古盐湖卤水温度对钾盐沉积的控制作用探讨

古盐湖卤水的温度对钾盐沉积的控制作用的定量研究是钾盐成矿机理分析的重点和难点。本文分析和测试陕北盐盆奥陶系马家沟组、四川盆地三叠系嘉陵江组、云南兰坪-思茅盆地白垩系及老挝沙空那空盆地白垩系等八个含盐系的石盐岩中的流体包裹体,并利用均一温度计算了古盐湖的蒸发速率。若以老挝白垩纪时盐湖的蒸发速率为标准值100,陕北奥陶纪、四川三叠纪、云南白垩纪的蒸发速率标准值分别为54、68和90,而目前在老挝和云南白垩系都找到了一定规模的钾盐矿,因此高温(气温及水温)是盐湖成钾的有利条件,在卤水演化成钾的过程中可以起到重要的"催化"作用。

从成像到反演：叠前深度偏移的理论、实践与发展

早期地震偏移的目标是通过寻找地下反射面的位置来落实井位。经过半个多世纪的发展,地震偏移技术日趋精深。特别是随着叠前深度偏移的广泛应用,地震偏移结果为解释人员进行精细的地质构造描述提供了较为可靠的资料。梳理并总结了叠前深度偏移的一些重要理论和应用现状,以及为满足生产需求所发展起来的一些方法和技术。从真振幅偏移理论出发,介绍了生产中常用的Kirchhoff偏移、射线束偏移和单程波偏移等叠前深度偏移方法,特别讨论了逆时偏移的理论和应用。介绍了逆时偏移研究中涉及的一些重要技术方法,如叠前道集输出、各向异性偏移、非弹性衰减补偿、组合炮记录偏移、成像中的鬼波补偿、多次波成像等等。讨论了最小二乘偏移的理论、方法以及其面临的主要困难,分析了偏移反褶积和最小二乘偏移的区别。全波形反演是近十年来勘探地球物理研究的热点,真振幅偏移理论可以作为联系成像与反演的纽带,全波形反演的算法核心仍然是基于反演的真振幅逆时偏移。对全波形反演的一些重要问题,如低频缺失、走时反演、反射波反演、多参数反演等方面进行了探讨,介绍了该领域所取得的一些新进展。自动化全波形反演大幅简化了处理流程、降低了工作成本、提高了成像精度。更重要的是,这一技术有助于反演出高精度的定量地质模型。

CSI：基于压缩感知的高精度高效率地震资料采集技术

介绍了CSI(Compressive Seismic Imaging)技术。该技术是基于压缩感知理论所开发出的一整套地震资料采集和处理综合技术,主要包括非规则最优化采样设计、地震信号的稀疏化处理、基于稀疏反演的数据重构及同时震源分离等内容。CSI利用非规则最优化设计和独立同时震源作业,极大地提高了采集效率,缩短了采集周期,从而以较低成本完成高品质、高密度的三维地震资料采集。在地震资料处理过程中,通过信号分离与数据重建来高保真地恢复叠前地震信号。海底节点、海上拖缆和陆地可控震源等生产项目中的应用结果表明,与宽频带处理以及叠前深度偏移技术相结合,CSI提供了高质量、高精度的地下成像结果。

正断层断距纵剖面图及其运动学:概念模型与地质实例(英文)

(中译文)断距纵剖面图(T-H图)是指以断层的垂直断距为横轴、以地层或地质年龄为纵轴所绘制的随地层或地质年龄所变化的断距分布图。断距纵剖面图为确定正断层类型、断层形成时间和断层的纵向演化史提供了一个简单迅捷的工具。概念模型表明,断距纵剖面图可以明确无误地区分出简单后沉积型正断层、后沉积拱顶拉张型正断层、同沉积生长型正断层及其复合型正断层。简单后沉积型正断层的断距不随地层年龄的变化而变化,其断距纵剖面图为一垂直线段。后沉积拱顶拉张型正断层的断距随地层年龄的增大而减小并趋向零值,同沉积生长型正断层的断距随地层年龄的增大而增大,复合型正断层则具其组合型断距纵剖面形态。除简单后沉积型正断层外,断距纵剖面图中的最大断距点代表了该断层的起始形成年代。

SegNet-based first-break picking via seismic waveform classification directly from shot gathers with sparsely distributed traces

Manually picking regularly and densely distributed first breaks(FBs)are critical for shallow velocitymodel building in seismic data processing.However,it is time consuming.We employ the fullyconvolutional Seg Net to address this issue and present a fast automatic seismic waveform classification method to pick densely-sampled FBs directly from common-shot gathers with sparsely distributed traces.Through feeding a large number of representative shot gathers with missing traces and the corresponding binary labels segmented by manually interpreted fully-sampled FBs,we can obtain a welltrained Seg Net model.When any unseen gather including the one with irregular trace spacing is inputted,the Seg Net can output the probability distribution of different categories for waveform classification.Then FBs can be picked by locating the boundaries between one class on post-FBs data and the other on pre-FBs background.Two land datasets with each over 2000 shots are adopted to illustrate that one well-trained 25-layer Seg Net can favorably classify waveform and further pick fully-sampled FBs verified by the manually-derived ones,even when the proportion of randomly missing traces reaches50%,21 traces are missing consecutively,or traces are missing regularly.

Inverse spectral decomposition using an I_p-norm constraint for the detection of close geological anomalies

An important application of spectral decomposition(SD)is to identify subsurface geological anomalies such as channels and karst caves,which may be buried in full-band seismic data.However,the classical SD methods including the wavelet transform(WT)are often limited by relatively low time-frequency resolution,which is responsible for false high horizonassociated space resolution probably indicating more geological structures,especially when close geological anomalies exist.To address this issue,we impose a constraint of minimizing an lp(0<p<1)norm of time-frequency spectral coefficients on the misfit derived by using the inverse WT and apply the generalized iterated shrinkage algorithm to invert for the optimal coefficients.Compared with the WT and inverse SD(ISD)using a typical l1-norm constraint,the modified ISD(MISD)using an lp-norm constraint can yield a more compact spectrum contributing to detect the distributions of close geological features.We design a 3 D synthetic dataset involving frequency-close thin geological anomalies and the other3 D non-stationary dataset involving time-close anomalies to demonstrate the effectiveness of MISD.The application of 4 D spectrum on a 3 D real dataset with an area of approximately 230 km2 illustrates its potential for detecting deep channels and the karst slope fracture zone.

Petroleum geoscience in Norden - exploration, production and organization

Offshore exploration in Norway and Denmark-in the North Sea, the Norwegian Sea and the Barents Sea-has involved drilling about 850 wildcat wells, resulting in about 300 oil and gas finds, of which 84 are fields with production. The recoverable resources of all these finds total about 65 billion barrels of oil equivalent. Almost all these hydrocarbons come from a Jurassic source and the main reservoirs and traps are Jurassic sandstones in fault blocks and Paleocene sandstones or Cretaceous chalks in gentle domes. The article describes four major fields-Ekofisk, Gullfaks, Ormen Lange and SnФhvitto illustrate some of the many challenges in developing and producing the hydrocarbons. Elsewhere in Norden, there has been much less exploration. Drilling results have mostly been negative in mainland Sweden, onshore Denmark, onshore Svalbard and on- and offshore West Greenland. Minor oil finds have been made in Palaeozoic rocks in the Baltic Sea. The first wells have recently been drilled off the Faroe Islands, resulting in one discovery. No drilling has taken place on- or offshore East Greenland. As a result of the hydrocarbon activities in Norway and Denmark, petroleum geoscience there has flourished, with 2000 geoscientists currently employed in the industry, many technical innovations made, a wealth of publically available information and a great increase in the understanding of the geology.

Deep resistivity "turnover" effect at oil generation "peak" in the Woodford Shale,Anadarko Basin,USA

The Devonian Woodford Shale in the Anadarko Basin is a highly organic,hydrocarbon source rock.Accurate values of vitrinite reflectance(R_o)present in the Woodford Shale penetrated by 52 control wells were measured directly.These vitrinite reflectance values,when plotted against borehole resistivity for the middle member of the Woodford Shale in the wells,display a rarely reported finding that deep resistivity readings decrease as R_o increases when R_o is greater than 0.90%.This phenomenon may be attributed to that aromatic and resin compounds containing conjugated pi bonds generated within source rocks are more electrically conductive than aliphatic compounds.And aromatic and resin fractions were generated more than aliphatic fraction when source rock maturity further increases beyond oil peak.The finding of the relationship between deep resistivity and R_o may re-investigate the previously found linear relationship between source rock formation and aid to unconventional play exploration.

China's National Oil Company and Energy Security

Demand and shortage of oil in China Rapid economic development requires huge energy Since the early 1980s, China has consistently been the most rapidly growing economy on earth, sustaining an average annual growth

美国中西部注水远程触发地震增强

近在美国中西部地震活动性的急剧增加可能与深部污水的注入有关。本文证明了有疑似人为地震的地方更易受到大型远震地震波带来的自然瞬态应力的触发。触发敏感性的增强表明了存在断层加载和潜在的高流体压力。远程触发灵敏度能清晰地感应到在注入开始和地震活动开始之间有长时间的推迟,且该区域6到20个月内持续发生了中小地震。因此,在诱发地震区域内,触发可能作为一种指示器,来表明流体注入使断层系统进入临界状态。

Comparison of lattice and pseudo 3D numerical simulation of tip screen out operation

Hydraulic fracturing(HF)is a commonly used technique to stimulate low permeability formations such as shale plays and tight formations.However,this method of well stimulation has also been used in high permeable unconsolidated sandstone formations to bypass near-wellbore formation damage and prevent sand production at some distance apart from the wellbore wall.The treatment is called frac-pack completion,where a short length but wide width fracture is formed by injecting aggressive concentrations of proppant into the fracture plane.This operation is known as tip screen-out(TSO).Detailed design of fluid and proppant,including an optimal pump schedule,is required to achieve satisfactory TSO.In this study,we first assess the lattice-based numerical method's capabilities for simulating hydraulic fracturing propagation in elastoplastic formation.The results will be compared with the same case simulation results using a pseudo 3D(P3D)model and analytical model.Second,we explore the Nolte(1986)design for frac-pack and TSO treatment using lattice-based software and the P3D model.The results showed that both models could simulate the hydraulic fracturing propagation in soft formation and TSO operation,while some differences were observed in generated geometry,the tip screenout time and net pressure profiles.The results are presented.It was noted that fracture propagation regime(viscosity/toughness),nonlocality and nonlinearity had an influence on the different geometries.The advantages of each model will be discussed.

Elimination of LWD (Logging While Drilling) Tool Modes Using Seismoelectric Data

Borehole acoustic logging-while-drilling (LWD) for formation evaluationhas become an indispensable part of hydrocarbon reservoir assessment [F. Citt ´a, C. Rus-sell, R. Deady and D. Hinz, The Leading Edge, 23 (2004), pp. 566-573]. However,the detection of acoustic formation arrivals over tool mode contamination has beena challenging problem in acoustic LWD technology. In this paper we propose a newmethod for separating tool waves from formation acoustic waves in acoustic LWD.This method is to measure the seismoelectric signal excited by the LWD acoustic waves.The LWD tool waves which propagate along the rigid tool rim can not excite any elec-tric signal. This is due to the effectively grounding of the drill string during the LWDprocess makes it impossible to accumulate any excess charge at the conductive tool —borehole fluid interface. Therefore, there should be no contribution by the tool modesto the recorded seismoelectric signals. To theoretically understand the seismoelectricconversion in the LWD geometry, we calculate the synthetic waveforms for the multi-pole LWD seismoelectric signals based on Pride’s theory [S. R. Pride, Phys. Rev. B, 50(1994), pp. 15678-15696]. The synthetic waveforms for the electric field induced by theLWD-acoustic-wave along the borehole wall demonstrate the absence of the tool mode.We also designed the laboratory experiments to collect simulated LWD monopole anddipole acoustic and seismoelectric signals in a borehole in sandstone. By analyzing thespectrum of acoustic and electric signals, we can detect and filter out the differencebetween the two signals, which are the mainly tool modes and noise.

Theoretical and Experimental Studies of Seismoelectric Conversions in Boreholes

We present theoretical and experimental studies on the effects of formationproperties on seismoelectric conversions in fluid-filled boreholes. First, we derive thetheoretical formulations for seismoelectric responses for an acoustic source in a borehole.Then, we compute the electric fields in boreholes penetrating formations withdifferent permeability and porosity, and then we analyze the sensitivity of the convertedelectric fields to formation permeability and porosity. We also describe the laboratoryresults of the seismoelectric and seismomagnetic fields induced by an acousticsource in borehole models to confirm our theoretical and numerical developmentsqualitatively. We use a piezoelectric transducer to generate acoustic waves and a pointelectrode to receive the localized seismoelectric fields in layered boreholes and theelectric component of electromagnetic waves in a fractured borehole model. Numericalresults show that the magnitude ratio of the converted electric wave to the acousticpressure increases with the porosity and permeability increases in both fast and slowformations. Furthermore, the converted electric signal is sensitive to the formationpermeability for the same source frequency and formation porosity. Our experimentsvalidate our theoretical results qualitatively. An acoustic wave at a fracture intersectinga borehole induces a radiating electromagnetic wave.