| Anomalous wireline logging data caused by gas hydrate dissociation in the Shenhu area, northern slope of South China Sea | |
Wang Xiu-Juan1,2; Wu Shi-Guo1; Wang Ji-Liang1,3 ; Yang Sheng-Xiong4; Wang Zhen-Zhen1,3; Wang, XJ
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| 2013-08-01 | |
| 发表期刊 | CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION
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| ISSN | 0001-5733 |
| 卷号 | 56期号:8页码:2799-2807 |
| 文章类型 | Article |
| 摘要 | During the gas hydrate drilling expedition, GMGS-1 indicated that gas hydrate was discovered above the gas hydrate stability zone with a thickness of 10 meters at site SH3 in the Shenhu area, the northern slope of South China Sea. Gas hydrate saturations derived from observed pore-water chloride values in core samples reach the highest value of 26% in the pore space. Higher resistivity, lower P-wave velocity and slightly increasing density were identified. To explain the lower P-wave velocity, the Simplified Three-Phase Biot-type Equation (STPBE) was used to calculate the water-saturated P-wave velocity. At the depth of 195 m, the P-wave velocity from wireline logging is lower than that of the water-saturated velocity of the normal sediments. The Archie's parameters used to calculate gas hydrate saturation from resistivity were defined from the cross plot between density porosity and formation factor. Gas hydrate saturation estimated from resistivity using Archie equation with a = 1. 1 and m=2. 3 is about 5 similar to 20% of the pore space, with a maximum value of 26. 8%, which shows that the distribution of gas hydrate is heterogeneous in vertical. The dissociation of gas hydrate (the mixture of free gas and water) may be caused by drilling. Either the in-situ free gas or gas released from gas hydrate dissociation can cause the low well-log P-wave velocity. Because surface seismic data were acquired before drilling, synthetic seismograms generated using different P-wave velocities were compared with the seismic data, which can be used to identify the cause of the low P-wave velocity observed in the well log.; During the gas hydrate drilling expedition, GMGS-1 indicated that gas hydrate was discovered above the gas hydrate stability zone with a thickness of 10 meters at site SH3 in the Shenhu area, the northern slope of South China Sea. Gas hydrate saturations derived from observed pore-water chloride values in core samples reach the highest value of 26% in the pore space. Higher resistivity, lower P-wave velocity and slightly increasing density were identified. To explain the lower P-wave velocity, the Simplified Three-Phase Biot-type Equation (STPBE) was used to calculate the water-saturated P-wave velocity. At the depth of 195 m, the P-wave velocity from wireline logging is lower than that of the water-saturated velocity of the normal sediments. The Archie's parameters used to calculate gas hydrate saturation from resistivity were defined from the cross plot between density porosity and formation factor. Gas hydrate saturation estimated from resistivity using Archie equation with a = 1. 1 and m=2. 3 is about 5 similar to 20% of the pore space, with a maximum value of 26. 8%, which shows that the distribution of gas hydrate is heterogeneous in vertical. The dissociation of gas hydrate (the mixture of free gas and water) may be caused by drilling. Either the in-situ free gas or gas released from gas hydrate dissociation can cause the low well-log P-wave velocity. Because surface seismic data were acquired before drilling, synthetic seismograms generated using different P-wave velocities were compared with the seismic data, which can be used to identify the cause of the low P-wave velocity observed in the well log. |
| 关键词 | Gas Hydrate Saturation Dissociation P-wave Velocity Shenhu Area |
| 学科领域 | Geochemistry & Geophysics |
| DOI | 10.6038/cjg20130828 |
| URL | 查看原文 |
| 收录类别 | SCI |
| 语种 | 英语 |
| WOS研究方向 | Geochemistry & Geophysics |
| WOS类目 | Geochemistry & Geophysics |
| WOS记录号 | WOS:000323854200028 |
| WOS关键词 | ELASTIC PROPERTIES ; MARINE-SEDIMENTS ; WAVE ; VELOCITY ; WELL |
| WOS标题词 | Science & Technology ; Physical Sciences |
| 引用统计 | |
| 文献类型 | 期刊论文 |
| 条目标识符 | http://ir.qdio.ac.cn/handle/337002/16286 |
| 专题 | 海洋地质与环境重点实验室 |
| 通讯作者 | Wang, XJ |
| 作者单位 | 1.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Peoples R China 2.Minist Land & Resources, Key Lab Marine Hydrocarbon Resources & Environm G, Qingdao 266071, Peoples R China 3.Univ Chinese Acad Sci, Beijing 100049, Peoples R China 4.MLR, Guangzhou Marine Geol Survey, Guangzhou 510075, Guangdong, Peoples R China |
| 第一作者单位 | 中国科学院海洋研究所 |
| 推荐引用方式 GB/T 7714 | Wang Xiu-Juan,Wu Shi-Guo,Wang Ji-Liang,et al. Anomalous wireline logging data caused by gas hydrate dissociation in the Shenhu area, northern slope of South China Sea[J]. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,2013,56(8):2799-2807. |
| APA | Wang Xiu-Juan,Wu Shi-Guo,Wang Ji-Liang,Yang Sheng-Xiong,Wang Zhen-Zhen,&Wang, XJ.(2013).Anomalous wireline logging data caused by gas hydrate dissociation in the Shenhu area, northern slope of South China Sea.CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,56(8),2799-2807. |
| MLA | Wang Xiu-Juan,et al."Anomalous wireline logging data caused by gas hydrate dissociation in the Shenhu area, northern slope of South China Sea".CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION 56.8(2013):2799-2807. |
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