Study On Inhibitting Technology Of Natural Gas Hydrate In Deepwater Drilling Fluid

With the increasing of domestic energy requirement and decreasing of onshore reserves,China started up the deepwater drilling and developing project. In the exploration of deepwater oil and gas fields,it was facing many complex technique difficulty. Such as natural gas hydrate can easily form in water-based drilling fluid during deepwater drilling,gas hydrate can block the annular, BOP, chokes and kill lines, conductor, marine riser, confine the behavior of the drill string, and destroy the property of the drilling fluid.There is a urgent need to solve the problem that how to inhibit the formation of natural gas hydrate and develop inhibitting gas hydrate deepwater drilling fluid formulation.Combining with the deepwater conditions in China South sea and based on the investigation of both here and abroad,inhibitting control mechanism of gas hydrate in deepwater drilling fluid was studied and the gas hydrate inhibitors and inhibitive drilling fluid formulations were evaluated by experiments,no gas hydrate formed in the deepwater drilling fluid formulation under the condition of 30MPa/2℃.First of all,the influence regularities of stirring velocity,degree of supercooling,bentonite content and drilling fluid additives on the formation of gas hydrate in deepwater drilling fluids were studied by using the evaluating euqipment of inhibitting gas hydrate.The inhibitive effection of kinetic inhibitors and thermodynamic inhibitors were researched and good inhibitors were developed by experiments.On the basic of inhibitting control mechanism of gas hydrate in deepwater drilling fluids,inhibitive drilling fluid formulations were developed by experimentally studying the compatibility and dosage of kinetic inhibitors and thermodynamic inhibitors.Evaluating results show that the formulations have good inhibitive capability and preferable rheology and can essentially satisfy the demand of deepwater drilling exploration.