致密轻质油藏不同CO_(2)注入方式沥青质沉积及储层伤害特征  

Characteristics of asphaltene precipitation and formation damage of tight light oil reservoirs under different CO_(2) injection modes

作　　者：黄兴[1,2] 李响 何梦卿 何晓明 李天太 张荣军[1,5] Huang Xing;Li Xiang;He Mengqing;He Xiaoming;Li Tiantai;Zhang Rongjun(School of Petroleum Engineering,Xi'an Shiyou University,Shaanxi Xi'an 710065,China;Shaanxi Cooperative Innovation Center of Unconventional Oil and Gas Exploration and Development,Shaanxi Xi'an 710065,China;School of Petroleum Engineering,University of Tulsa,Tulsa OK 74104,USA;CNOOC Iraq Limited,Maysan 62001,Iraq;Xi'an Key Laboratory of Tight Oil(Shale Oil)Development,Shaanxi Xi'an 710065,China)

机构地区：[1]西安石油大学石油工程学院,陕西西安710065 [2]陕西省非常规油气勘探开发协同创新中心,陕西西安710065 [3]Tulsa大学石油工程系,美国俄克拉何马州74104 [4]中海石油伊拉克有限公司,伊拉克米桑省62001 [5]西安市致密油(页岩油)开发重点实验室,陕西西安710065

出　　处：《石油学报》2021年第12期1665-1674,共10页Acta Petrolei Sinica

基　　金：国家自然科学基金项目(No.52004221,No.51974254);中国石油科技创新基金项目(2019D-5007-0204);陕西省教育厅科研计划项目(21JY034)资助。

摘　　要：致密轻质油藏注CO_(2)会引发沥青质沉积现象。为厘清不同CO_(2)注入方式下沥青质沉积特征及其对储层的伤害机理,以鄂尔多斯盆地延长组7段储层轻质原油为例,在明确CO_(2)注入量和压力对沥青质沉淀量影响的基础上,通过开展不同注入压力下CO_(2)吞吐和驱替实验,辅以核磁共振在线扫描技术,研究了不同注气方式下沥青质在岩心中的沉积特征,定量评价了不同注气方式下沥青质沉积对储层物性、润湿性和孔隙结构的伤害程度,从微观孔隙尺度剖析了沥青质沉积对储层的伤害机理。研究结果表明,沥青质主要在岩心入口端大量沉积,且越接近岩心出口端沉积量越小,驱替方式下的沥青质沉淀量和沉积区域大于吞吐方式;两种注入方式下孔隙度变化率相差较小,但驱替方式下的渗透率伤害率远高于吞吐方式;沥青质沉积引发岩石润湿性向亲油反转,润湿反转指数随注入压力的升高而增大,且驱替方式下的润湿反转指数大于吞吐方式;微观尺度下沥青质主要在大孔隙中沉积,但吞吐方式下大孔隙(0.092μm≤T_(2)<4.500μm)堵塞率随注入压力的升高而增大,小孔隙(0.009μm≤T_(2)<0.092μm)堵塞率则先下降、后上升;驱替方式下小孔隙和大孔隙堵塞率均随注入压力的增加而增大。CO_(2) injection in tight light oil reservoir may lead to serious asphaltene precipitation.To clarify the characteristics of asphaltene precipitation under different CO_(2) injection modes and the mechanism of formation damage,the reservoir of light crude oil of Member 7 of Yanchang Formation in Ordos Basin is studied in this study.Based on defining the impact of CO_(2) injection volume and pressure on the amount of asphaltene precipitation,through performing CO_(2) huff-puff and flooding experiments under different injection pressures,and with the assistance of online NMR scanning technique,this paper investigates the characteristics of asphaltene precipitation in the core under different gas injection modes,quantitatively evaluates the damage degree of asphaltene precipitation to physical reservoir properties,wettability and pore structure under different gas injection modes,and analyzes the damage mechanism of adphaltene precipitation to formation on the micro-pore scale.The results show that a great amount of asphaltene is deposited at the inlet end of core,and the closer to the outlet end of core,the smaller the amount of asphaltene precipitation,and the amount and scale of asphaltene precipitation under flooding mode is larger than those of huff and puff.The difference in porosity change rate is slight under two injection modes,but the permeability damage rate under the flooding mode is much higher than that of huff and puff.Asphaltene precipitation leads to the reversal from wettability to lipophilicity in rock;the wettability reversal index goes up as the injection pressure increases,and that under under the flooding mode is greater than that under the huff and puff mode.Asphalene is mainly deposited in large pores on the micro scale,but the plugging rate of large pores(0.092μm≤T_(2)<4.500μm)under the huff and puff mode goes up as the injection pressure increases,while that of small pores(0.009μm≤T_(2)<0.092μm)drops first and then rises;the plugging rate of small and large pores under the flooding

关 键 词：致密油藏 轻质原油 沥青质沉淀 CO_(2)驱替 CO_(2)吞吐 

分 类 号：TE357.7[石油与天然气工程—油气田开发工程]