四川盆地龙王庙组气藏渗流数学模型的建立与应用

应力敏感与高速非达西效应是影响气井产能的两个重要因素,有必要在实验室内对两者进行研究,确定其对产能的影响。为此,利用智能化岩心驱替实验系统,对四川盆地川中地区下寒武统龙王庙组白云岩岩心进行了变围压和变流压的应力敏感实验,以及储层有效应力状态下的气体流态测试,并结合气藏储层实际情况对应力敏感与流态实验的测试结果进行了分析,建立起了龙王庙组白云岩气藏渗流数学模型,进而分析了两种效应对气井产能的影响。结果表明:龙王庙组白云岩有效应力可以用Terzaghi有效应力来描述,渗透率与有效应力呈幂函数关系,应力敏感引起的单井产能损失达27%;单相气体渗流规律遵循Forchheimer方程,非达西渗流系数(β)比常规砂岩小1个数量级,储层高速非达西效应弱,对气井产能影响不大。该研究成果对于气井合理配产和开发动态预测具有指导意义。

Establishment and application of seepage mathematical model of Longwangmiao Fm gas reservoirs in the Sichuan Basin

Stress sensitivity and high speed non Darcy effect are the two major factors affecting gas well productivity, so it is necessary to make experimental studies of them and their influence on well productivity. Therefore, stress sensitivity experiments with changing confining pressures and changing flowing pressures and the gas flow regime test under the effective stress of the reservoir were applied to the Lower Cambrian Longwangmiao Fm dolomite core by utilizing the intelligent core displacement experiment system. In combination with the actual geological condition of such gas reservoirs, the results of the stress sensitivity and flow regime were analyzed to build the permeability mathematical model of the Longwangmiao Fm dolomite gas reservoirs, on this basis, to further analyze the influence of the said two effects on the gas well productivity. The results indicated that the effective stress of the Longwangmiao Fm dolomite can be expressed by the Terzaghi effective stress, that is, the permeability is in a power function relationship with the effective stress, and the productivity loss of a single well caused by the stress sensitivity reaches 27%; the single phase gas permeability rule follows the Forchheimer formula and the non Darcy flow parameter (β) is one order of magnitudes less than that of the conventional sandstone, the high speed non Darcy effect has very little influence on the reservoir and thus on the gas well productivity. The research result plays a major guidance role in the rational production allocation of gas wells and the prediction of exploration dynamic performance.