The Origin Analysis By Hydro-Chemical Characters And Sr Isotope Of Oil Field Brines In West Of Qaidam Basin

There have much oilfield brine developed in the Tertiary strata in the western Qaidam Basin, which will be likely become the brine resources to make up for the limited salt lake resources in future. Basing on known data and the filed work, we collected some oilfield brine samples from petroleum drills in Xiaoliangshan, Nanyishan, Youquanzi, Kaitemilike, Youdunzi and Youshashan tectonic anticlines of the representative Mangya Depression as major objects and referenced salt lake brine and intercrystalline bittern. Through analyzed on their basic characters of hydrochemistry and the date of 87Sr/86Sr, we discussed their chemical evolution and origins. This research is of important significance to enrich basic theory such as isotope trace, water-rock reciprocity etc. Also, it's of practical prominent value to discuss the oilfield brine resources'chemical evolution and origins exactly and to analyze the potential of exploitation better. It may create long-term societal economic benefit.Through compared with evapo concentrated seawater and Qinghai Lake water and analyzed on their basic characters of hydrochemistry and the date of 87Sr/86Sr, we discovered that the oilfield brine, the salt rocks and the quaternary salt lake water have the same origin. They all were mixed by two liquid elements.One is of high 87Sr/86Sr but low Sr2+content from the earth's crust, the other is contrarily of low 87Sr/86Sr but high Sr2+content from the earth's mantle. Both the surface water and deep underground water are concerned with the oilfield brine's formation.The chemical evolution of oilfield brine is mainly controlled by the interaction of water-rock, deep water mix and evaporation ordissolution of salts. The result provides that the oilfield brine resource is of high mineralization and reserves and is flush of source of replenishment, the concentration of resources such as K, B and Li in oilfield waters is much higher than the industrial grade and Sr, Br also up to the lowest industrial grade, which means that oilfield waters have excellent foreground for synthetic utilization.