Experimental Study On Gas Condensate Relative Permeability In Porous Media

Experimental and theoretical study on relative permeability of gas condensate in long core under formation condition, as an exploratory subject, rather tough and profound, with high theoretical value and application value, is the foundation of exploitation project establishment for gas condensate reservoir.It is long time conducted in the lab to mainly research on phase behavior of gas condensate system in PVT cell to be reference of gas condensate reservoir exploitation performance. The study does not consider the effects of porous media on phase behavior, which is proved by the work of many doctorate dissertations. Besides, the experimental study on gas condensate percolation law in real long core is very insufficient. Therefore, experimental and theoretical study on phase behavior and relative permeability in real porous media under formation condition is very important. The important parameters, such as dew-point pressure, CCS (critical condensate saturation) and so on, are not accurately measured currently due to technique limits. And the depletion law of gas condensate in long core is not systematically studied in lab.The dissertation systematically studies the common depletion regulation of gas condensate based on the established ultrasonic apparatus. Compares the relative permeability curves by respectively imputing traditional relative permeability curve (nitrogen-kerosene relative permeability curve) and improved relative permeability (equilibrium condensate and gas relative permeability) in compositional simulator of CMG software to simulating the experimental data. Then points out the limits of currently permeability functions according to the results of simulation, further theoretical research work is conducted.The following three aspects are highlighted in this dissertation. The first oneis about investigating the possibility of establishing the high temperature and high pressure ultrasonic apparatus to measure the phase behavior and condensate saturation during depletion. The second is about systematically research on depletion regulation through nine depletion experiments using three kinds of condensate gas system on two real long core under different formation condition and determine the special parameters using ultrasonic apparatus. The third is about the measurement, comparison and evaluation of traditional and improved permeability curve, pointing out the current limits of the relative permeability function in simulator.The primary achievements of the dissertation are: Ultrasonic signals can directly reflect the phase behavior character andthe condensate saturation during dynamic depletion in long core undercertain conditions. The real dew-point pressure of the gas condensate system, CCS and the recovery of condensate and natural gas are all influenced by interstitial water saturation and depletion velocity. The constant volumetric depletion (CVD) in PVT cell can not represents the real depletion regulation in the porous media. Dew-point pressure and production gas condensate ratio in real long core depletion are lower than those in CVD, condensate recovery is higher and natural gas recovery is nearly the same. The traditional relative permeability curve and function can't represent the true gas condensate percolation law. The improved relative permeability curve and function are required to determine the specific relative permeability of gas condensate.