东海平湖油气田放鹤亭平湖组P11层低渗储层成藏特征

平湖组P11层为一套中孔低渗中细粒长石岩屑石英砂岩。通过岩石薄片、扫描电镜以及油气包裹体实验,建立该储层孔隙度演化过程和油气充注史。结果表明P11储层为强压实、中胶结、中溶解相,经历了两期油气充注,且以第Ⅰ期为主要充注期,高峰时间约在2~4 Ma前。在油气充注前,储层已经处在致密化过程中,造成P11层含油饱和度偏低。第Ⅱ期天然气充注对Ⅰ期充注的原油气侵分馏,同时受储层非均质性影响,流体分异不明显,油气水界面混乱。深部致密气藏的特点揭示了放鹤亭深部寻找优质储层难度加大,寻找局部甜点和低渗气藏的有效开发成为油气田后期保产的重点。

The Accumulation Characteristics of P11 Low-permeability Reservoir in Pinghu Oil and Gas Field,the East China Sea

P11 oil bearing reservoir is mainly consist of lithic arkose quartzose sandstone, which has the characteristics of medium porosity and low permeability. Through the experiments of rock slices, scanning electron microscopy and oil-gas inclusions, the porosity evolution process and oil-gas charging history of the reservoir are established. The results show that the P11 reservoir is a medium cemented and dissolved phase in strong compaction. P11 oil bearing reservoir has experienced two periods of gas-oil charging, and the first period is the primary oil charging process occurring nearly 2-4 Ma ago. Before the oil-gas charging, the reservoir was already in the process of densification, which results in low oil saturation of the P11 layer. The second period of hydrocarbon invaded and fractionated the previous crude oil. Consequently, the disordered gas-oil-water interfaces are formed by the serious anisotropy of the P11 reservoir. The features of deep tight oil or gas reservoirs reveal that it is more difficult to find high-quality reservoirs in Fangheting, and finding local sweets reservoirs and effective development of low-permeability gas have become the focus of late production preservation in oil and gas fields.