伊朗MIS油田高含硫裂缝性超低压油层钻井液技术

Drilling Fluid Technology for Ultra-low Pressure Fractured Reservoir with High H_2S Content in M.I.S,Iran.

伊朗MIS油田属裂缝性碳酸盐岩圈闭型油气藏,油气层压力经过百年开采后,为衰竭性异常低压((0.4±0.02)MPa/100 m),覆盖层上部含高压盐膏水层,而且圈闭气顶高含硫化氢、下部含边水。该油田水平井钻井液,需要满足上部防盐膏水层发生复杂及事故的要求,因此采用了聚磺饱和盐水钻井液;还需要保障异常低压定向井段的钻井安全以及防H_2S污染的能力,因此在产层采用了具有防喷、防硫化氢功能的可循环无固相泡沫钻井液。可循环无固相泡沫钻井液既能满足MWD无线随钻信号传输要求,又可以利用泡沫的"气锁"和凝胶暂堵作用,达到即钻即漏即堵、稳定漏失液面的目的,同时避免了由大漏后引发的硫化氢泄漏风险,应用效果理想。该钻井液技术的成功应用为今后老油田异常超低压、漏失性灰岩地层的水平井钻井提供了参考依据。

The M.I.S Oilfield(Iran) is an old oilfield developed for more than one hundred years.The lowest formation pressure is only 0.4±0.02 MPa/100 m.Wells drilled in this area penetrate salt/gypsum formations and formations containing high concentration of H_2S.A saturated salt polymer mud is used to drill the salt/gypsum formations,and a solids-free stiff foam mud to drill the low pressure zones in which the buildup section resides.Field application showed that this foam mud,apart form satisfying the need for solids carrying,mud loss control,it also satisfy the need for MWD signal transmission.H_2S is also suppressed because of the use of this foam mud having a reasonable density and fluid alkalinity.The successful use of the drilling fluids provides a clue for the drilling fluid operation in depleted reservoirs.