JZ25-1S油田水平井控制压力钻井技术

Managed Pressure Drilling Technique for Horizontal Wells in JZ25-1S Oilfield

JZ25-1S油田水平井在钻进过程中,随着水平段长度增长会发生井漏问题,为此应用了控制压力钻井技术,控制井底循环压力低于地层漏失压力来解决该问题。首先根据地层漏失压力、井底循环压力和单位井段环空压力损失,计算井斜角90°时的安全钻进水平段长度,如果该水平段长度不符合开发要求,则再根据油气层厚度、油水界面、产层以上井段循环压力以及单位井段环空压力损失,计算安全钻进的最大井段长度和最大井斜角。JZ25-1S油田JZ25-1S-A17井水平段井斜角为90°时,安全钻进水平段长度只有965.00m,通过计算得知,如果产层井段井斜角不大于86.67°便可以增加产层段长度,从而提高单井产量。实钻表明,该井控制产层井段井斜角不大于86.67°,使产层井段长度达到1 068.00m,且未出现井漏。表明该方法能有效解决JZ25-1S油田水平井段钻进过程中,随水平段增长发生漏失的问题。

In order to deal with the loss of circulation caused by extension of horizontal section, Man- aged pressure drilling was applied to keep downhole circulating pressure under leak-off pressure during drilling. Allowable length of horizontal hole section with 90~ inclination was calculated based on leak-off pressure,downhole circulating pressure and annular pressure loss in each meter of hole. If above length can＇t meet the requirements of development, the longest horizontal length and inclination angle are calcu- lated for safe drilling according to the thickness of pay zone, depth of oil-water contact , circulating pressure above pay zone, and annular pressure loss for each meter of hole. It was predicted that horizontal well length for safety drilling was only 965 m for Well JZ25-1S-17 in JZ25-1S Oilfield. To enhance the well yield,it was estimated that length of hole could be extended in pay zone with less than 86.67° inclination. Actually with the well inclination controlled under 86.67°, the well length in pay zone reached to 1068 m without fluid loss. It showed that the method could effectively prevent the loss of circulation caused by ex- tension of horizontal section while drilling.