深水钻井浅水流声学特征模拟实验及模型应用

Simulation experiment on acoustic characteristics of shallow water flow and model application in deepwater drilling

深水钻井一旦钻遇浅水流极易出现井漏甚至井喷等重大事故。常规地震剖面进行定性预测浅水流的准确性较低,为此提出了一种基于模拟实验的定量预测浅水流压力并对风险等级进行评价的方法。根据声波在水中及饱和岩石介质中的传播速度特征,进行了浅水流声学模拟实验。研究表明:纵波在深水浅水流地层中的传播速度随着地层压力的增大而增大,地层孔隙度越大,声波传播速度越小;通过数据拟合得到纵波速度与浅水流地层压力、孔隙度之间呈幂指数函数关系,根据实验结果建立了声速与浅水流地层压力、孔隙度的双参数模型,用于根据声速预测浅水流地层压力;利用有限元软件进行了浅水流地层的地质建模及放喷模拟,定义浅水流对钻井造成不同风险等级的压力系数范围。在中国南海深水区进行了浅水流声学预测及风险评价方法现场应用,验证了深水浅水流声波识别预测技术的可行性。

In deepwater drilling,major accidents such as well leakage or even blowout are likely to occur once drilling encounters shallow water flow.The accuracy qualitatively predicted by shallow water flow with conventional seismic sections is low.Therefore,a method based on simulation experiments to quantitatively predict shallow water flow pressure and evaluate the risk level is proposed.According to the propagation velocity characteristics of sound wave in water and saturated rock medium,the acoustic simulation experiment on shallow water flow was carried out.The research shows that:the propagation velocity of longitudinal wave in deep water and shallow water flow formations increases with the increase of formation pressure,the larger the formation porosity,the slower the sound wave propagation velocity.Through data fitting it is found that that the longitudinal wave and shallow water formation pressure,porosity shows a power exponential function relationship.Based on the experimental results,a dual-parameter model of sound velocity and shallow water flow formation pressure,porosity was established,so as to achieve the purpose of predicting shallow water flow formation pressure according to sound velocity.By using the finite element software,the geological modeling and blowout simulation of the shallow water flow formation were performed,and the pressure coefficient range of different risk levels upon to drilling because of the shallow water flow was defined.The acoustic prediction of shallow water flow and the risk assessment method has been applied in the deepwater area in the South China Sea,which verifies the feasibility of the sound wave recognition and prediction technology for shallow water flow in deepwater drilling.