Abstract: To make clear the inhibition mechanism and action mode of multi-stage oil charging on the pressure solution of middle-deep clastic reservoirs, the effect of multi-stage oil charging on the pressure solution of glutenite reservoirs in the lower submember of Member 3 of Shahejie Formation in the northern zone of Chezhen sag was explored based on the observation and identification of fluorescent rock thin section, reconstruction of burial history, temperature measurements of fluid inclusions, and laser Raman spectroscopy test. The glutenite reservoirs in the lower submember of Member 3 of Shahejie Formation in the north zone of Chezhen sag have a buried depth of 2 800 m to 4 500 m, strong compaction and pressure solution, as well as developed under-compaction. The lithic grains of quartz, feldspar and carbonate rocks have suffered pressure solution. The glutenite reservoirs in the lower submember of Member 3 of Shahejie Formation have experienced two stages of oil charging. The first stage of oil charging occurred at 35.8 Ma to 24.6 Ma, the crude oil emits yellow fluorescence, and the contemporaneous brine inclusions have a homogenization temperature of 90 ℃ to 120 ℃; the second stage of oil charging started at 11.2 Ma, the crude oil emits blue fluorescence, and the contemporaneous brine inclusions have a homogenization temperature of 110 ℃ to 130 ℃. The oil film formed by oil charging on the particle surface can prevent the particle surface from contacting the pore water, so that the pressure dissolved substances are insoluble and can not be migrated by pore water, thus stopping pressure solution. At the contact zone of the particle where the water film is developed, the pressure dissolved substances can be migrated by diffusion through the loosely bonded water film on particle surface, so that the pressure solution can be sustained. The inhibition of oil charging on pressure solution is closely related to oil fullness. Two models of influence of oil charging on pressure solution in the lower submember of Member 3 of Shahejie Formation in the north zone of Chezhen sag were established as below: (1) The first stage of oil charging in the northern zone of Chexi area had low fullness, with thin and discontinuous oil film on the particle surface, and weak inhibition on pressure solution. (2) The second stage of oil charging had low reservoir porosity, and the blue fluorescent oil film was less developed in this stage, thus leading to the weak inhibition on pressure solution; the first stage of oil charging in the northern zone of Dawangbei area had high oil fullness, and yellow fluorescent oil film was generally formed on the particle surface. During the second stage of blue fluorescent oil charging, a blue fluorescent oil film was further formed on the particle surface, which had a more significant inhibition on pressure solution. The reservoirs containing some oil wetting carbonate rock particles are more likely to develop oil film after oil charging, which can improve the anti-pressure solubility of the reservoirs; the earlier oil charging and the higher oil fullness are more conducive to the formation of oil film and the development of high quality reservoirs in middle-deep layers.

Key words: oil charging, glutenite reservoir, oil film on particle surface, pressure solution, Chezhen sag

摘要： 为探讨多期石油充注对中—深层碎屑岩储层压溶作用的抑制机理及作用模式,综合荧光岩石薄片观察与鉴定、埋藏史恢复、流体包裹体测温、激光拉曼光谱测试等资料,探讨了多期石油充注对车镇凹陷北带沙河街组三段(沙三段)下亚段砂砾岩储层压溶作用的影响。车镇凹陷北带沙三段下亚段砂砾岩储层埋深在2 800~4 500 m,压实和压溶作用强,同时发育欠压实作用,石英、长石及碳酸盐岩岩屑颗粒均发生压溶。沙三段下亚段砂砾岩储层经历了两期石油充注,第1期石油充注发生于35.8~24.6 Ma,原油发黄色荧光,同期盐水包裹体的均一温度为90~120 ℃;第2期石油充注始于11.2 Ma,原油发蓝色荧光,同期盐水包裹体的均一温度为110~130 ℃。石油充注在颗粒表面形成油膜可阻碍颗粒表面与孔隙水的接触,压溶物质无法被孔隙水溶解运移,使压溶作用停止。在发育水膜的颗粒接触处,压溶物质可以通过颗粒表面的弱结合水水膜以扩散方式迁移,使压溶作用持续进行。石油充注对压溶作用的抑制能力与石油充满度密切相关,建立了车镇凹陷北带沙三段下亚段石油充注影响压溶作用的2种影响模式:车西地区北带第1期石油充满度低,颗粒表面油膜厚度小且不连续,对压溶作用的抑制能力较弱,第2期石油充注时储层孔隙度较低,第2期蓝色荧光油膜发育较少,对压溶作用的抑制相对较弱;大王北地区北带第1期石油充满度较高,颗粒表面普遍形成黄色荧光油膜,第2期蓝色荧光油充注时,在颗粒表面进一步形成蓝色荧光油膜,对压溶作用的抑制效果更明显。含有一定油润湿性碳酸盐岩颗粒的储层在石油充注后更容易发育油膜,进而可以提高储层的抗压溶能力;石油充注时间越早、充满度越高,越有利于油膜的形成和中—深层优质储层的发育。

关键词: 石油充注, 砂砾岩储层, 颗粒表面油膜, 压溶作用, 车镇凹陷