核磁共振T_2谱M-P广义逆反演研究

基于广义逆和奇异值分解理论,研究核磁共振T2谱反演的截断法和阻尼法。首先给出反演问题的M-P广义逆解;然后对系数矩阵进行奇异值分解求其M-P广义逆,对奇异值进行截断或者加阻尼,保证解的稳定性兼顾其分辨率;最后利用迭代技术实现解的非负约束。数值仿真实验和岩心T2谱反演表明:对于双峰谱,在信噪比SNR≥10时,截断法和阻尼法反演T2谱的分辨率和稳定性都很高;截断法截断因子选择范围小,在SNR<10时解的分辨率和稳定性差;阻尼法阻尼因子选择范围大,在SNR<10时解的稳定性好,但短组分分辨率低,长组分分辨率高。对于三峰谱,当SNR≥20时,截断法和阻尼法反演的T2谱光滑连续,具有三峰结构;当SNR<20时两者均不能反演出与构造谱接近的三峰谱。因此,2种方法可应用于SNR≥10的双峰谱和SNR≥20的三峰谱反演;从分辨率和稳定性、平滑噪声及截断和阻尼因子的选取上,阻尼法略优于截断法。

鸡西市农村饮水安全工程建管探索与实践

农村居民的饮水安全是关系农村居民的身体健康和正常生活质量,是农村致富奔小康的基础工程。鸡西市在农村居民饮水工程建设上起步较早,兴建了一大批饮水工程,为农民群众解决了饮用水难的问题。

Rough interfaces and ultrasonic imaging logging behind casing

Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to casing corrosion and rough fluctuations at the cement-formation interface. The ultrasonic obliquely incidence could effectively stimulate the flexural waves. The defects owing to casing corrosion change the amplitude of the early- arrival flexural wave, which gradually decrease with increasing defect thickness on the exterior walls and is the lowest when the defect length and wavelength were comparable. The scattering at the defects decreases the energy of flexural waves in the casing that leaks directly to fluids. For rough cement-formation interface, the early-arrival flexural waves do not change, whereas the late-arrival flexural waves have reduced amplitude owing to the scattering at rough interface.

Mechanism of mine water-inrush through a fault from the floor

The mechanism of mine water inrushes in coal mines in China differs considerably from that in other countries.In China, most water inrushes occur from floor strata, where the water-inrush sources are karstic limestone aquifers.Our study describes the mechanism of mine water inrushes through a fault in the mine floor using principles of strata mechanics and the path of water inrush from an aquifer to the working face.A criterion to judge whether a ground water inrush will occur through a fault or not is also described, together with a case history of water inflow in the Feicheng coalfield, China.

Reservoir reconstruction technologies for coalbed methane recovery in deep and multiple seams

Multiple coal seams widely develop in the deep Chinese coal-bearing strata. Ground in situ stress and coal seam gas pressure increase continuously with the increase of the mining depth, and coal and gas outburst disasters become increasingly severe. When the coal is very deep, the gas content and pressure will elevate and thus coal seams tends to outburst-prone seams. The safety and economics of exploited firstmined coal seams are tremendously restricted. Meanwhile, the multiple seams occurrence conditions resulted in different methane pressure systems in the coal-bearing strata, which made the reservoir reconstruction of coal difficult. Given the characteristics of low saturation, low permeability, strong anisotropy and soft coal of Chinese coal seams, a single hydraulic fracturing surface well for reservoir reconstruction to pre-drain the coalbed methane(CBM) of multiple seams concurrently under the different gas pressure systems has not yet gained any breakthroughs. Based on analyses of the main features of deep CBM reservoirs in China, current gas control methods and the existing challenges in deep and multiple seams, we proposed a new technology for deep CBM reservoir reconstruction to realize simultaneous high-efficiency coal mining and gas extraction. In particular, we determined the first-mined seam according to the principles of effectiveness and economics, and used hydraulic fracturing surface well to reconstruct the first-mined seam which enlarges the selection range of the first-mined seam. During the process of mining first-mined seam, adjacent coal seams could be reconstructed under the mining effect which promoted high-efficiency pressure relief gas extraction by using spatial and comprehensive gas drainage methods(combination of underground and ground CBM extraction methods). A typical integrated reservoir reconstruction technology, ‘‘One well for triple use", was detailed introduced and successfully applied in the Luling coal mine. The application showed that the proposed technology could effectively promote coal mining safety and simultaneously high-efficiency gas extraction.

The mechanism and criterion of tectonic zone around karstic collapse column reactivation-induced water-conducting

In order to study the mechanism of tectonic zone around karstic collapse col-umn reacts to leak water and prevent water invasion in mine. According to the character of the surrounding cracks- penetrated water KCC, The fracture mechanics theory can be used to study the propagation and perforation process of cracks and hitches around the KCC. The criterion of crack start rupture and the length of secondary crack and criterion of crack propagation have been attained. The influencing factors of KCC reacts to water con-duction were analyzed.

Automatic drawing of the geologic profile of an underground mine based on COMGIS

This paper introduces a method of building a prototype system of geologic profile auto-drawing.A.NET development platform and integrated environment was used along with a component based design,a B/S system model,and XML techniques.Knowledge rules for creating geologic profiles and generating virtual drilling data from existing bore data and expert,hand-drawn geologic profiles were acquired. Then a prototype system was established by utilizing the known knowledge rules,topological relationships, and semantic relationships among strata.This system has a friendly human-computer interface and can meet requirements of mutual queries between attribute and spatial data.The generated profile map is editable.This study provides a new powerful tool for underground mine work.

Finite element analysis for inclined wellbore stability of transversely iso-tropic rock with HMCD coupling based on weak plane strength criterion

The finite element analysis(FEA) technology by hydraulic-mechanical-chemical-damage(HMCD) coupling is proposed in this paper for inclined wellbore stability analysis of water-sensitive and laminated rock, developed basing on the recently established FEA technology for transversely isotropic rock with hydraulic-mechanical-damage(HMD) coupling. The chemical activity of the drilling fluid is considered as phenomenological hydration behavior, the moisture content and parameters of rock considering hydration could be determined with time. The finite element(FE) solutions of numerical wellbore model considering the chemical activity of drilling fluid, damage tensor calculation and weak plane strength criterion for transversely isotropic rock are developed for researching the wellbore failure characteristics and computing the time-dependent collapse and fracture pressure of laminated rock as shale reservoirs. A three-dimensional FE model and elastic solid deformation and seepage flow coupled equations are developed, and the damage tensor calculation technology for transversely isotropic rock are realized by introducing effect of the hydration and the stress state under the current load. The proposed method utilizing weak plane strength criterion fully reflects the strength parameters in rock matrix and weak plane. To the end, an effective and reliable numerically three-step FEA strategy is well established for wellbore stability analysis. Numerical examples are given to show that the proposed method can establish efficient and applicable FE model and be suitable for analyzing the timedependsolutions of pore pressure and stresses, and the evolution region considering the hydration surrounding wellbore,furthermore to compute the collapse cycling time and the safe mud weight for collapse and fracture pressure of transversely isotropic rock.