摘要
水平井多段体积压裂是目前致密气藏开发的主要手段,体积压裂后井筒周围将产生形态各异的复杂裂缝网络,但目前大部分适用于压裂水平井的试井渗流模型仅假定压裂缝为单一主裂缝,使得试井解释结果与实际情况之间存在着较大的误差,以致于无法准确获取改造区的缝网特征参数。为此,基于非结构化离散裂缝模型,建立了一种考虑复杂裂缝网络的致密气压裂水平井试井模型,然后利用三角单元和线单元混合的有限元方法对模型进行求解,进而获得了不同缝网形态(矩形、椭圆形及双曲形)下的水平井试井典型曲线;在此基础上,分析试井曲线特征及其影响因素,并与常规单一裂缝模型的试井曲线进行了对比,最后应用新模型对鄂尔多斯盆地庆阳气田二叠系山1段气藏一口多段体积压裂水平井进行了试井解释。研究结果表明:①缝网模型与单一裂缝模型试井曲线的最大区别在于早期阶段,改造区拟径向流特征取代了第一线性流特征;②改造区拟径向流阶段结束的时间主要由改造区大小和形状决定,改造区越大则改造区拟径向流阶段持续的时间越长,改造区形状越趋近于长条形则新模型试井曲线特征越接近于单一裂缝模型;③改造区拟径向流阶段的压力导数值主要由缝网导流能力和缝网密度决定,改造区缝网密度越大或者导流能力越大,井筒储存效应阶段结束得越早,改造区拟径向流压力导数值越小且水平线特征越明显。结论认为,新模型具有可靠性和实用性,据此既可以获得准确的储层参数,又可以获得体积压裂有效改造区的大小及缝网导流能力,有助于体积压裂改造效果评价及压后生产动态预测。
Multi-stage volume fracturing of horizontal wells is the main means to develop tight gas reservoirs.Complex fracture networks of various shapes are generated around the wellbore after volume fracturing.At present,however,most of the well test models suitable for fracturing horizontal wells take all hydraulic fractures as single main fractures,which results in a large error between well test interpretation result and actual situation.As a result,the fracture network characteristic parameters of the stimulated areas cannot be obtained accurately.To this end,a well test model for complex fracture networks in tight-gas fracturing horizontal wells was established on the basis of the non-structural discrete fracture model.Then,this model was solved by using the finite element method with combined triangular elements and linear elements.And accordingly,the well test type curves of a horizontal well under different fracture network patterns(rectangular,elliptical and hyperbolic)were prepared.Based on this,well test type curves were analyzed from the aspects of characteristics and influential factors and were compared with those obtained from the conventional single-fracture model.Finally,the new model was applied in well test interpretation of one multi-stage volume fracturing horizontal well in the gas reservoir of Permian Shan 1 Member in the Qingyang Gas Field of the Ordos Basin.And the following research results were obtained.First,the biggest difference of well test type curve between the fracture network model and the conventional single-fracture model occurs in the early stage,the characteristics of first linear flow regime are replaced with the characteristics of pseudo-radial flow regime in the stimulated area.Second,the end time of the pseudo-radial flow regime in the stimulated area is mainly dominated by the size and shape of the stimulated area.The larger the stimulated area is,the longer the pseudo-radial flow regime lasts.As the shape of the stimulated area approaches to be elongated,the characteristics of
作者
欧阳伟平
孙贺东
韩红旭
OUYANG Weiping;SUN Hedong;HAN Hongxu(Changqing Downhole Technology Company,CNPC Chuanqing Drilling Engineering Co.,Ltd.,Xi'an,Shaanxi 710018,China;PetroChina Research Institute of Petroleum Exploration&Development,Langfang,Hebei 065007,China;Project Supervision Department,PetroChina Changqing Oilfield Company,Xi'an,Shaanxi 710018,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2020年第3期74-81,共8页
Natural Gas Industry
关键词
致密气藏
水平井
体积压裂
复杂裂缝系统
数学模型
数值试井
离散裂缝模型
有限元
鄂尔多斯盆地
庆阳气田
Tight gas reservoir
Horizontal well
Volume fracturing
Complex fracture system
Mathematical model
Numerical well test
Discrete fracture model
Finite element
Ordos Basin
Qingyang Gas Field
