Characterizing distinctive drilling mud properties using new proposed hyperbolic fluid loss model for high pressure and high temperature conditions

Abstract

The currently in use fluid loss model (American Petroleum Institute (API)) was developed using the Darcy relationship and assuming that there is no changes in the permeability, solid content in the filter cake and filter cake thickness during the 30 min of fluid loss. Hence, in the current API model, the fluid loss is directly propositional to the square-root of time. In this study, a new proposed hyperbolic fluid loss model has been developed based on a time dependent variation in the filter cake properties. Also, the new proposed model has the power to quantify the short-term and long-term fluid losses (more than 30 min). Moreover, the new model has a limit on the total fluid loss compared to the current API model that shows an infinite fluid loss with time. The new model parameters are related to the applied pressure and temperature using nonlinear power models. The new model predictions are verified with the fluid loss results reported in the literature (225 °C and 300 psi) and tests performed in the laboratory at high pressure and high temperature on bentonite drilling muds during this study. The laboratory tests are both limited to 2% and 8% (by weight) bentonite drilling muds at 100 °C and 100 psi (689.5 kPa) up to 420 min (7 hrs) till the end of the fluid loss. The new model predicts the experimental results on maximum fluid loss and changes in the filter cake porosity, permeability, solid content, and thickness with time, pressure and temperature very well.

Keywords

• API fluid loss model
• New hyperbolic fluid loss model
• Filter cake
• Permeability
• Porosity
• Thickness