Electrical Response Of Filtrate Invasion In Near-Well Zone Of Tight Sandstone Gas Reservoir

In recent years,the exploration and Development of unconventional natural gas resources have achieved remarkable results.The compact sandstone gas has made an important contribution to natural gas exploration and development,and the proportion of natural gas production is increasing.The tight sandstone reservoir generally has the characteristics of low porosity,low permeability,high capillary pressure and rich clay mineral,which leads to the easy intrusion of the working liquid filtrate into the reservoir during the well completion process,and then changes the fluid distribution in the near well zone,which affects the electrical logging accuracy.The study on the response of the electrical parameters of tight sandstone to filtrate intrusion is of great significance to the fine interpretation and evaluation of well logging.Taking the tight sandstone gas reservoir of Tarim J block as the research object,this paper analyzes the geologic factors of the filtrate invasion of drilling completion fluid,and studies the electrical parameter response characteristics of the gas reservoir in the different leachate intrusion process.The geological characteristics of the compacted sandstone reservoirs in the area are studied.The pore structure of the gas reservoir is complex,the natural fracture develops,and the high salinity formation water exists,in which the clay minerals are mainly illite,the interlayer minerals,and the rocks are middle wetting.The intrusion of liquid filtrate in the process of drilling and completion is more common,which affects the logging interpretation and other work.The changes of core resistivity of compacted sandstone under the condition of variable salinity fluid,variable water saturation and variable effective stress are analyzed experimentally.With the increase of fluid salinity,salt-sensitive damage occurred in cores,the average pore throat radius decreased and permeability decreased,and the formation factor F and cementation index m increased with the increase of salinity,and when salinity reached a certain value,the rising trend slowed down.The electrical parameter A is about 1.2,and the saturation exponent n is about 1.7.With the increase of effective stress,the electrical parameter a decreases and the cementation exponent in increases.The intrusion process of filtrate filtrate of drilling fluid is simulated,and the response relationship between the resistivity of cores and the change of water saturation in the intrusion process is discussed.In the early stage of filtrate intrusion,the water saturation of cores increased rapidly,and when the water saturation reached ?number,the increasing amplitude slowed down to a stable.In the process of intrusion,the core resistance decreases with the increase of water saturation,and the decreasing trend is in agreement with the change of moisture saturation.The changes of water saturation and resistivity of the well circumference during the filtrate intrusion were calculated.With the invasion of filtrate,the water saturation of well week is obviously changed,and in the range of intrusion zone,the radial water saturation decreases with the increase of depth,and the resistivity increases with the depth.