页岩气水平井多段压裂缝—井筒流动耦合模型研究

发布时间：2018-03-25 18:15

本文选题：页岩气藏　切入点：分段压裂　出处：《西南石油大学》2017年硕士论文

【摘要】：页岩储层属于低孔低渗储层,开发过程中多使用水平井多段压裂工艺来提高气井产能。不同于常规气藏,页岩储层内发育有天然微裂缝,压裂后在地层内形成复杂的缝网系统。开采过程中,人工裂缝间会产生干扰,且开发过程中伴随有吸附解吸过程。现有的水平井分段压裂产量预测模型中,分别针对页岩气吸附解吸、气体扩散、气体滑脱现象有深入研究,但考虑整个流动过程中影响因素的模型较少。现有的页岩气井产量预测模型考虑水平井筒内压降损失较少。在调研国内外有关页岩气水平井分段压裂产量预测模型的基础上,本文针对页岩气藏开发过程中的气体流动特性,建立了分段压裂缝-水平井筒耦合不稳定流动模型,完成了产量预测研究。研究完成工作及取得的认识如下:(1)通过文献调研总结页岩气藏地质特征、开发特征及渗流特征,分析了页岩气扩散、滑脱及吸附解吸过程对页岩气开发的影响规律,为模型推导奠定理论基础。(2)针对页岩气藏渗流过程,推导出页岩基质—天然裂缝—人工裂缝—水平井筒的流动模型,模型使用考虑了页岩气滑脱的表观渗透率作为基质渗透率,质量守恒方程中加入解吸项,同时考虑人工裂缝间的干扰现象。(3)由动量定理,质量守恒,综合考虑水平井筒内的摩擦压降和加速压降,推导出水平井筒内压降模型。(4)根据压力、产量的连续性对模型进行耦合。编制MATLAB计算程序,对模型进行迭代求解。(5)综合考虑页岩的解吸过程、人工压裂缝形态和缝间干扰现象的耦合模型对页岩气不稳定渗流描述的适用性较好。(6)水平井筒内沿指端至跟端方向,压力逐渐降低,每条裂缝的视井底流压不为定值。(7)页岩气水平井日产气量与气藏厚度、页岩基质孔隙度及天然裂缝渗透率呈正相关,与井底流压呈负相关。(8)页岩气水平井日产气量与人工裂缝条数、人工裂缝长度、人工裂缝宽度、人工裂缝间距及人工裂缝渗透率呈正相关。(9)布缝模式影响页岩气井产量,哑铃型布缝模式产量较高,矩形布缝模式次之,纺锤型布缝模式最低。
[Abstract]:Shale reservoir is a low porosity and low permeability reservoir. In the development process, horizontal wells and multiple fracturing techniques are often used to improve gas well productivity. Different from conventional gas reservoirs, natural micro-fractures are developed in shale reservoirs. After fracturing, a complex fracture network system is formed in the formation. During the exploitation process, the artificial fractures will produce interference, and the process of adsorption and desorption will be accompanied during the development process. In the existing prediction model of horizontal well fracturing production, For shale gas adsorption and desorption, gas diffusion, gas slippage, However, there are few models considering the influencing factors in the whole flow process. The existing production prediction models of shale gas wells take into account the loss of pressure drop in horizontal wells less. Based on the investigation of domestic and foreign models for predicting fracturing production of shale gas horizontal wells, According to the gas flow characteristics in shale gas reservoir development, a piecewise fracture-horizontal wellbore coupled unstable flow model is established in this paper. Through literature investigation, the geological characteristics, development characteristics and percolation characteristics of shale gas reservoirs are summarized, and the diffusion of shale gas is analyzed. The influence of slippage and adsorption desorption on shale gas development, which lays a theoretical foundation for model derivation.) aiming at the seepage process of shale gas reservoir, the flow model of shale matrix, natural fracture, artificial fracture and horizontal wellbore is derived. In the model, the apparent permeability of shale gas slippage is used as the matrix permeability, the desorption term is added to the mass conservation equation, and the interference between artificial fractures is considered. Considering the friction pressure drop and acceleration pressure drop in horizontal well, the model of pressure drop in horizontal well is deduced. According to the continuity of pressure and output, the model is coupled. MATLAB calculation program is compiled. Considering the desorption process of shale, the coupling model of artificial fracturing morphology and interfracture interference is suitable for describing the unsteady seepage of shale gas, and the horizontal well bore is in the direction of finger to heel. The daily gas production of shale horizontal wells is positively correlated with gas reservoir thickness, shale matrix porosity and natural fracture permeability. There is a negative correlation between the daily gas production and the number of artificial fractures, the length of artificial fractures, the width of artificial fractures, the spacing of artificial fractures and the permeability of artificial fractures. The output of dumbbell pattern was higher than that of rectangular pattern, and that of spindles was the lowest.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE377

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