玛湖油田MaHW1602水平井低活度钻井液技术

玛湖油田MaHW1602井地层条件复杂，目的层三叠系百口泉组含硬质泥岩、疏松砾岩等，水平段钻进过程中易发生坍塌掉块等井下故障。由于该地区近年使用的“去磺”钻井液存在防塌性不足的问题，为此，在分析该井地层特点及钻井液难点的基础上，通过室内试验优选了活度调节剂、封堵剂和抑制剂，形成了非磺化低活度钻井液体系。室内试验结果显示，低活度钻井液封堵率超过90%，平均水活度为0.863，满足现场钻井要求。该钻井液在MaHW1602井三开井段进行了现场应用，疏松易塌井段无明显的井径扩大现象，井眼规则，平均井径扩大率6.5%，且钻进中无明显托压现象，电测、下套管顺利，未出现钻井液性能突变、下钻或开泵漏失等问题。研究与应用表明，低活度钻井液具有较好的封堵和防塌性能，能够满足玛湖油田长水平段水平井安全钻进的需求。 

Low-Activity Drilling Fluid Technology for the MaHW1602 Horizontal Well in the Mahu Oilfield

Well MaHW1602 in Mahu Oilfield owns complex formation conditions, the target layer in the Triassic Baikouquan Formation contains hard mudstone and loose conglomerate, and downhole events such as collapse and caving are prone to occur during horizontal section drilling. Due to the insufficient collapse resistance of the " desulfurization” drilling fluid applied in this area in recent years, through analyzing the formation characteristics and the challenges in drilling fluids, the activity modifier, plugging agent and inhibitor were preferably selected in the laboratory, and the non-sulfonated low-activity drilling fluid system was further developed. The results of indoor test show that the plugging rate of low-activity drilling fluid exceeds 90%, and the average water activity is 0.863, which meets the requirements of field drilling. The drilling fluid was applied in the third spud section of Well MaHW1602, there was no obvious hole enlargement in the loose and collapsing-prone section, the wellbore was regular, and the average hole enlargement rate was 6.5%. In addition, there was no obvious weight stacking during drilling, the electrical logging and casing RIH were performed smoothly without any problems such as the rapid changes in drilling fluid properties, lost circulation during RIH or pump starting, etc. Research and field application suggest that the low-activity drilling fluid has good plugging and anti-sloughing properties, which can meet the requirements for safe drilling of long lateral horizontal wells in the Mahu Oilfield.