乌夏断裂带二叠系风城组油藏压裂返排异物成因分析及对策

Genetic Analysis and Countermeasures for Foreign Body of Fracturing Flowback in the Reservoirs of Permian Fengcheng Formation in Wuxia Fault Belt

针对新疆油田准噶尔盆地乌夏断裂带二叠系风城组油藏压裂返排出现返胶和返排异物的情况进行了研究和成因分析。研究发现返排异物为胍胶和无机盐的混合物,返排液碱性强,且富含地层矿物离子。分析原因是由于地层矿物离子极易溶于胍胶冻胶中,导致胍胶压裂液冻胶脱水,溶解的CO2-3,HCO-3增强了压裂液的碱性环境,胍胶基液与地层中的交联离子作用加强了交联结构使得压裂液不能完全破胶。根据返胶及返排异物成因分析,研究开发了酸性疏水缔合聚合物压裂液体系,并现场实施9井次,压后无返胶和返排异物情况出现。

In view of returned gel and flowback of foreign body of fracturing in the reservoir of Fengcheng Formation in Wuxia Fault Belt of Junggar Basin in Xinjiang Oilfield,the genesis was analyzed.It was found out in the study that the unidentified object was the mixture of guar gum and inorganic salt,flowback fluid was strong alkaline,and rich in mineral ion from the formation.The reason was that the mineral ions were easily soluble in fracturing fluid,and it induced dewatering in fracturing fluid,and the dissolved CO2-3 and HCO-3enhanced the alkaline environment of fracturing fluid,reaction of guar gum with cross-linked ion strengthened the cross-linking properties,thus the fracturing fluid can not completely break the gel.According to the analysis of return gel and flowback of foreign body,an acidic hydrophobically associating polymer fracturing fluid system is studied and developed,and it is used in 9 wells,after fracturing,no returned gel and flowback of foreign body occur are appeared.