f Gelation and Time-Dependent Effect on Oil / Synthetic Based Drilling Fluids Rheology

Gelation and Time-Dependent Effect on Oil / Synthetic Based Drilling Fluids Rheology Drilling fluid gelation is the desired property to improve the cutting carrying capacity of fluid and to prevent the precipitation of formation particles and chemical additives in the colloidal system. However, additional energy is required to break the gelled structure and to initiate the fluid flow that leads to pressure increment in the well bore. An increase in the circulation pressure may fracture the weak formations; trigger the penetration of drilling fluid into these weak zones and reservoir fluid influx to the well bore can start (kick). Meanwhile this problem can cause to have a blow out or risk losing the well, human and investment. This study is conducted to examine the transient stress responses and gel-breaking pressure of time-dependent fluids by considering the aging and temperature effects. Synthetic Based Drilling (SBM) fluid is used as a sample fluid in the experiments. The rheological properties and gelation behavior of SBM have been determined with different temperatures and aging time values in an experimental way. In addition to deformation tests, flow tests have been conducted with different temperatures and resting conditions. In the theoretical aspect, a mathematical model is developed based on the structure kinetic theory to explain the rheological behavior of time-dependent fluids. Parameters in this proposed model have been determined via deformation tests; also have been validated by flow-loop tests.