致密砂岩气井修正扩展指数递减模型及其应用  

Modified SEPD model and its application to tight sandstone gas wells

作　　者：蔡振华 刘世界 王文升 秦鹏 Cai Zhenhua;Liu Shijie;Wang Wensheng;Qin Peng(Engineering Technology Company,CNOOC Energy Technology&Services Limited,Tianjin 300452,China)

机构地区：[1]中海油能源发展股份有限公司工程技术分公司

出　　处：《天然气勘探与开发》2018年第1期63-68,共6页Natural Gas Exploration and Development

基　　金：国家科技重大专项(编号:2011ZX05009);中国海洋石油总公司科技项目<致密砂岩气产能指数及预测方法研究>;海油发展工程技术公司科研项目(编号:GCJSXMHT-1618)

摘　　要：致密砂岩气是我国重要非常规天然气,一般需要增产措施才能获得工业气流,因此多以压裂直井或多段压裂水平井开发为主。由于致密砂岩储层具有应力敏感和较强的非均质性等特征,考虑这些因素的渗流模型复杂,难以求解,而常规递减模型往往预设了较为理想条件,难以应用到实际致密砂岩气井的预测,或者难以真实描述其渗流动态。鉴于这种情况,许多学者提出了经验递减模型,其中扩展指数递减模型广泛应用于非常规天然气井,在致密砂岩气井和页岩气井取得很好的应用效果,尤其在美国页岩气井取得了较好的效果。将本模型引入国内致密气井时,发现产量由于季节性调峰或者人为关井等因素,使得模型精度有限。以扩展指数递减方法(SEPD)为基础,引入了累计产气量和套压,降低数据噪点,并以鄂尔多斯盆地苏里格气田实际生产数据为例进行拟合分析和生产预测,发现修正指数递减模型(Modified SEPD)既可以用于压裂直井,也可用于多段压裂水平井,计算简便实用,可以预测气井采出量和采出程度。For tight sandstone gas,a kind of important unconventional gas in China,to obtain the commercial flow often needs stimulation.Therefore,fractured vertical wells and multi-stage fractured horizontal wells are the main development means.Tight sandstone reservoirs are characterized by stress sensitivity and strong heterogeneity.If these percolation characteristics are taken into account,the model can be hardly solved.Conventional decline models are often restricted in many aspects,so they are unsuitable to predict tight sandstone gas wells or describe the percolation performance actually.So,many scholarships propose empirical declines models,among which the stretched exponential production decline model(SEPD)is extensively applied to unconventional gas wells,and its application to tight sandstone or shale gas wells is good,especially in many shale gas wells in America.When this model is introduced into the tight gas wells in China,however,its accuracy is limited for the production rate is impacted by seasonal peak shaving or artificial well shutdown.In this paper,cumulative gas production and casing pressure were introduced into SEPD model,because cumulative gas production is stable enough to decrease noise points of data.Then,the actual production data of a certain block in Ordos Basin was taken as the example for fitting analysis.It is demonstrated that the modified SEPD is applicable to not only fractured vertical wells,but also multi-stage fractured horizontal wells.Besides,it is simple and practical,and can be used to predict the gas production and the degree of reserves recovery.

关 键 词：致密砂岩气藏 压裂气井 产量递减 指数模型 

分 类 号：TE37[石油与天然气工程—油气田开发工程]