基于油藏实际的稠油层内水热催化裂解机理研究

开展了稠油层内水热催化裂解技术在胜利油田的先导实验,五口井平均周期单井增油653 t,稠油初期降黏率达79.8%,措施14周后降黏率仍大于62%。利用Brookfield DV-Ⅲ黏度计、ElementarVario EL III元素分析仪、Knauer K-700蒸气压渗透仪、Agilent 6890N气相色谱仪和EQUINOX 55傅里叶变换红外光谱仪等,对措施前后稠油的物化性质进行分析。结果表明,层内水热催化裂解后稠油黏度及平均分子量减小、轻烃含量增加、重质组分含量减少、氢碳原子比增加、杂原子含量减小。稠油层内裂解反应受催化剂体系、高温水及储层矿物因素控制,催化剂是促进稠油裂解的主要因素,供氢剂及分散剂等助剂有助于提高裂解效果,高温水的酸碱性质及储层矿物对稠油具有催化裂解作用。多因素协同作用下使稠油发生脱侧链、分子链异构、断链、加氢、开环、成环、脱硫等系列反应,使得稠油大分子分解成小分子物质,降低了稠油黏度,改善了稠油品质,证实该技术在现场应用中具有可行性。

Mechanism of underground heavy oil catalytic aquathermolysis

Field tests of underground heavy oil catalytic aquathermolysis were carried out in Shengli oilfield, the average period oil increment for 5 test wells reached to 653 t, and the viscosity of heavy oil was reduced by 79.8%, and still decreased by more than 62% after 14 weeks. The chemical and physical properties of heavy oil before and after the reaction were investigated using DV-III Ultra-Brookfield rheometers, Elementar Vario EL III elemental analyzer, Knauer K-700 Vapor permeability tester, Agilent 6890N gas chromatograph and EQUINOX 55 Fourier transform infrared spectrometer,etc. The results indicate that the heavy oil viscosity and average molecular weight are decreased and the content of resin and asphaltene is reduced after the reaction. The H/C ratio of heavy oil and the content of saturate and aromatic are increased. The amount of heteroatom in heavy oil is also decreased after the treatment. The reaction of underground heavy oil catalytic aquathermolysis is mainly affected by the catalyst system, high temperature water and reservoir mineral, in which the catalyst is the key control factor, and the hydrogen donating accelerator and dispersing agent can improve the cracking. In addition, the acid-base properties of water under high temperature and the reservoir mineral can promote the reaction. During the aquathermolysis, many reactions including the removal of alkyl side chain, the molecular chain isomerization, the hydrogenation, the ring opening, the ring closing and the desulfuration are involved, which can lead to the reduction of viscosity and improvement of heavy oil quality. The results suggest that the underground heavy oil catalytic aquathermolysis is feasible in field use.