RELATIONSHIP BETWEEN DIAGENESIS, MATURITY AND PHYSICAL PROPERTIES OF TIGHT SANDSTONE RESERVOIRS IN SULIGE GAS FIELD

摘要

Diagenesis and maturity are critical elements influencing the physical properties of tight sandstone reservoirs. The relationships between diagenesis, maturity and physical properties of He8 members in the Southeast Sulige Gas Field, Ordos Basin, China, were systematically investigated by core observation, scanning electron microscopy, X-ray diffraction analysis, physical properties analysis, particle size analysis and cathode luminescence data. The results show the following: (1) The diagenesis of the reservoir in the study area as it reaches the middle diagenesis stage B. (2) The porosity reduction and loss rate of different rock types are obviously different under different diageneses. During compaction of quartz sandstone, the porosity reduction caused by compaction was 6.4310.35% and the porosity reduction rate was 18.6229.71%. For compaction of lithic quartz sandstone, the porosity reduction caused by compaction was 6.65-10.66%, and the porosity reduction rate was 19.54%—31.77%. Then, during compaction of lithic sandstone, the porosity reduction caused by compaction was 5.66%—11.57% and the pore reduction rate was 17.50-36.06%. During cementation, the average porosity loss rates of quartz sandstone, lithic sandstone and lithic sandstone caused by cementation were 31.32%, 33.85% and 36.13%, respectively. (3) Rock types and maturity directly determine the physical properties of tight reservoirs. Reservoir porosity and face ratio have a good positive correlation with the relative content of quartz, and the reservoir porosity is negatively correlated with the content of debris. The sandstone with high compositional maturity and structural maturity still has a large number of original pores after compaction. The porosity and permeability of the sandstone reservoir are positively correlated with the average grain size of rock particles.