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The SPE has split the former "Management & Information" technical discipline into two new technical discplines:
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Eremenko, A.A. (Institute of Mining, Siberian Branch, Russian Academy of Sciences) | Eremenko, V.A. (Institute of Mining, Siberian Branch, Russian Academy of Sciences) | Seryakov, A.V. (Institute of Mining, Siberian Branch, Russian Academy of Sciences) | Keller, V.Y. (Evrazholding Joint-Stock Company) | Erastov, V.V. (Evrazholding Joint-Stock Company)
ABSTRACT Iron-ore deposits of Siberia are mined at great depths in seismically active regions. The concentration of stresses in separate local parts of rock mass causes dynamic phenomena of different intensity. Dynamic manifestation of rock pressure considerably impedes development, face-entry drivage, and stoping operations in mines as well as leads to heavy expenses for reclamation. Blasting operations are referred to as a technological process that exerts the greatest effect on the state of a rock mass. After technological explosions with a seismic energy of 10-10 J, the dynamic events in the form of shocks, microshocks, and rockbursts are frequently recorded. The authors have established the connection between blasting and rock pressure manifestations. The velocities of shock and seismic waves in rock mass during large-scale blasts are determined. Preventive actions including the use of explosion energy are developed for safe and effective mining of ore deposits. The most important means of increase in efficiency of ore extraction is improvement of blasting in underground mining of rockburst-hazardous iron-ore deposits of Siberia. It is a peculiarity of the region, where deposits are located, that it has an increased seismic activity due to deep tectonic processes, high stress level, and type of rocks prone to brittle failure (Fig. I). Due to the influence exerted by mining operations on seismic activity, local redistributions of stress take place in the rock mass, and the stress field inhomogeneities intensify. This becomes a reason of increased after-effects of earthquakes and dynamic phenomena caused by anthropogenic action on natural environment, Kurlenya (2003). Investigation of seismic activity in Siberia is aimed at determination of earthquake energies and establishment of connections between the energies of earthquakes and features of tectonics of folded structures, reoccurrence of earthquakes, and character of failure and deformations of rock mass. The Richter rnagnitude 3–8 earthquakes have been observed in the region in question from the 18th century. The latest earthquakes with the magnitude 2–10 have been taking place in the North-West of the Altai-Sayan folded region (Kochurinsk deposit, Tashtagol town) and in Gorny Altai (Kosh-Agach center) from 1988 to 2003. (Figure in full paper) Figure 2. Bar chart of distribution of aftershocks of the earthquakes and dynamic phenomena in rock mass during blasting: I - aftershocks of the Kochurinsk earthquake; 2 - aftershocks of thc Altaisk earthquake; 3 - dynamic phenomena; 4 - blasting. During the earthquakes roads were destroyed, electric mains were broken, soil sagged, cracks formed in the buildings, chimneys were demolished, etc. Within the same period of time, it was recorded that in rock mass of the deposits, the stress concentration increased. As a consequence of this, rock-tectonic shocks and microbursts occurred in the Tashtagol and Sheregesh deposits. In the epicentral zone of the Kochurinsk earthquakes, there were more than 2000 aftershocks with a seismic energy from 102 to 10101, Kurlenya et al (2001).
Abstract PGDBK Technology is used for the stimulation of oil and gas wells to enhance productivity. The pulsating pressure generated upon combustion of caseless cylindrical powdered charges overcomes the tensile strength of formation rock to create multiple fractures. These fractures, with horizontal and vertical orientation, extend more than 100 feet in diameter from the wellbore. Combustion of PGDBK generators takes place near a selected pay zone in a well under a hydrostatic column sustained by a tamp fluid. Through a combined effect of mechanical, thermal, and chemical actions, the use of PGDBK increases pressure communication between the extended reservoir and the wellbore. The pressure pulsating action of generated non-combustible gases erodes fracture walls keeping the flow channels opened for a long period of time without propping agents. High temperature generated through the combustion process cleans the wellbore region of heavy hydrocarbons, reduce the viscosity of oil and enhance relative permeability of oil to water. Additional oil is also recovered through the reduction of the surface tension by the chemical actions of the combustion products. The in-situ process ends with a negative pressure gradient towards to the wellbore, washing impediments from flow channels. Wells are immediately swabbed or circulated to remove debris, equipment re-installed, and well brought back on line. This paper describes the PGDBK stimulation technology. It further presents case studies of successful field applications in three different USA sedimentary basins in the summer of 2000 and recent treatments in Russia. Introduction In the summer of 2000, GEOTEC Thermal Generators in collaboration with Federal Research & Production Center "ALTAI" (Russia) introduced the treatment of oil and gas wells in three different basins in the USA. Twenty wells were treated in the Powder River Basin, Anadarko Basin, and the Austin Chalk Trend. Caseless charge-powdered pressure generators (in Russian - Poroxovie Generatorie Davlenea BesKorpusnie - PGDBK) have been effectively, safely and economically applied in over 30,000 wells around the world to increase productivity. This is a state of the art stimulation technology that enhances the productivity of wells with a combination of mechanical, thermal, and chemical actions. The gas generated acts on reservoir rocks by creating multiple fractures that enhance the flow of oil and gas from the reservoir into wellbore (see Figure 1). These fractures are far-reaching and long lasting. They contribute significantly in reducing skin effect and increasing the permeability of the wellbore region. The decline in a well's productivity may largely be attributed to deterioration of flow properties around the wellbore region. The flow channels are usually obstructed with formation fines, sediments of heavy-end hydrocarbons and contaminants from external fluids and materials during drilling and production. If no remedial action is taken to clear the flow channels larger pressure drawdown will be required to sustain production. This will cause the movement of more formation fines thus exacerbating the wellbore damage effect. The most effective way to improve the flow properties of reservoir rock is to create fractures around wellbore. This improves hydrodynamic communication between the wellbore and the deeper region of the reservoir. Conventionally, fractures are created by hydraulic fracture, and acid fracture techniques. These are usually expensive and create only single fractures along least stress planes. The PGDBK powdered gas pressure generators have been used successfully to create desired multiple fractures around the wellbore. Some of the advantages of this technology are the simplicity of its application, high mobility, less downtime, and minimal cost of personnel, equipment, and other resources. The PGDBK technology is applicable to diverse geological, technical, and climatic field conditions.
Miletenko, I. (Institute of Complex Development of Mineral Resources, Russian Academy of Sciences, Moscow) | Odintsev, V.N. (Institute of Complex Development of Mineral Resources, Russian Academy of Sciences, Moscow) | Slonim, M.E. (Institute of Complex Development of Mineral Resources, Russian Academy of Sciences, Moscow)
ABSTRACT: In situ studies of the influence of steeply dipping slaty cleavage on rock displacement caused by exploitation of vein deposits have revealed a protective effect of slaty zones. A mathematical technique is proposed for prognostic rock displacement evaluation allowing for this effect in terms of influence factors. The account of the protective effect can result in exploitation of additional ore reserves previously ascribed to losses in protective pillars. Advance forecast of rock displacement promotes the selection of proper mining technologies diminishing environmental damage. 1 GENERAL CONSIDERATIONS Rock displacement is known to be one of the most essential factors affecting both steady pace and environmental safety of mining operations. This is why prognostic evaluation of rock displacement and surface subsidence caused by mining is a very important geomechanical problem at mine design as well as at exploitation stage. Geological features considerably complicate this problem owing to difficulties associated with the account of structural disturbances. Slaty cleavage is one of widely distributed forms of geological disturbances typical for nonferrous vein deposits of East Kazakhstan and the Altai Ore Region. Slaty zones are usually considered to be unfavourable factors strongly deteriorating mining and environmental conditions all over the zones affected by mining. However, an analogy with some of problems in physics (sometimes even not related with mining problems) allows us to suppose that this is not always true. Moreover, our special studies have proven the favourable role of steeply dipping slaty cleavage zones acting in some cases like protective screens. This conclusion was drawn basing on calculations and the analysis of in situ measurements conducted at vein ore deposits in East Kazakhstan and the Altai Ore Region. 2 THEORY In order to evaluate rock displacement and rock mass deformations caused by extraction of a vein orebody with varying dip angle and thickness, we divide the orebody into elements characterized by roughly invariable thickness and dip angle. Corresponding boundary mathematical problem for such an element can be formulated as follows (see Fig.1). Let the length of the orebody element on the dip be 2L, its mined thickness be m, and dip angle be α. It is convenient to introduce a local coordinate system OX1Y1 in the section across the strike so that OX1 axis would be directed to the rise of hanging wall and OY1 axis directed perpendicular to it. The account of structure can be achieved by means of special influence factors. To find these factors for slaty cleavage zones, long-term in situ measurements at different sections of Vasilievskoye deposit were conducted. Mining and geological conditions at the deposit are typical for vein deposits of East Kazakhstan and the Altai Ore Region. The studies have shown that the influence factor is equal to 1 Within a zone bounded by points of maximum inclination ix, to 0.5 in the neighbourhood of these points, and 0.25 outside the zone. This means that the slaty zone reducts the displacements (down to 1/4 of corresponding value in a continuous rock mass) at sites located at certain distance from stoping blocks, i.e. acts like a protective screen. The comparison of in situ measured data and calculated displacements obtained using adjusted solution (1)-(3) for orebody 2 of Vasilievskoye deposit is shown in Fig.2. The difference does not exceed 10 per cent. 3 IN SITU MEASUREMENTS In situ observations were carried out at Irtysh ore deposit (East Kazakhstan) located in the Vicinity of a 50 to 80 m thick almost vertical slaty zone (Fig.3).