沁南郑庄区块煤层气空气钻井井壁稳定性研究及工艺技术设计

发布时间：2018-05-07 22:22

本文选题：煤层气 + 空气钻井　；参考：《中国矿业大学》2017年硕士论文

【摘要】：沁水盆地南部郑庄区块地质构造简单、地层含水性弱、煤储层压力处于正常到稍微欠压状态,煤层气地质特征适合使用空气钻井。本文在详细分析研究区地质资料、试井资料和岩心参数等数据的基础上,结合空气钻井井壁稳定性理论,对研究区煤层气空气钻井井壁稳定性进行研究,并提出空气钻井过程中防止地层出水的技术措施,设计出有利于研究区井壁稳定性的空气钻井工艺参数、井身结构、钻井方式等。井壁围岩的稳定性主要由地层最大、最小水平主应力的差值以及岩石本身的力学参数决定。根据空气钻井井壁稳定性理论模型计算出研究区地层井壁稳定性的内聚力临界值,并与围岩本身内聚力值进行对比,得出在空气钻井过程中煤层段井壁会发生剪切破坏,上部砂岩段井壁可以保持稳定,通过计算得出保持煤层段井壁稳定的最小钻井液密度为0.55~0.57g/cm~3。研究区泥页岩整体坚硬,分散性弱,表面裂隙发育,与地层水接触会发生水化反应,水化膨胀率为13%左右,水化后岩石的弹性模量变小,泊松比增大,内聚力和内摩擦角降低,水化后泥页岩易于破碎。水化后径向应力降低,切向应力先增大后减小,并在井壁内部达到最大值,且最大值大于未水化时井壁切向应力值,会导致井壁发生坍塌破坏,不利于井壁的稳定性。利用FLAC~(3D)软件进行模拟分析,结果显示流固耦合时井壁的变形量要大于非流固耦合时;流固耦合时围岩应力值明显增大,并且会在最小应力方向发生应力集中,导致在最小应力方向井壁易发生坍塌破坏,不利于井壁的稳定性。利用岩屑沉降末速度理论,计算得出空气流量为30~70m~3/min,机械钻速在8m/h左右时井底产生的岩屑能够被完全的携带出井口。根据研究区地层特征以及钻井设备的工作特性,泵压值为1.4~2.0MPa,钻压为15~30k N,钻进软地层时转速在30~45r/min,钻进中硬地层时转速在25~40r/min时能够保持空气钻井安全钻进。当地层出水量小时,选择全井段欠平衡钻进;当地层出水量较大时,采用常规水基泥浆钻井与空气钻井相结合的钻进方式。
[Abstract]:The geological structure of Zhengzhuang block in the south of Qinshui Basin is simple, the formation water content is weak, the pressure of coal reservoir is in a normal to slightly underpressure state, and the geological characteristics of coalbed methane are suitable for air drilling. Based on the detailed analysis of geological data, well test data and core parameters in the study area, combined with the theory of air drilling sidewall stability, this paper studies the stability of coal bed methane air drilling sidewall in the study area. The technical measures to prevent formation effluent during air drilling are put forward, and air drilling parameters, wellbore structure and drilling methods are designed which are beneficial to the stability of borehole lining in the study area. The stability of wall rock is mainly determined by the difference between the maximum and minimum horizontal principal stresses and the mechanical parameters of the rock itself. According to the theoretical model of air drilling wellbore stability, the cohesion critical value of formation wall stability is calculated, and compared with the cohesion value of surrounding rock itself, it is concluded that shear failure will occur in coal seam section during air drilling. The borehole lining of the upper sandstone section can be kept stable, and the minimum drilling fluid density is 0.55 ~ 0.57 g / cm ~ (3). In the study area, the shale is hard, weak in dispersion, and the surface fissures are developed. The hydration reaction will take place in contact with formation water. The hydration expansion rate is about 13%. After hydration, the elastic modulus of the rock becomes smaller, the Poisson's ratio increases, and the cohesion and friction angle decrease. Shale is easily broken after hydration. After hydration, the radial stress decreases, the tangential stress increases first, then decreases, and reaches the maximum value inside the shaft wall, and the maximum value is larger than the value of the wall tangential stress when the hydration is not hydrated, which will lead to the collapse of the shaft wall, which is not conducive to the stability of the shaft wall. The simulation analysis with FLACX / 3D software shows that the deformation of shaft wall is larger than that of non-fluid-solid coupling, and the stress value of surrounding rock increases obviously in fluid-solid coupling, and the stress concentration occurs in the direction of minimum stress. In the direction of minimum stress, the shaft wall is liable to collapse and destroy, which is not conducive to the stability of the shaft wall. Based on the theory of cuttings' terminal velocity, it is calculated that the air flow rate is 30 ~ 70mg / min, and the cuttings produced at the bottom of the well can be completely carried out from the wellhead when the mechanical drilling speed is about 8m/h. According to the formation characteristics of the studied area and the working characteristics of drilling equipment, the pump pressure value is 1.4 ~ 2.0 MPa, the drilling pressure is 15 ~ 30kN, the rotational speed of drilling in soft formation is 30 ~ 45r / min, and the rotational speed of drilling in middle hard formation can keep air drilling safely at 25~40r/min. When the water output of the local formation is small, the under-balanced drilling in the whole well section is selected, and the conventional water-base mud drilling combined with air drilling is adopted when the water output of the local formation is large.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD842

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