考虑重力及气体非达西效应影响的边水气藏边水突破时间预测模型

现有边水突破时间预测模型都是基于平面，然而实际气藏与水平面总存在一定的倾角，所以不能忽略重力作用的影响。基于气水两相渗流力学理论，综合考虑地层倾角、气体非达西流动效应、气水流度比和气井距边水的长度等因素，建立实际倾斜边水气藏新模型，并进行敏感性分析。实例分析表明，与已有预测模型相比，新模型预测的边水突破时间更接近实际。敏感性分析表明，边水突破时间与地层倾角呈二次抛物线关系，在地层倾角为90°时边水突破时间达到最大；与气井距边水的长度呈幂函数关系，在气井距边水的长度达到500 m 后，边水突破时间的增加量每100 m 增加7 d；与气井产量及气体非达西系数都呈反比关系，在开发前期边水突破时间的降低程度接近90%，当气井水淹后则基本对边水突破时间无影响；与气水流度比及储层厚度都呈线性关系，边水突破时间在气水流度比值每增加1 倍时增加30 d，在储层厚度每增加1 m 时则增大49 d。因此在气井生产初期，准确确定这些参数显得尤为重要。研究成果可对实际边水气藏的高效开发提供技术支撑。

Model for prediction of edge-water breakthrough time in reservoirs with edge water with consideration to effects of gravity and non-Darcy effect of gases

All existing models for prediction of edge-water breakthrough time are based on horizontal plane. However, actual gas reservoirs always have certain dips from the horizontal plane. It is necessary to consider effects of the gravity. According to the theories for gas-water flow mechanics, and with consideration to dip angles, non-Darcy flow effects of gases, gas/water mobility ratios, distances between gas well and the edge water, and other factors, a new model for inclined gas reservoirs with edge water was built. Then, sensitivity analysis was performed for the new model. Compared with existing prediction models, the new model can predict breakthrough time of edge water closer to actual time. Sensitivity analysis shows that edge-water breakthrough time is in quadratic parabola relationship with dip angles. The maximum edge water breakthrough time can be observed at the dip angle of 90°. The edge-water breakthrough time is in power-function relationship with the distance between the gas well and the edge water. With such distance of 500 m or more, the edge-water breakthrough time increases 7 d for every 100 m. Moreover, the edge-water breakthrough time is in inverse relationship with both gas well productivity and non-Darcy factors of relevant gases. In earlier stage of development, the breakthrough time of edge water reduces up to 90%. When the gas well is flooded, effects on breakthrough time of the edge water are ignorable. Furthermore, the edge-water breakthrough time is in liner relation with both gas/water flow rate and reservoir thickness. The edge-water breakthrough time increases 30 d when the gas/water flow rate is doubled, and increases 49 d for every additional meter in reservoir thickness. It is very important to determine these parameters accurately in early stage of gas well production. The research results can provide necessary technical supports for high-efficiency development of gas reservoirs with edge water.