TITLE:
Study on Geological Genesis and Sedimentary Model of Complex Low Resistivity Reservoir in Offshore Oilfield — A Case of NgIII Formation of X Oilfield in Bohai Sea
AUTHORS:
Wentong Zhang, Jie Tan, Feiteng Wang, Songru Mu, Bowei Liu
KEYWORDS:
Low Energy Braided River, Low Resistivity Reservoir, Irreducible Water Saturation, Clay Minerals, Paleoclimate, Hydrodynamic Force
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.11 No.4,
April
28,
2023
ABSTRACT: In order to study the micro genetic mechanism and main geological
controlling factors of low resistivity reservoir in NgIII formation of X oilfield in Bohai
sea in China, the clay mineral composition, irreducible water
saturation, salinity and conductive minerals of low resistivity reservoir were
studied by using the data of core, cast thin section and analysis, and compared
with normal resistivity reservoir. At the
same time, the control effect of sedimentary environment on low resistivity
reservoir was discussed. The results show that the additional conductivity of
high bound water content and high montmorillonite content in the reservoir
together leads to the significant reduction of reservoir resistivity,
which is the main microscopic cause of the formation of low resistance, and is mainly controlled by
the sedimentary background such as paleoclimate and sedimentary cycle. During
the deposition period of NgIII formation,
the paleoclimate was dry and cold, and it was
at the end of the water advance of the medium-term sedimentary cycle. The
hydrodynamic force of the river channel was weak, the carrying capacity of the
riverbed was weak, and the river channel swayed frequently, resulting in fine
lithologic particle size, high shale content and complex pore structure of the
reservoir, resulting in significant reduction of reservoir resistance. The research conclusion
would have strong guiding significance for the development of low resistivity
reservoirs in this area.