摘要
致密气藏多级压裂水平井的渗流规律复杂,影响气井产能的因素较多。首先引入单裂缝评价的思路,在基质中建立了有限导流裂缝引起的渗流数学模型,通过Fourier积分变换求解,以此为基础,在裂缝中建立了考虑井筒聚流作用的变流量渗流模型,通过数值求解Fredholm型积分方程拟合出了裂缝导流能力影响函数,最终得到了单一裂缝的产能公式。利用井筒管流作用建立了多级压裂水平井从地层到井底全过程流动的产能预测方程组,同时考虑相邻裂缝间的相互干扰,并给出了完整的算法。应用该方程组计算了实例气井及各压裂段在不同井底流压下的产量,并分析了该井水平段压降和产量分布及无阻流量随有效裂缝半长和导流能力的变化情况,为评价各裂缝参数和压裂效果提供了依据。
The general completion technique for horizontal wells in tight gas is by multi-stages hydraulically fracturing,and the flow characteristics in horizontal well with multiple transverse fractures are very complicated.Conventional methods,taking well as an evaluation unit,are difficult to accurately predict production capacity of each fracture and productivity differences between wells with different number of fractures.So single fracture is as the minimum evaluation unit,matrix,fractures and lateral wellbore model are combined integrally to approximate horizontal well with multiple transverse hydraulic fractures in tight gas.This paper presents a new semi-analytical methodology for predicting the production capacity of horizontal well with multiple transverse hydraulic fractures in tight gas reservoirs.Firstly,mathematical flow model in matrix,which is disturbed by finite-conductivity vertical fractures and rectangular shaped boundaries,is established and solved by Fourier integral transform.Then the idea of single stage fracture analysis is incorporated to establish linear flow model within single fracture with variable rate.Fredholm integral numerical solution is applicable for the fracture conductivity function.Finally,pipe flow model along lateral wellbore is employed to couple multi-stages fracture mathematical models,and the equation group of predicting productivity of multi-stage fractured horizontal well,considering the whole process flow from matrix to bottom hole and production interference between adjacent fractures,is established.Meanwhile,corresponding iterative algorithm of the equations is given.In this case analysis,the productions of actual well and every fracture are calculated under the different bottom hole flowing pressure,and this method also contributes to obtain the distribution of pressure drop and production for every horizontal segment and its changes with effective fracture half-length and conductivity.Application of this technology will provide gas reservoir engineers with a better tool for predicting well and every fracture productivity,and optimizing transverse hydraulic fractures configuration and conductivity along lateral wellbore.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2016年第6期1101-1109,共9页
Natural Gas Geoscience
基金
国家科技重大专项"天然气开发关键技术"项目(编号:2011ZX05015)资助
关键词
致密气藏
水平井多级压裂
单裂缝
裂缝干扰
产能预测
Tight gas
Multi-stage hydraulically fractured horizontal well
Single fracture
Production inter-ference between adjacent fractures
Productivity prediction
