焦石坝区块页岩气井井底流压计算方法评价

Evaluation of calculation methods of bottomhole flow pressure in shale gas wells:a case study of Jiaoshiba block

为了更准确地计算页岩气井井底流压,精确评价气井产能,探寻气井生产规律,掌握气井开发动态,通过分析多种管流压降计算模型,利用涪陵页岩气田气井的各类静、动态资料,明确了不同压降模型应用于涪陵页岩气田气井的适用条件及影响其计算结果的主要因素,并在原有模型基础上建立了一种修正简化模型。研究表明,对于涪陵页岩气田的气井,当其气液比>7000 m^(3)/m^(3),单相流模型可做拟单相流计算,误差<5%;当其气液比<7000 m^(3)/m^(3),且气井瞬时产量大于临界携液流量时,气井可采用两相流Hagendorn&Brown模型计算井底流压,误差<10%,同时针对积液状态气井建立修正简化模型可进一步降低两相流模型计算结果误差。研究为具有相同背景的页岩气井井底流压预测提供了参考。

In order to calculate the bottomhole flow pressure more accurately,make a refined evaluation of the productivity,explore the production patterns,and have the knowledge of the development dynamics in shale gas wells,the static and dynamic data of gas wells in Fuling shale gas field are used to define the application conditions of different pressure drop models to gas wells in Fuling shale gas field and their main factors affecting their calculation results by reviewing and comparing various calculation models for pipe flow pressure drop,so that a modified simplified model is established on the basis of the original model.The results show that the single-phase flow model can be used to simulate the single-phase flow with small error for the gas well in Fuling shale gas field when the gas-liquid ratio is more than 7000m^(3)/m^(3),with the error less than 5%.The two-phase flow model can be used to calculate the bottomhole flow pressure when the gas-liquid ratio is less than 7000m^(3)/m^(3),with the error less than 10%.In this paper,it is analyzed that the main factor affecting the calculation error is that the gas well is not capable of reaching the liquid carrying flow rate,resulting in wellbore fluid accumulation,and the modified simplified model can reduce the error to a certain extent.This study affords a reference for prediction of bottomhole flow pressure in shale gas wells with the same conditions.