Evaluation of reservoir environment by chemical properties of reservoir water‒A case study of Chang 6 reservoir in Ansai oilfield, Ordos Basin, China

Abstract

The development of oil and gas resources has always been highly concerned by scholars at home and abroad. The chemical property of the reservoir water is very important to the evaluation of reservoir, and is an important indicator of the sealability of reservoir oil and gas resources. Therefore, the caprock of Chang 6 oil reservoir in Yanchang Formation was evaluated. This paper selects water samples from 30 wells in the Chang 6 reservoir of Ansai Oilfield in the basin to test and analyze water chemical characteristics. The results show that the Chang 6 reservoir water in Ansai Oilfield is dominated by calcium chloride water type, and its sodium chloride coefficient is generally less than 0.5; the chloride magnesium coefficient is between 33.7 and 925.5, most of which are greater than 200.The desulfurization coefficient ranges from 0.21 to 13.4, with an average of 2.227; the carbonate balance coefficient is mainly concentrated below 0.01, with an average of 0.008; the calcium and magnesium coefficient ranges from 0.08 to 0.003, with an average of 0.01.The above results combined with the characteristics of the four corners territory of the reservoir water show that the graphics are basically consistent.