Reconstruction of the diagenesis of the fluvial-lacustrine- deltaic sandstones and its influence on the reservoir quality evolution-- Evidence from Jurassic and Triassic sandstones, Yanchang Oil Field, Ordos Basin

The reservoir quality of Jurassic and Triassic fluvial and lacustrine-deltaic sandstones of the Yanchang Oil Field in the Ordos Basin is strongly influenced by the burial history and facies-related diagenetic events. The fluvial sandstones have a higher average porosity (14.8%) and a higher permeability (12.7×10?3 ?m2) than those of the deltaic sandstones (9.8% and 5.8 ×10?3 ?m2, respectively). The burial compaction, which resulted in 15% and 20% porosity loss for Jurassic and Triassic sandstones, respectively, is the main factor causing the loss of porosity both for the Jurassic and Triassic sandstones. Among the cements, carbonate is the main one that reduced the reservoir quality of the sandstones. The organic acidic fluid derived from organic matter in the source rocks, the inorganic fluid from rock-water reaction during the late diagenesis, and meteoric waters during the epidiagenesis resulted in the formation of dissolution porosity, which is the main reason for the enhancement of reservoir-quality.     

Experimental research on reservoir sensitivity to stress and impacts on productivity in Kela 2 Gas Field

Kela 2 Gas Field, with high formation pressure (74.35MPa), high pressure coefficient (2.022) and difficulty of potential test and evaluation, is the largest integrated proved dry gas reservoir in China so far and the principal source for West-East Gas Development Project. In order to correctly evaluate the elastic-plastic deformation of rocks caused by the pressure decline during production, some researches, as the experiment on reservoir sensitivity to stress of gas filed with abnormal high pressure, are made. By testing the rock mechanic properties, porosities and permeabilities at different temperature and pressure of 342 core samples from 5 wells in this area, the variations of petro-physical properties at changing pressure are analyzed, and the applicable inspection relationship is concluded. The average productivity curve with the reservoir sensitivity to stress is plotted on the basis of the research, integrated with the field-wide productivity equation. The knowledge lays a foundation for the gas well productivity evaluation in the field and the gas field development plan, and provides effective techniques and measures for basic research on the development of similar gas fields.     

中风化花岗岩地区洁净厂房地面随机振动响应分析

现代高科技生产设备对振动的要求越来越严格,在某洁净厂房的建设过程中,由于生产线扩大,需要将生产厂房的部分非微振区改建为微振区。本文针对生产厂房整体结构在地面环境随机振动下的微振动问题,建立了生产厂房的有限元动力分析模型。以实测的自由场地微振动加速度时程为激励,对结构系统的随机振动响应情况进行分析。并对3种工况情况下,结构特定节点的振动情况进行对比分析,表明加密柱网能够有效减小结构振动,从而为工程设计提出合理建议。     

The Advance of Petrologic Mechanism of Dehydration Embrittlement in Intermediate-depth Earthquakes

The mechanisms of intermediate depth earthquakes were always attracting extensive researches of interest. Among various hypotheses about the mechanisms, the close relationship between the dehydration embrittlement and earthquakes is generally accepted. The intermediate-depth earthquakes in subducting slabs occur mainly in two distinct layers, corresponding with the dehydration respectively in the hydrous meta-basalts and the serpentinite layers. In the past decades, theory researches, interpretations of seismic data and laboratory experiments have been widely adopted as the major approaches to attest the hypothesis of dehydration embrittlement. However, in the latest ten years, pseudotachylytes and some brittle structures have been discovered in paleo-subduction zones like Alps, shedding a light for a new way to study intermediate-depth earthquakes.     

民和盆地窑街煤田油页岩沉积环境分析及开发前景预测

通过岩芯钻井资料的综合分析,对民和盆地窑街煤田油页岩沉积特征、层序地层、古地理演化和成矿规律进行了研究。结果表明,油页岩段主要为水进体系域和高水位体系域发育时期,油页岩主要形成于沼泽和浅湖-半深湖相的沉积环境中。其中油四层油页岩品质较好,平均含油率>8%,属于湖泊沼泽相,具有良好的工业品位。研究区油页岩具有中含油率高灰分的特征,资源总储量为2.3×108t,具有良好的开发前景。     

1998-2012年青藏高原TRMM 3B43降水数据的校准

运用1998-2012年青藏高原的TRMM 3B43降水数据以及气象台站实测降水数据,对比分析了青藏高原地区TRMM 3B43降水数据偏差分布规律。结果表明:(1) TRMM 3B43降水数据在青藏高原地区存在明显误差,特别是降水量大的地区和月份,偏差量较大。(2)青藏高原地区TRMM 3B43降水数据偏差分布与海拔、经纬度、降水量存在密切的关系。用偏差分布规律,加法修正法结合随机森林算法对青藏高原地区TRMM 3B43降水数据进行了校准。经过校准之后,数据精度得到显著提高,有效增加了数据的可用性,多年月平均数据决定系数R²最大可达到0.9(3、10月),最小也接近于0.5(12月),效率系数E均为正值,最大可达到90(3、10月);多年季平均和多年平均降水数据中除了第一季度结果稍差外(决定系数R²为0.58),其余数据校准效果均较好。     

Bayesian Spatial Modelling of Gamma Ray Count Data

Gamma ray logging is a method routinely employed by geophysicists and environmental engineers in site geology evaluations. Modelling of gamma ray data from individual boreholes assists in the local identification of major lithological changes; modelling these data from a network of boreholes assists with lithological mapping and spatial stratigraphic correlation. In this paper we employ Bayesian spatial partition models to analyse gamma ray data spatially. In particular, a spatial partition is defined via a Voronoi tessellation and the mean intensity is assumed constant in each cell of the partition. The number of vertices generating the tessellation as well as the locations of vertices are assumed unknown, and uncertainty about these quantities is described via a hierarchical prior distribution. We describe the advantages of the spatial partition modelling approach in the context of smoothing gamma ray count data and describe an implementation that may be extended to the fitting of a more general model than a constant mean within each cell of the partition. As an illustration of the methodology we consider a data set collected from a network of eight boreholes, which is part of a geophysical study to assist in mapping the lithology of a site. Gamma ray logs are linked with geological information from cores and the spatial analysis of log data assists with predicting the lithology at unsampled locations.