The Key Drilling Techniques On Gas Hydrate In Mohe Basin Well MK-1and MK-2

Gas hydrate is a clean energy to replace oil and coal, and also important potential futureresources, and it has huge reserves. Studies have shown that the amount of resources equal to twicethe world’s coal, oil and gas resources. The investigation and evaluation of gas hydrate has beenincluded in the2015plan by China’s Ministry of Land and Resources. The gas hydrates are widelydistributed in the bottom sediments (such as the continental shelf slope zone, mid-ocean ridges,trenches and Ridge, etc.) and terrestrial permafrost zone (such as the Arctic tundra and high-altitudepermafrost zone). China is the third large country in the world of the permafrost, the area of whichis2.15million square kilometers, accounting for22.3%of the total land area. Permafrost zone inChina are mainly distributed in the Northeast Daxinganling region and the Qinghai-Tibet Plateau,and scattered in some mountains. Mohe basin annual average temperature is low, the geothermalgradient was1.9°C, well developed permafrost and adequate source of gas for the formation of gashydrate, provided favorable conditions for formation of gas hydrate. China Geological Surveyjointed College of Construction Engineering of Jilin University and related scientific research unitsconducted the gas hydrate drilling construction in order to obtain the gas hydrate samples in theMohe basin, lay the foundation for gas hydrate of the permafrost research and the resourcesevaluation.In the gas hydrate resources exploration process, drilling for the samples of gas hydrate coreand conducting a scientific test well is to carry out the premise of the gas hydrate development work.By analyzing the core, we can assess the amount of resources of gas hydrate, the occurrence, thescale, the nature and other geological parameters of gas hydrate, which have great significance forthe development of gas hydrates.In the exploration of the resources of gas hydrate in Northeast permafrost zone (Engineeringfor drilling test well) project, as the major participating units, College of Construction Engineeringof Jilin University was mainly responsible for drilling the test wells, drilling for obtaining gashydrate samples, while conducted the research for scientific drilling equipment and drillingtechnology method for gas hydrate of the permafrost zone, to complete the formation of thescientific drilling specifications for gas hydrate of permafrost.The author had participated in the whole process of drilling for gas hydrate in the Mohe basin in2010and2012. Through the program, the author had analyzed the key technologies involved inthe drilling for gas hydrate in Mohe permafrost,which mainly refer to the large diameter wire-linecore drilling technology,the low temperature mud technology, the mud cooling system applied tothe construction of gas hydrate drilling in Mohe, wellhead pressure control equipment applied to heconstruction of gas hydrate drilling in Mohe, gas hydrate drilling parameter measuring systemapplied to he construction of gas hydrate drilling in Mohe. The author had concluded the experienceof gas hydrate drilling construction in permafrost, had analyzed the accidents and the equipmentfailures in the the whole drilling construction process, and proposed appropriate solutions andsuggested improvements to the inadequacies of the equipment improvement. The author hadoptimized gas hydrate drilling construction process methods in permafrost, which has great guidingsignificance for gas hydrate drilling construction in Mohe region and other permafrost regions.