Genetic Analysis of Jurassic Low Resistivity Reservoir in Hongde Area, Ordos Basin

Abstract

AbstractHongde area is located in the southwest of Ordos Basin, spanning two structural units of Yishan slope and Tianhuan depression. Low resistivity reservoirs (LRRs) are widely developed in Jurassic in this area. Aiming at this phenomenon, this paper analyzes the genesis of LRRs, aiming to provide a theoretical basis for reservoir fluid logging identification. On the basis of previous work, this study systematically collates the basic data of formation water analysis, nuclear magnetic resonance, oil-water relative permeability and drilling fluid resistivity of the target strata in the study area, and deeply analyzes the causes of LRRs in the study area from the aspects of formation water salinity, irreducible water saturation, nose bulge structure amplitude and drilling fluid invasion. The results show that the formation water resistivity is the main controlling factor for the development of LRRs in this area. With the increase of formation water salinity, the apparent resistivity of the reservoir decreases obviously. There is an obvious corresponding relationship between the difference of formation water salinity and the apparent resistivity of the reservoir in Jurassic. With the increase of irreducible water saturation content and the decrease of nose bulge structure amplitude, the apparent resistivity of reservoir shows a decreasing trend, but the correlation degree is lower than the formation water salinity. This paper analyzes and summarizes the control factors of LRRs in Hongde area, and defines the influence degree of each factor for the first time. In the follow-up work, according to the main control factors of LRRs, we can explore the suitable identification method of reservoir fluid type and improve the logging interpretation accuracy. KeywordsOrdos BasinJurassicLow resistivity reservoirGenetic analysis