鄂尔多斯盆地陇东地区长7段致密油储层可动流体赋存特征及影响因素

Characteristics and Influencing Factors of Movable Fluid in Chang 7 Tight Oil Reservoir in Longdong Area,Ordos Basin

鄂尔多斯盆地陇东地区致密油储层主要分布在延长组长7段。通过长7段致密砂岩样品的核磁共振测试和场发射扫描电镜分析,对致密油储层可动流体赋存特征及影响因素进行了研究。结果表明：致密油砂岩岩心的最佳离心力为1.448 MPa;核磁共振T2谱截止值分布范围较宽,平均为20.64ms;可动流体饱和度低,平均为40.27%,主要被0.05~1.00μm的喉道所控制,且喉道在0.10~0.50μm区间时,致密油岩样可动流体饱和度最高、下降速度最快。整体上,可动流体饱和度与物性呈现出一定的正相关性,且在长71段,储层物性相对较好,可动流体饱和度较高。微裂缝发育程度、溶蚀孔隙、黏土矿物和石英颗粒充填孔隙等储层微观孔隙结构特征是可动流体的主要影响因素。其中,微裂缝、溶蚀孔隙的发育在一定程度上提高了储层可动流体饱和度;而黏土矿物及石英颗粒充填孔隙则导致储层可动流体饱和度的降低。关于长7段储层可动流体赋存特征的认识对鄂尔多斯盆地致密油资源开发具有一定的指导意义。

The Upper Triassic Yanchang Formation tight oil reservoir in Longdong area ol Urclos basra is distributed mainly over Chang 7 oil reservior sets. The Chang 7 tight oil sandstone samples were tested by nuclear magnetic resonance and FESEM. The characteristics of movable fluid include the following aspects： The bess centrifugal pressure is 1. 448 MPa for tight oil sandstones. T2 cutoff value distribution of nuclear magnetic resonance is relatively wide with the average value of 20.64 ms. Meanwhile, the content of mova- ble fluid saturation is also low with the average value of 40.27~/oo. O. 05--1.00 /~m regions for roared size mainly controlled the movable fluid. Especially, 0. 10- 0. 50 btm regions, the content of movable fluid reached the highest, and decreased rapidly. The property is in positive correlation with the movable fluid saturation. Especially in the member 71 of Yanchang Formation,the reservoir properties and movable fluid saturation are relatively high. The micro-pore structure is vitally important for the existing state of fluid. The main influencing factors of movable fluid include micro-fracture, dissolution pores, filling degree of clay mineral and authigenic quartz in pores. The micro fracture and dissolution pores are the main factors which could improve the movable fluid saturation. However the degree of clay,minerals and authigenic quartz in the pores causes a reduction of the movable fluid saturation. The identification of characteristics of movable fluid in the Chang 7 oil reservoir sets has great significance to the development of tight oil resources in Ordos Basin.