Diverse fracture properties and their impact on performance in conventional and tight-gas reservoirs, Saudi Arabia: The Unayzah, South Haradh case study
Diverse fracture properties and their impact on performance in conventional and tight-gas reservoirs, Saudi Arabia: The Unayzah, South Haradh case study
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DOI：
10.1306/06011110148
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发表时间：
2012-03
期刊：
影响因子：
3.5
通讯作者：
M. Ameen;K. Macpherson;Maher Almarhoon;Z. Rahim
中科院分区：
文献类型：
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作者：
M. Ameen;K. Macpherson;Maher Almarhoon;Z. Rahim
沙特阿拉伯南哈拉德的上二叠统-石炭纪Unayzah组包括两个主要的机械和岩石物理层，它们被富含页岩的区域分开。开放的构造裂缝群是罕见的，并不是在Unayzah A区，具有高孔隙度和渗透率的流体流动所必需的。然而，这种裂缝群对于Unayzah B/C致密气藏的生产动态是必不可少的，并且影响该生产动态。Unayzah组构造裂缝的出现与岩石力学性质有关，这些性质随孔隙度、页岩体积、胶结物类型和结构而变化。B/C单元比A单元更破裂，但其层的破裂程度不同。B/C单元内裂缝发育的变化导致基于生产剖面的压裂增强渗透率的差异，其中流动被限制在优先压裂的机械层，该机械层缺乏与其他层的有效垂直流体连通。我们确定了两个构造断裂系统：一个较老的下属完全矿化系统和一个年轻的主要开放系统。在新特提斯期开启时，早期伸展裂缝（包括节理和断层）平行于基底断层发育。这些是完全矿化的，几乎没有或没有流体导管的功能。较年轻的系统包括开放式断裂群，这些断裂群主要平行于或几乎平行于扎格罗斯（自晚白垩世以来一直活跃）的区域东北-西南-西北最大水平应力，并且独立于局部构造。因此，这些裂缝是由远程应力控制，而不是基底根强制褶皱和断层。在这篇文章中，我们证明，在Unayzah B/C，天然裂缝是必不可少的渗透率，并在某些地区，孔隙度，因此，储层性能。这项研究的结果正在实施井布局和完井设计，以优化开放式裂缝群的交叉点，并取得了积极的初步结果。
The Upper Permian–Carboniferous Unayzah Formation in South Haradh, Saudi Arabia, includes two major mechanical and petrophysical layers that are separated by shale-rich zones. Open tectonic fracture clusters are rare and not essential for fluid flow in the Unayzah A zone, which has high porosity and permeability. However, such fracture clusters are essential to, and impact, the production performance in the Unayzah B/C tight-gas reservoir. The occurrence of the tectonic fractures in the Unayzah Formation is linked to the rock mechanical properties, which vary with porosity, shale volume, cement type, and texture. The B/C unit is more fractured than the A unit, but its layers vary in the degree of fracturing. The variation in fracture development within the B/C unit results in differences in fracture-enhanced permeability based on production profiles where flow is restricted to preferentially fractured mechanical layers that lack effective vertical fluid communication with other layers. We identify two tectonic fracture systems: an older subordinate fully mineralized system and a younger primary mostly open system. Early extensional fractures including joints and faults developed parallel to the basement faults during the opening of the Neotethys. These are fully mineralized and have little or no function as fluid conduits. The younger system includes open-fracture clusters that are predominantly parallel or nearly parallel to the regional east-northeast–west-southwest maximum horizontal stress of the Zagros (that has been active since the Late Cretaceous) and is independent of local structures. Therefore, these fractures are controlled by remote stresses instead of the basement-rooted forced folds and faults. In this article, we demonstrate that in the Unayzah B/C, natural fractures are essential to permeability and, in some areas, to porosity, and thence, to reservoir performance. The results of this study are being implemented in well placement and completion design to optimize the intersection of open-fracture clusters with positive preliminary results.