南海高温高压气田密集丛式井表层Ф660.4 mm井段安全钻井技术

Safe drilling technologies for the Ф660.4 mm surface section in dense cluster wells with high temperature and high pressure,South China Sea

南海高温高压气田采用丛式井模式,表层Ф660.4 mm井段集中批钻作业面临着上层隔水导管鞋易漏失、浅部松软地层钻进造斜率难保证、密集型井槽井眼碰撞的难题,限制了表层钻井的作业时效。为此,针对性地采取井槽防窜漏工艺、优化井眼预斜钻具组合、开展表层防碰设计及安全钻进参数控制,形成了适合该区域的丛式井表层Ф660.4 mm井段安全钻井关键技术。现场应用效果表明:①Ф660.4 mm井段钻井采用顺序"跳打"方式,在隔水导管内清淤,出隔水导管后实施钻进参数控制,并在固井时实施中间液附加量和排量控制,解决了表层大尺寸井眼、槽口密集环境下的井间窜漏问题;②优选大尺寸马达导向工具,根据预斜情况调整马达弯角至1.5°,提高了在浅部松软地层海水钻进作业的预斜效果;③钻具组合中配套MWD工具、新增Mob Stab工具,满足一趟钻预斜、稳斜、防碰要求;④基于隔水导管不同偏斜角度的表层防碰设计及安全钻进参数控制的关键在于1~3个立柱钻进的钻井液类型选择、提拉与划眼操作选择以及不同位置的高低排量选择来确保造斜效果。结论认为该套技术能有效缓解该气田表层Ф660.4 mm井段作业中的窜漏和防碰压力,作业提效50%以上。

Cluster-well drilling is a development mode used in many high-temperature and high-pressure gasfields,South China Sea.In the process of drilling the Ф660.4 mm surface section in batch,there are several problems,such as leakage of the upper riser shoes,difficult to guarantee the slope of drilling in shallow and unconsolidated formations,and collision in intensive slotted borehole,resulting in the decrease of penetration rate.Therefore,some safe drilling technologies were developed for the Ф660.4 mm surface section in cluster wells,including anti-leakage of surface wellbore,optimization of pre-kickoff bottomhole assembly,surface anti-collision design,and controlling of safe drilling parameters.Field application shows that:(1)in the Ф660.4 mm surface section,"skip drilling"is useful,washing the riser is helpful,drilling parameters should be controlled after getting out of the riser;and the addition of intermediate cementing fluid and pump displacement should be controlled.All these measures may reduce channeling and leaking in certain zones with large-sized borehole and dense rabbets;(2)selecting large-sized motor steering tools and adjusting the motor bending angle to 1.5°according to pre-kickoff condition can improve the pre-kickoff effect while drilling shallow and unconsolidated formations in seawater;(3)MWD and Mob Stab tools equipped with bottomhole assembly can meet the requirements of pre-kickoff and stabilize deviation and anti-collision in a run;and(4)not only surface anti-collision design but also safe drilling parameter control based on different deviations of the riser should focus on how to select drilling fluid,lifting and reaming operation,and selecting high and low displacements at different positions in 1-3 drilling columns.It is concluded that these technologies can reduce the channeling and leaking and anti-collision pressure and increase the penetration rate of more than 50%in theФ660.4 mm surface section in the high-temperature and high-pressure gasfields,South China Sea.