基于三重介质模型的体积压裂后页岩气储层数值模拟方法

发布时间：2018-02-03 02:46

本文关键词： 页岩气次生裂缝三孔双渗页岩气储层体积压裂模型体积压裂数值模拟　出处：《油气地质与采收率》2016年06期 　论文类型：期刊论文

【摘要】：页岩气储层渗透率极低,基本无产能,须进行体积压裂改造形成裂缝网络才能开采。一般采用双重介质模型进行页岩气储层数值模拟,但该模型无法准确模拟远井地带由于压裂开启并相互连通的天然裂缝。为此,针对压裂后的页岩气储层,建立三孔双渗页岩气储层体积压裂模型来描述不同区域渗透率变化与气体吸附解吸过程。新建模型考虑了页岩气的吸附机理,将基质作为气源,将二级次生裂缝与一级次生裂缝视为2个等效的多孔连续体,压裂主裂缝则作为离散裂缝予以描述。对比新建模型与传统的双重介质模型模拟结果后发现,所建三孔双渗页岩气储层体积压裂模型计算的日产气量和累积产气量均高于双重介质模型,结合双重介质模型模拟产量一般低于实际产量的情况,认为采用考虑天然裂缝的三孔双渗页岩气储层体积压裂模型能够更准确地描述水力压裂井的产量变化。各级裂缝渗透率和初始吸附气含量对生产动态的影响结果表明:二级次生裂缝渗透率对累积产气量影响较大,在生产中应当采取措施提高二级次生裂缝渗透率;而初始吸附气含量对累积产气量影响并不明显。
[Abstract]:The permeability of shale gas reservoir is extremely low and there is basically no productivity, so it is necessary to form fracture network by volume fracturing in order to be exploited. The numerical simulation of shale gas reservoir is usually carried out by using double heavy medium model. However, the model can not accurately simulate the natural fractures which are opened and connected by fracturing in the far well zone. Therefore, the shale gas reservoir after fracturing can not be simulated accurately. A reservoir volume fracturing model was established to describe the permeability change and gas adsorption and desorption process in different regions. The new model considered the adsorption mechanism of shale gas and used matrix as gas source. The secondary fracture and the primary secondary fracture are regarded as two equivalent porous continuum, and the main fracture is described as discrete fracture. The daily gas production and cumulative gas production calculated by the volume fracturing model of three-pore and dual-permeability shale gas reservoir are higher than that of the dual medium model, and the simulation production with dual medium model is generally lower than the actual production rate. It is considered that the volume fracturing model with three porosity and double permeability shale gas reservoir considering natural fractures can more accurately describe the production changes of hydraulic fracturing wells. The effect of fracture permeability and initial adsorption gas content on production performance is discussed. Indicates that:. The permeability of secondary fracture has great influence on cumulative gas production. Measures should be taken to increase the permeability of secondary fractures in production. The effect of initial adsorption gas content on cumulative gas production is not obvious.
【作者单位】：西南石油大学油气藏地质及开发工程国家重点实验室;
【基金】：国家自然科学基金项目“基于非结构六面体网格模型和并行计算的裂缝性油藏数值模拟研究”(51174169) 国家科技重大专项“山西沁水盆地南部煤层气直井开发示范工程”(2011ZX05060)
【分类号】：TE357.11
【正文快照】： 页岩气是指赋存于页岩裂缝及微小孔隙内的天然气,储气方式以游离气和吸附气为主,由于储层基质渗透率极低[1-2],气体流动困难,须通过体积压裂进行储层改造才能获得较高产能。页岩气储层具有天然裂缝发育的地质特征,但是由于地应力场的作用,这些裂缝多处于闭合状态,对整体气藏的

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