No abstract

The geological strength index (GSI) is one of the most exceptional rock mass classification system which is used to evaluate very weak and highly jointed rock mass by different approaches and related to rock mass geomechanical properties including generalized Hoek & Brown constants, deformation modulus, strength properties, and Poisson’s ratio for an appropriate design of tunnels, caverns, and other engineering structures. The distinctiveness of this system over the rock mass rating (RMR), Q-system, and other empirical methods is as follows: it utilized field observations, blockiness of rock mass, and surface joint characteristics during the evaluation process of rock mass and efficiently espoused as an empirical tool for estimation of geomechanical properties of rock mass required for pre-post stability of engineering structures using numerical modeling. This study presents the review of the 19 years of research studies conducted by different researchers about the GSI in a systematic way, i.e., origination, modifications, applications, and limitations. Furthermore, this study will provide a better understanding to field professionals (geologists, mining and civil engineers) about the qualitative and quantitative estimation of the GSI and its application as an empirical estimating tool for an appropriate design of engineering structures in rock mass environments.

In recovering additional oil from extensively fractured reservoirs, cyclic water pulsing has been found helpful. Cyclic gas pulsing can be even more effective. This study indicates that by judiciously combining the two methods some of the limitations of each could be overcome and additional oil recovery amounting to as much as 25 percent of the pore space contacted could be achieved. Introduction Low-permeability reservoirs that are dissected extensively by a network of interconnected fractures, solution channels, and vugs are generally not suited for waterflooding or gas injection. The injected fluid tends to channel through the high-conductivity network and bypass the low-permeability, oil-bearing matrix. Methods for improving sweep, such as treatment with silica gel, foam, and finely ground solids, generally are not applicable to such reservoirs. A production method that is applicable to extensively fractured reservoirs is waterflood imbibition displacement. This process is based on the concept that water imbibed into an oil-bearing, water-wet rock causes the countercurrent expulsion of oil. The high-conductivity fracture network simultaneously serves as a source of water for imbibition and as a sink for produced fluids. While this method has proved successful in recovering oil both in the laboratory and in the field, the rate of oil production that is imbibition controlled is too slow to be economical. Some field tests in which water was injected at rates higher than the imbibition rate showed a decline rather than an increase in oil production rate. It was hypothesized that the injection production rate. It was hypothesized that the injection of water at rates higher than imbibition rate interfered with the countercurrent flow of oil. An outgrowth of the waterflood imbibition displacement process, and one that is also applicable to highly fractured process, and one that is also applicable to highly fractured reservoirs, is waterflood pressure pulsing. This method consists of alternately pressuring and depressuring the reservoir. During the pressuring phase, the injected water is forced under high pressure from the fracture network into the low-permeability, oil-bearing matrix. During the depressuring phase, the fluids are produced out of the low-permeability matrix into the fracture network, which transmits them to the producing wells. The high-conductivity network alternately serves as a source of water for injection and a sink for the produced fluids. The steps of alternate pressuring and depressuring -- a pressure cycle -- are pressuring and depressuring -- a pressure cycle -- are repeated as often as economically feasible. Owens and Archer showed that, in the laboratory, cyclic water pressure pulsing is an effective technique for recovering oil in the amount of 5 to 10 percent of pore space contacted from water-wet and simulated oil-wet sandstone and limestone cores containing oils of 1.2- to 360-cp viscosity. Felsenthal and Ferrell, confirmed these results in tests in water-wet Berea sandstone models and further showed that the oil yield of a gas-water pressure pulsing cycle, in which a gas is injected ahead of water. is greater than that of a water pressure pulsing cycle. They attributed this to the beneficial effect of replenishing the expulsive energy with gas. Moreover, they reported that no oil was recovered in tests in which gas alone was used for pressure pulsing. JPT P. 1467

No abstract

Purpose. Technology has advanced significantly but still mining industry faces a higher number of accidents. The purpose of the research is to identify the common hazards and associated risk which are the root causes of accidents in surface mines of Pakistan and to suggest the preventive measures to enhance safety at workplace. Methods. Integrated approach used in this research work involves: collection of mine accidents data from related Government departments; occupational safety data collection from mine sites with questionnaire; fault tree analysis method applied based on three groups of factors/causes obtained from 3E’s Model i.e. Engineering, Education and Enforcement that causes accidents in mine; risk assessment and suggestion of preventive measures. Findings. In this study forty three root causes of accidents in surface mines are identified and presented as basic events and undeveloped events in the Fault Trees. A compressed picture of the root causes is revealed leading to accidents in mine. The main causes identified are human errors, unsafe operating procedure, lack of machinery, lack of personal protective equipment, environmental and haulage related hazards and violation of law. Originality.The root causes of accidents in surface mines have been identified. For the first time, the visual paths to accidents causation in surface mines of Pakistan are outlined through fault tree analysis technique. Practical implications. The identified causes of accidents along with the suggested preventive measures can be used to avoid/curtail the number and severity of accidents in surface mines and can save lives of workers and economy. Keywords: hazards identification, surface mine, accidents, fault tree analysis, risk assessment, preventive measures