无黏土相盐水储层钻井液体系研究

Study on Clay-free Brine Reservoir Drilling Fluid System

针对伊拉克Missan油田群储层段钻井作业中存在着卡钻、漏失、气侵、溢流、井壁失稳、井径扩大等复杂事故,为了减少作业事故的发生,提高储层保护的效果,室内通过外加剂的优选,建立了一套无黏土相盐水储层钻井液体系。该体系以改性生物聚合物为流型调节剂,可降解的抗温淀粉作为降滤失剂,并采用NaCl盐水基液和CaCO3复合加重的方式进行体系的密度调节。钻井液性能评价结果表明,该体系抗温可达140℃,滚动回收率达到了95.46%,同时体系还具有较好的抗侵污能力和储层保护效果。

Missan Oilfield was located in Missan Province in southeast Iraq.There existed complicated accidents happened in the reservoir drilling of Missan Oilfields,such as sticking,lost circulation,gas cutting,overflowing,wellbore instability and hole enlargement,etc.In order to reduce the drilling accidents and improve the effects of formation protection,a clay-free brine reservoir drilling fluid system was developed by optimizing the additives in laboratory.A modified biological polymer was used as flow pattern conditioner,a degradable temperature-resistant starch was selected as filtration reducer and NaCl brine combined with CaCO3 was used to adjust the density of the drilling fluid.The evaluation results show that the anti-temperature of the drilling fluid system can reach 140℃,and the rolling recovery rate is up to95.46%.Meanwhile,the drilling fluid system has good ability to resist the contamination of high salinity formation water and good effect for formation protection.