复杂地质条件气藏储气库库容参数的预测方法

国内复杂地质条件气藏型地下储气库经过10余周期注采后工作气量仅为建库方案设计工作气量的一半,运行效率偏低。为此,利用气藏地质、动态及建库机理,建立了地下储气库注采运行剖面模型,根据气藏开发、气藏建库及稳定注采运行过程中纵向上流体的分布特征及其变化趋势,将地下储气库剖面分成4个区带(建库前纯气带、气驱水纯气带、气水过渡带及水淹带);按区带确定了影响建库有效孔隙体积的主控因素(储层物性及非均质性、水侵和应力敏感)及其量化评价方法,进一步考虑束缚水和岩石形变的影响,并引入注气驱动相,根据注采物质平衡原理建立了气藏型地下储气库库容参数预测数学模型。该模型涵盖了地质、动态及建库机理,从微观和宏观角度综合评价了影响建库空间的主控因素,大大提高了预测结果的准确度和精度,使建库技术指标设计更趋合理,目前已广泛应用于中国石油天然气集团公司气藏型地下储气库群的建设当中。

A prediction model of storage capacity parameters of a geologically-complicated reservoir-type underground gas storage (UGS)

The current working gas volume was only half as much as it was designed after more than ten injection-withdrawal cycles for a reservoir-type UGS under complex geological conditions in China, and the operation efficiency was lower as a result of inactive inventory suffered from reservoir properties, heterogeneity, water invasion, and stress sensitivity. In view of this, based on the geological conditions, dynamic performance of such a complex gas reservoir, and the UGS conversion mechanism, a cross-section model was built simulating the injection-withdrawal operation of the UGS. According to the flow distribution and changing trend in the vertical direction in the whole process from reservoir development, UGS conversion, to the follow-up stabilized UGS operation, the cross-section profile was divided into four zones: pre-UGS gas zone, gas-drive-water gas zone, gas-water transition zone, and watered-out zone. On this basis, the main controlling factors on the effective storage space were determined including reservoir petrophysical properties, heterogeneity, water invasion, and stress sensibility, as well as their quantitative evaluation methods. Furthermore, in light of the injection-withdrawal mass balance principle, the corresponding mathematical forecasting model was thus established taking into account the impacts of the deformation of irreducible water and rock pores and the injected gas volume. From both micro and macro perspectives, this forecasting model not only significantly improves the accuracy of UGS storage capacity, but evaluates the major controlling factors of the storage capacity parameters, making the designed indexes more reasonable. This model has been widely applied to many PetroChina's reservoir-type UGS construction projects.