Petrophysical properties assessment using wireline logs data at well#3 of Srikail gas field,Bangladesh

This study focused on the quantitative analysis of the petrophysical parameters in characterizing the reservoir properties of the Srikail gas field using multi-scale wireline logs. Petrophysical parameters (shale volume, porosity, water saturation and hydrocarbon saturation) were estimated from the combination of gamma ray log, resistivity log, density log and neutron log for three hydrocarbon (gas)-bearing zones at well#3. At the first time, log records at 0.1 m and 0.2 m intervals were read for this study. Result showed the average shale volume is 21.07%, 53.67% and 51.71% for zone-1, zone-2 and zone-3, respectively. For these zones, the estimated average porosity was 35.89%, 29.83% and 28.76%, respectively. The average water saturation of 31.54%, 16.83% and 23.39% and average hydrocarbon saturation of 68.46%, 83.17% and 76.61% were calculated for zone-1, zone-2 and zone-3, respectively. Thus zone-2 is regarded the most productive zone of well#3. It was found that the values of some parameters (porosity, hydrocarbon saturation and permeability) are higher than the existing results. Therefore, this study confirmed that the log reading at minute/close interval provides better quantitive values of the reservoir’s petrophysical properties. It is expected that this result will contribute to the national gas field development program in future.©2022 China Geology Editorial Office.     

声波测井中首波与次首波的理论研究

本文讨论了裸眼井中由点状声源激发的首波与次首波问题,认为:首波与次首波分别是以地层纵波速度V_c和地层横波速度V_s传播的几何衰减波。同时给出了泄漏波的解析式,而泄漏纵波和泄漏横波的截止频率分别为远场处的首波与次首波的传播特征频率。     

双侧向测井曲线形状的影响因素研究

为研究井眼、层厚和侵入带对双侧向测井曲线形状的影响,利用正演模拟技术分别对各种常见情况计算了双侧向曲线。结果显示,井径增大使曲线变化趋缓,且幅度降低;泥浆电阻率与地层电阻率反差的增加则使曲线棱角更加分明;层厚在1m以下时高侵层无双尖峰现象,2m以上厚层曲线形态变化不大,低侵层厚度〉4m时,曲线在地层中部开始出现平顶;侵入带厚度较小时,曲线的侵入特征更明显,厚度大时趋于无侵入高阻层的形态;侵入带与地层和围岩的电阻率对比决定曲线的形状和幅度。     

北京东北旺-小汤山断裂存在的证据

对位于北京市西北侧的东北旺-小汤山断裂是否存在、走向与活动性的认识长期以来一直存在较大差异。通过新近开展的北京城市活断层探测工作中的物探数据与钻孔联合剖面分析,认为东北旺-小汤山断裂是存在的,为一条隐伏断裂,长约40km,走向NNE,倾向SE。以南口-孙河断裂为界,该断裂东北段称之为小汤山断裂,西南段称之为东北旺断裂。小汤山断裂的最新活动时代为早更新世或中更新世早期,中更新世中期以来不活动。东北旺断裂的最新活动时代为中更新世末期,晚更新世以来不活动     

一种基于遗传算法的测井曲线高分辨率处理方法

测井曲线高分辨率处理是提高薄层测井解释精度的一条重要途径.在纵向分辨率匹配技术基础上,利用遗传算法进行测井曲线分辨率处理：先由遗传算法在频率域确定滤波器,然后使用分辨率匹配技术提高测井曲线分辨率.利用该方法对中原油田和新疆塔河油田多口井的八侧向、深感应、自然伽马等多种方法的测井数据进行处理,测井曲线的分辨率得到明显提高,使得其更加适合薄层高分辨率处理解释的需要.     

Looking into a volcanic area: An overview on the 350 m scientific drilling at Colli Albani (Rome,Italy)

A 350 m deep borehole was drilled in the Colli Albani volcanic district (Central Italy) in order to: understand the shallow crust structure beneath the volcanic complex; characterize the rock physical properties especially through in-situ measurements and, afterward, laboratory experiments; assess the local present-day stress field; install a broad-band seismometer at depth. The borehole is located adjacent to the western rim of the Tuscolano–Artemisio caldera, where several phenomena of unrest recently occurred. In 1989–90 a seismic swarm affected this area and a related uplift was recognized. In addition, high gas concentrations (mainly CO₂ and H₂S), in aquifers and soils, caused illnesses and casualties among inhabitants and animals in the past.     

基于Android系统的测震台网日志管理平台设计

为实现测震台网日志产出的统一化和标准化,提高工作效率,减轻人员负担,基于Android系统,设计开发测震台网日志管理平台,用户可通过手机APP完成地震速报、编目及系统运维日志的增、删、改、查和统计操作。该平台的应用解决了日志管理散乱、查询不便等难题,可为测震台网统一化管理提供支持。     

Compensating elastic transmission losses for P-wave attenuation estimation from sonic logs

The decay of seismic amplitude is caused by a variety of physical phenomena that can be divided broadly into elastic transmission losses (including geometrical spreading, interface transmission losses and scattering attenuation) and intrinsic attenuation, where wave energy is converted into heat due to viscous friction. The so-called statistical averaging method is currently considered as the most advanced sonic wave attenuation estimation method, and there exist various implementations of this method. But the way elastic transmission losses – that mask the true intrinsic attenuation – are compensated for appears to be an issue and in some cases this correction has been overlooked. In this paper, we revisit the statistical averaging method for intrinsic attenuation estimation with particular focus on the role of elastic transmission losses. Through synthetic examples, we demonstrate the importance of compensating for elastic transmission losses even if the variation of velocity and density with depth is not notable. Our implementation of the method uses finite-difference simulations thereby providing a versatile and accurate way to generate synthetic seismograms. We use a combination of elastic and viscoelastic finite-difference simulations to demonstrate the significant error without accurate compensation of the elastic transmission losses. We apply our implementation of the method to sonic waveforms acquired in an exploration well from Browse basin, Australia. The resulting intrinsic attenuation estimates are indeed indicative of gas-saturated zones identified from petrophysical analysis in which viscous friction are thought to be of importance.     

Between plate and salt tectonics—New stratigraphic constraints on the architecture and timing of the Dead Sea basin during the Late Quaternary

The Dead Sea is an extensional basin developing along a transform fault plate boundary. It is also a terminal salt basin. Without knowledge of precise stratigraphy, it is difficult to differentiate between the role of plate and salt tectonics on sedimentary accumulation and deformation patterns. While the environmental conditions responsible for sediment supply are reasonably constrained by previous studies on the lake margins, the current study focuses on deciphering the detailed stratigraphy across the entire northern Dead Sea basin as well as syn and post-depositional processes. The sedimentary architecture of the late Quaternary lacustrine succession was examined by integrating 851 km of seismic reflection data from three surveys with gamma ray and velocity logs and the stratigraphic division from an ICDP borehole cored in 2010. This allowed seismic interpretation to be anchored in time across the entire basin. Key surfaces were mapped based on borehole lithology and a newly constructed synthetic seismogram. Average interval velocities were used to calculate isopach maps and spatial and temporal sedimentation rates. Results show that the Amora Formation was deposited in a pre-existing graben bounded by two N-S trending longitudinal faults. Both faults remained active during deposition of the late Pleistocene Samra and Lisan Formations—the eastern fault continued to bound the basin while the western fault remained blind. On-going plate motion introduced a third longitudinal fault, increasing accommodation space westwards from the onset of deposition of the Samra Formation. During accumulation of these two formations, sedimentation rates were uniform over the lake and similar. High lake levels caused an increase in hydrostatic pressure. This led to salt withdrawal, which flowed to the south and southwest causing increased uplift of the Lisan and En Gedi diapirs and the formation of localized salt rim synclines. This induced local seismicity and slumping, resulting in an increased thickness of the Lisan succession within the lake relative to its margins. Sedimentation rates of the Holocene Ze'elim Fm were 4–5 times higher than before. The analysis presented here resolves central questions of spatial extent and timing of lithology, deposition rates and their variability across the basin, timing of faulting at and below the lake floor, and timing and extent of salt and plate tectonic phases and their effect on syn and post-depositional processes. Plate tectonics dictated the structure of the basin, while salt tectonics and sediment accumulation were primarily responsible for its fill architecture during the timeframe examined here.