关键词: 深水, 钻井液, 气体水合物, 抑制剂, 钻井液添加剂

Abstract:

The formation of gas hydrate caused by shallow gases is one of the most potential hazards in deepwater drilling.Gas hydrate can exist steadily under the circumstance of low temperature and high pressure.Once it generates in deepwater drilling pipes,severe blocking will occur in an air tube, conductor,riser or subsea blowout preventer (BOP) and can not be readily eliminated,which may badly endanger the security of both engineering operators and drilling platforms.The present paper primarily investigated the effects of agitation conditions,bentonite contents and additives of drilling fluids on the gas hydrate formation by means of a newly-developed simulating apparatus for the assessment on inhibiting the gas hydrate formation.The investigation indicated that the existence of either agitation or bentonite could promote the formation of gas hydrate,while most of drilling fluid additives could only inhibit to a certain extent the formation of gas hydrate.The performance of commonly used inhibitors was dealt with and experimental results showed that the dynamic inhibitor could not restrain the formation of gas hydrate completely and its optimum dosage was 1.5%;meanwhile,the thermodynamic inhibitor could ultimately terminate the formation of gas hydrate if its dosage was great enough,in which NaCl was better than glycol.A good synergism of the dynamic and thermodynamic inhibitors could be achieved by confecting them in different proportions and a formula,fit for the 3000 m deepwater drilling,was worked out based on the experimental selection.

Key words: deepwater, drilling fluid, gas hydrate, inhibitor, drilling fluid additives