Experimental research of carbonate rocks dissolution characteristics in Paleozoic group of Nanpu sag and surrounding bulge areas

Key words:  carbonate rock  dissolution experiment  buried condition  Nanpu sag  high-quality reservoir

Abstract:

To study the dissolution characteristics of samples in the burial conditions, a series of experiments were conducted to analyze seven Paleozoic carbonate rock samples collected from Nanpu sag and its surrounding areas, and their associated acetic acid conditions. The results show that the carbonate dissolution rate increases with the temperature and pressure increasing under the same flow rate. In the cases of lower temperature and pressure, the dissolution rate of dolomite is less than that of calcite. With temperature and pressure increasing, dolomite becomes easier to dissolve than limestone. For dolomite bearing limestone, the more dolomite content (or the dolomitization degree), the higher dissolution rate. Under the condition of the same pressure but different temperature and flow rate, the dissolution rate of limestone in the Majiagou formation increases with temperature from 200-250℃, reaches its maximum at about 250℃, and then decreases with temperature increasing when it is higher than 250℃. Combining with the analysis of buried hill reservoir in outcrop observation and physical property data, we conclude that compared with limestone, dolomite, dolomitic carbonate and lime dolomite are more conducive to form dissolution space and high-quality reservoir inner buried hill.