Experimental Study On Rock Electrical Properties Of Porous Hydrate Reservoir In Permafrost Region Of Qilian Mountains

Natural gas hydrate is a new type of energy with abundant reserves.Chinese scientists have found natural gas hydrate in the permafrost region of Qilian Mountains in middle and high latitudes,which makes the exploration and development of natural gas hydrate in the permafrost region of Qilian Mountains a hot issue.Natural gas hydrate is mainly characterized by the abnormal log response of high resistivity and sound wave velocity.The exploration results obtained by single exploration method have many solutions,so it is necessary to further determine the results by other means.Through rock physical experiments,hydrates are synthesized in rock samples of the permafrost region of Qilian Mountains.It is very important for the reservoir prediction and exploration of the natural gas hydrate in the permafrost region of Qilian Mountains to understand the influence of the hydrates existence on rock resistivity.In this paper,rock samples of the permafrost region of Qilian Mountains and artificial cores are selected to simulate the in-situ formation conditions of natural gas hydrate in the permafrost region,and a large number of hydrate synthesis experiments are carried out.According to the change of rock samples resistivity,several stages of hydrate formation are divided,and some phenomena in the experiment of the continuous hydrate synthesis are explored.The relationship between rock samples resistivity and hydrate saturation is analyzed,and the formation factor and saturation index of the experimental rock samples are calculated,and the reliability of the log interpretation results is analyzed according to the experimental data.The main conclusions are as follows:(1)When hydrate synthesis is sufficient in the rock sample of the study area,the resistivity curve will appear obvious demarcation point at the hydrate saturation of 10%.When the hydrate saturation is less than 10%,the resistivity rises slowly and the hydrate saturation is about 10%,the resistivity rises sharply and then rises slowly.Finally,it tends to be stable.(2)It is found that the typical resistivity-hydrate saturation curve of hydrate formation in rock samples is similar to that of curve of hydrates formation in marine sediments.(3)The values of a and m are 0.9245 and 1.903 respectively.The variation range of the saturation index n value is 1.15~2.78.The relationship between the resistivity and saturation of the rock samples obtained by the experiment is of reference and guidance to the log interpretation.