【作者】 陶树；

【导师】 汤达祯；

【作者基本信息】 中国地质大学（北京） ， 矿产普查与勘探， 2011， 博士

【摘要】 为了探讨开发过程中煤储层渗透性的动态变化及产能的动态响应,论文通过大量的测试数据、煤层气井工程数据及开发数据分析、各种煤层气地质与开发理论知识的运用,分别探讨了煤储层物性对煤储层渗透率的贡献、影响气井产能和渗透率动态变化的地质、工程因素,定量—半定量化主要因素对渗透率的影响程度,建立了地质、工程因素→渗透率动态变化→产能动态响应的评价模型,最后在此基础上提出了与研究区相适应的开发建议。主要取得如下认识:沁南煤储层孔隙以吸附孔为主,孔裂隙之间的连通性较差;裂隙以C、D类较小裂隙发育为主,裂隙彼此间的连通性较差且多被矿物质充填。这种孔裂隙发育特征决定了沁南煤储层渗透率整体偏低。影响沁南煤层气井产能高低的地质因素主要包括煤层埋深、含气量、临储比、地下水动力条件及气井所处的构造部位,主要工程因素包括煤层气井的排采制度、压裂效果及井网部署等。同时通过耦合分析煤储层渗透率动态变化与地质条件及开发制度的关系,阐明影响开发过程中渗透率动态变化的地质及工程影响因素,最终建立了地质、工程因素→渗透率动态变化→产能动态响应的评价模型。经过计算,得出开发过程中沁南地区煤储层绝对渗透率由于煤基质自身的弹性模量平均下降10.0%;500m埋深的煤层在开发过程中,绝对渗透率降低8.8%;1000m埋深的煤层在开发过程中,绝对渗透率降低11.5%。通过驱替压差实验得出在驱替压差未到达压降临界值之前,煤岩渗透率不发生变化,当驱替压差大于压降临界值时,煤岩渗透率降低,降低幅度与驱替压差之间呈明显的指数关系。针对沁南地区煤储层地质特征,建议首选顶板埋深500-700m、含气量大于15 m3/t、远离断层、临储比大于0.6煤层作为煤层气开发目标层;采用欠平衡钻井技术并在施工前对钻井液进行改善;采用地面垂直井、水平井及多分支水平井开发。对于连片开发地质条件较好的区域,可以采取丛式井网形式开发;开发期间,在早期排水期,建议采取比较大的降压幅度和比较大的排采冲次,分别为0.022MPa/d和3.0次/min;出现产气高峰后,开始缓慢降压和降低冲次,分别为0.002MPa/d和0.4次/min。更多还原

【Abstract】 In order to investgate the dynamic variation of coal reservoir permeability and the dynamic response of productivity during the development process, this thesis discusses the contribution to coal reservoir permeability from physical properties, the geological and engineering factors that influence the dynamic variation of gas wells productivity and permeability, semiquantitative to quantitative characterization of changes in coal bed permeability caused by main factors on the basis of massive test datas, engineering datas and development datas analysis, various theoretical knowledge application of coalbed methane (CBM) geology and development. Then this work builds an evaluation model of the geological and engineering factors that drive dynamic changes in permeability, which in turn drive the dynamic response in terms of productivity. Finally, development proposals which are suitable to the southern Qinshui Basin are proposed. Main conclusions are listed as follows:Pore types of coal reservoir in southern Qinshui Basin are main absorption pores, and the connectivity among them is relatively poor. Meanwhile, fractures are main small ones as C and D types, and the connectivity among them is relatively poor and infilling of minerals. The development features of pores and fractures decide that the permeability of coal reservoir is generally low in southern Qinshui Basin.Main geological factors determine whether CBM wells achieve a high and stable yield, which include buried depth, gas content, critical desorption/reservoir pressure, hydrodynamic conditions, and tectonic positions that CBM wells are in. Main engineering factors include drainage system, fracturing effect, well pattern arrangement and so on. Meanwhile, by the coupling analysis of the relationship between dynamic variation of coal reservoir permeability and geological conditions and development system, it clarifies the geological and engineering factors which influence the dynamic variation of permeability during the development process of CBM. Finally, it builds an evaluation model of the geological and engineering factors that drive dynamic changes in permeability, which in turn drive the dynamic response in terms of productivity. After calculation, the absolute permeability of the coal reservoir decreases by about 10.0% during the development process due to elastic modulus, and decreases 5.5% and 14.3% at buried depths of 500m and 1000m respectively. In displacement pressure experiment, when the displacement pressure is not reach the critical value of pressure drop, coal permeability will not change. But when it reaches, coal permeability drops, and it has an exponential relationship between the pressure drop range and the displacement pressure drop.According to geological features of coal reservoir in southern Qinshui Basin, this paper recommends that the development reservoir should contain some conditions, which include buried depth at 500~700 m, gas content greater than 15 m3/t, critical desorption/reservoir pressure greater than 0.6, and far away from faults. In engineering aspect, we should use under-balanced drilling technology and improvement the drilling fluid before construction; adopt development styles of surface vertical well, horizontal well and multi-branch horizontal well, and for a whole area which has a great geological condition, we can use cluster well pattern form. During the development, this study suggest that a larger pressure drop (about 0.022MPa/d) and stroke (3.0/min) are favorable in the early drainage period, and a smaller pressure drop (0.002MPa/d) and stroke (0.4/min) should be applied when the gas peak appears.更多还原