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

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