弱碱三元复合驱矿场动态特征及结垢问题

Field Performance of Industrial Alkalescent Alkaline/Surfactant/Polymer Flood in Daqing and Related Scaling Problems

大庆首个弱碱三元复合驱工业化试验区位于大庆北三区西部,面积1.5 km2,有采油井14口,注入井13口,使用Na2CO3（12 g/L）/重烷基苯磺酸盐（2.5 g/L）/聚合物（1.4 g/L）溶液,2002-11-08开始注剂,到2006年5月共注入化学剂0.315 PV,完成设计量的45.6%。注入、产出剖面,注入量、注入压力,产液量、含水率等动态资料表明,采油井B2-J1-P50和注入井B2-20-48的生产状况在注剂的前期和中期有很大改善,而后期则恶化,认为结垢是造成这一现象的一个原因。元素分析和SEM观测表明,注入井内垢样主要成分是碳酸钙结晶。弱碱三元溶液的pH值为9.23,高于采出污水（8.53）,是引起结垢的主要因素。有机铬交联剂与弱碱三元溶液形成的复合铬凝胶,pH为8.45,黏度、界面张力（100mN/m数量级）变化不大,阻力系数、残余阻力系数较三元溶液急剧增大,随聚铬比增大（10∶1-80∶1）而减小。在注三元溶液后注压力迅速上升的B2-1-P56井,2006-12-27-2007-03-11以100 m3/d的排量注入聚铬比30∶1的复合铬凝胶期间,注入压力短暂上升至12.6 MPa后逐渐下降至11 MPa,吸液剖面改善,流量计内未见垢生成;恢复三元溶液注入后注入压力回升,2007年10月达到12.6 MPa,调剖效果丧失。由此推断,该复合铬凝胶可清除弱碱三元复合溶液在地层内的垢沉定。

The first industrial alkalescent alkaline/surfactant/polymer（ASP） flood trial covered 14 producing and 13 injecting wells in an area of 1.5 km2 in the west of Northern District III,Daqing.The ASP fluid used was composed of NaCO3（12 g/L）,heavy alkylbenzene sulfonate（2.5 g/L）,and HPAM polymer（1.4 g/L）and the injection started Nov 8,2002 and 0.315 PVof ASP fluid,or 45.6% of the total volume designed,was injected up to May 2006.The field data of intake and outflow profile,injection volume and pressure,and volume and watercut of produced fluid showed that the performance of producing well B2-J1-P50 and injecting well B2-20-48 was significantly improved at the initial and intermediate stages of ASP fluid injection and became worse at the later stage owing to scale creation as an important factor.An element analysis and an SEM observation indicated the main ingredient of scaled substanes in injecting wells being of CaCO3 crystal.The pH value of the ASP fluid used was of 9.23,being higher than of the produced water,8.53,which was considered to be the main factor of scaling.A chromium gelling ASP fluid,composed of the alkalescent ASP fluid and an organochromium preparate,was suggested,having lowered pH 8.45,similar or slightly varied viscosity and interfacial tension（of magnititude 100 mN/m）,and much more incrased resistance factor and residual resistance factor,which were decreased with increasing polymer to chromium ratio from 10∶1to 80∶1.The injecting pressure in well B2-1-P56 fast raised in the course of ASP fluid injection,a chromium gelling ASP fluid of polymer to chromium ratio 30∶1 was injected into the well at a pumping rate 100 m3/d from Dec 12,2006 to March 11,2007 and the injecting pressure,being raised to 12.6 MPa in a short time,gradually dropped down to 11 MPa meanwhile the fluid intake profile became improved and no scaled substances created in the metering device;the injecting pressure of followed ASP fluid raised and reached 12.6 MPa in Oct 2007 and the intake profile became worse again.It was concluded that the alkalescent ASP/chromium gelling fluid did remove the scaled substances created by the alkalescent ASP fluid in the reservoir.