Coal Exploration Research Articles

Research on the Characteristics of Gas Geology in Yongshanqiao Mining Area, Jiangxi Province

The coal and gas outburst is very serious in Yongshanqiao Mining Area of Jiangxi province, so it is of significance to research the characteristics of gas geology and their controlling factors. Based on the statistical analysis of gas data during coal exploration and coal mining, the regularity is revealed of the characteristics of gas geology in Yongshanqiao Mining Area. From east to west and from south to north, the relative gas emission rate and the absolute gas emission rate tend to increase, the frequency and intensity of coal and gas outbursts rise, the gas contents also tend to increase. The controlling factors of characteristics of gas geology in Yongshanqiao Mining Area are researched in this paper. The work reveals that: corresponding to characteristics of gas geology, the distribution characteristics of coal quality, the characteristics of geological structure and the lithology characteristics of the roof and the floor of the coal seams in Yongshanqiao Mining Area present regular changes, and are all favorable to gas generation and gas preservation. So, the characteristics of gas geology in Yongshanqiao Mining Area are the result of comprehensive effects by geological factors

Coal geophysics expands with growing global demands for mine safety and productivity

Coal geophysics in the United States was once the exclusive domain and best-kept secret of one major coal company. The company was able to develop a full spectrum of remote-sensing technologies to address its complex upstream and downstream challenges. The program started in the 1970s, and greatly expanded a decade later with more robust and diverse applications. Innovative geophysical surveys were routinely conducted to enhance the company's coal exploration, engineering, and environmental programs.

Nuclear geophysical logging for Gondwana coal exploration: a case study at Phulbari Coal Basin, northern part of Bangladesh

Different methods of lithology predictions from geophysical data have been developed in the last 15 years, among which the conventional logs are as follows: sonic, neutron–neutron, natural gamma, and density (backscattered gamma–gamma). This article concentrates on the nuclear geophysical suite, in particular, gamma and gamma–gamma logging, which, to date, provide the most accurate geophysical means of identifying coal seams and estimating their thickness. From the gamma and gamma–gamma logs of boreholes AEN 002, 007, 044, 045, 063, 085, and 105, which were carried out at the Phulbari Coal Basin of Bangladesh, two coal seams—upper and main with two lower seams of limited occurrence and of varying thickness—were identified, together with their regional occurrence.

Noise Reduction of the Transient Electromagnetic Weak Signal under Strong Noise Based on Power Detection of EMD

The method of Transient Electromagnetic(TEM) detection is widely applied to the field of coal mine and oil exploration. But since Transient Electromagnetic signal is a non-stationary , nonlinear , weak signal under the background of heavy noise , traditional method which is based on the signal superposition is only suited to the signal of the superficial layer , it can not fetch the weak signal of the deep layer. noise reduction of the transient electromagnetic weak signal under heavy noise based on power detection of EMD decomposition is presented in this paper. This method does not need prior information. Through the method, the transient electromagnetic weak signal under heavy noise is decomposed to several intrinsic mode functions. Then by power detection, the noise leading component is extracted and reduced .At last the transient electromagnetic weak signal is obtained adaptively. The example of this paper show: when the received TEM signal of deep layer is -30db SNR, This method can reduce the most of noise, obtain the transient electromagnetic weak signal which contains geological information, and improve the depth and accuracy of the TEM detection.

APPLICATION OF REMOTE SENSING TECHNOLOGY IN THE COAL BED GAS EXPLORATION IN SOUTH-EAST OF ORDOS BASIN

Based on the practical demands for coal bed gas exploration in the loess highlands of the Ordos Basin, the authors, by interpreting the remote sensing images in the study area and utilizing the Statistics and Analysis of Fracture Density method, have predicted the high permeation belt of the coal bed gas in the study area, and made a preliminary evaluation on the favorable sectors for coal bed gas exploration. The result has provided important references for the coal bed gas in the oil field.

Deep 3D structure of the Sydney Basin using gravity modelling

A detailed deep 3D geological model is an important basis for many types of exploration and resource modelling. Renewed interest in the structure of the Sydney Basin, driven primarily by sequestration studies, geothermal studies and coal seam gas exploration, has highlighted the need for a model of deep basin geology, structure and thermal state. Here, we combine gravity modelling, seismic reflection surveys, borehole drilling results and other relevant information to develop a deep 3D geological model of the Sydney Basin. The structure of the Sydney Basin is characteristic of a typical intracontinental rift basin, with a deep north–south orientated channel in the Lachlan Fold Belt basement, filled with up to 4 km of rift volcanics, and overlain with Permo-Triassic sediments up to 4 km thick. The deep regional architecture presented in this study will form the framework for more detailed geological, hydrological and geothermal models.

A Research of Environmental Conflict Factors at the North of the Yellow River

Situated at the north of the Yellow River, the contiguous area of Shanxi, Inner Mongolia and Shanxi province is playing an especially important role in the development of energy industry throughout the country and the distribution of energy base construction. But there are many acute ecological problems all through the ages because of the co-existing situations of both the affluent resources on energy and mine and the fragile ecological environment such as drought, moving sand by wind, and serious soil erosion, etc, which show separate relationships. With the exploration of coal and charcoal resources and the rapid development of energy base construction in recent years, a series of new environmental conflicts are produced and have become very important impediments of the regional sustainable development. This paper analyzes the situations of crisis environment and the factors of environmental conflict and provides approaches to alleviating environmental conflict to facilitate regional sustainable development.

Explosion-Proof Design for Coal Mine Rescue Robots

The explosion-proof design for coal mine robots that are used to explore environment and rescue after coal mine disaster must be adopted. In order to carry out the explosion-proof design for coal mine robots reasonably, based on the analysis of coal mine robots and their explosion-proof design, the explosion-proof types for robots are studied on. The conclusions are as follows: (1) the mixed explosion-proof design including integrated and partial explosion-proof design can be adopted in the robots design; (2) protection types for robots mainly include flameproof enclosure, pressurized enclosure, intrinsic safety, and combination of them. Based on this, the explosion-proof structures of the mobile systems of a track-type robot and a rocker-type robot for coal mine environment exploration are introduced. According to the different structure of the two robots, the concentrated and dispersed flameproof enclosures are respectively designed for the track-type robot and a rocker-type robot. This paper can provide reference for the explosion-proof design for coal mine robots.

The changing face of Queensland's petroleum industry

The cycles and related changes in exploration targets identified in this study show the evolution of the Queensland petroleum industry from conventional petroleum to coal seam gas dominance. Delineation of these cycles was undertaken using petroleum exploration well data, and production and reserves statistics. Although the cycles are defined on the basis of exploration activity, there is a very different history in the types of targets and commodities explored for in the Bowen-Surat and Cooper-Eromanga basins. Trends in exploration success have been influenced by technology improvements, better understanding of target reservoirs, proximity to infrastructure, government policy and world oil prices. Four distinct exploration cycles have been identified from the data. During the first cycle (1959–74) exploration focused predominantly on the shallower Jurassic-aged reservoirs in the Bowen-Surat basins resulting in the discovery of most of the major conventional oil and gas fields. The second cycle (1979–89) saw exploration begin in earnest in the Cooper-Eromanga basins and a switch to predominantly Triassic-aged reservoirs in the Bowen-Surat basins. The first coal seam gas exploration wells were drilled during this cycle. The third cycle (1990–99) shows a decrease in the number of conventional petroleum wells across both regions and the beginning of the switch to the present dominance of coal seam gas. The fourth cycle (2000–present) shows a significant decrease in the number of conventional exploration wells drilled across both regions, but an increase in the success rates. All conventional discoveries in the Bowen-Surat basins during cycle four have been in Permian-aged reservoirs, reflecting a change in the exploration focus to deeper parts of the Bowen Basin. Coal seam gas exploration has expanded significantly, with the Walloon Coal Measures being targeted, resulting in nearly four coal seam gas wells drilled for each conventional petroleum exploration well state-wide since 2000. Examination of coal seam gas exploration highlights the many false starts since the first well was drilled in 1980. Exploration has shifted from area to area as companies tested different exploration concepts and completion techniques. The most obvious shift has been from Permian-aged targets of the Bowen Basin into the Jurassic-aged Walloon Coal Measures in the Surat and Clarence-Moreton basins, as its prospectivity was realised.

Coal seam gas exploration and production in NSW: the new access argument

The legal frameworks around access to coal seam gas (CSG) resources in NSW are perhaps less developed than in Queensland. Coal appears to be favoured in terms of accessibility over CSG in the premier state. This paper will examine the rules relating to access to CSG resources in NSW; explain the long-standing policy favouring coalover CSG; and, will argue that the state may have to move to amend or overhaul its gas land access arrangements in the next few years.As CSG players look for further reserves in the largely untapped area of NSW coal provinces, the legal arguments about access to extant coal reserves are likely to heat up.

Prestack Kirchhoff time migration of 3D coal seismic data from mining zones

Conventional seismic data processing methods based on post-stack time migration have been playing an important role in coal exploration for decades. However, poststack time migration processing often results in low-quality images in complex geological environments. In order to obtain high-quality images, we present a strategy that applies the Kirchhoff prestack time migration (PSTM) method to coal seismic data. In this paper, we describe the implementation of Kirchhoff PSTM to a 3D coal seam. Meanwhile we derive the workflow of 3D Kirchhoff PSTM processing based on coal seismic data. The processing sequence of 3D Kirchhoff PSTM includes two major steps: 1) the estimation of the 3D root-mean-square (RMS) velocity field; 2) Kirchhoff prestack time migration processing. During the construction of a 3D velocity model, dip moveout velocity is served as an initial migration velocity field. We combine 3D Kirchhoff PSTM with the continuous adjustment of a 3D RMS velocity field by the criteria of flattened common reflection point gathers. In comparison with post-stack time migration, the application of 3D Kirchhoff PSTM to coal seismic data produces better images of the coal seam reflections.

Application of Neurofuzzy pattern recognition method in borehole geophysics

Geophysical data are specific physical responses of geological formations distributed over an area. These data are normally the physical parameters such as density, velocity, resistivity, susceptibility etc. of geological sources and hence bring a pattern of geological structures. It is conceived accordingly that this pattern recognition of such geophysical data will throw light on the spatial distribution and physical attributes of their geological sources. The well logging method considered as one of the geophysical method for the exploration of hydrocarbon, coal and base-metals, also has a strong role in finding the location and evaluation of geological resources.A novel approach known as Adaptive Neurofuzzy Inference System technique (ANFIS) is made to identify stratigraphy of Prydz Bay basin, east Antarctica. A geological stratum in terms of 1D model is made using datasets obtained from this area. The 1D model deduced as an ANFIS result is able to make geological sense of even additional thin sand sa...

Reconsideration of the sediment characteristics of the second member of the Triassic Xujiahe Formation in Sanhuiba, Huaying Mountain

The second member of the Triassic Xujiahe Formation in the Sanhuiba area in Huaying Mountain is an important section of sedimentary delta facies in the Chongqing Tianfu Geological Survey and Training Base. In spite of some initial efforts on its lithology and lithofacies, the existing research is yet to be completed and suffers from contradictory conclusions and inadequate evidence. Starting from the sedimentary microfacies types and cyclic features, we analyzed the vertical sequence of a sedimentary delta model and discovered that this section is a constructional delta deposit. Eight incomplete and asymmetric regressive cycles are marked off, given that frequent erosion surfaces appeared in the section. Based on the analysis of structural characteristics of every monocycle, we summarized the system of cycles, tracts and sequence characteristics of the overall section. In view of this systematic series of cycles, we discussed the features of the syndepositional tectonic movements in the area and conclude that, due to frequent erosion, migration and diversion of a sub-channel branch was brought about by oscillating movements of the crust. In a comparison with neighboring sections, we explored the cause of erosion and the relations between erosion and cycles. This study greatly strengthens existing research and theories, makes an important and comprehensive contribution to geological surveys and training in the area and provides essential suggestions for coal exploration, oil and gas evaluation and in general to exploration and development in the target stratum.

New Zealand’s deepwater frontier

New Zealand’s deepwater frontier

Utilising current technologies to understand permeability, stress azimuths and magnitudes and their impact on hydraulic fracturing success

In coal seam gas exploration and appraisal, stress and permeability are often inter-related and play a large role in deliverability, particularly affecting hydraulic fracturing effectiveness. Generally, the structural setting for a coal seam gas (CSG) play can be defined by indirect data such as petroleum wells, core wells, or seismic data; however, the viability of a structure to be highly conducive to CSG development also requires direct measurements to fully define the effects associated with this interdependency of stress and permeability. Unfortunately, this interdependency may not be as apparent during the exploration phase as within the planning, execution and evaluation of a hydraulic fracturing program. We will present data from a limited area of the Surat Basin, in the Walloon coal measures, where initial regional and well data were available to allow drilling to evaluate a small, localised, structural setting for CSG development. While some permeability data were encouraging in the initial program, subsequent drilling indicated that permeability might become variable across this structure. Thus, further investigations were made and included novel, cross-dipole sonic logging in combination with acoustic and more advanced resistivity imaging logs. These data indicated that the stress and permeability azimuths may be aligned to take advantage of hydraulic fracturing. Thus, a hydraulic fracturing program was initiated in this area incorporating diagnostics to understand the potential benefit of this technology. The results of this program, while localised, do indicate that a potential pitfall can exist in some environments where the stress magnitudes along with stress and dominant permeability axes are not ideally positioned to take advantage of hydraulic fracturing. We will show how the data in this case were acquired, evaluated and integrated to support the overall understanding and interpretation of the results. Due to space constraints, this paper focusses primarily on the overall data process and is unable to elaborate fully on all diagnostics used and the fullness of their determinations; however, adequate supporting evidence is supplied in order to illustrate the problems in executing and achieving effective stimulation in similar structural settings.

Evaluation of coal structure and permeability with the aid of geophysical logging technology

Coal structures and the associated permeability were studied by a combined investigation of geophysical logging data and well tests from coal reservoirs of Huainan and Huaibei coalfields in China. A large amount of the site observations on coal sections of mining faces and the macroscopic investigations on textures of drilling coal cores were carried out, providing experimental information for classification of coal structures. Geophysical log was implemented in 600 boreholes for exploration of coal and coalbed methane (CBM) resources, including 10 CBM wells which were used for permeability tests. The permeability tests were conducted by using injection/fall-off method. The results, together with the log data obtained from geophysical log technologies, have been analysed by using geological statistics, permitting correlation of the permeability of coal seams to the log responses. The correlation developed in this study provides better evaluation of coal reservoir permeability, resulting in an improved CBM exploration in the given coalfields.

Sustainable development of the Indian coal sector

Abstract Increased availability of energy, especially electricity, is important for India to help advance economic and human development. Coal, which currently accounts for more than 50% of total primary commercial energy supply in the country and for about 70% of total electricity generation, is likely to remain a key energy source for India for at least the next 30–40 years. Thus, sustainable development of the Indian coal sector is necessary to ensure the ability to sustain the increased production of coal in the country and to do so in an environmentally and socially sustainable manner. The main challenges to such a development of the coal sector pertain to (a) systems of coal exploration, extraction, and processing, (b) ensuing environmental and social concerns, and (c) increasing and high demand for coal in the power sector. Overcoming these challenges will require an assessment and resolution of relevant technical, economic, and institutional issues. This, in turn, requires a long-term vision and systematic planning and policy development in a transparent and inclusive manner. Promoting the engagement of all stakeholders in these processes can help reconcile the seemingly-intractable conflict between the increasing demand for coal, supply constraints, and local socio-environmental needs, and thus facilitate a transition towards sustainable development of the sector.

Azimuthal imaging challengers in coal-scale 3D multi-component seismic reflection

In certain geological situations, improved characterisation of the subsurface can be achieved through the integration of conventional P-wave seismic reflection and PS-wave (converted, or C-wave) reflection. Initial noteworthy successes for this technology related to offshore petroleum targets, which were difficult to image with standard P-wave methods (e.g. Barkved et al., 1999; Hanson et al., 1999). More recently, integrated interpretation of P and PS imagery has been shown to yield improved geological interpretation of coal targets, including detection of new fault structures, improved determination of fault geometries, and superior imaging of top-of-coal for shallow open-cut targets (e.g. Hearn, 2004; Velseis, 2003, 2007). Application of PS-wave techniques is arguably more challenging in the onshore situation, due partly to severe S-wave receiver statics. These statics are more problematic with shallow high-resolution data, where maintenance of high frequencies is critical. In the P-wave arena, there is an increasing trend toward 3D surveys since these produce a better spatial interpretation. It would be reasonable to assume that 3D PS-wave surveys would also lead to an improved geological interpretation. However, 2D PS-wave surveys have identified a number of issues that will make 3D PS exploration more challenging than the conventional case. For example, different geological interpretations may result from images created with positive (forward shooting) or negative (back shooting) offsets. Additionally, the asymmetry of PS-wave paths means that it is more difficult to achieve regular azimuthal and offset distributions when designing 3D grids. Associated with this is the fact that PS offsets may be more restricted due to phase effects. PS path asymmetry is generally more pronounced at the shallower depths appropriate to coal exploration (50-500m). There is also a greater tendency to use rays having higher incidence angles. Hence we believe that the problems noted here are likely to be more severe at coal depths than at petroleum depths. In this paper, the discussion of these issues is largely based on prior 2D experience, and numerical modelling of 3D effects. It represents the design phase of a 3D converted-wave field experiment to be carried out in late 2008 (ACARP, 2008). Although we emphasise the peculiarities of the shallow coal exploration environment, the discussion is of more general relevance.

Revisiting the Vibroseis wavelet

The well-established Vibroseis source has been heavily used since its development in the 1950s (Crawford, et. al., 1960). Typically, a swept-frequency signal (or sweep) of length 2 - 10s is injected into the earth. The raw reflection record is complicated and uninterpretable. However, crosscorrelation with the theoretical reference sweep, or with a measured base-plate reference, simplifies the recording. The output is assumed to be the earth response convolved with the autocorrelation of the sweep (referred to as the Klauder wavelet). Since Vibroseis was first developed a number of variations to the standard linear sweep have been investigated, with the general aim of optimising the character of the correlated Vibroseis wavelet. These include Vari and encoded sweeps (e.g. Edelmann and Werner, 1982), non-linear sweeps (e.g. Goupillaud, 1976), and pseudo-random Vibroseis (Cunningham, 1979). Often, decisions regarding sweep parameters are made in the field, based on unprocessed field records. There has been some research into the effects of phase (Cambios, 2000), and the influence of such processes as deconvolution (Gibson and Larner, 1984). However, this research does not seem to be widely considered in pragmatic Vibroseis sweep evaluation. Hydrocarbon exploration is now targeting increasingly subtle traps, relying on incremental improvements in seismic technology. At the same time, for reasons of economics, Vibroseis technology is being deployed in new target areas (e.g. Coal Seam Gas (CSG) and coal exploration). For these reasons, it is timely to revisit the fundamental importance of the Vibroseis wavelet in seismic interpretation, and the many factors which control its character. A primary purpose of this paper is to give an example of how Vibroseis wavelet evaluation can extend beyond a simplistic comparison of sweep autocorrelations to include the influence of earth attenuation, phase distortion and processing. We also comment briefly on the choice of reference signal for correlation.

Sub-basalt coal seam structure imaging - results from numerical modelling

Tertiary volcanic basalts (high velocity layers) exist in both the Bowen and Sydney Basins of Eastern Australia. The use of conventional seismic for coal mine planning is often compromised and produces sub-surface images of variable quality because the wave propagation through these heterogeneous basalt layers becomes complex. The difficulty of exploring beneath the Tertiary volcanics makes these areas less attractive for coal mining exploration. Workers involved in sub-basalt imaging in the petroleum sector, mainly give the following reasons for the difficulties in imaging beneath high-speed surface layers: 1. The strong impendance contrast between the basalts and the underlying sedimentary rocks prevents the penetration of seismic energy into target zones (Fruehn et al., 1998; Behera, 2006). 2. The roughness of the basalt boundaries causes significant disruption and scattering of the transmitted wavefield (Behera, 2006). 3. The scattering of heterogeneity of the basalt (Ziolkowski et al., 2001; Hobbs, 2002). To improve seismic imaging in these cases, modifications to data acquisition and data processing procedures which improve data quality and increase S/N were proposed (Fliedner and White, 1999; Hu et al., 2003). Commonly used techniques involve long offset, low frequency and converted wave data acquisition (Ryu, 1997; Wombell et al., 1999; Hanssen et al., 2003; Lau et al., 2007; Spitzer et al., 2008). In data processing, procedures such as pre-stack depth migration, have improved the quality of sub-basalt images (Fruehn et al., 1999; Reshef et al., 2003; Gallagher and Dromgoole, 2008). Wave-equation modelling techniques have also been used to investigate the influence of high speed layers on seismic wave propagation (Battig and Hearn, 2001; Hanssen et al., 2003). In this paper, we use a 2D finite-difference-based full elastic wave-equation forward modelling algorithm to further investigate the effects and characteristics of seismic wave propagation under different basalt settings. Our objective is to provide some insights into the seismic wave propagation and guidance for improving the quality of seismic sections for coal mine investigations.