Study On Forward Response Of Array Induction Logging Based On Dynamic Mud Intrusion

Array lateral logging tools are rich in radial detection curves,which can accurately reflect the distribution characteristics of reservoir well resistivity,and have important significance for qualitative evaluation and quantitative calculation of reservoir fluid properties.However,the array lateral logging is seriously affected by factors such as mud intrusion,which often causes the apparent resistivity curve to be distorted.Mud intrusion is a seepage process that changes dynamically with time,which directly affects the radial variation of the dielectric resistivity of the reservoir well.In the intrusion horizon,there is a significant difference in the apparent resistivity of the lateral logging of the array with different intrusion times.Mud intrusion into the reservoir section may even cause misjudgment of reservoir fluid properties.However,the existing research on the forward response of the array lateral logging based on mud intrusion is difficult to reflect the dynamic changes of the intrusion depth and the intrusion band resistivity with the intrusion time,resulting in a large difference between the inversion resistivity and the formation true resistivity.In order to accurately evaluate the true resistivity of the formation,it is necessary to study the forward response characteristics of the array lateral logging instrument under dynamic mud intrusion conditions.In this paper,a dynamic mud intrusion model is constructed using two-phase seepage-convection diffusion theory.Combined with the pore permeability characteristics of the actual study block,the reservoir properties are divided into three categories.The distribution characteristics of three kinds of physical resistivity under different intrusion time,mud filtrate and formation water salinity,well column and formation pressure difference,mud cake permeability,reservoir relative pore-permeability,and original formation water saturation are studied.Then the finite element method is used to establish the array lateral logging forward modeling model.The effects of well angle,wellbore size,mud resistivity,surrounding rock resistivity,target layer thickness,intrusion radius and intrusion band resistivity on the lateral logging response of the array were studied.And the array lateral logging well environment calibration plate,layer thickness/surrounding rock correction plate and static mud intrusion correction chart were drawn.The finite element method is used to construct a forward modeling study of dynamic mud intrusion array lateral logging,and the three-phase coupling of two-phase percolation-convection diffusion-electric field is realized.Then studied the influences of different intrusion time,mud filtrate and formation water salinity,well column and formation pressure difference,mud cake permeability,reservoir relative pore-permeability,and original formation water saturation on the apparent resistivity of array lateral logging.The apparent resistivity difference coefficient??is defined to characterize the variation law of apparent resistivity.The larger the??is,the more serious the apparent resistivity distortion is.As the intrusion time increases,the apparent resistivity of different detection modes gradually decreases,the apparent resistivity is a significant positive amplitude difference,the apparent resistivity correction coefficient gradually decreases,and the apparent resistivity difference coefficient??gradually increases.For the same intrusion time,the apparent resistivity distortion of the type II reservoir is the most serious.For the class III reservoir,the class I reservoir is the smallest.The apparent resistivity of the five detection modes of the three types of reservoirs decreases with the increase of the intrusion pressure difference,and??gradually increases.Under the condition of different mud cake permeability,the range of??of the type I reservoir is the largest,and the apparent resistivity of the R₅ detection mode is most affected by the intrusion.For similar physical reservoirs,the apparent resistivity of array lateral logging decreases with increasing formation porosity.In the range of 40%-65%of the original formation water saturation,the apparent resistivity and apparent resistivity difference coefficient of the array lateral logging of the three types of physical reservoirs decrease with the increase of the original formation water saturation..Finally,this paper combines the actual data analysis of the study area to verify the effect of specific interval mud intrusion on the qualitative identification and quantitative calculation of reservoir lateral logging reservoir fluid.