A case study of land slide in Assam hills

A devastating land slide occurred on the early hours of 24 July, 1999 in the hill slopes close to downtown Guwahati. Widespread rain over the NE region and incessant rains over Guwahati area on 23 and 24 July was main reason for the slide which claimed ten (10) human lives almost instantaneously besides damage to property. The various meteorological and geological factors responsible for the land slide have been examined in this study.

Improving the carbonate reservoirs development efficiency on the example of the Tournaisian stage deposits

The article deals with the issue of carbonate strata of complex geological structure development efficiency improving. Such facilities, as a rule, have deteriorated reservoir properties, parameter anisotropy and are complicated by secondary cavernosity. All of these factors affect the recovery efficiency and are often reflected in development indicators. On the example of Tournaisian stage deposits an example of a methodological approach to the development analysis which takes into consideration various geological factors is presented. As a result, various dependencies were obtained, which when taken into account determin the most promising areas in terms of development efficiency. The issues of the waterflooding system efficiency and the ways of its efficiency increasing are considered separately. Keywords: oil fields development; carbonate reservoirs; development efficiency; waterflooding system.

Optimization of Exploration Prospects Based on Ant Colony Algorithm and XGBoost Combined Optimization Model

Traditional exploration prospect optimization is uncertain due to human factor, the primary reason of that problem is the complex nonlinear relationship between trap quality and related geological factors. Some researchers proposed use artificial neural network (ANN) to solve the problem of the comprehensive geological evaluation of traps, because ANN can describe the nonlinear relationship of multiple geological factors. Considering ANN has some drawbacks, such as it is need lots of parameters for training, and the learning process can not be observed. In this paper we proposed a combined optimization model to accomplish optimization of exploration prospects, and express the affinity order between the prospects and its related geological factors, also can provide the data support for exploration. Based on trap data of an oilfield in Africa, there are 12 geological factors related to trap quality, including trap coefficient, trap depth, trap scale, trap area, Reservoir coefficient, Preservation coefficient, hydrocarbon source coefficient, resources etc.. The ant colony algorithm is used for feature selection, and irrelevant and redundant features are eliminated through multiple iterations, making it suitable for model processing and improving training speed. Based on ant colony algorithm, we get the key parameters for XGBoost model training, namely trap area, reservoir coefficient, preservation coefficient, resource, and the key features are used in XGBoost model for training and prediction. Finally, we compared our prediction results with expert prediction, the error is 0. In this paper, we proposed a combined optimization model based on ant colony algorithm and XGBoost for exploration prospect optimization. We recognized the key geological factors and different characteristic rules for exploration prospect optimization, in the process of optimization, ant colony discards the bad features that interfere with classification and recognition, and retains the features that contribute greatly to classification. In comprehensive geological evaluate of trap, the proposed combined optimization model is suitable for complicated nonlinear geological relationship, and express the affinity order between the prospects, the proposed method can work as an auxiliary way in petroleum exploration, also the proposed method can provide decision support for exploration prospect optimization, and finally can fulfill cost decreasing and benefit increasing.

A Case Study of Thaumasite Sulfate Attack in Tunnel Engineering

There existed ever-increasing structural diseases in the Dugongling tunnel after the completion of the construction. Systematic research was carried out based on the information of tunnel engineering geology, disease development, mineral composition of surrounding rock and concrete, and laboratory tests. Results showed that (1) the concrete structure from the Dugongling tunnel suffered from a typical thaumasite sulfate attack (TSA); (2) tunnel diseases developed under the influence of multiple geological factors such as groundwater, karst, gypsum bearing stratum, and geological tectonics. Groundwater aggravated the appearance of engineering defects of various geological factors and accelerated the softening and swelling of surrounding rock. Moreover, the additional load of supporting structure increased, and the concrete structure was prone to sulfate attack; (3) the development of tunnel diseases showed long-cycle and large-scale characteristics, and the types of diseases are heterogeneous. The tunnel diseases develop rapidly in the third year after the construction. The structure collapse disease, one of the most serious diseases of tunnel lining, occurred in the fifth year after construction; and (4) according to the conditions of TSA, technical treatment measures were proposed. These measures included blocking the flow of CO 3 2 − , improving the impermeability of concrete structures, and decreasing the diffusion of external ions and groundwater. This work provides a solution for the treatment of similar tunnel disease and mechanism analysis.

Study of Liquefaction Potential at Sabo dam Construction on Poi and Bangga River, Sigi Regency, Central Sulawesi

The Palukoro fault, an active sinistral fault that cuts through Sulawesi Island, was the cause of the earthquake and liquefaction disaster in Palu and Sigi Regency in 2018. A series of studies related to liquefaction have been carried out since then but more focused on the west side of the Palu River. This research will raise the potential for liquefaction on the eastern side of the Palu river, precisely in the sabo dam area at Poi and Bangga River. These rivers are located on the opposite side of the Sibalaya liquefaction area. Liquefaction potential was calculated using the Simplified Procedure Method based on NSPT values. Fifteen and twelve boreholes are located at Bangga and Poi rivers, respectively. The qualitative analysis assessed the criteria of vulnerability based on geological factors, groundwater levels, and seismicity. The Liquefaction Potential Index method was used and calculated using several earthquake scenarios based on historical data and potential earthquakes of The Palu-koro fault. Based on LPI analysis, the Poi River has meager potential at the middle stream area and moderate level potential at the downstream. Bangga River has moderate to high liquefaction potential downstream and low to very low potential at the middle stream.

The influence of intrusion on change characteristic of coal in Mallawa Formation of South Sulawesi Province

Coal that is deposited in the same depositional environment, age, and formation will usually have the same characteristics. However, the influence of geological conditions in an area can cause differences in the characteristics of coal in the same formation. This study aims to analyze geological factors that can affect differences in the characteristics of coal in the same depositional environment, age and formation. The study was conducted at three different locations, namely Mallawa District, Maros Regency; Lanne District, Pangkep Regency; and Massenrengpulu Region, Bone Regency. The coal sampling method in the study area uses the channel sampling method (ply by ply) which represents the bottom, middle and top coal seams. The results of the proximate analysis of coal in the Mallawa District Maros Regency showed an average moisture content of 7.78%, an average ash content of 39.99%, volatile matter 32.85%, and fixed carbon 19.39%. While in the area of Lanne District, Pangkep Regency shows an average moisture content of 9.65%, an average ash content of 40.41%, volatile matter 33.80%, and fixed carbon 16.16%. The results of proximate analysis in the Massenrengpulu area of Pangkep Regency showed an average moisture content of 3.86%, an average ash content of 23.16%, volatile matter 35.53%, and fixed carbon 37.46%. Coal from Mallawa and Lanne District has relatively the same characteristics, while the Massenrengpulu coal has lower moisture and ash content, and higher fixed carbon caused by the intrusion of igneous rocks in the area which causes the coal maturation process to be faster than the other two regions.

Features of filling reservoirs with hydrocarbons in the territories with a low maturity of the oil and gas parent rocks (a case study of Jurassic hydrocarbon traps in the Uvat district)

The article is devoted to the results of an analysis of geological factors that had a great influence on the filling of Jurassic traps with hydrocarbons. Based on the results of paleotectonic analysis, three key stages of reconstructions of the structural plans of sedimentary cover deposits were identified. Each stage was characterized not only by the appearance of new traps in the interval of Jurassic deposits, but also by the sinking of rocks of Bazhenov formation to a certain depth. It is revealed that in most of the territory of the Uvat district, Bazhenov formation didn't have time to fully realize its hydrocarbon-generating potential. In the Central and Eastern regions it entered the main zone of oil formation only in the Paleogene. Since the development of the relief of modern structural plans of Jurassic deposits in this area occurred in several stages, both the formation of traps and the lateral migration of hydrocarbons also occurred in stages. The first stage of migration occurred at the boundary of the lower and upper Cretaceous, the second stage occurred at the beginning of the Paleogene. As a result, the combined influence of lateral migration of hydrocarbons and the gradual formation of local structures in different areas of the Uvat district led to selective filling of Jurassic hydrocarbon traps.

Modeling of stress states in intact layered rock massifs

Предложена структурная модель анизотропной среды для расчета напряженнодеформированного состояния в нетронутых массивах горных пород, которая учитывает ряд горнотехнических и горно-геологических факторов. Результаты аналитического решения позволили объяснить известные из практики натурных наблюдений факты (возможность превосходства горизонтальных напряжений над вертикальными, кусочно-линейный характер напряжений и т.д.), которые находились в противоречии с широко распространенными гипотезами о распределении напряжений в породных массивах. A structural model of an anisotropic medium is proposed for calculating the stressstrain state in intact rock massifs, which takes into account a number of mining and geological factors. The results of the analytical solution allowed us to explain the facts known from the practice of field observations (the possibility of the superiority of horizontal stresses over vertical ones, the piecewise linear nature of stresses, etc.), which were in contradiction with the widespread hypotheses about the distribution of stresses in rock massifs.