煤层分支水平井井眼稳定性模拟研究

应用分支水平井技术开发煤岩气藏，具有单井产量高、采出程度高、经济效益好的优势。如何保证分支连接处的力学完整性、水力完整性和再进入能力，是煤层分支水平井顺利实施的关键技术。根据煤岩力学性质特征，运用有限元力学理论建立了数值模拟模型，对煤层分支水平井的井眼稳定性进行了分析。结果表明，分支水平井在井眼连接段出现应力集中；分支井眼与主井眼夹角为15°时，随压差的增大该处应力集中更加严重，同时连接井段随着井筒压差的增大有发生失效破坏的可能性。通过对比夹角为60°和15°时的结果得出，夹角增大有利于井眼稳定。该认识对于煤层气井的保护储层钻井、完井和生产设计具有重要意义，可进一步推广应用。

Simulation study on borehole stability of branch horizontal wells in coal bed

By applying branch horizontal well techniques to the development of coal-bed methane (CBM) reservoirs, the perwell yield and the degree of reserves recovery will be increased, good economic results will be obtained. The key technology to drillbranch wells is how to make sure the mechanics integrality, waterpower integrality, and reentering ability in the joint of embranchment.According to the mechanical properties of coal bed, a finite element model for studying branch wells is set up by use of the finiteelement mechanics theories. The hole stability of coal-bed branch horizontal wells is analyzed. Results show that horizontal wells havestress concentration in hole connecting sections and the concentration gets more serious as the pressure difference increases when theangle between the horizontal well hole and the main well hole is 15°. It is possible to result in failure and damage to the connectingsections, as the pressure difference increases. By comparing the different results when the angles are 60o and 15o respectively, it isfound that the hole gets more stable when the angle increases. The result is of great significance to the protection of reservoir drilling,completion, production and design of CBM wells, it can be further applied.