稳定煤岩地层的钻井液体系研究

当下我国石油行业急需多种技术,尤其是具有较优的常规性能(如流变性、滤失性)的钻井液。本文通过综合考虑成本和环境保护因素,采用水基钻井液体系,初步确立了实验所用钻井液体系:4%~5%膨润土+0. 2%中分子降失水剂JNP(聚合物)+0. 5%~1. 5%LV-CMC+2%~3%磺化酚醛树脂+1%~1. 5%降粘降滤失剂Redu^2+2%~3%干粉/磺化沥青+1%乳化沥青,通过钻井液流变性、滤失量以及抑制性和封堵性实验等,对钻井液体系性能进行表征,优选出这种适用于煤岩地层的稳定井壁钻井液体系。

考虑割理面时煤层造斜段坍塌压力变化规律研究

在武威盆地太原组水平井钻进作业时,依据井史数据调研发现,煤层段卡钻、井径扩大、钻具掉落等井壁坍塌导致的井下复杂事故发生,严重制约了煤层气勘探开发的进程。由于煤岩交错割理性(面割理、端割理)弱结构面发育,使煤岩在造斜钻进时井壁破坏在力学上呈现为非连续性和非均质性。建立了考虑弱面的井壁坍塌数学模型。通过分析煤岩矿物成分、微宏观结构,确定煤岩井壁坍塌为力学机制占主导因素,得出割理导致的煤岩碎裂成块是井壁失稳的根本原因,建议在后续煤层钻井中优化井眼轨迹、优化钻井液性能进行井壁防塌,并引入煤岩井壁坍塌实时监测系统。

贵州省陆相成煤环境特征分析

为了最大限度客观反映贵州省陆相成煤环境典型矿床的基本地质特征,在收集以往地质勘查资料及现场踏勘了解现状的基础上,合理确定煤炭沟煤矿和罗州煤矿采样位置及数量,并对煤岩样进行分析。研究得出,2个煤矿的样品固结较好,均能代表陆相成煤环境特征,具有相应的煤类特征。同时,通过实地调查选定赫章县可乐乡作为实测剖面位置,采集并保存含煤岩系地层中具有代表性的不同规格的岩石、煤炭、化石标本和钻孔样品。结果表明,宣威组主要是由灰色细砂岩、粉砂岩、粉砂质泥岩、泥质粉砂岩、黏土岩及煤层组成的韵律层,较明显地反映了含煤地层宣威组(P_(3)x)的沉积环境特征,为一套陆相地层的含煤沉积建造。

岩溶陷落柱的形成机理

通过对地壳运动作用力所产生的褶皱、断裂、节理等地质构造现象的观察，结合对具有岩溶现象地区煤岩地层间接触关系特征的研究，论述了岩溶陷落柱的形成机理，为陷落柱的分析、探测和综合治理提供了新的理论依据。

浅析岩溶陷落柱的形成机理

通过对矿井生产中所暴露的褶皱、断裂、节理等地质构造现象的观察分析,论述了岩溶陷落柱的形成机理,初步摸清了陷落柱的一般规律,为正确指导生产提供了科学依据。

EXPERIMENTAL RESEARCH ON EFFECTS OF INITIAL JOINTS ON SURFACE DISPLACEMENT DUE TO COAL MINING

Surface displacement caused by underground coal mining is influenced by many factors such as the depth and thickness of the coal seam and joints in overburben rocks. Extensive efforts have been devoted to the ground surface displacement. Nevertheless, the joints have not been taken into consideration for a long time. In fact, there exist numerous joints and cracks in rocks.As a result, the joints in overburden rocks have to be taken into account. The joints in rocks can be treated as initial damage theoretically. In this paper, two kinds of physical model, one containing no initial joints and anotber containing some initial joints, are employed to systematically investigate effecs of initial joints on surface subsidence. Moreover, within the framework of damage mechanics, the statistical relationships between the characteristic value for surface displacement and damage variable are obtained.

Analytical and numerical method assessing the risk of sinkholes formation in mining areas

Voids, which have not been liquidated and associated with shallow mining excavations, pose a serious threat of potential formation of sinkholes. This threat is connected with the loss of stability of voids that had been formed as a result of mining operations in the deeper strata. Taking into account the impact of lower coal seams mining on shallow excavations and based on the example of a region that had been intensely exploited, this paper proposes a methodology for analysing the stability of shallow mine voids in the rock mass. Deformations in the excavation region were calculated by using FLAC2D computer pro- gram and assigning the Coulomb-Mohr model to the rock mass. Based on the numerical analysis, this paper evaluated the stability of the void in the event of a roof support fall. The results indicate the like- lihood of void formation. Based on the Budryk-Knotbe theory, the deformations of rock mass and sand- stone strata in the roof of the void, which had been caused by mining exploitation in consecutive years, were calculated. The results of numerical calculations and analyses were compared with the limit defor- mations values of sandstone in tension. It is concluded that the exploitations cause the void to break down. The proposed method can forecast the discontinuous deformations threats in the areas that have undergone shallow undermining exploitation and the areas of underground urban.

SHRIMP dating of volcanic rock in the Zhangwu-Heishan area, West Liaoning province, China: Its relationship with coal-bearing strata

The Zhangwu-Heishan area is located to the east of the Fuxin-Yixian Basin and is mostly covered with volcanic rock. At various periods, different geologists had varying opinions about their age and periods of volcanic eruptions, especially on sequences between volcanic rock and main coal-bearing strata, which affect the direction of searching for coal, as well as prospecting the entire research area. During our study, we carried out detailed field investigations in this research area： observed and recorded the main representative outcrops of volcanic rock. We collected over 20 volcanic rock samples and tested the Sensitive High Resolution Ion Microprobe II （SHRIMP If） U-Pb isotope age of 11 samples. The age of our volcanic rock samples ranged between 56.0 ± 2.9 and 132.3 ± 2.3 Ma. After taking earlier investigations into consideration, we concluded that, except for a suite of paleogene olivine basalt, the volcanic rock in the Zhangwu-Heishan area is younger than the coal-bearing Shahai Formation. It is therefore most unlikely to find coal seams equivalent to those of the early Cretaceous Shahai Formation in Fuxin Basin below vol- canic rock.

SEDIMENTARY-STRUCTURAL EVOLUTION OF A STRIKE-SLIP COAL BASIN IN CENTRAL YUNNAN,CHINA

The Kebao coal basin is located at the middle segment of the Xiaojiang fault zone in the central part of Yunnan Province. The coal-bearing strata of Tertiary age are made up of alluvial fan-lacustrine-swamp genetic sequences. Sinistral strike-slip motion of the N-S trending fault zone has created a locally transtensional or transpres sional tectonic environment, giving rise to the relative movement of fault blocks in the basement, and the development of a strike-slip coal basin at the surface. Based on de tailed sedimentary-structural analyses, the paper proposes geodynamic models for the coal basin formation and its deformation.

Distribution pattern of front abutment pressure of fully-mechanized working face of soft coal isolated island

The front abutment pressure of a fully-mechanized workface of 11061 soft coal isolated island of Liangbei Coal Mine was measured and studied using a self-developed mining-induced stress monitoring system associated with electromagnetic radiation technology, and the effects of abutment pressure distribution on strata behavior we discussed. The results indicate that the miningdnduced influencing distance advanced at the fully-mechanized working face of soft coal isolated island is larger than that at the gen- eral working face at the isolated island, besides the fracture zone in front of working face was widened to some extent, and the influencing range caused by relaxations on both roadways became bigger with the advancing working face. Moreover, it can be indicated that mining has significant effect on strata behav- ior of fully-mechanized working face of soft coal isolated island, which is mostly distributed in the area of stress concentration. The research results have an important reference value for revealing the distribution pattern of the front abutment pressure of a fully-mechanized working face of soft coal isolated island, and controlling the coal-rock dynamic disaster occurrence under similar mining conditions.

Variation in the temperature field of rocks overlying a high-temperature cavity during underground coal gasification

High temperature affects rocks in a way that changes the physical and mechanical properties of them. The temperature field in rock overlying a high temperature zone has been estimated using experimental research on thermal conductivity of the overlying strata. Numerical analysis software was used to esti- mate rock thermal conductivity at different temperatures. These estimates were then used with COMSOL Multiphysics to perform a numerical analysis with the heat conduction model. The results show that rock thermal conductivity decreases as the temperature increases and that various lithologies show similar behavior. The thermal conductivity of each rock type differs from the others at a given temperature. Exact values for the temperature distribution in the overlying strata during the process of underground coal gasification are obtained from the numerical simulation. The temperature in the rock changes with the height and direction from the gasifier. Temperature gradients vary for different types of rock. This result provides an important reference for further study of the strength of overlying strata subject to the process of underground coal gasification.

Relationship between the rock mass deformation and places of occurrence of seismological events

Static effort of rock mass very rarely causes of rock burst in polish coal mines. Rock bursts with source in the seismic tremor within the roof rock layers are prevailing. A seismic tremor is an effect of rupture or sliding in roof layers above the exploited panel in coal seam, sometime in a distance from actual exploitation. Sliding, as a rule occurs in fault zone and tremors in it are expected, but monolithic layer rupture is very hard to predict. In a past few years a practice of analyzing state of deformation in high energy seismic tremors zones has been employed. It let gathering experience thanks to witch determination of dangerous shape of reformatted roof is possible. In the paper some typical forms of roof rocks deformations leading to seismic tremor occurrence will be presented. In general these are various types of multidirectional rock layers bending. Real examples of seismic events and rock bursts will be shown.

Roadway failure and support in a coal seam underlying a previously mined coal seam

The influence of an upper,mined coal seam on the stability of rock surrounding a roadway in a lower coal seam is examined.The technical problems of roadway control are discussed based on the geological conditions existing in the Liyazhuang Mine No.2 coal seam.The stress distribution and floor failure in the lower works after mining the upper coal is studied through numerical simulations.The failure mechanism of the roof and walls of a roadway located in the lower coal seam is described.The predicted deformation and failure of the roadway for different distances between the two coal seams are used to design two ways of supporting the lower structure.One is a combined support consisting of anchors with a joist steel tent and a combined anchor truss.A field test of the design was performed to good effect.The results have significance for the design of supports for roadways located in similar conditions.

Relationship between joint development in rock and coal seams in the southeastern margin of the Ordos basin

To predict joint development characteristics of coal seams, joint characteristics of rock seams from 88field stations were observed and comparisons were made between joint characteristics of coal and rock seams at 10 coal outcrops. Additionally, detailed joint measurements of underground coal seams were taken at two coal mines. This study investigated the effects of seam thickness, lithology, and structure on joint development and established the relationship between joint development of coal and rock seams, which allowed predictions of predominant joint densities for the No.5 coal seam in the southeastern margin of the Ordos basin. The results show that outcrop and underground coal seams exhibit the same joint systems as rock seams. The joints are mainly upright. Predominant joints strike 55° on average, followed by joints striking 320°. The joint density of the coal seam is 18.7–22.5 times that of the sandstone seam at the same thickness. The predominant joint density of the No.5 coal seam, controlled by the structure, is 4–20 joints per meter. Joint densities exhibit high values at intersecting areas of faults and folds and decrease values in structurally stable areas. The permeability increases exponentially with increasing density of the predominant joints.