超高温高密度防腐防窜水泥浆

An Ultra-High Temperature High Density Corrosion Inhibitive Anti-Channeling Cement Slurry

南海西部油田高温高压储层是南海万亿大气田的主力产区,乐东某区块目的层温度达210℃、压力系数为2.20~2.29、压力窗口仅为0.04~0.05,且存在CO_(2)等腐蚀气体,勘探开发难度极大,其中超高温高密度防腐防窜水泥浆体系的研发是制约气田开发的关键技术之一。针对上述复杂井况,以还原铁粉、锰矿粉、不同目数硅粉等进行颗粒级配作为固相材料,以低活性MgO为晶格膨胀剂防止水泥环回缩,以特种胶乳为防腐、防气窜材料,以有机、无机插层聚合物为高温悬浮稳定剂等构建了耐温达220℃、防环空气窜、防CO_(2)腐蚀的超高密度2.40~2.60 g/cm^(3)水泥浆体系。室内评价结果表明,在CO_(2)分压为50%、养护压力为100 MPa、养护温度为180~220℃的腐蚀条件下,腐蚀180 d后,抗压强度增加明显,是腐蚀前的3倍左右,渗透率略增加(<0.01 mD),水化产物由腐蚀前的硬硅钙石C_(6)S_(6)H转变为CaCO_(3)、SiO_(2)。220℃养护24 h后的抗压强度大于25 MPa,SPN值不大于0.5,稠化时间易调节,下灰时间不大于40 s,水泥石上下密度差小于0.01,满足现场施工要求。

The oilfield in the west of the South China Sea,in which high temperature high pressure gas reservoirs are drilled,is a main gas production area.In this oilfield the formation temperature of the target zone in the Ledong area is 210℃,the formation pressure coefficient 2.20-2.29 and the safe pressure window only 0.04-0.05.These formation characteristics together with the existence of CO_(2)in the same target zone make it difficult for the energy to be explored and developed.One of the key technologies for the gas development in this area is the development of a corrosion-resistant cement slurry for use in ultra-high temperature high pressure environment.To efficiently develop the gas resource,a cement slurry,having its densities ranging between 2.40 g/cm^(3)and 2.60 g/cm^(3)and with CO_(2)corrosion resistance is developed.In this cement slurry,a reduced iron powder,a manganese ore powder and a silica of different particle sizes are sized and used as the solid material,a low activity MgO as the lattice swelling agent to prevent shrinkage of the cement sheath,a special latex as the corrosion inhibitor and anti-channeling agent,and an organic and an inorganic intercalated polymers as the high temperature suspending stabilizer.Laboratory evaluation experiment shows that under CO_(2)partial pressure of 50%,aging pressure of 100 MPa and aging temperature of 180-220℃,the compressive strength of the set cement after being corroded for 180 d is three times of the compressive strength of the set cement before being corroded.At the same time,the permeability of the set cement is only slightly increased(<0.01 mD).The hydration products of the cement change from C_(6)S_(6)H,an xonotlite before corrosion of the set cement,to CaCO_(3)and SiO_(2)after corrosion.The set cement,after being aged at 220℃for 24 h,has compressive strength of greater than 25 MPa,and SPN value of less than or equal to 0.5.The thickening time of the cement slurry is easy to adjust,the cement is easy to flow,and the difference between the density of the slurry at the bottom and that of the slurry at the top is less than 0.01.These properties of the cement satisfy the requirements of the field operation.