鄂尔多斯盆地东部气田盐下高含硫储层安全高效钻井技术

Safe and Efficient Drilling in Presalt High-Sulfur Reservoirs in the Eastern Gas Fields of Ordos Basin

鄂尔多斯盆地东部气田盐下高含硫储层主要为奥陶系马家沟组,其碳酸盐岩-膏盐岩互层发育,存在破碎屑岩层、大段膏盐层及压力异常地层,钻井过程中易出现井壁垮塌、井眼缩径、含H2S高压天然气侵、井漏及卡钻等井下故障及复杂情况,导致机械钻速低、安全高效钻进难度较大。为此,开展了“储层专打”井身结构设计,集成高抗H2S井控装备、防喷工具及工具的标准配套,研究应用了“高效PDC钻头+大扭矩单弯螺杆+MWD+随钻震击器”的储层复合钻井防斜防卡打快技术,探索性应用了精细控压钻井技术,优选复配出具有强“抗盐、抗钙、抗泥”能力的高密度饱和盐水钻井液,形成了鄂尔多斯盆地东部气田盐下高含硫井储层安全高效钻井技术。鄂尔多斯盆地东部气田的5口井应用了该技术,平均钻井周期54.3 d,平均机械钻速8.35 m/h,其中三开储层段平均钻井周期11.67 d,较前期完钻的MT1井缩短了52.03%,储层段平均机械钻速6.85 m/h,较MT1井提高了69.97%,平均井径扩大率6.16%,电测一次成功率100%,未发生井下故障和复杂情况。该技术为鄂尔多斯盆地东部气田盐下高含硫气藏安全高效勘探开发提供了技术支撑。

The main presalt high-sulfur reservoirs are located in the Ordovician Majiagou Formation,eastern gas field of the Ordos Basin,interbedded and developed with carbonate zone and gypsum zone.In addition,broken clastic rock,large interval of gypsum,and formations with abnormal pressure are observed.Further,wellbore collapse,tight hole,high-pressure natural gas containing H2S invasion,lost circulation,stuck drilling,and other downhole failures and complex situations are easily encountered while drilling,leading to a low rate of penetration(ROP)and difficulties in safe and efficient drilling.Therefore,the casing program optimization design of“special drilling for particular reservoir”was carried out,which integrated high H2S well control equipment,blowout prevention equipment,and equipment standards.Combination drilling,anti-deviation and fast drilling technologies,i.e.“high-efficiency polycrystalline diamond compact(PDC)bit+high-torque single-curved screw+measurement while drilling(MWD)+drilling jar”were studied and applied.A pilot test used precisely managed pressure control drilling technology was carried out.The high-density saturated brine drilling fluid system with strong anti-salt,anti-calcium,and anti-mud was optimized and compounded,forming the technology for safe and efficient drilling of presalt high-sulfur reservoirs in eastern gas fields of Ordos Basin.The technology was applied in five wells,with an average drilling duration of 54.3 d and an average ROP of 8.35 m/h.Specifically,there was an average drilling duration of 11.67 d in the third section,52.03% shorter than that of the early drilled well,MT1,an average ROP of 6.85 m/h for the reservoir interval,69.69% higher than that of MT1,and an average hole enlargement ratio of 6.16%.The electrical logging had a success rate of 100% for a first run.There is no downhole failure or complex situation.It provides a technical support for safe and efficient exploration and development of presalt high-sulfur gas reservoirs in the eastern gas fields of Ordos Basin.