HUANG Cheng-gang1, YUAN Jian-ying1, CAO Zheng-lin1, ZHANG Shi-ming1, WANG Ying2, SHE Min2
1. Key Lab of Reservoir Description, Research Institute of Petroleum Exploration & Development-Northwest(NWGI), Lanzhou 730020, China;
2. Key Lab of Carbonate Reservoir, Hangzhou Research Institute of Geology, Hangzhou 310023, China
Abstract: The deposition environment of the southern western Qaidam basin was mainly a saline lacustrine basin in the Cenozoic. Many great exploration breakthroughs have been made in this area. Some previous studies indicated that the saline environment can improve the conversion rate of hydrocarbon, such will be beneficial for the hydrocarbon generation, but there are only limited researches on the alteration of reservoir in the saline environment. This study simulated physical-chemical reactions between fluid and rock in geological conditions and investigated the influence of saline water on reservoirs. The analyses of reservoir properties and capillary pressure alteration pre-or post-interaction suggested that saline environment has negative effect on reservoirs. The mechanism might be as blow: The precipitation of saline minerals has negative effects on reservoir properties; the saline minerals occupy certain intergranular pores and reduce reserving attributes, part of thinner throats are blocked that make deviation of pore structure and permeability, the fluids of saline basin enrich potassium ion, which has inhibiting effect on dissolution of feldspathic, therefore the formation of dissolved pore is unfavorable, the saline fluids contain a large amount of potassium ion which provide materials for the reactions of smectite and andreattite changing into illite. The higher is the potassium ion concentration, the more slender illite generate. These slender minerals block throats and pores to lower the permeability of the rock.
Keywords: saline lacustrine basin saline minerals precipitation fluid-rock interaction
*Corresponding Author, E-Mail: klhcg@163.com
Bulletin of Mineralogy, Petrology and Geochemistry Vol. 34, No.2, 2015, page 343-348
