Observations “Detections” of Shallow Unconventional Qusaiba Shale Gas Reservoirs North Part of Saudi Arabia

There are many oil and gas conventional reservoirs in Saudi Arabia have been exploited, but still there are also need to be explored and produced especially in the fields of unconventional shale gas. Investigation the extending of rock source of the hot shale gas Qusaiba formation in North part of Saudi Arabia, the most important rock source in the word, is crucial for one of the most promising shallow shale gas reservoir in the region. Most previous studies in the area were a geological, petrographical, petrophysical, geochemical characteristics or well logs studies which are not enough to show the continuously of the reservoir and map the diverse of the depth changes. The lack of the geophysical studies in the area inspiring to perform such study and image how the continuously and behavior of the reservoir subsurface. Imaging the geological stratigraphy of area utilizing a multiple geophysical methods is a crucial step to disclosure the unconventional reservoir and understand the source rock extending underneath the North region of Saudi Arabia. A good achievement is shown in this study using this integration of seismic migrated image and gravity geological model. This integration provides a robust and true subsurface geological formations, structures, and determined thickness and depth of the Lower Silurian Sharawra Qusaiba and Sarah formations. This work would be a valuable contribution in unconventional reservoirs exploration in shale gas in Saudi Arabia.

中阿拉伯盆地Khuff—Sudair组油气藏地质特征及成藏模式

Khuff—Sudair组油气成藏组合是中阿拉伯盆地重要的油气成藏组合。通过对该成藏组合古地理演化、烃源岩、储集层、盖层、成藏过程和模式的分析认为,下志留统Qusaiba段烃源岩于中侏罗世卡洛夫期开始生油,早白垩世土仑期开始生气;生成的油气通过断层、裂缝垂直运移和上覆地层砂岩水平运移到上二叠统Khuff组储集层内;下三叠统Sudair组提供了有效的区域盖层;由于石油的生成和排烃早于圈闭的形成,所以很难聚集成藏,而天然气的生成和排烃时间与圈闭的形成时间一致,所以天然气在基底活动形成的构造圈闭中聚集成藏。目前世界最大的天然气田North-South Pars气田特有的Khuff—Sudair组油气成藏组合是中阿拉伯盆地今后油气勘探的重点。

中东地区古生界油气分布规律及成藏主控因素分析

古生界是中东地区重要的天然气和轻质原油勘探层系,阿拉伯板块构造--沉积演化为古生界油气聚集成藏提供了有利的石油地质条件。分析认为,前寒武纪—寒武纪早期Huqf群和志留纪Qusaiba段两套优质成熟的烃源岩、多套有利的储盖组合以及一系列大型基底隆起或盐拱成因背斜、断背斜圈闭控制着古生界油气的分布,构成了古生界Huqf和Qusaiba两套主要的含油气系统,每套含油气系统均包括多个油气成藏组合。受早期继承性古隆起和盐构造、有利储盖组合以及断裂通道3个主控因素的影响,古生界油气成藏以下生上储侧向+垂向断裂输导运聚成藏模式为主。

Main Controls on Hydrocarbon Accumulation in the Paleozoic in Central Saudi Arabia

Sandi Arabia is renown for its rich oil and gas Mesozoic. However, the discovery of Paleozoic fields in resources with the bulk of the reserves reservo/red in the the late 1980s has encouraged further exploration in the Paleozoic. This paper reviews the salient features of the Paleozoic petroleum geology in central Saudi Arabia and discusses the main factors controlling hydrocarbon accumulation in the Paleozoic. The Lower Silurian Qusaiba hot shale is the principal source rock for the hydrocarbons discovered in the Ordovician to Permian reservoirs. Of them, the Permo- Carboniferous Unayzah and Upper Ordovician Sarah Formations have the best exploration potential. The key factors controlling hydrocarbon accumulation in the Unayzah Formation are migration pathways and reservoir petrophysics. The key factors controlling hydrocarbon accumulation in the Sarah Formation are reservoir petrophysics and the development of structural traps.

波斯湾盆地Khuff组成藏组合地质特征

Khuff组成藏组合是波斯湾盆地最重要的天然气成藏组合,二叠系Khuff组储层和层间硬石膏盖层构成了成藏组合的基本要素。下志留统Qusaiba段热页岩是Khuff组成藏组合的烃源岩,其分布广、有机质含量高,在晚白垩世大面积成熟生烃,而大部分圈闭形成早于主生烃期,且基底断裂发育,充当了烃类由Qusaiba段热页岩向Unayzah组砂层运移的垂向通道,Unayzah储层充当了主要的油气平面运移通道;面积广阔、沉积相稳定的Khuff组内碳酸盐岩和硬石膏旋回层序既提供了储层,也提供了成藏组合内绝大部分气田的优质盖层。同时,储层的原始物性好,鲕粒、球粒、生物泥粒灰岩及粒屑灰岩都具有很好的印模孔隙和粒间孔隙,此外,后期的淋滤作用加上白云岩化产生的晶间孔隙极大地改善了储层的质量。在大部分区域内,后期断层活动并没有破坏盖层的封闭性,天然气资源的散失量小。Khuff组成藏组合的未来勘探地区主要分布在Qusaiba段烃源岩的成熟区内,最有潜力的地区为层间硬石膏与Qusaiba段烃源岩成熟区重合的部分,包括波斯湾水域、波斯湾西北部及加瓦尔油田以南地区。大型低幅度构造的识别是将来的重点工作之一,同时,由于中东地区油气勘探生产的经济门限较高,相对较小规模的油气藏的开发要依赖高气价的推动作用。