火山岩气藏压裂水平井非稳态产能模型及敏感性分析

目前我国已探明的火山岩气藏地质储量达数千亿立方米,储量规模属世界最大。与常规砂岩气藏相比,火山岩气藏储集层裂缝发育,储集层物性差、渗流机理复杂。现场多利用压裂水平井技术开发火山岩气藏,有利于改善火山岩气藏渗流状况,降低单井成本,提高单井产能。但目前缺乏适合于火山岩气藏压裂水平井的复杂双重介质的非稳态产能预测模型。利用该研究综合考虑火山岩气藏双重介质特性及有限导流裂缝的情况,建立火山岩气藏压裂水平井非稳态产能预测模型,应用Laplace变换和Duhamel原理,同时结合Stehfest数值反演对模型进行求解。应用建立的产能预测模型,结合XS气田火山岩气藏P1井实际储集层及压裂参数,绘制P1井的产能递减曲线,分析了裂缝半长,裂缝条数,裂缝间距及导流能力对火山岩气藏压裂水平井产能递减曲线的影响。同时,应用正交试验进行了多因素分析。研究所获得的结果有助于提高对火山岩气藏压裂水平井产能递减规律的认识,同时,也可为评价预测火山岩气藏压裂水平井产能及优化其压裂裂缝参数提供依据。

An Unstable productivity Model for Fractured Horizontal Well in Volcanic Rock Gas Reservoirs and Analysis of Sensitivity

At present, the proved geologic reserves are more than hundreds of billions of cubic meters in China which has the largest volcanic rock gas reservoirs in the world. Compared with conventional gas reservoirs in sandstone formation, volcanic rock gas reservoirs developed cracks with a poor reservoirs property and complex percolation mechanism. Fracturing horizontal well technology is commonly used to develop the volcanic rock gas reservoir. Through this way not only can improve the seepage state of the reservoir, but also can save the cost of the single well and improve the productivity of that. However, there are no suitable unstable state productivity prediction methods for fractured horizontal well in volcanic rock gas reservoirs with complex dual-media. Therefore, according to the characteristic of dual-media in volcanic rock gas reservoirs and finite conductivity fractures, a productivity model of fractured horizontal well in volcanic rock gas reservoirs has been established. Laplace transform and the principle of Duhamel in combination with Stehfest numerical inversion algorithm are used to solve the model. The productivity decline curves are plotted and the influence of the fracture half length, the number of fracture, the fracture spacing and the flow conductivity in volcanic rock gas reservoirs is analyzed through combining the established productivity model with the fact parameters in the field. Meanwhile, utilize orthogonal experiments to go on the analysis of multi-factor. The results can help people to understand the productivity decline law of fractured horizontal well in volcanic rock gas reservoirs and provide the productivity evaluation and the fractured optimization of fractured horizontal well in volcanic rock gas reservoirs.