Waterflooding Characteristics of Extra-Low Permeability Reservoirs in Chang 6 Member, Ansai Oilfield

doi:10.7657/XJPG20250312

Abstract

Abstract:

To understand the sweep efficiency and water washing behaviors during waterflooding of extra-low permeability reservoirs in the Chang 6 member of the Ansai oilfield, 9 sealed coring inspection wells were systematically deployed at different orientations around Well W16-15 in the WY block. Using logging and scanning electron microscopy (SEM) data, the water washing behaviors, sweep efficiency, and microstructural changes in the reservoir were examined. The results show that the Chang 61-21 sublayer with good physical properties is strongly water washed, whereas the Chang 61-31 sublayer with poor physical properties is weakly or not water washed. The smaller the angle between the producer orientation and the principal stress direction or the closer to the injector, the greater the water washing degree and the water-washed reservoir thickness. The vertical sweep efficiency of the inspection well group in Chang 6₁ is 0.51, closely matching the calculated sweep efficiency (0.55) of the original well group. In the medium water-washed and strongly water-washed intervals of Chang 6 reservoir, long-term washing by injected water leads to the migration and swelling of clay minerals, enhancing the reservoir heterogeneity.

Key words: Ansai oilfield, Chang 6 member, extra-low permeability reservoir, waterflooding characteristic, water washing degree, sweep efficiency, reservoir, microscopic characteristic

CLC Number:

TE331

DUAN Wenbiao, ZHANG Yongqiang, GAO Chunning, ZHANG Jie, WANG Jinghua, ZHOU Jin, ZHANG Chuanbao, ZENG Shan. Waterflooding Characteristics of Extra-Low Permeability Reservoirs in Chang 6 Member, Ansai Oilfield[J]. Xinjiang Petroleum Geology, 2025, 46(3): 353-359.

Figures/Tables 10

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肉眼观察		滴水实验				沉降实验	塑料袋密闭实验	水洗级别
颜色	含水情况	滴水级别	渗入性	时间/min	水珠形状	颗粒沉降状态	塑料袋密闭实验	水洗级别
灰白色	明显含水，可见水外渗	1	速渗或缓渗	1~2	无水珠	团状	雾浓，袋壁有水珠	强
浅棕色	少量含水，手触有潮感	2	缓渗	10	凸镜状	絮凝状	有雾，水珠不明显，袋内明显有潮感	中
棕褐色	含水不明显	3	微渗	10	半珠状	絮状	雾稀薄	弱
深褐色	不含水，无潮感	4	不渗	10	近珠状	分散	无雾	无

井名	层位	砂体厚度/m	油层厚度/m	水洗厚度/m
井名	层位	砂体厚度/m	油层厚度/m	强	中	弱	合计
WJ16-151井	长61-21 小层	12.40	17.60	5.84	2.35	2.51	10.70
WJ16-151井	长61-31 小层	10.00	17.60
WJ16-152井	长61-21 小层	13.80	15.70			7.05	7.05
WJ16-152井	长61-31 小层	9.20	15.70
WJ16-153井	长61-21 小层	11.40	14.20		2.51	3.20	5.71
WJ16-153井	长61-31 小层	12.10	14.20
WJ16-154井	长61-21 小层	14.10	15.70	5.60	1.25		6.85
WJ16-154井	长61-31 小层	8.70	15.70			0.69	0.69
WJ16-155井	长61-21 小层	12.10	16.80	8.32		1.15	9.47
WJ16-155井	长61-31 小层	11.50	16.80			0.75	0.75
WJ16-156井	长61-21 小层	12.10	14.80		3.43	2.97	6.40
WJ16-156井	长61-31 小层	8.10	14.80			0.82	0.82
WJ16-157井	长61-21 小层	10.20	13.10		5.51	1.37	6.88
WJ16-157井	长61-31 小层	11.50	13.10
WJ16-158井	长61-21 小层	11.30	16.90		3.36	5.98	9.34
WJ16-158井	长61-31 小层	12.30	16.90			0.69	0.69
WJ16-159井	长61-21 小层	14.10	15.20		1.90	4.07	5.97
WJ16-159井	长61-31 小层	9.40	15.20			0.13	0.13

层位	类别	样品块数	石英含量/%	长石含量/%	岩浆岩岩屑含量/ %	变质岩岩屑含量/%				沉积岩岩屑含量/ %	黑云母含量/%	绿泥石含量/%
层位	类别	样品块数	石英含量/%	长石含量/%	岩浆岩岩屑含量/ %	石英岩	片岩	千枚岩	板岩	沉积岩岩屑含量/ %	黑云母含量/%	绿泥石含量/%
长61-21 小层	未水洗段	19	22.06	51.37	2.52	2.79	0.86	2.34	0.03	0.33	5.91	0.06
长61-21 小层	水洗段	90	26.08	47.68	2.59	1.56	0.83	1.51	0.91	0.01	4.89	0.35
长61-31 小层	未水洗段	30	20.64	48.86	3.04	4.24	1.41	1.65	0.11	0.30	5.80	0.12
长61-31 小层	水洗段	36	25.59	46.13	2.51	1.35	1.13	1.87	0.74	0.01	3.39	0.56

层位	样品块数	水洗程度	伊利石含量/ %	绿泥石含量/ %	方解石含量/ %	浊沸石含量/ %	硅质含量/ %	长石含量/ %	其他/%
长61-21 小层	6	强	0.3	3.1	1.3	0.7	0.6	0	0
	22	中	0.2	5.1	1.2	1.1	0.5	0.1	0.4
	23	弱	0.6	8.8	1.2	0.3	0.6	0.3	1.3
长61-31 小层	23	中	0.5	6.8	2.6	2.3	0.3	0	0.6
长61-31 小层	5	弱	0.2	10.6	1.5	1.3	0.5	0.3	1.4

层位	样品块数	水洗程度	面孔率/%	粒间孔/%	长石溶孔/%	浊沸石溶孔/%	其他孔隙/%
长61-21 小层	6	强	7.2	6.2	0.8	0.5	0.3
	22	中	5.8	4.9	0.6	0.6	0.3
	23	弱	5.4	4.2	0.9	0.4	0.2
长61-31 小层	23	中	3.4	2.5	0.4	0.3	0.3
长61-31 小层	5	弱	2.9	2.2	0.5	0.3	0.2