摘要
基于页岩气一井一藏及工厂化作业的开发特点,一次性部署开发井是区块效益开发的关键,故合理的井网井距对于提高页岩气采收率具有重要的意义。为此,以国家级页岩气开发示范区长宁区块为例,以单井动态分析结果为依据,以"多井平台"数值模拟为分析手段,建立以基质接触面积、缝间干扰、井间干扰、裂缝—基质流入流出4种关系为核心的井网井距优化设计方法,并论证井网井距优化流程:(1)通过干扰测试分析和施工参数类比,定性判断井距范围;(2)建立以支撑剂总体积为约束的裂缝参数优化模型,形成页岩气开发井距理论分析方法,定量评价以簇为单元的主裂缝长度、间距、条数、导流能力以及裂缝穿透比,确定最优井距;(3)通过网格指数加密精细数值模拟,初步论证了下志留统龙马溪组一段采用"W"形的上下两层交错水平井部署的立体开发效果。结果表明:天然裂缝是影响井距优化的关键因素,长宁示范区天然裂缝不发育,现有压裂规模下采用300 m井距、采用"W"形的上下两套水平井部署立体开发,页岩气采收率可提高15%以上。
Shale gas is often developed under a factory-like mode with one well in one reservoir so that the layout of a development well pattern in one effort will be essential to the efficient development of a shale gas zone. Therefore, the determination of a proper well pattern and spacing is important for the enhancement of shale gas recovery rates. In view of this, the national shale demonstration Changning block was taken as an example to demonstrate the process of well pattern and spacing optimization. Based upon the single-well production performance analysis, "multi-well pad" numerical simulation was carried out to develop a method of pattern and spacing optimization realized by balancing four flow relationships, i.e., matrix contact area, inter-fracture interference, well interference and fracture–matrix inflow/outflow. First, through a comparative analysis on the interference tests and operation parameters, the well spacing was determined qualitatively. Then, an optimization model with the proppant volume as the constraint for dynamic parameters was established to develop a theoretical well-spacing analysis method, by which the optimal well spacing was determined after a quantitative evaluation, with a cluster as a basic unit, on the length, spacing, quantity, flow conductivity and penetration ratio of primary fractures. Finally, through a fine grid numerical simulation, the efficiency of the "W-shape" deployment of horizontal wells in two layers is primarily demonstrated on the development of the first member of the Longmaxi Fm shale gas reservoir. Natural fractures is the key factor for the well spacing optimization but in this case study of the Changning Block with undeveloped natural fractures, the "W-shape" deployment of horizontal wells in two layers was adopted with the 300 m well spacing as the main well pattern to enhance the shale gas recovery factor by more than 15% as a good result.
引文
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