Reservoir characteristics and control mechanism of resistivity low-contrast oil pays in Chang 8 tight sandstone of Longdong West area, Ordos Basin

Abstract Log interpretation and evaluation of tight sandstone reservoir in Chang 8 Member Longdong West area, Ordos Basin, China, are facing great challenges due to the co-development normal oil pay resistivity low-contrast pay. To better guide exploration development resources this characteristics control mechanism were studied. Firstly, reservoirs divided into (RLP) (NP) based on relative value apparent increase rate. Then, difference between RLP NP is analyzed by comparing a series experimental data real logging those two types. Finally, was studied from micro-factors regional macro-factors, respectively. It found that chlorite illite most abundant clay minerals NP, Compared with reservoir, average porosity better, but pore space mainly composed micropores, which lead smaller throat radius poor structure. The high irreducible water saturation formation salinity reduced micro-aspect. Besides, hydrocarbon expulsion capacity source rock controlled distribution NP. Comprehensive consideration macro-factors important carry out effective evaluation.