| Author's Name: LI Kai, XIE Shuyun, LEI Lei, BAO Zhengyu, HE Zhiliang,
WO Yujin, ZHANG Dianwei, ZHANG Hai |
| Institution: Guangdong Nuclear Power Engineering Exploration Institute |
| Abstract: |
| As one of the most important reservoirs of oil and gas resources, the formation and evolution of pore-hole-fracture in oolitic carbonate reservoirs had attracted extensive attention. Based on oolitic carbonate slice, we observe the microstructure and chemical characteristics of the samples before and after the dissolution experiments in dilute sulfuric acid, through the microscope, scanning electron microscope(SEM) and energy spectrum(EDS). The results show that the dissolution of carbonates varied according to the structure and compositions of the samples. On microstructure observation, oolitic dolomites can produce much more dissolution pore to form effective reservoir than the oolitic limestones. The weight losing percentage of oolitic dolomite(1.04%) caused by dissolution in 12 hour is more than that of the oolitic limestone(0.70%). Through the EDS, we find that the variance of compositions is the key factor of dissolution. The sites with various element contents are easier to dissolute. It is shown that in oolitic dolomites there is lower Mg/Ca value(0.6 ~ 0.8) at the dissolution part than at the other parts. The higher degree of dissolution depends on the higher content of Mg element, resulting in the decreasing of Mg/Ca. We also find that there is weak dissolution at the site with high contents of Si and Al in oolitic limestone. This shows that the quartz and feldspar might prevent sample from dissoluting. It is concluded that oolitic dolomite could form a large number of interconnected pore-hole-fracture in formation water enriching dilute sulfuric acid or H2S, which is conducive to the migration and reservoir formation of oil and gas. |
| Keywords: oolitic carbonate; selective dissolution; microphotography; effective pore system; experiment |
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投稿时间：
2017-05-03 |
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