A Comparative Study on Microscopic Characteristics of Volcanic Reservoirs in the Carboniferous Kalagang and Haerjiawu Formations in the Santanghu Basin, China

Wells Ma 67 and Ma 36 obtained self-injection high-yield oil flow in the Hargau volcanic rock Formation in the Santang Lake Basin, which shifted the prospectors' attention from the Karagang formation, which was generally considered to have good physical properties, to the Hargawu formation. In order to further explain the reason why the volcanic rocks of the Hargawu formation was poor in physical properties but the oil flow can spew itself, On the basis of physical properties and mineral analysis, in the target area, for the first time, unconventional testing methods such as low-temperature nitrogen adsorption(LTNA), high-pressure mercury injection(HPMI), and constant-speed mercury injection(CSMI) were used to carry out a systematic comparative study of the micropore structure of volcanic rocks. Studies have shown that the pore permeability of the volcanic rocks of the Karagang Formation is relatively high, but the micropores have a wide range of pore size distributions, high structural coefficients, and strong heterogeneity. The pore throat configuration is of a type with large pores connected to a small roar, and the pore throat ratio Relatively high, which is conducive to the occurrence of tight oil and gas, but not conducive to flow; Although the volcanic permeability of the volcanic rock in the Hargawu Formation is relatively low, the pore throat configuration belongs to the type of small pores connected to large throats. The pore throat ratio is relatively low, the structural coefficient is low, and the homogeneity is good. It is a favorable condition for tight hydrocarbon accumulation. This evaluation result also fully shows that the evaluation of volcanic tight reservoirs can not only take porosity and permeability as the first indicators of good or bad reservoir evaluation, but also pay more attention to the overall evaluation of microscopic pore structure, It also explains the geological factors of the self-jetting high-yield oil flow wells in the Hargawu Formation from the perspective of microscopic pore structure, and new ideas and comparison methods for reservoir evaluation in other areas are provided.