裂缝性高温基岩气井硫酸钙溶垢研究及现场应用

Study and Field Application of Calcium Sulfate Scaling in Fractured High Temperature Bedrock Gas Wells

柴达木盆地尖北、东坪气田储层温度为170℃,且垢样沉积具有多样化,对硫酸钙的溶垢研究提出了很大的挑战,为了解决该区块连续出现井筒结垢,影响气井生产及各项测试作业开展的难题。通过分析垢样组份、明确结垢机理和调研溶垢方法,针对现场垢样开展溶垢研究,区分井筒垢样沉积、储层结垢分别形成了碳酸盐置换溶垢、酸性有机磷酸溶垢配方及工艺,开展了现场应用。结果表明,井筒垢样成份为高纯度硫酸钙及少量的碳酸盐、铁质;垢样来源为高矿化度地层水中成垢离子随着压力逐渐降低,水份蒸发在井筒,炮眼、近井地带沉积结垢;碳酸盐物相置换溶垢法适用于井筒沉积的硫酸钙溶垢,可利用储层高温达到所需反应温度且对井筒管柱无腐蚀;酸性有机磷酸螯合剂溶垢法适用于沉积在炮眼、储层近井地带的硫酸钙溶垢,可同时结合相应的酸化液体系开展复合酸化工艺,减缓二次沉淀造成的储层伤害。最终有针对性的形成了2套溶垢剂配方及相应的溶垢工艺,可有效溶解储层硫酸钙,解决了现场技术难题,为气田增产、稳产做出了巨大的贡献。

The reservoir temperature of Jianbei and Dongping gas fields in Qaidam Basin is 170℃,and the scale deposits are diverse,which poses a great challenge to the study of calcium sulfate scale dissolution,problems affecting gas well production and test operation.In this paper,through analyzing the composition of scale sample,defining the scaling mechanism,investigating the scale dissolving method,the scale dissolving research is carried out for the scale sample on the spot,the formula and technology of carbonate displacement scale dissolution and acid organic phosphoric acid scale dissolution were formed by distinguishing the deposit of Wellbore scale sample and reservoir scale formation respectively.The results show that the sample is composed of highpurity calcium sulfate and a small amount of carbonate and iron,and the source of the sample is the scaling ion in the formation water with high salinity The carbonate phase displacement scale dissolving method is suitable for calcium sulfate scale dissolving in wellbore.The high temperature of reservoir can reach the required reaction temperature and has no corrosion to wellbore string The acid organic phosphate chelating agent scale dissolving method is suitable for the calcium sulfate scale dissolving in the drill hole and near the well of the reservoir,and can be combined with the corresponding acidizing liquid system to develop the complex acidizing process at the same time,which can slow down the formation damage caused by the secondary precipitation.Finally,two sets of scale solubilizer formulation and corresponding scale dissolving process are formed,which can effectively dissolve reservoir calcium sulfate,solve the field technical problems,and make great contribution to increasing and stabilizing production of gas field.