油气藏评价与开发 ›› 2022, Vol. 12 ›› Issue (5): 784-793.doi: 10.13809/j.cnki.cn32-1825/te.2022.05.010

• 方法理论 • 上一篇    下一篇

超低渗油藏水平井注CO2多周期吞吐原油性质变化规律研究

廖松林1(),夏阳2,崔轶男1,刘方志1,曹胜江1,汤勇3   

  1. 1.中国石化华东石油局,江苏 泰州 225300
    2.中国石油长庆油田公司第五采气厂,陕西 西安 710000
    3.西南石油大学油气藏地质及开发国家重点实验室,四川 成都 610500
  • 收稿日期:2021-06-21 出版日期:2022-10-26 发布日期:2022-09-27
  • 作者简介:廖松林(1994—),男,硕士,助理工程师,从事油气田开发及CO2驱油一体化技术研究。地址:江苏省泰州市海陵区南通路99号,邮政编码:225300。E-mail: 1154364969@qq.com
  • 基金资助:
    国家自然科学基金项目“超低渗透油藏CO2强化采油过程中多孔介质相态及微观渗流机理研究”(51974268)

Variation of crude oil properties with multi-cycle CO2 huff-n-puff of horizontal wells in ultra-low permeability reservoir

LIAO Songlin1(),XIA Yang2,CUI Yinan1,LIU Fangzhi1,CAO Shengjiang1,TANG Yong3   

  1. 1. Sinopec East China Oil and Gas Company, Taizhou, Jiangsu 225300, China
    2. The 5th Oil Production Plant of PetroChina Changqing Oilfield Company, Xi'an, Shaanxi 710000, China
    3. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China
  • Received:2021-06-21 Online:2022-10-26 Published:2022-09-27

摘要:

水平井压裂后注CO2吞吐技术能有效改善原油性质,提高超低渗油藏采收率。结合典型超低渗透储层油藏H区地质及流体特征,采用室内实验和数值模拟相结合的手段,开展超低渗油藏水平井注CO2多周期吞吐机理及原油性质变化规律的研究。结果表明:注入CO2使得原油饱和压力升高、体积膨胀、黏度降低、体系变轻质;注CO2吞吐不同阶段的主要作用机理不同,注入阶段补充地层能量、溶于原油、降低原油黏度,焖井及开井生产初期降低原油黏度,扩大CO2波及范围,开井生产中后期萃取轻质烃和少量中间组分烃;采用定时定点的方式,分析油藏中不同距离的油相中CO2含量,推测出H区块注入CO2沿裂缝的横向波及半径介于24~40 m,随着吞吐周期的增多,油相中CO2摩尔含量的增幅由第一周期的增加451倍,降到第三吞吐周期的0.44倍,注入的CO2溶于原油的量相对减小,对原油性质的影响逐渐减小。该研究对CO2吞吐机理的认识提供了新的分析方式,为进一步推广超低渗油藏水平井CO2多周期吞吐技术提供一定的理论支撑。

关键词: 超低渗油藏, CO2多周期吞吐, 原油性质, 组分变化, 数值模拟

Abstract:

CO2 huff-n-puff after fracturing of horizontal wells can effectively improve the properties of crude oil and increase the oil recovery of ultra-low permeability reservoirs. Combined with the geology and fluid characteristics of a typical ultra-low permeability reservoir, Block H, the mechanism of multi-cycle CO2 injection in horizontal wells and the variation of crude oil properties in ultra-low permeability reservoirs are studied by means of laboratory experiment and numerical simulation. The results show that after CO2 injection, the saturated pressure of crude oil increases, the volume expands, the viscosity decreases, and the system becomes lighter. And the main action mechanism of different stages of CO2 huff-n-puff are different: in the injection stage, the main mechanism is to supplement the formation energy, dissolve in crude oil, and reduce the crude oil viscosity; in the soaking and the initial stage of production, the main mechanism is to reduce the crude oil viscosity and expand the scope of CO2; in the middle and late period of well opening production, the light hydrocarbons and a small amount of intermediate component hydrocarbons in the oil phase are extracted. The CO2 content in oil phases at different distances in the reservoir is analyzed by the method of fixed time and fixed point, and it is deduced that the lateral sweep radius of CO2 injection along the fracture in H block is 24~40 m. With the increase of the huff-n-puff cycle, the increase of molar content of CO2 in the oil phase decreased from 451 times in the first cycle to 0.44 times in the third cycle. The dissolved amount of injected CO2 in crude oil decreases relatively, and the effect on the properties of crude oil also gradually decreases. The above research provides a new analysis method for understanding the mechanism of CO2 huff-n-puff, and provides some theoretical support for further popularizing the multi-cycle CO2 huff-n-puff technology of horizontal wells in ultra-low permeability reservoirs.

Key words: ultra-low permeability reservoir, CO2 multi-cycle huff-n-puff, crude oil properties, component change, numerical simulation

中图分类号: 

  • TE341