Sweet Spot Prediction of Shale Gas Reservoirs in Wulalike Formation, Majiatan Area, Ordos Basin

doi:10.7657/XJPG20250303

Abstract

Abstract:

The Middle Ordovician Wulalike formation is the primary target for marine shale gas exploration in the Majiatan area of the Ordos Basin. The reservoir is dominated by siliceous shale and characterized by thin layers and strong horizontal heterogeneity, seriously challenging the seismic identification. By utilizing geological, logging, and core data from the Majiatan area, a petrophysical analysis was performed on the marine shale reservoir, a shear-wave prediction method was proposed, and the optimal petrophysical parameters for characterizing the sweet spots of the marine shale gas reservoir were identified. By integrating drilling and gas testing results, the evaluation criteria for geological and engineering sweet spots of the marine shale gas reservoir were established. By combining post-stack seismic waveform-indicated simulation with self-organizing neural network fusion techniques, the distribution of sweet spots in the shale gas reservoirs was predicted. The results show that the geological and engineering sweet spots are primarily distributed in a band-like pattern in the western and central parts of the study area. The drilling results confirm that the seismic prediction method for sweet spots of shale gas reservoirs is worthy of promotion.

Key words: Ordos Basin, Majiatan area, Wulalike formation, marine shale gas reservoir, shear-wave prediction, seismic prediction

CLC Number:

TE122.1

ZHAO Yuhua, WANG Yating, HUANG Yan, ZHAO Deyong, CAO Yongliang. Sweet Spot Prediction of Shale Gas Reservoirs in Wulalike Formation, Majiatan Area, Ordos Basin[J]. Xinjiang Petroleum Geology, 2025, 46(3): 273-279.

Figures/Tables 8

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Table 1.

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Fig. 6.

Table 2.

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甜点分类	地质甜点评价参数					工程甜点评价参数				试气产量/（10⁴ m³·d^-1）
甜点分类	地层厚度/m	深度/m	纵波阻抗/ （m·s^-1·g·cm^-3）	孔隙度/ %	总有机碳含量/%	剪切模量/GPa	杨氏模量/GPa	横波阻抗/ （m·s^-1·g·cm^-3）	脆性指数	试气产量/（10⁴ m³·d^-1）
Ⅰ类	45~80	4 200~4 600	11 200~13 200	>2.5	0.25~1.80	17~19	41~50	6 600~7 300	0.45~0.76	>4
Ⅱ类	30~60	4 250~4 500	11 800~14 200	1.5~2.5	0.25~1.80	18~21	45~58	6 700~7 500	0.45~0.80	1~4
Ⅲ类	0~35	4 100~4 300	10 600~12 600	<1.5	<0.40	16~19	40~49	6 600~7 200	0.35~0.74	<1

井名	乌拉力克组顶面海拔/m	地层厚度/ m	有效储集层厚度/m	试气结果/ （10⁴m³·d^-1）	地震甜点预测结果
井名	乌拉力克组顶面海拔/m	地层厚度/ m	有效储集层厚度/m	试气结果/ （10⁴m³·d^-1）	地质甜点	工程甜点
J32井	-2 992.95	56.2	24.9		Ⅰ类	Ⅰ类
J22井	-2 736.08	85.3	40.0		Ⅰ类	Ⅱ类
J10井	-2 640.73	36.0	0		Ⅰ类	Ⅱ类
J23井	-2 566.66	12.0	0		Ⅲ类	Ⅲ类
J21井	-2 639.51	57.8	18.2		Ⅱ类	Ⅱ类
J9井	-2 590.56	46.6	0		Ⅰ类	Ⅱ类
J20井	-2 688.12	48.0	32.6	<1.0	Ⅰ类	Ⅰ类
J18井	-2 747.18	47.0	11.8		Ⅰ类	Ⅰ类
J11井	-2 594.56	43.2	0		Ⅰ类	Ⅱ类
J6井	-2 586.93	28.2	12.5		Ⅰ类	Ⅰ类
J25井	-2 560.98	44.3	0		Ⅱ类	Ⅲ类
J24井	-2 554.82	25.2	8.2		Ⅱ类	Ⅲ类
J19井	-2 798.18	54.7	29.2	<1.0	Ⅱ类	Ⅲ类
J17井	-2 824.61	77.5	11.6		Ⅱ类	Ⅲ类
J12井	-2 737.32	56.0	0		Ⅱ类	Ⅱ类
J4井	-2 612.64	38.0	20.3		Ⅲ类	Ⅲ类
J13井	-2 820.93	61.4	0.9	<1.0	Ⅰ类	Ⅰ类
J16井	-2 873.11	37.0	29.3	>4.0	Ⅰ类	Ⅰ类
J3井	-2 672.49	45.0	0		Ⅱ类	Ⅲ类
J26井	-2 603.00	33.0	1.3	<0.1	Ⅲ类	Ⅲ类
J14井	-2 860.35	59.1	15.5	<1.0	Ⅰ类	Ⅱ类
J15井	-2 956.04	49.0	45.4	>10.0	Ⅰ类	Ⅰ类
J5井	-2 768.09	21.0	0		Ⅱ类	Ⅲ类
J7井	-2 847.28	36.0	11.9		Ⅲ类	Ⅲ类
J8井	-2 828.65	11.8	0		Ⅰ类	Ⅲ类