC). In this paper, a set of systematiclogging evaluation methods for the gas content of shale gas reservoirs was developed based on a comprehensive study of the shalegas reservoirs of Lower Silurian Longmaxi Fm in the southern Sichuan Basin. First, a calculation model for the key parameters of Langmuirequation was built up by conducting isothermal adsorption experiments on shale cores. And the calculation accuracy of adsorbedgas content was improved by analyzing and correcting its main influential factors, such as reservoir temperature, reservoir pressure andTOC. Second, porosity and water saturation of shale reservoirs are precisely evaluated to provide a basis for accurate calculation of freegas content. And third, the adsorbed methane occupies a certain pore space, so the calculated gas content is more accurate after the effectof adsorbed gas volume is excluded, and it is consistent with the core analysis data. To sum up, the calculation method for gas contentof shale gas reservoirs in the Sichuan Basin is developed experimentally and theoretically, and is of good adaptability in this block. So itprovides an effective technical support for production testing horizon selection and block resource potential evaluation.