带边底水气藏的递减规律认识
The Understanding of Decline Law of Gas Reservoir with Edge or Bottom Water

带边底水气藏，水侵后产能下降快，利用常规方法很难准确预测开发趋势。本文以雅克拉凝析气藏开发实践出发，对气藏递减规律进行了研究，分别采用水侵体积系数法、采气速度法和数值模拟法预测开发趋势。其中水侵体积系数法是本论文首次提出，将微观实验与矿场生产关联到一起，用来定量描述水侵量与气藏递减特征关系。在长岩芯驱替实验中，当注入水驱替体积达到0.35~0.4倍孔隙体积时，天然气采出程度不再增加，表明在水的作用下一部分天然气被封存在孔隙内，难以采出。水侵体积系数法是基于水驱气藏物质平衡方程提出来的，通过物质平衡方程计算出水侵量及水侵体积系数，是长岩芯水驱气实验的宏观表现。经矿场验证，水侵体积系数达到0.35时，气藏边部井相继见水，进入快速递减期。该方法与数值模拟方法、采气速度方法所得结果一致。水侵体积系数法可推广应用到其它水驱气藏，提前预测递减规律，为气藏及早优化调控提供指导。
For gas reservoirs with edge or bottom water, the productivity decreases rapidly after water inva-sion, so it is difficult to accurately predict the development trend by conventional methods. Based on the development practice of Yakela condensate gas reservoir, this paper studies the decline law of gas reservoir, and predicts the development trend by using water invasion volume coefficient method, gas production rate method and numerical simulation method respectively. The water in-vasion volume coefficient method is proposed for the first time in this paper, which is used to quan-titatively describe the relationship between water invasion and gas reservoir decline characteris-tics by combining microscopic experiments with field production. In the long core displacement experiment, when the displacement volume of injected water reaches 0.35~0.4 times of pore vol-ume, the recovery degree of natural gas will not increase any more, indicating that a part of natural gas is sealed in the pores under the action of water, so it is difficult to recover. The water invasion volume coefficient method is proposed based on the material balance equation of water drive gas reservoir. The water influx and water invasion volume coefficient are calculated by the material balance equation, which is the macroscopic performance of long core water drive gas experiment. The field verification shows that when the water invasion volume coefficient reaches 0.35, the gas reservoir edge wells will see water one after another, and enter the fast decreasing period. The re-sults obtained by this method are consistent with those obtained by numerical simulation method and gas production rate method. The water invasion volume coefficient method can be extended to other water drive gas reservoirs to predict the decline law in advance and provide guidance for the early optimization and control of gas reservoirs.