Using the Modified Resistivity–Porosity Cross Plot Method to Identify Formation Fluid Types in Tight Sandstone with Variable Water Salinity
Yufei Yang,
Kesai Li,
Yuanyuan Wang,
Hucheng Deng,
Jianhua He,
Zehou Xiang and
Deli Li
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Yufei Yang: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Kesai Li: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Yuanyuan Wang: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Hucheng Deng: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Jianhua He: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Zehou Xiang: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Deli Li: Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
Energies, 2021, vol. 14, issue 19, 1-14
Abstract:
It is generally difficult to identify fluid types in low-porosity and low-permeability reservoirs, and the Chang 8 Member in the Ordos Basin is a typical example. In the Chang 8 Member of Yanchang Formation in the Zhenyuan area of Ordos Basin, affected by lithology and physical properties, the resistivity of the oil layer and water layer are close, which brings great difficulties to fluid type identification. In this paper, we first analyzed the geological and petrophysical characteristics of the study area, and found that high clay content is one of the reasons for the low-resistivity oil pay layer. Then, the formation water types and characteristics of formation water salinity were studied. The water type was mainly CaCl 2 , and formation water salinity had a great difference in the study area ranging from 7510 ppm to 72,590 ppm, which is the main cause of the low-resistivity oil pay layer. According to the reservoir fluid logging response characteristics, the water saturation boundary of the oil layer, oil–water layer and water layer were determined to be 30%, 65% and 80%, respectively. We modified the traditional resistivity–porosity cross plot method based on Archie’s equations, and established three basic plates with variable formation water salinity, respectively. The above method was used to identify the fluid types of the reservoirs, and the application results indicate that the modified method agrees well with the perforation test data, which can effectively improve the accuracy of fluid identification. The accuracy of the plate is 88.1%. The findings of this study can help for a better understanding of fluid identification and formation evaluation.
Keywords: Ordos Basin; fluid identification; formation water salinity; low-resistivity oil pay; modified resistivity–porosity cross plot plates (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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