沥青质微观聚集特征的分子动力学研究  

Molecular dynamics study of microcosmic aggregation of asphaltenes

作　　者：王鹏 黄世军[1,2] 赵凤兰[1,2] 赵大鹏[1,2] WANG Peng;HUANG Shijun;ZHAO Fenglan;ZHAO Dapeng(MOE Key Laboratory of Petroleum Engineering,China University of Petroleum(Beijing),Beijing City,102249,China;College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing City,102249,China)

机构地区：[1]中国石油大学(北京)石油工程教育部重点实验室,北京102249 [2]中国石油大学(北京)石油工程学院,北京102249

出　　处：《油气地质与采收率》2021年第4期77-85,共9页Petroleum Geology and Recovery Efficiency

基　　金：国家自然科学基金面上项目“页岩储层条件下水对甲烷-二氧化碳竞争吸附的影响及相互作用机制研究”(51974328);中国石油天然气集团有限公司-中国石油大学(北京)战略合作科技专项“鄂尔多斯盆地致密油-页岩油油藏工程方法及关键技术研究”(ZL⁃ZX2020-02-04)。

摘　　要：为了探究沥青质分子性质和微观聚集特征,进一步揭示沥青质沉积的微观作用机理,采用分子动力学方法,建立代表性沥青质平均分子构型,并以此构建沥青质模拟体系初始构型来模拟沥青质在地层岩石中的运移。模拟实验结果表明:沥青质作为典型的非晶体,其径向分布特征总体表现为近程有序、远程无序;退火优化可以充分释放分子结构应力,有利于还原分子结构的能量基态,随着分子间距增加,分子间的范德华力相互作用减弱,静电相互作用将占据系统非成键作用中的主导地位。从沥青质模拟体系的运移终态可以看出:沥青质分子的芳核主体及部分脂肪族链倾向于逐渐被吸附到二氧化硅分子层表面,这会使岩石表面的润湿性由亲水性向亲油性转变;沥青质芳核的π-π堆积作用是引发沥青质分子聚集的驱动力,从而导致沥青质絮凝并从原油中沉积出来。润湿性反转和岩石孔喉堵塞是沥青质沉积造成原油采收率降低的重要机理。To investigate the molecular properties and microscopic aggregation of asphaltenes and the microcosmic mecha⁃nism of asphaltene deposition,we adopt molecular dynamics methods to establish the average molecular configuration of representative asphaltenes.It can be utilized to construct the initial configuration of the asphaltene simulation system to simulate the migration of asphaltenes in the formation rock.The simulation experiment results indicate the radial distribu⁃tion of asphaltenes,as typical amorphous matter,are generally in the pattern of short-range order and long-range disorder.In addition,simulated annealing optimization can fully release stress from the molecular structure,which is conducive to re⁃ducing its energy ground state.As the distance between molecules increases,the Van der Waals interaction between the molecules becomes weak,but the electrostatic interaction becomes dominant among non-bonding interactions of the system.It can be observed from the final migration state of the asphaltene simulation system that the main body of aromatic nucleus and part of the aliphatic chain of the asphaltene molecules tend to be gradually adsorbed to the surface of the silica molecu⁃lar layer,altering the wettability of the rock surface from hydrophilic to lipophilic.Theπ-πstacking of the aromatic nucle⁃us drives the asphaltene molecules to aggregate,leading to the flocculation and deposition of asphaltenes from crude oil.Wettability alteration and the pore-throat blockage of rock are important mechanisms for the reduction of oil recovery caused by asphaltene deposition.

关 键 词：分子动力学 沥青质平均分子构型 径向分布函数 润湿性 Π-Π堆积作用 

分 类 号：TE319[石油与天然气工程—油气田开发工程]