Abstract. The paper reviews the method of determining the shape and size of the coal self-heating source on coal pit benches and in coal piles during mining of coal by the open method. The method is based on the regularity found in the 1970s of the previous century and related to the distribution of potential of the natural electrical field arising from the temperature in the vicinity of the center of self-heating. The problem is reduced to the solution of inverse ill-posed problem of mathematical physics. The study presents the developed algorithm of its solution and the results of numerical simulation.
-The success of coalbed methane field development is largely determined by the effectiveness of using special gas production stimulation methods. The need of implementing of such methods is driven by features of location and movement of methane in the coal body. The process of hydraulic fracturing as the most frequently used method for the stimulation of a well production capacity at commercial production of methane from the coal seams is described. The use of quartz sand as a propping agent for the hydraulic fracturing cracks when extracting the methane from coal seams is proved. The information about the companies using quartz sand for hydraulic fracturing in Russia is provided. The mineral resource potential of the Kemerovo region in sand mining is marked. The results of the researches in sand from the deposits of the Kemerovo region as the proppants for the hydraulic fracturing cracks are shown. The received results allow to draw a conclusion on high prospects of use of local sands at extraction of coal bed methane in Kuzbass.
The article gives a theoretical propagation of the development of hydrofractures in coal seams from the position of geomechanics, including the possibilities and conditions for the fracture to intersect a natural crack. A technique is proposed for carrying out experimental studies of the effect of inhomogeneities on the extension of hydraulic fractures by physical modeling on samples of equivalent materials and the facility for their conduct. The results of experiments based on the proposed technique on samples made on the basis of cement, sand, fly ash, and water are presented, with modeling of inhomogeneities of various types. The results made it possible to conclude that when the closed cavities intersect in the form of gaping cracks of limited prevalence, their rupture fluid envelops with the preservation of the rupture plane. It is noted that when crossing unbounded gaping cracks, the established enveloping phenomenon will obviously occur along the “bridge” at the points of contacts of the opposite banks of cracks that take place in a real massif, and the very intersection of the fracture of the natural crack, mainly, depends on its deformation properties, the magnitude of the angle between the planes of the fracture and the crack, and also the fluid pressure.
Аннотация:Работа посвящена вопросам технологии проведения гидравлического разрыва угольных пластов. Приведены общие сведения о развитии данной технологии и об используемых закрепляющих материалах. Отмечена целесообразность применения местных песков для закрепления трещин гидроразрыва при добыче метана из угольных пластов. Дано обоснование наиболее подходящей модели течения гидросмеси (жидкости-песконосителя с пропантом) в трещине гидроразрыва. В качестве одного из параметров процесса закрепления принята критическая (минимальная безосадочная) скорость движения гидросмеси в трещине. Подробно рассмотрен метод определения критической скорости, основанный на понятиях теории подобия и анализа размерностей. Другим важным параметром, влияющим на закрепление трещин гидроразрыва, является степень отфильтровывания жидкой фазы гидросмеси в проницаемый угольный пласт. Явление отфильтровывания транспортирующей жидкости приводит к уменьшению скорости потока гидросмеси в трещине, что, соответственно, ведет к повышению интенсивности осаждения закрепляющего материала. Это может стать причиной невозможности дальнейшего полноценного качественного закрепления (заполнения пропантом) трещины гидроразрыва. Поэтому для оценки расхода транспортирующей жидкости построена модель течения гидросмеси в горизонтальной и вертикальной трещине. В результате получены выражения для определения интенсивности фильтрации транспортирующей жидкости в проницаемый угольный пласт. Результаты позволяют обоснованно определять режимы подачи гидросмеси и концентрацию пропанта в ее составе.Ключевые слова: метан угольных пластов, гидравлический разрыв пласта, пропант, песок, проницаемость, гидравлическая крупность, критическая скорость, фильтрация. Abstract:The article is devoted to the issues of hydraulic coal seam fracturing technology. General information about the development of this technology and the used propping agents is given. The expediency of using local naturally occurring sands for propping fractures, when extracting methane from coal seams, is noted. The most suitable model of the proppant-laden slurry flow in hydraulic fracture is proved. The critical (minimum non-settling) velocity of the slurry flow in fracture is taken as one of the parameters of the process of propping fractures. The method of determining the critical velocity based on concepts of the theory of similarity and the dimensional analysis is considered in detail. Another important parameter affecting hydraulic fracture propping is the filtration of the liquid phase of slurry into the permeable coal seam. The phenomenon of fracturing fluid filtration leads to a decrease in the rate of slurry flow in fracture that increases the intensity of proppant settling. It may cause the impossibility of further full high-quality propping (filling with proppant) of hydraulic fracture. Therefore, the model of the slurry flow in horizontal and vertical fracture is developed to estimate the fracturing fluid flow rate. Вестник Кузбасского государственного технического университета. 2019. № 4, с.90-9...
The paper presents a method of choosing the design of horizontal coalbed methane well by estimation of a coal seam permeability on the results of one-dimensional and two-dimensional geomechanical modeling. The differences in the preparation of one-dimensional geomechanical models of coalbed methane fields from models for conventional oil and gas fields are noted. The results of preparation of one-dimensional geomechanical model based on data from one of the vertical exploration coalded methane wells and two-dimensional geomechanical modeling of coal seam for three common designs are presented. The obtained results allow us to conclude that geomechanical modeling is a suitable tool for estimation of coal seam permeability changes and choosing the most effective well design for the considered mining and geological conditions. In particular, in the coal seam under study, a multilateral well can cause the greatest increasing of permeability.
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