| There are abundant oil and gas resources and geothermal resources in microbial dolomite reservoirs of
Wumishan Formation in Renqiu buried hill, Jizhong Depression, but the characteristics and main controlling factors of the
high-quality reservoirs are not clear, which constrained the exploration and development process. Based on the outcrop,
drilling core, petrographic thin section, logging data and experimental analysis data, the characteristics as well as types of
microbial dolomite reservoirs in Wumishan Formation are investigated, and the controlling factors and evolution of high
quality reservoirs are generalized. The reservoirs in Wumishan Formation dominated by microbial dolomite, which
associated with the microbial mound and shoal. The microbial dolomites consists of stromatolite dolomite, thrombolite
dolomite, laminite dolomite, oncolite dolomite, while the microbial related granular dolomites are mainly dolarenite and
dolorudite. The storage space of microbial dolomite can be divided into three types(pores, fractures, vugs), and the reservoirs
overall have poor physical properties with average porosity of 3.55% and average permeability of 0.89×10-3 μm2, which
belongs to the pore-vug-fracture composite type with the characteristics of low porosity and low permeability. The
microbial dolomite reservoir can be divided into type I, type II, and type III, different types of reservoirs have big
differences in lithology and physical property. Depositional environment are the basis of reservoir formation and
evolution, which controls the facies distribution and the porosity development. Dissolution are the key to the formation of
multiple types of reservoir space, which determine the modification and distribution of the reservoirs. Tectonic disruption
is an important complement to form effective storage space, for the structural fractures generated by tectonic disruption
are constructive for the reservoir properties in increasing the reservoir physical property and the seepage ability. Analysis
shows that the evolution of the microbial dolomite reservoirs of Wumishan Formation in the study area can be mainly
divided into five stages: sedimentation-penecontemporaneous pore formation stage, phaseⅠsupergene pore increasement
stage, shallow burial pore reduction stage, fold and fault transformation phaseⅡsupergene pore increasement stage, deep
burial pore reduction stage. The combined effects of multiple factors ultimately formed a porosity of 2% to 5% today.
Key words：microbial dolomite; buried hill; reservoir characteristics; controlling factor; reservoir evolution; Wumishan
Formation; Jizhong Depression |
