Stability of the Fault Systems That Host-Induced Earthquakes in the Delaware Basin of West Texas and Southeast New Mexico

The Delaware basin of west Texas and southeast New Mexico has experienced elevated earthquake rates linked spatiotemporally to unconventional petroleum operations. Limited knowledge of subsurface faults, the in situ geomechanical state, and the exact way in which petroleum operations have affected pore pressure (Pp) and stress state at depth makes causative assessment difficult, and the actions required for mitigation uncertain. To advance both goals, we integrate comprehensive regional fault interpretations, deterministic fault-slip potential (DFSP), and multiple earthquake catalogs to assess specifically how faults of two systems—deeper basement-rooted (BR) and shallow normal (SN)—can be made to slip as Pp is elevated. In their natural state, the overall population faults in both the systems have relatively stable DFSP, which explains the low earthquake rate prior to human inducement. BR faults with naturally unstable DFSP and associated earthquake sequences are few but include the Culberson–Mentone earthquake zone, which is near areas of wastewater injection into strata above basement. As a system, the SN faults in the southcentral Delaware basin are uniformly susceptible to slip with small increases in Pp. Many earthquakes sequences have occurred along these shallow faults in association with elevated Pp from shallow wastewater injection and hydraulic fracturing. Our new maps and methods can be used to better plan and regulate petroleum operations to avoid fault rupture.

INVESTIGATION OF THE GEOMECHANICAL STATE OF SOFT ADJOINING ROCKS UNDER PROTECTIVE CONSTRUCTIONS

The conditions of coal seam mining in the mines of Ukraine have been considered. The problem of conducting coal mining by longwalls in the conditions of soft adjoining rocks, which concerns the protection of mine roadways located near the face, has been revealed. In such conditions, the existing protective constructions are ineffective due to the fact that they yield and get pressed into the soft rocks of the footwall. This indicated the need for research into the geomechanical state of soft rocks of the footwall. According to the results of known studies on the mechanism of rock mass failure around roadways and the data of physical and mechanical properties of the coal mass, which is represented by soft rocks, the correlation dependence has been obtained, the use of which allowed for the determination of the parameters of the rock deformation diagram and the establishment of the stability criterion of footwall rocks under the protection means and stability conditions of the geotechnical system “protective construction – adjoining rocks.” They are the basis of a new approach to ensure the stability of the roadways, which are supported behind the faces, by controlling the stress state in the system “protective construction – adjoining rocks.” This may be the basis for the development of new methods of protecting roadways in conditions of soft adjoining rocks.

THE CONCEPT OF ENSURING WATER PROTECTION OF THE KIMBERLITE MINES OF YAKUTIA

The article provides examples of the development of mines near water bodies, as well as summarizes the experience of water protection of mines in the kimberlite deposits of Yaku-tia, which allowed us to form a number of principles that can increase the safety and efficien-cy of the mining system in the conditions under consideration. It is shown that one of the directions of the strategy for the development of mining operations near water bodies should be the control of the mutual correspondence of the pa-rameters of geotechnology and the geomechanical state of the mountain range.

CALCULATION OF THE GEOMECHANICAL STATE OF MINE WORKING SUPPORT AND SURROUNDING ROCK MASS IN CONDITIONS OF MINING ORE DEPOSITS IN EAST KAZAKHSTAN

The statement of the problem of determining the stress-strain state of support and rock mass around the mine working in unstable rocks, in case of voids filling with phenol resins is proposed. The initial parameters used in the calculations correspond to the conditions of mining ore deposits in East Kazakhstan. The distribution character of stress fields in the support and their change depending on geometric sizes of the area filled with phenol resins is determined. It is shown that using phenol resins causes formation of a uniform pressure of surrounding rocks on the arch part of the support and facilitates an increase in its stability.

http://www.mining-science.ru/download/2020/3/04.pdf

Introduction. Reliable forecasts of pillars geomechanical state are required to ensure rhythmic and safe work when mining a coal bed. Research aim is to construct a state model of the coal pillar located between the headways, based on the fundamental methods of elasticity theory and mechanics of a granular media, carry out a computational experiment within the model, and analyse the results. Methodology. The stress field in the coal pillar has been constructed in the course of solving the elastoplastic problem. By replacing the ultimately stressed marginal zone of the bed with the stresses which act within the zone, the problem has been reduced to the second exterior boundary value problem of elasticity theory and has been solved by the boundary element method. Ordinary and special Coulomb–Mohr criteria simultaneously fulfilled for the coal bed and rock mass contact are the criterion of the limit state onset. Actual pillar load is determined by integrating the vertical stress curve along the bed roof, which has been obtained from elastoplastic problem solution, while the ultimate load is determined from the condition that the whole pillar is in ultimately stressed state. Results. The dependence between the safety factor of the pillar between two identical headways, determined by V. D. Shevyakov method, and the growth of its width represents a graph in the form of a monotonically increasing curve. The curve flattens as soon as the depth increases. Summary. The results from the developed model of coal rock mass geomechanical state can be successfully used as coal pillar strength forecasts.