千方污水回注井储层损害诊断及酸化延效技术

针对渤海C油田群日注水量达上千方的污水回注井面临注入量大幅下降、酸化低效的问题，利用储层特征及岩石物性分析、水质普查及分析、结垢预测、软件模拟等综合手段，找出了此类井型的伤害主因是微粒运移，伤害半径为0.3～0.5 m，伤害次因是结垢、固相等堵塞，结垢类型为碳酸钙，两种注入水的结垢量分别为287.6 mg/L和357.1 mg/L，固相堵塞物主要是白云石类矿物，伤害半径为0.2 m。同时分析了以往酸化低效的原因是，由于采用在线酸化工艺，导致千方污水回注井的注水量远超注酸量，酸液浓度稀释比例过大，同时酸液无法有效解除复合伤害而产生的。采用盐酸、乙酸、氟硅酸、氟硼酸、HEDP主酸复配柠檬酸、季铵盐、SDBS等添加剂，研发了HLCHEM-Y酸化体系，解决了复合伤害问题。采用3.0～4.8 m3/min大排量拖轮注酸工艺，解决了海上平台空间受限条件下，千方污水回注井低排量注酸工艺效果差的难题。配套技术在C油田群开展了16井次应用，取得了酸化后单井平均增注从116 000 m3延长至399 000 m3，平均有效期从44 d延长至152 d的显著效果。

Reservoir Damage Diagnosis and Acidizing Extended Effect Technology of Massive Sewage Reinjection Wells with Thousands of Cubic Meters

The sewage reinjection wells in Bohai C oilfield group with a daily injection volume of thousands of cubic meters which are facing the problems of sharp decline in injection volume and low efficiency of acidification. Using the integration methods of reservoir characteristics and rock physical property analysis, water quality survey and analysis, scaling prediction, software simulation, it is found that the main cause of damage of the well type is particle migration, and the damage radius is 0.3 m~0.5 m. The secondary cause of damage is scaling, solid plugging. The scaling type is calcium carbonate. The scaling amounts of the two kinds of injected water are 287.6 mg/L and 357.1 mg/L respectively. The solid plugging is mainly dolomite minerals, and the damage radius is 0.2 m. At the same time, it is analyzed that the reason for the low efficiency of acidification in the past is the use of online acidification process, which leads to the water injection volume of massive sewage reinjection well far exceeding the acid injection volume, the acid concentration dilution ratio is too large, and the acid can not effectively remove the compound damage. HLCHEM-Y acidification system was developed by using hydrochloric acid, acetic acid, fluorosilicic acid, HEDP main acid, citric acid, quaternary ammonium salt, SDBS and other additives can be used to solve problem of compound injur. The 3 m3/min~4.8 m3/min large displacement tug acid injection process is adopted to solve the problem of poor effect of low displacement acid injection process in massive sewage reinjection well under the limited space of offshore platform. The supporting technology has been applied in 16 wells of C Oilfield Group which has achieved significant results in extending the average injection rate increase from 116,000 m3 to 399,000 m3 after acidification, and the average validity period extend from 44 days to 152 days.