| 摘要: |
| 页岩储层孔隙结构复杂,基质渗透率低,天然裂缝发育,水平井体积压裂为其主要生产手段,表现出以裂缝系统裂缝渗流为主,基质系统扩散流、滑脱流以及吸附-解吸附现象共同作用的多尺度流动特点。基于离散裂缝建立页岩气渗流数学模型,利用有限元分析方法进行数值求解,通过实例研究分析页岩气生产动态特征,以及开发过程中压裂级数和裂缝半长对储层压力分布和页岩气井生产动态特征的影响。结果表明:页岩气井初期产量高,但递减快,生产周期长;开发初期以裂缝渗流为主,压裂级数起主导作用,级数越多,压力波传播越快,储层压力下降明显,产能主要集中在生产初期;开发后期以基质渗流为主,裂缝半长作用增强,产量递减率下降,生产井附近压力接近废弃压力,生产能力下降。 |
| 关键词: 页岩气 离散裂缝模型 裂缝流 动态特征 |
| DOI：10.3969/j.issn.1673-5005.2015.03.017 |
| 分类号::TE 33 |
| 基金项目:国家“973”计划项目(2013CB228005);中国石油大学(北京)科研基金项目(2462013YJRC012) |
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| Characterization and dynamic analysis of shale gas production based on discrete fracture model |
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MI Lidong1, JIANG Hanqiao1, LI Tao2, LI Junjian1
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(1.MOE Key Laboratory of Petroleum Engineering in China University of Petroleum, Beijing 102249, China;2.Shenzhen Branch of CNOOC Energy Techonology & Serrices Limited, Shenzhen 518067, China)
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| Abstract: |
| Shale gas reservoirs are of complex pore structure, low matrix permeability and well developed natural micro fractures, and horizontal-wells with segmented multi-cluster fractures have been used as the major production technology. The process of gas production can be characterized as a multi-scale flow system, including gas seepage in fractures and gas desorption, slip and diffusion in shale matrix. A numerical simulation model for the gas seepage flow in fractures was established based on a discrete fracture model, and a finite element method was used for the solutions of the nonlinear partial differential equations. The dynamic characteristics of the shale gas production process were analyzed in terms of the effects of fracture half-length and the segment number of multi-cluster fracturing on reservoir pressure distribution and well performance. The results show that high production rate can be observed in the initial stage of the gas production, but it decreases rapidly and has a long production period. During the initial stage of gas production, the flow in fractures plays a leading role. The more fractures, the faster reduction of the reservoirs pressure, and the productivity of wells is mainly relied on this stage. In the late stage of the gas production, flows in matrix dominate the process, and the positive effect of fracture half-length can be observed, in which the decline rate of production can be reduced if longer fracture length is obtained. For field optimization, the numbers of the segmented fracturing and the fracture half-length can be adjusted to meet the production requirement based on the production rate and cumulative production curves of single wells. |
| Key words: shale gas discrete fracture model fracture flow dynamic characteristics |
