Mechanism Study On The Main Causes Of Forming Low Resistivity Pay

In the article the genetic mechanism of low resistivity pay is studyed by the numbers and in-depth under the action of additional conductivity of clay and magmatic inrush at the base of rock physics research , which starts with the study of geophysics logging response characteristic and adopts the method of experiment analysis integrated with numerical simulation, and has some new cognitions and innovations as following.1) Holding the essential of analysing the causes of low resistivity pay and the principal parameter that is the rate of resistance augment, the action of additional conductivity of clay and magmatic inrush which maybe the main genetic mechanism of low resistivity pay are analysed by adopting the method of rock physics research integrated with numerical simulation.2) After a systematical rock physics research of the amount of cation exchange, the distributing shape of the clay, the salinity of stratum-water, the stratum temperature and so on, we will know that the ability of additional conductivity of clay is the function of the influence factors above. We can get the real reason that the additional conductivity of clay generates low resistance pays well and truly by analysing all kinds of factors synthetically. We can make several conclusions as following:a) The distributing shape is various because of different ore-forming processes.Silk clay film overlaying the framework grains inproves the the ability of the additional conductivity greatly through ameliorating the conduct meshwork enormously,and decreases the resistivity of the pays.So the resistance of oil layer maybe low even through there are no other influence factors.b) No matter what the salinity of stratum-water is high or low, the additional conductivity influence of clay may make pay have low resistance. In the same condition, the lower the salinity of stratum-water and the stronger the additional conductivity influence, the easier the make of low resistance oil layer.c) When the amount of cation exchange increases, the value of resistivity log reduces, and exponential relation is between them. The variable rule in them is consistent with idiographic reservoir in the different region and stratification pay, but the idiographic quantized relation has a few difference, which lies on the kind of reservoir's clay, the factor of its relative content aspects, and so on.d) In the regionality of the lower amount of cation exchange, the speed which the rate of resistance augment reduces with the increase of the amount of cation exchange is very fast.When the equal amount of cation exchange changes , the reduced value of the rock resistance which has high salinity water is big in contrast.3) This chapter studies response characteristic of resistivity log after theintrusion of fresh mud, salty mud, saturated salty mud deeply and thoroughly, then specify the genetic mechanism of low resistivity pay formed by magmatic intrusion as following:a) Intrusion of fresh mud will increase dual lateral resistivity of water layer and oil-water layer. The increment is proportional to the saturation of water. However, intrusion of fresh mud will reduce dual lateral resistivity of pay. The reduction is proportional to the saturation of oil. But the slope of reduction is much smaller than the slope of increment above. This will reduce the difference between the resistivity of water layer and the resistivity of oil layer ,and form a low resistivity oil layer.b) Intrusion of fresh mud will increase dual induction resistivity of water layer and oil-water layer, but the increment is not large. However, the dual induction resistivity of oil layer reduces greatly after intrusion. The reduction is proportional to the saturation of oil.This will reduce the difference between the resistivity of oil layer and the resistivity of water layer, and form a low resistivity oil layer.c) When salty mud intrudes into water layer, the dual lateral resistivity will reduce. The reduction is proportional to the ratio of the salinity of mud filtrate and that of strata water (Cmf/Cw). However, when salty mud intrudes into oil layer, the dual lateral resistivity reduces greatly. The reduction is not only proportional to Cmf/Cw, but also proportional to the saturation of oil. When salty mud intrudes into the layer, the reduction of water layer is small, but the reduction of oil layer is great. This will form a low resistivity oil layer.