空气钻水平井注入参数优化分析

空气钻井与水平井技术相结合为开发低压、低渗、低产油气藏开辟了一条技术途径，然而诸如井斜、注入参数、岩屑沉降等很多技术问题还有待进一步解决。加之实际工程中因特定地质、地层环境需要，所钻水平井曲率半径不一，故所需的注入参数也不一样。为定量比较其区别，基于计算流体动力学方法，建立了空气钻水平井井筒内流体流动的数学模型，通过数值模拟得出了不同注入参数条件下井筒内的流场分布，并结合井眼净化与冲蚀效应评价标准进行了多组次模拟对比分析。研究结果为注入压力及井口回压等实际工程参数设计提供了依据。

An analysis on the optimization of the injecting parameters in horizontal wells by air drilling

The combination of air drilling with horizontal well technology can greatly reduce the formation damage and en-large the exposure area of reservoirs, providing an important technical measure for developing the low-pressure, low-permeabil-ity, and low-yield hydrocarbon reservoirs. Although the application of this combined technology achieved success to some de-gree in some oil and gas fields in China, many technical problems have been left unsettled such as well deviation, injecting pa-rameters, cuttings settlement, and so on. Under specific geological and reservoir environment, horizontal wells are drilled with different curvature radius and different injecting parameters. For finding their difference in quantity, based on the method of computational fluid dynamics, a mathematical model was set up for fluids flow in the wellbore when this combined drilling tech-nology was used, and by numerical simulation the distribution of flow fields of the wellbore was got under different injecting parameters. As for the horizontal wells with different curvature radius, the proper values of injecting pressure and back pres-sure were obtained by simulation results and comparison analysis according to the requirement for hole cleaning and the criteria for critical velocity of erosion flow. As for the horizontal wells with the same injecting parameters, the smaller the curvature ra-dius is, the higher increase degree of the flow velocity of fluids in the annulus will be; otherwise, the larger the curvature radi-us becomes, the smaller amplitude reduction of flow velocity of fluids at the joint area of drilling tools will be. The obtained re-suits from this study provide reference for the design on the actual drilling parameters when this combined drilling technology is adopted.