RESEARCH PAPER PETROLEUM EXPLORATION AND DEVELOPMENT Volume 43, Issue 1, February 2016 Online English edition of the Chinese language journal Cite this article as: PETROL. EXPLOR. DEVELOP., 2016, 43(1): 97–105. Received date: 29 Jun. 2015; Revised date: 08 Dec. 2015. * Corresponding author. E-mail: yangzjqh@petrochina.com.cn Foundation item: Supported by PetroChina Qinghai Oil Field Project (2011-ZG-006004). Copyright © 2016, Research Institute of Petroleum Exploration and Development, PetroChina. Published by Elsevier BV. All rights reserved. Deep profile adjustment and oil displacement sweep control technique for abnormally high temperature and high salinity reservoirsDeep profile adjustment and oil displacement sweep control technique for abnormally high temperature and high salinity reservoirs YANG Zhongjian 1, *, JIA Suogang 1 , ZHANG Lihui 1 , WU Xingcai 2 , DOU Hongmei 1 , GUO Ziyi 1 , ZENG Lijun 1 , LI Hongwei 1 , GUO Liqiang 3 , JIA Zhiwei 1 , FANG Wei 4 1. Drilling and Production Technology Research Institute of PetroChina Qinghai Oilfield Company, Gansu 736202, China; 2. PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China; 3. Sinopec Zhongyuan Oilfield Company, Henan 457001, China; 4. Southwest Petroleum University, Sichuan 610000, China Abstract: To improve water flooding sweeping efficiency and oil displacement efficiency in reservoirs with abnormally high tempera-ture and high salinity during late development stage, taking Gasikule E 3 1 reservoir as the research object, lab study and field test of sweep control technique (SCT) were conducted. Performance evaluation and field test results of soft microgel (SMG) agent show that: SCT has good thermal stability in the target reservoir and an effective period of 100?120 d in the field test, and the success rate of SCT can be greatly increased by adjusting particle size and concentration of the gel. Unlike polymer flooding or polymer-gel flooding which im-proves oil recovery by enhancing sweep efficiency, SCT can improve oil displacement and water sweep efficiency, and its displacement mechanisms have been confirmed by the lab experiment and field test. The SCT has been applied in six well groups in the target reser-voir, resulting in a cumulative oil increment of 1.03?10 4 tons, water production drop of 4.79?10 4 m 3 , and an input-output ratio of 1:2.09. But when international oil price is low, SCT project may have high failure risk in application to reservoirs with abnormally high tempera-ture and high salinity. Key words: high temperature high salinity reservoir; soft microgel; sweep control technology; deep profile control; oil displacement mechanism; economic benefit Introduction In the late waterflooding development stage of heterogene-ous reservoirs, due to heterogeneity and various development factors, more scattered and complicated in distribution, the remaining oil is mostly left in low permeability zones unswept by water and microscopic pores or throats [1?7] . Although polymer flooding and polymer gel flooding can achieve effec-tive sweep control and enhance oil recovery, they had short-comings in field test like poor thermal stability of polymer in high temperature and high salinity environment, and forma-tion damage of polymer gel to non-target layers [8?14] . Wu Xingcai proposed a new improved oil recovery (IOR) method, Sweep Control Technology (SCT) [15] , different from conven-tional polymer flooding or polymer gel flooding in IOR/EOR mechanism which enhance oil recovery mainly by enlarging sweep volume, in SCT, a new high temperature and salinity resistant soft micorgel (SMG) is injected into the deep zones of reservoir to improve sweep factor and oil displacement efficiency [15?17] . Since 2010, the SCT has been field tested and applied in many medium to high temperature, high salinity oil reservoirs in the Liaohe, Dagong and Huabei oilfields, ect, and achieved satisfactory results [15, 18, 19] . In this study, the SCT field test in the E 3 1 block in Gasikule oilfield with abnormally high temperature (126 ?C) and high salinity (17?18×10 4 mg/L, Ca 2+ and Mg 2+ concentration 2 350 mg/L) has been investigated, to get a better understanding on its IOR mechanisms. 1. Properties evaluation for SMG 1.1. Size distribution and expansion property Filtered formation water was used to prepare SMG solution at a concentration of 5 000 mg/L, which was then put into an oven at a constant temperature of 126 ?C for 15 days. The particle size of the solution was measured by laser particle
