深水钻井液中水合物抑制剂的优化

The inhibitor optimization of gas hydrates in deepwater drilling fluids

深水钻井遇到的重大潜在危险因素之一是浅层气所引起的气体水合物问题。气体水合物稳定存在于低温、高压条件下,如果在深水钻井管线中生成,会造成气管、导管、隔水管和海底防喷器等的严重堵塞,且不易解除,从而危及工程人员和钻井平台的安全。利用新研制的天然气水合物抑制性评价模拟实验装置,初步探索了搅拌条件、膨润土含量及钻井液添加剂对气体水合物生成的影响规律。研究表明,搅拌和膨润土的存在可以促进水合物的生成,而多数钻井液添加剂则对水合物的生成有一定抑制作用。研究了常用水合物抑制剂作用效果,实验表明,动力学抑制剂不能完全抑制水合物的生成,其最佳加量为1.5%;热力学抑制剂虽能最终抑制水合物的生成,但加量较大,NaCl抑制效果好于乙二醇;动力学与热力学抑制剂复配具有很好的协同作用。在实验基础上优选了适合于3 000m水深的深水钻井液用水合物抑制剂配方。

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 3 000m deepwater drilling,was worked out based on the experimental selection.