Analysis Of Factors Influencing Stability Of Water-based Foam Drilling Fluid

Foam drilling fluid is the one of main kinds of the underbalanced drilling fluid.The drilling speed can be improved,formation and drilling tools can also be protected by using it.The quality of drilling fluid is affected by foaming and foam stability,in which the foam stability directly affects the drilling engineering process.Many scholars have some research on the foam stability,however,they just discuss a single drainage mathematical equation or a single gas diffusion mathematical equation.This paper studies the influential elements and performance evaluation of the stability of water-based foam by micro and macro analysis.Moreover,the foam drainage mathematical equation and gas diffusion coefficient are comprehensive analyzed.Research is carried out by the following aspects.Firstly,the 780mL foaming volume and the 605s half-life foaming agent YLB is selected through the foaming performance and foam stability evaluation of eight different kinds of foaming agent.The paper also makes a comparative analysis between foaming agent YLB and foaming agent K12 by using a stereo microscope and Nano Measure software.The result shows that K12 particle size distribution is 56.49?540.35?m and the average particle size of up to 246.94?m;YLB particle size distribution is 29.38?260.72?m and the average particle size of 86.29?m.The stability of YLB is better than K12.Secondly,the stability of YLB is researched at the different kinds of elements(such as concentration,temperature,viscosity,pH,mineral salt)and the grain size of YLB and K12 are measured by Scion Image at different conditions(such as concentration,temperature,time,pH)in order to analyze the microscopic mechanism of foam stability in the experiments.Finally,the paper makes a mathematical fitting of the drainage volume variation with time and also makes a fitting of the liquid content variation and the grain size of YLB with time by using the K Feitosa model.The gas diffusion coefficient calculation method is presented based on Lemlich theory.The result shows that the Deff upper foam was changed between 0.93?0.96×10-6cm2/s and the lower foam was changed between 0.81?0.93×10-6cm2/s.Both the upper and lower foam had little change with time.It also proves that YLB is more stable than K12.