基于自适应杂交遗传算法的CO_2地质封存的储层参数反演研究

二氧化碳地质封存是减少温室气体排放和减缓温室效应的重要手段.二氧化碳封存的一个重要组成部分是地震监测,即用地震的方法监测封存后的二氧化碳的分布变化.为了实现这个目标,需要建立储层参数与地震性质之间的关系(岩石物理模型)和从地震监测数据中反演获得储层流体的饱和度等参数.首先,本文以Biot理论为基础,结合多相流模型研究了多个物理参数(孔隙度、二氧化碳饱和度、温度和压力等)对同时含有二氧化碳和水的孔隙介质的波速和衰减等属性的影响.结果表明:孔隙度和二氧化碳饱和度对岩石的频散和衰减属性影响强烈,而温度和压力通过孔隙流体性质对岩石的波速产生影响.然后,本文基于含多相流的Biot理论,应用抗干扰能力强、且具有更好的局部搜索能力和抗早熟能力的自适应杂交遗传算法对实际数据进行了反演研究.对岩心实验数据的反演研究表明了算法的有效性,而且表明含多相流的Biot理论能够很好地解释水和二氧化碳饱和岩石的波速特征.最后,我们将自适应杂交遗传算法应用于实际封存项目的地震监测数据,获得了封存后不同时期的二氧化碳饱和度,达到了用地震方法监测二氧化碳分布的目的.

Reservoir parameter inversion of CO2 geological sequestration based on the self-adaptive hybrid genetic algorithm

Carbon dioxide geological sequestration is an important approach to reduce carbon emission and to mitigate global warming. An important part of CO₂ sequestration is seismic monitoring, which is to monitor carbon dioxide distribution variation using the seismic method after sequestration. To achieve this goal, we need to establish the relationship between reservoir parameters and seismic properties (rock physics model), and to obtain parameters like reservoir fluid saturation through inversion of seismic monitoring data. First, based on the Biot model and multiphase model, we investigate the effects of several physical parameters (porosity, CO₂ saturation, temperature and pressure, et al.) on seismic properties such as wave velocity and attenuation of carbon dioxide and water saturated porous media to obtain the regular understanding. The results show that porosity and CO₂ saturation have a huge impact on the properties of wave dispersion and attenuation, and temperature and pressure can affect the rock velocity through the properties of porous fluids. Next, based on Biot theory with multiphase flow, we apply the self-adaptive hybrid genetic algorithm, which has stronger anti-interference capacity and better ability of local search and anti-interference, to perform inversion of actual data. The inversion of core experimental data indicates the validity of the algorithm, and shows that Biot theory with multiphase flow can explain the wave velocity characters of CO₂ and water saturated rock. At last, we apply the self-adaptive hybrid genetic algorithm to the seismic monitoring data of actual sequestration project, and obtain the CO₂ saturation distribution at different periods after sequestration and achieved the purpose of using the seismic method to monitor carbon dioxide distribution.