摘要
我国煤层气直井的排采是经过储层改造后进行的,且不同的排采阶段,水相渗透率的值不同。为了更加准确地定量评价煤储层改造后煤层气直井排采的井间干扰程度,基于沃伦-茹特渗流模型,结合压裂时的压降曲线,构建了压裂后渗透率预测模型;根据排采过程中气/水所占比例的差异,分别构建了气/水两相流低产阶段和稳产阶段水相相对渗透率模型;把不同排采阶段的水相渗透率模型嵌入经典的无越流补给的库萨金水压影响模型中,得出了不同排采阶段水压传播距离的数学模型。以柿庄南区块典型井组的干扰试井及勘探资料为基础,验证了理论模型的准确性。根据数学模型建立了渗透率-压力梯度-影响距离图版。结果表明:储层压力梯度不变的情况下,随着渗透率的增加,影响距离呈指数型增加;渗透率不变的情况下,随着储层压力的增加,影响距离呈线性增加。当储层压力梯度为0.5MPa/hm,压裂后渗透率一般为(0.5~8.0)×10-3μm2时,长轴影响距离一般为95~120m,短轴影响距离一般为56~75m,该储层条件下井网应小于240m×150m。该方法可以为无越流补给且煤体结构为原生或碎裂煤储层条件下井网优化提供理论依据。当煤体结构为碎粒煤或糜棱煤为主或有越流补给时,该方法的计算结果仅能作为一种参考。
The drainage of vertical coalbed methane wells in China is carried out after the reservoir reformation,and the values of the water phase permeability are different in different drainage stages.In order to more accurately and quantitatively evaluate the degree of cross-well interference in coalbed gas vertical well drainage after coal reservoir reformation,a prediction model of post-fracture permeability was constructed based on the Warren-Rut flow model and the pressure drop curve during fracturing.According to the difference of the proportion of gas/water in the process of drainage,the relative permeability model of water phase in the low-yield and stable production phases of gas/water two-phase flow was constructed.The water permeability models in different drainage stages were embedded in the classical,and the mathematical models about water pressure propagation distance in different drainage stages were obtained.Based on the interference well testing and exploration data of the typical well group in the southern block of Shizhuang,the accuracy of the theoretical model was verified.A permeability-pressure gradient-impact distance map was established based on a mathematical model.The results showed that when the reservoir pressure gradient was constant,the influence distance increased exponentially with the increase of permeability.When the permeability was constant,the influence distance increased linearly with the increase of reservoir pressure.When the reservoir pressure gradient was 0.5 MPa/hm and the permeability after fracturing was generally(0.5~8.0)×10^-3μm,the influence distance in the long axis direction was 95~120 m and that in the short axis direction was 56~75 m,and the well pattern under this reservoir condition should be less than 240 m×150 m.This method can provide theoretical basis for well pattern optimization under the condition that there was no overflow recharge and coal structure is primary or fractured coal reservoir.When the coal structure was dominated by granular coal or mylonite coal and overflow recharge,the calculation results of this method can be used as a reference.
作者
王文升
张海锋
张亚飞
段宝江
刘灵童
倪小明
冯毅
WANG Wensheng;ZHANG Haifeng;ZHANG Yafei;DUANG Baojiang;LIU Lingtong;NI Xiaoming;FENG Yi(CNOOC Energy Tech-Drilling & Production Co.,Tianjin300450,China;China United Coalbed Methane Corporation Ltd.,Beijing100010,China;School of Energy Science and Engineering,Henan Polytechnic University,Jiaozuo454000,China)
出处
《煤炭科学技术》
CAS
CSCD
北大核心
2019年第9期119-125,共7页
Coal Science and Technology
基金
国家科技重大专项资助项目(2017ZX05064-003)
关键词
煤层气
井间干扰
渗透率
库萨金公式
定量评价
coalbed methane
cross-wells interference
permeability
Kusakin formula
quantitative evaluation
