天然气水合物深水深孔钻探取心系统研制

海底天然气水合物在低温（0～10 ℃）、高压（大于10 MPa）、有充分的烃类连续补给并在水参与的条件下形成。对其常规取心和提取到地面的过程中，伴随温度压力的改变，很容易从固态变为气态，造成天然气散失而影响储层评价的可靠性。为此优选超高真空绝热方式设计金属保温筒和压力补偿方式实现保温保压功能，进而研制成功了天然气水合物深水深孔钻探取心系统：在取心实施过程中，利用取心专用钻杆将绳索取心内筒组合送入海底进行取心作业，取心结束后，从井口放入绳索提起取心内筒总成，带动活塞上行，产生负压使球阀关闭，实现保温保压取心；当需要进行全面钻进时，从井口投入全面钻进钻头塞堵塞流道，实现取心钻头快速钻进；连续取心时，用绳索提出钻头塞组合，然后投入取心内筒总成，实现取心作业。在胜利油田浅海区域成功地进行了该取心系统工作性能试验和现场模拟试验，结果证明：该系统能够实现保温保压取心的目的。

Research and development of a gas hydrate coring system in the deep sea water

Natural gas hydrate on the seafloor is formed under deep sea environment with low temperature(0-10 ℃),high pressure(>10 MPa),and fluent hydrocarbon supply in the presentation of water.If the regular coring method is adopted,the hydrate samples will easily turn from solid to gas state due to the changes of temperature and pressure from sea floor to surface,which will result in gas lost and the unreliability of reservoir evaluation.In view of this,the ultra high vacuum insulated mode is optimized to design a metal-insulated cylinder and the pressure compensation method is applied to achieve pressure and temperature preservation.In this way,a gas hydrate coring system adaptable for deep holes and deep water is successfully developed.During the coring operation process,the well-line coring drilling tool combination is sent down to the sea floor through the specific drilling pipe;after coring is completed,the coring tool combination is lifted up through the string at the wellhead to propel the upstroke of the piston,thus the ball valve will be shut off by the resulted negative pressure,as a result,the coring is smoothly done with both pressure and temperature well preserved.When a drilling operation is needed,the plugged coring bit is tripped down to keep on drilling ahead;but when the coring operation is needed,the plugged bit is then replaced by the coring bit combination.The working performance experiments and pilot tests were carried out in the shallow sea area by the Shengli Oilfield Company.As a result,this system can not only achieve coring but realize temperature and pressure preservation.The successful research and development of this gas hydrate coring system for deep water provides an effective means for natural gas hydrate exploration and development.