摘要
鄂尔多斯盆地延长组长7致密油藏储集层原油充注程度高,平均含油饱和度超过70%,局部存在超低含水饱和度现象。前人开展致密岩心原油充注实验时,在实验方法上很少考虑岩心出口端加回压对油水流动的影响,驱替时仅有入口端附近的液体在驱替压力下建立起孔隙压力用以克服流动阻力,出口端则为大气压,导致驱替得到的含水饱和度与测井分析含水饱和度差异明显。为了研究回压对致密油藏储集层原油充注时超低含水饱和度形成过程的影响,选取鄂尔多斯盆地延长组长7致密油藏岩心,开展了饱和水岩心出口端加回压来模拟不同孔隙压力下的单相渗流实验,根据实验结果选出实验回压开展原油充注实验。实验结果表明:单相渗流时,回压下能够显著降低测得稳定视渗透率时所需的驱替压力梯度,且在相同低压力梯度下能够测得更大流量;两相驱替时,回压下驱替得到的含水饱和度与测井解释结果具有很好的一致性,说明回压下能够再现超低含水饱和度的形成过程。研究认为,加回压对于提高致密岩心液体流动实验测试效率和模拟原油充注超低含水饱和度形成过程均有重要意义。
The crude oil charging degree is high in the Chang 7 tight oil reservoir of Yanchang formation in Ordos basin, the average oil saturation is more than 70%, and ultra-low water saturation is observed in the reservoir locally. Previous researchers seldom considered the influence of the back pressure at the outlet end of the core on oil and water flowing behavior when they carried out crude oil charging experiments on tight cores. During the displacement, only the fluid around the inlet formed the pore pressure under displacement pressure to overcome flow resistance and the pressure at the outlet end was atmospheric pressure, resulting in significant differences between the water saturation obtained from the displacement and the water saturation gained from logging analysis. In order to study the influences of back pressure on ultra-low water saturation forming process during crude oil charging in tight oil reservoirs, the core from Chang 7 tight reservoir of Yanchang formation is selected to carry out a single-phase flowing simulation experiment under different pore pressures with added back pressure at the outlet end, and crude oil charging experiment is performed based on the selected back pressure. The experiment result shows that with the added back pressure the required displacement pressure gradient significantly decreases during the single phase flow,whereas, with the same low pressure gradient a larger flowing rate can be measured. During two phase displacement, the obtained water saturation with the added back pressure is consistent with the result interpreted by logging data, indicating that the forming process of ultralow water saturation can be represented under the added back pressure. It is considered that an added back pressure is of great significance to improve the test efficiency of liquid flowing experiment for tight cores and to simulate the ultra-low water saturation forming process during crude oil charging.
作者
田键
康毅力
罗平亚
游利军
TIAN Jian;KANG Yili;LUO Pingya;YOU Lijun(State Key Laboratory of Oil/ Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu,Sichuan 610500,China)
出处
《新疆石油地质》
CAS
CSCD
北大核心
2018年第6期701-707,共7页
Xinjiang Petroleum Geology
基金
国家自然科学基金(51674209)
关键词
鄂尔多斯盆地
延长组
致密油藏
超低含水饱和度
回压
原油充注
实验模拟
Ordos basin
Yanchang formation
tight oil reservoir
ultra-low water saturation
back pressure
crude oil charging
experimental simulation