注N井井筒温度压力耦合下的井底流压计算

A calculation model for the bottom hole flowing pressure of nitrogen injector with coupled wellbore temperature and pressure

金永进 林伯韬 王如燕 金衍

JIN Yongjin LIN Botao WANG Ruyan JIN Yan

中国石油大学北京石油工程学院 中国石油新疆油田分公司工程技术研究院

College of Petroleum Engineering, China University of Petroleum (Beijing), Beijing 102249, China Engineering Technology Research Institute, PetroChina Xinjiang Oilfield Company, Karamay 834000, Xinjiang, China

在注N₂提高采收率的过程中，井底流压的大小是影响驱油效果的重要因素，在计算气井的井筒压力分布时，通常采用Cullender-Smith模型。但是氮气的物性参数随温度和压力的变化而变化，为了精确的计算注氮气井井底流压的大小，以注水井转注氮气井作为研究对象，根据垂直管流的能量平衡方程，结合适用于氮气的物性参数密度、黏度、偏差因子及摩阻等计算方法，提出了注氮气井井筒温度和压力分布耦合的井底流压计算模型，应用四阶龙格－库塔迭代方法，用MATLAB软件计算了井底流压的大小，最后评价了注氮气井的启动压力、注气速度和井底流压的关系。根据对红浅井区氮气试注试验的测井数据分析，表明新压力预测模型计算结果与现场实测结果相吻合，注气初期注入压力受注入量变化影响较小，注入压力高低主要与储层物性有关。

When nitrogen injection is used for enhancing oil recovery, the bottom hole flowing process is the important factor affecting oil displacement effect. And Cullender-Smith model is generally adopted to calculate borehole pressure distribution of gas wells. However, the physical property parameters of nitrogen vary with temperature and pressure. In order to accurately calculate the bottom hole flowing pressure of nitrogen injectors, the nitrogen injector transformed from the water injector was taken as the study object. The bottom hole flowing pressure calculation model for nitrogen injector with coupled wellbore temperature and pressure distribution was proposed according to the energy equilibrium equation of vertical conduit flow, combined with the calculation methods suitable for the physical property parameters of nitrogen (e.g. density, viscosity, deviation factor and friction resistance). Then, by means of the fourth order Runge-Kutta iteration, the bottom hole flowing pressure was calculated using the software MATLAB. Finally, the relationships of threshold injection pressure and injection speed of nitrogen vs. bottom hole flowing pressure were evaluated. The analysis on the logging data of nitrogen injection test in Hongqian well block shows that the calculation result of new pressure prediction model is accordant with the measured value. It is indicated that the injection pressure in the early stage of gas injection is less affected by the variation of injection rate and it is mainly dominated by the physical properties of reservoirs.

10.13639/j.odpt.2018.04.015