Mudcake Buildup and Invasion in Low Permeability Formations; Application toPermeability Determination by Measurement While Drilling. Topical Report, September 1991-August 1993

摘要

The authors have developed a method to predict the rate of filtrate invasion intolow to medium permeability formations, given the formation characteristics and the appropriate mudcake parameters. The authors have also developed a laboratory test procedure to measure mudcake properties under dynamic filtrate conditions. The necessary mudcake parameters are extracted by history-matching a 4-step laboratory test with a mudcake buildup simulator. All the theory behind the development of the mudcake buildup simulator is explained in this topical report. In the report, the authors include the results of the laboratory tests made on typical bentonite mud systems, and the authors' analyses of those laboratory data. The authors have clearly linked the behavior of the mudcake to the mud composition and factors affecting mud particle adhesion and erosion. These factors are quantifiable in the laboratory. The results from the mudcake buildup model can be used as input into a near wellbore simulator or to analyze data from MWD logging measurements. Proper simulation of the mudcake and mud filtrate invasion rates is required to analyze time-lapse logging data.