Research and Application of Micronized Barite Drilling Fluid in HPHT Wells of the Western South China Sea

Abstract

When drilling wells in high temperature and high pressure (HTHP) fields, the drilling fluid properties are of utmost importance. If the viscosity of high density drilling fluid is too low, it will lead to barite sag and poor cuttings carrying capacity. However, lost circulation will occur due to high surge pressure and Equivalent Circulating Density (ECD) caused by high viscosity. High density drilling fluid performance is largely dependent on the use of the weighting material. The contradiction between rheological properties and barite sag of API Barite High Density Drilling Fluid (HABF) is great in the condition of HTHP. This article describes a novel weighting material that has resulted in a ten-fold reduction in the particle size of API barite. With this micronized barite, the contradiction of high density drilling fluid can be solved. The rheology, sag stability and lubricity of high density drilling fluid weighted by micronized barite and API barite is investigated in the laboratory. And the mechanism of micronized barite to improve the performance of high density drilling fluid is discussed by using size distribution, surface charge, and microscopic shape method. Micronized Barite High Density Drilling fluid (HMBF) was first applied in two HTHP exploration wells with good gas show recently, which are in Western South China Sea. HMBF exhibited good rheological properties, sag stability and lubricity in the drilling process. Drilling task was successfully completed, without complicated situation.