Impact of Foaming Agent on the Performance of Colloidal Gas Aphron Drilling Fluid for Geothermal Drilling

摘要

Colloidal Gas Aphron(CGA) drilling fluid with micro-bubbles (diameter from 10 to 100μm) is generated by surfactant and polymer. It has been successfully applied in drilling depleted oil and gas formations recently. In view of the good plugging performance and near-balance drilling characteristics of CGA drilling fluid, its introduction into geothermal drilling can be helpful to improve drilling efficiency and protect geothermal reservoirs. In this paper, the anionic surfactant sodium dodecyl sulfonate (SDS) and the zwitterionic surfactant cocamidopropyl betaine (CAB) were used as foaming agents and Xanthan gum (XG) was used as viscosifier. The effects of foaming agents on the performance of CGA drilling fluid, including stability, rheology and filtration loss, were studied. The analysis showed that: 1) The half-life and foaming volume of CGA fluid with SDS are generally higher than CAB 2) CGA drilling fluid prepared with SDS or CAB has obvious shear thinning property. The low shear rate viscosity (LSRV) of CGA drilling fluid prepared with CAB is generally higher than SDS 3) Herschel-Bulkley model is the best model to describe the rheological behavior of CGA drilling fluid 4) The filtration loss of CGA drilling fluid prepared with different amounts of SDS and CAB is not much different, and the API fluid loss in 30min is within 12-15mL.