晋城矿区2014ZX-U-01H煤层气水平井井壁稳定性研究

发布时间：2018-04-23 19:37

本文选题：煤层气 + 水平井　；参考：《西安科技大学》2017年硕士论文

【摘要】：煤层气是一种高效洁净能源,我国储量丰富,抽采煤层气能减少矿井灾害、增加能源供给、减轻环境污染。水平定向钻井技术能使井眼沿煤层延伸,增大解析面积,提高抽采效率,因而被广泛采用。但随着开发深入,其井壁失稳问题日益突出,在水平段钻遇煤层时尤为明显,严重影响了钻井安全和经济效益。该问题受众多因素影响,但目前相关研究十分有限,分析其稳定性、探索失稳机理迫在眉睫。从地质、工程两方面总结了影响煤层气地面水平钻井稳定性的因素,并对赵庄井田2014ZX-U-01H井失稳情况统计,发现3#煤层上部水平段是重点失稳区,处理其失稳严重影响了工程进度。由此,基于Mohr-Coulomb强度准则,在进行井眼应力坐标变换后,采用实测岩石力学参数,通过软件MIDAS GTS NX建立了该水平井的三维有限元模型。研究了水平段井斜角、泥皮厚度、地应力方向等因素对井壁的应力分布特征、变形形式、位移量、井眼形状的影响规律,定量评价了失稳情况,找出了影响水平段井眼稳定性的主要因素,结果表明:(1)随水平段延伸井壁所受Von Mises应力逐渐增大,但3#煤层性质较差且存在纵向差异,井壁最终失稳程度同样受钻遇地层性质影响;(2)失稳时井壁以沿X轴方向变形为主,且底部位移量大于顶部,变形截面呈椭圆型,最大变形区位于3#煤层上部水平段;(3)地应力对破碎地层的变形破坏影响显著,对稳定地层影响较小;井斜角主要影响井壁塑性变形区半径;护壁泥皮则能改善整体井眼的应力集中现象;(4)影响该井水平段稳定性的主次因素顺序:地应力方向、井斜角、泥皮厚度。在研究范围内,随井眼走向与最大主地应力夹角增大、井斜角减小、泥皮厚度增大,井壁稳定性增强;(5)提出井田煤层气井水平段井眼走向与地应力夹角45°、井斜角84°、泥皮厚度1.2cm的最安全钻井组合方案,此时井壁最大Von Mises应力0.52MPa,最大变形量3.04cm,井眼最稳定。研究同实钻现象吻合,解决了传统方法耗时长、成本高、可重复性差、考虑因素不全面等缺点,且在计算原理、荷载条件、材料控制方面优势明显,结果直观、清晰。证明了采用有限元方法研究煤层气水平井稳定性的可行性与合理性,研究思路对开展同类井眼稳定性研究有借鉴意义。
[Abstract]:Coal bed methane (CBM) is a kind of high efficient and clean energy, which is rich in reserves in China. Extraction of CBM can reduce mine disaster, increase energy supply and reduce environmental pollution. The horizontal directional drilling technology can make the hole extend along the coal seam, increase the analytic area and improve the extraction efficiency, so it is widely used. However, with the further development, the problem of shaft wall instability is becoming more and more prominent, especially when the horizontal section is drilled into coal seam, which seriously affects the drilling safety and economic benefits. This problem is affected by many factors, but the relevant research is very limited at present, it is urgent to analyze its stability and explore the mechanism of instability. This paper summarizes the factors influencing the stability of surface horizontal drilling of coalbed methane from geological and engineering aspects, and statistics the instability of 2014ZX-U-01H well in Zhaozhuang mine field. It is found that the upper horizontal section of coal seam is the key unstable area, and the treatment of instability seriously affects the progress of the project. Thus, based on the Mohr-Coulomb strength criterion, the 3D finite element model of the horizontal well is established by using the measured rock mechanics parameters and the software MIDAS GTS NX after the well stress coordinate transformation is carried out. The influence of factors such as slope angle of horizontal section, thickness of mud crust and direction of in-situ stress on the stress distribution, deformation form, displacement and hole shape of borehole are studied, and the instability situation is quantitatively evaluated. The main factors affecting the hole stability of horizontal section are found out. The results show that the stress of Von Mises increases gradually with horizontal section extension, but the coal seam is poor in character and has longitudinal difference. The final instability degree of the shaft wall is also affected by the formation properties of drilling. When the shaft wall is unstable, the main deformation is along the X axis, and the displacement at the bottom is greater than that at the top, and the deformation section is elliptical. The maximum deformation zone is located in the upper horizontal section of coal seam.) the in-situ stress has a significant effect on the deformation and failure of the fractured formation, but has little effect on the stability of the formation, and the inclined angle of the well mainly affects the radius of the plastic deformation zone of the shaft wall. The primary and secondary factors affecting the stability of the horizontal section of the well are the direction of in-situ stress, the angle of well slope, and the thickness of mud crust. In the range of study, with the increase of the angle between the borehole strike and the maximum main stress, the inclined angle of the well decreases and the thickness of the mud crust increases. The best combination scheme of borehole strike and ground stress in horizontal section of coalbed methane well in the well field is put forward, which is 45 掳angle between hole strike and ground stress, 84 掳inclined angle and 1.2cm thickness of mud crust. The maximum Von Mises stress of wellbore is 0.52MPa, the maximum deformation is 3.04 cm, and the borehole is the most stable. This paper studies the phenomenon of matching with real drilling, solves the disadvantages of traditional methods, such as long time consumption, high cost, poor repeatability and incomplete consideration of factors, and has obvious advantages in calculation principle, load conditions and material control, and the results are intuitive and clear. The feasibility and rationality of using finite element method to study the stability of coalbed methane horizontal wells are proved.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712.6

【参考文献】