Measurement and Result of Soil Gas Radon and Soil Gas Mercury in the Exploration of Haihe Hidden Fault

In the exploration of the hidden Haihe fault,radon and mercury in soil gas were measured by using FG-3017 radon detector and XG-4 mercury analyzer.In this paper,based on the measurement results of 12 fault gas profiles,and integrating with the exploration results of artificial seismic prospecting,the relationship between anomalous site of fault gas and fault location is analyzed.Using the relationship between anomalous strength of fault gas and fault activity,the activity of Haihe fault is studied,thus the location and activity segmentation of the Haihe fault in Tianjin region are presented.This study shows that the method of fault gas detection can not only identify the preliminary location of fault,but also make preliminary segmentation of fault activity.The fault detected by the method of fault gas measurement is shown as a band.Through contrasting with exploration results of artificial seismic prospecting and analyzing,we find that the fault is located inside the band.According to the measurements of soil gas radon,the Haihe fault can be divided into east and west segments and the activity of the east segment of Haihe fault is stronger than that of the west segment.This is only a relative result,and it is difficult to judge whether the fault is active or not with this result.

Features of the fault system and its relationship with migration and accumulation of hydrocarbon in Liaodong Bay

The fault system of Liaodong Bay developed extensively under the control of the Tanlu Fault. The fault system can be grouped into strike-slip faults of grade Ⅰ, trunk faults of grade Ⅱand branch faults （induced faults） of grade Ⅲ respectively based on its developmental scale. The faults of grade Ⅰ and Ⅱwere deep, early and large while the faults of grade Ⅲwere shallow, late and small. The formation, evolution and distribution features played a significant role in controlling the migration of oil and gas in both horizontal and vertical directions. The fluid transfer in the fault system occurred in the process of faulting. The strike-slip and trunk faults moved actively forming predominant pathways for oil and gas migration. The branch faults, with weak activity, generally controlled the development of traps and were beneficial for the accumulation and preservation of oil and gas. The faults of grade Ⅰ and Ⅱ formed the major migration pathways for oil and gas, but their fault activity rates appeared to vary along their strikes. The zones with a relatively low fault activity rate might be favorable for oil and gas accumulation. When the activities of strike-slip, trunk, and branch faults came to a halt, the fault seal behavior had a vitally important effect on the accumulation of oil and gas. The controlling role of the fault over fluid distribution was further analyzed by calculating the fault activity quantitatively.

Activation characteristics analysis on concealed fault in the excavating coal roadway based on microseismic monitoring technique

In order to effectively monitor the concealed fault activation process in excavation activities, based on the actual condition of a working face containing faults with high outburst danger in Xin Zhuangzi mine in Huainan, China, we carried out all-side tracking and monitoring on the fault activation process and development trend in excavation activities by establishing a microseismic monitoring system. The results show that excavation activities have a rather great influence on the fault activation. With the working face approaching the fault, the fault activation builds up and the outburst danger increases; when the excavation activities finishes, the fault activation tends to be stable. The number of microseismic events are corresponding to the intensity of fault activation, and the distribution rules of microseismic events can effectively determine the fault occurrence in the mine. Microseismic monitoring technique is accurate in terms of detecting geologic tectonic activities, such as fault activations lying ahead during excavation activities. By utilizing this technique, we can determine outburst danger in excavation activities in time and accordingly take effective countermeasures to prevent and reduce the occurrence of outburst accidents.

Influencing factors and prevention measures of casing deformation in deep shale gas wells in Luzhou block,southern Sichuan Basin,SW China

Based on structural distribution and fault characteristics of the Luzhou block,southern Sichuan Basin,as well as microseismic,well logging and in-situ stress data,the casing deformation behaviors of deep shale gas wells are summarized,and the casing deformation mechanism and influencing factors are identified.Then,the risk assessment chart of casing deformation is plotted,and the measures for preventing and controlling casing deformation are proposed.Fracturing-activated fault slip is a main factor causing the casing deformation in deep shale gas wells in the Luzhou block.In the working area,the approximate fracture angle is primarily 10°-50°,accounting for 65.34%,and the critical pore pressure increment for fault-activation is 6.05-9.71 MPa.The casing deformation caused by geological factors can be prevented/controlled by avoiding the faults at risk and deploying wells in areas with low value of stress factor.The casing deformation caused by engineering factors can be prevented/controlled by:(1)keeping wells avoid faults with risks of activation and slippage,or deploying wells in areas far from the faulting center if such avoidance is impossible;(2)optimizing the wellbore parameters,for example,adjusting the wellbore orientation to reduce the shear force on casing to a certain extent and thus mitigate the casing deformation;(3)optimizing the casing program to ensure that the curvature radius of the curved section of horizontal well is greater than 200 m while the drilling rate of high-quality reservoirs is not impaired;(4)optimizing the fracturing parameters,for example,increasing the evasive distance,lowering the single-operation pressure,and increasing the stage length,which can help effectively reduce the risk of casing deformation.

Geochemical characteristics of soil gas in the Yanhuai basin,northern China

The geochemical backgrounds and origins of soil gases in the Yanhuai basin are discussed based on the regional seismogeological data and concentrations of Rn, Hg, CO2, H2, He and CH4 in soil gas measured at 422 investigating sites in field during September to October 2007. The geochemical background values of Rn, Hg, CO2, H2, He and CH4 are （8105.8±5937.4） Bq/m^3, （9.7±5.8） ng/m^3, （395.9±35.3）×10^-6, （4.0±2.3）×10^-6, （15.9±10.4）×10^-6 and （12.7±8.1）×10^-6, respectively. The geochemical backgrounds of the soil gases are higher in the eastern part of the Yanhuai basin. The main factors affecting the gasgeochemical backgrounds are gaseous origins, structure of the crust, faults, straaun and microbe activity. The higher values of gasgeochemical backgrounds in the eastern part are attributed to the existence of low-velocity zones in the upper crust, stronger tectonic activity and more contributions of Hg and He derived from the deep-earth and Rn origi- nated from granite, corresponding to stronger seismic activity. The results can be applied to identifying seismic precursor from monitoring data of gases in the studied area.

The Active Yakutat （Kula？） Plate and Its Southcentral Alaska Megathrust and Intraplate Earthquakes

Alaska geology and plate tectonics have not been well understood due to an active Yakutat plate, believed to be part of the remains of an ancient Kula plate, not being acknowledged to exist in Alaska. It is positioned throughout most of southcentral Alaska beneath the North American plate and above the NNW subducting Pacific plate. The Kula？ plate and its eastern spreading ridge were partially ＂captured＂ by the North American plate in the Paleocene. Between 63 Ma and 32 Ma, large volumes of volcanics erupted from its subducted N-S striking spreading ridge through a slab window. The eruptions stopped at 32 Ma, likely due to the Pacific plate fiat-slab subducting from the south beneath this spreading ridge. At 28 Ma, magmatism started again to the east; indicating a major shift to the east of this ＂refusing to die＂ spreading ridge. The captured Yakutat plate has also been subducting since 63 Ma to the WSW. It started to change to WSW fiat-slab subduction at 32 Ma, which stopped all subduction magmatism in W and SW Alaska by 22 Ma. The Yakutat plate subduction has again increased with the impact/joining of the coastal Yakutat terrane from the ESE about 5 Ma, resulting in the Cook Inlet Quaternary volcanism of southcentral Alaska. During the 1964 Alaska earthquake, sudden movements along the southcentral Alaska thrust faults between the Yakutat plate and the Pacific plate occurred. Specifically, the movements consisted of the Pacific plate moving NNW under the buried Yakutat plate and of the coastal Yakutat terrane, which is considered part of the Yakutat plate, thrusting WSW onto the Pacific plate. These were the two main sources of energy release for the E part of this earthquake. Only limited movement between the Yakutat plate and the North American plate occurred during this 1964 earthquake event. Buried paleopeat age dates indicate the thrust boundary between the Yakutat plate and North American plate will move in about 230 years, resulting in a more ＂continental＂ type megathrust earthquake for southcentral Alaska. There are, therefore, at least two different types ofmegathrust earthquakes occurring in southcentral Alaska： the more oceanic 1964 type and the more continental type. In addition, large ＂active＂ WSW oriented strike-slip faults are recognized in the Yakutat plate, called slice faults, which represent another earthquake hazard for the region. These slice faults also indicate important oil/gas and mineral resource locations.

断层逸出气体的δHe／Ar值变化与地震活动的关系

论述了１９９０年６月底至１９９１年１２月期间塔院断层气体中δＨｅ／Ａｒ值变化与几次地震的关系。从已获得的几次震例来看，有的地震δＨｅ／Ａｒ出现负异常，而有的出现正异常。δＨｅ／Ａｒ值具有较好的映震能力。