鄂尔多斯盆地东部神木区块二叠系山西组致密砂岩气低产主控因素分析

Main controlling factors of low production of tight sandstone gas of Permian Shanxi Formation in the Shenmu block,eastern Ordos Basin,China

鄂尔多斯盆地神木区块二叠系山西组是继太原组之后新的致密砂岩气接替层系,单井产量低、研究程度浅、认识不足的特点制约了该区山西组致密砂岩气的有效勘探开发。通过铸体薄片、物性分析、核磁共振等技术手段,深入剖析了山西组致密砂岩气低产原因及主控因素。低孔低渗、孔喉结构复杂、应力敏感性较强的差储层品质及束缚水饱和度远远大于初始含水饱和度的超低含水饱和度现象导致储层渗流较差,易形成水锁,是致密砂岩气低产的原因;而沉积非均质性和破坏性的成岩作用极大地降低了储层物性,使气井外围储层流体补给不畅,是低产的主控因素。研究为制定合理的储层压裂改造工艺措施、提高单井产量以及实现致密砂岩气藏的规模有效开发提供了重要的地质依据。

Permian Shanxi Formationhas become the new gas producing strata of tight sandstone after Taiyuan Formation.Effective exploration and development of tight sandstone gas of Shanxi Formation is restricted by the features of low single well production, low degree of exploration and insufficient recognition.The reasons and the main controlling factors of low production of tight sandstone gas have been analyzed with different kinds of technologies including casting thin sections, physical property analysis, nuclear magnetic resonance and so on.The reason of low production of tight sandstone gas is that the tight sand- stone reservoir has the features of low porosity, low permeability, complex pore structure, strong stress sensitivity and ultra-low water saturation.Ultra-low water saturation is the phenomenon that bound water is greater than initial water saturation, which will cause poor reservoir seepage and is easy to form water block.The main controlling factors of low production of tight sandstone gas are sedimentary heterogeneity and the destructive diagenesis,because they decrease the reservoir property greatly and block the gas supply.This study provides a significant reasonable geological basis for the reservoir fracturing process, the improvement of single well production and the effective development of tight sandstone gas.