页岩气藏水平井HEGF裂缝网络渗流模型研究

发布时间：2018-08-07 20:33

【摘要】：高能气体压裂(HEGF)技术可以克服我国水利资源短缺对页岩气开发的限制,为页岩气开发提供支持,针对页岩气储层基质中广泛分布纳米级孔隙的特点和高能气体压裂裂缝特征,以及吸附气体的存在和气体流动形式复杂的情况,本文基于Langmuir等温吸附方程、Polanyi吸附理论、FHH吸附理论推导得到三种吸附厚度计算公式,通过Knudsen数表示出划分流动形式的临界孔道直径,利用质量通量物理意义推导得到表征基质中多种流动形式共存时气相表观渗透率,在微分方程中加入气体解吸项进行修正后得到了页岩气藏水平井HEGF裂缝网络渗流模型,求解并进行了参数分析,主要得到以下结论:(1)吸附气体厚度随着压力升高而增大并逐渐稳定,三种吸附厚度计算方法具有不同适用性;(2)在储层条件下,划分不同气体流动形式的临界孔道直径不受温度影响,压力较小时,临界孔隙直径随压力增加而迅速减小,当压力增大到25MPa以上时,该值趋于稳定;(3)表观渗透率随压力增加而减小,而考虑吸附情况下,使得该值相对更小,在储层压力下,考虑吸附的表观渗透率减小量为13%左右;另外表观渗透率受流动形式影响大,单一Fick扩散表观渗透率比单一滑脱流动表观渗透率小2个数量级;(4)页岩气生产影响因素分析可知:①在定产量条件下,基质与裂缝渗透率越高、垂直裂缝长度越长、宽度越大,所需要的生产压差越小;②Langmuir体积与Langmuir压力越大,储层压力下降越缓慢;③人工改造区域长度比例越大、储层形状因子越大,在定产量条件下,井底压力下降幅度越小;④页岩气井生产压差与裂缝渗透率和人工改造区域长度比例存在非线性负相关关系,追求过高渗透率裂缝和过大比例的改造体积并不可取。
[Abstract]:High-energy gas fracturing (HEGF) technology can overcome the limitation of water resources shortage on shale gas development in China and provide support for shale gas development. Aiming at the characteristics of widely distributed nano-pore in shale gas reservoir matrix and fracture characteristics of high-energy gas fracturing. Based on the Langmuir isothermal adsorption equation and the Langmuir adsorption theory, three kinds of formulas for calculating the adsorption thickness are derived. The critical pore diameters of flow form are expressed by Knudsen number, and the gas phase apparent permeability is derived by using the physical meaning of mass flux to characterize the coexistence of multiple flow forms in the matrix. After the gas desorption term is added to the differential equation, the seepage model of HEGF fracture network in horizontal well of shale gas reservoir is obtained, and the parameter analysis is carried out. The main conclusions are as follows: (1) the thickness of adsorbed gas increases with the increase of pressure and gradually stabilizes. The critical pore diameter of different gas flow forms is not affected by temperature. When the pressure is small, the critical pore diameter decreases rapidly with the increase of pressure, and when the pressure increases above 25MPa, the critical pore diameter decreases rapidly. (3) the apparent permeability decreases with the increase of the pressure, but it is smaller when the adsorption is considered, and the apparent permeability decreases by about 13% under the reservoir pressure. In addition, the apparent permeability is greatly affected by the flow form, and the apparent permeability of single Fick diffusion is two orders of magnitude smaller than that of single slippage flow. (4) the analysis of the influencing factors of shale gas production shows that under the condition of constant production, the apparent permeability of single Fick diffusion is two orders of magnitude smaller than that of single slippage flow. The higher the permeability of matrix and fracture is, the longer the vertical fracture length is and the wider the width is. The smaller the production pressure difference is, the bigger the volume of Langmuir and the pressure of Langmuir are. The bigger the reservoir shape factor is, the smaller the downhole pressure drop is, the negative nonlinear relationship exists between the production pressure difference and fracture permeability and the ratio of artificial revamping area length. It is not advisable to pursue too high permeability fractures and too large proportion of reconstruction volume.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE31

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