伊朗MIS油田裂缝性高含硫枯竭油气层钻井液技术

Drilling Fluid Technology for Depleted Fractured Reservoir with High H_2S Content in M.I.S,Iran

伊朗MIS油田裂缝性碳酸盐岩油气藏,经过近百年的开采,油气层压力异常低,而且气顶高含H2S。钻井过程中,一旦出现先漏后喷情况,就会造成严重的人身伤害和设备损失。因此,经过反复论证和实验室研究,决定在H2S气层采用具有防喷、防漏和防H2S功能的LCM随钻堵漏钻井液,在异常低压油层使用可循环泡沫钻井液。现场应用结果表明:随钻堵漏钻井液能成功地封堵裂缝,达到即漏即堵的效果,既节省了施工时间和钻井液材料,又避免了由先漏后喷引起的H2S泄漏风险,效果非常好。可循环泡沫对MIS油田异常低压碳酸盐岩油层具有良好的防漏效果,既可防止井眼漏失,又不影响取心作业。随钻堵漏技术与可循环泡沫相结合是MIS项目缩短钻井周期,降低作业成本的有效途径。

Reservoirs in M.I.S area in Iran are fractured carbonate reservoirs with ultra-low pressures and high hydrogen sulfide(H2S) content.To avoid mud losses in the low pressured formation,which may lead to blowout,a drilling fluid with lost circulation material(LCM) formulated into the mud was used in the gas top drilling;the mud density was reduced to as reasonably low as possible in an effort to avoid mud loss.Use sulfide scavenger in the mud,plus high pH value of the mud to eliminate the eruption of H2S.After the gas top was penetrated,a recyclable foam was used to drill the ultra low reservoir formation.This mud formulation,combined with appropriate mud property maintenance,was successful in the whole drilling process of the low pressured formations.Coring of the hole in the reservoir section was also smoothly and successfully done,with a core recovery of greater than 99.0%.