Analysis of granitoid type of Bukit Nunggal Village, Air Mesu, Central Bangka Regency

The research was conducted in Bukit Nunggal Air Mesu Village, Pangkalan Baru District, Central Bangka Regency, an IUP PT Tanjung Bukit Nunggal with a height of ± 210 meters. This study is to find out more details about the type of granitoid rock which is a unitary hill but it is estimated that it is the intrusion body of several types of granitoid rock. The research method includes analysis of mineralization content and geochemical analysis in the form of XRF. The steps to be taken include literature studies, field research, laboratory analysis including mineralogical analysis and microscopic observations as well as geochemical testing of rock samples using XRF. The sampling procedure for analysis is carried out based on the height and changes in rock texture, on the number of rock types / lithologies available to be observed and examined for their mineralization content. Regionally, the study area consists of a hill which is interpreted as a potential rock for construction mining. It is hoped that this research can produce an analysis of the existing granitoid types by studying the lithology / rock, geological structure and mineral textures. There are 2 types of granite found in Nunggal Hill, namely granite and granite alterated (gneiss), with its main minerals are quartz, feldspar, biotit, opaq and sericytic and chlorite minerals.

A Novel Naturally Fractured Reservoirs Classification Plot Through the Liaison of Dynamic Data, Depositional Environments and Rock Texture

Naturally Fractured Reservoirs (NFR) represent a challenge for petroleum industry because they are characterized by complex dynamics associated to the fluids motion and geological events that originated them million years ago, where diagenetic processes have played a transcendental role. In carbonates, the movement of fluids within the reservoir is highly influenced by the fracture systems present in the formation, however, these are intimately related to rock texture and quality, depositional environments, facies changes, regional and local stresses, tectonism and of course, diagenesis. Regarding the dynamic behavior, we can highlight the importance of the type of fluid present in the system and the acting drive indices, which govern the behavior of pressure and production in this type of reservoirs, whose analysis usually goes further of conventional techniques commonly used for its evaluation. One of the problems faced by reservoir engineers is the classification or categorization of these types of reservoirs to know their true potential and try to estimate the recoverable reserves as accurately as possible, since the complex dynamic behavior of NFR hinders its exploitation when the most important parameters for its correct evaluation are not known. From the above, a novel and practical Naturally Fractured Reservoirs (NFR) classification plot is proposed based on the Nelson's classification (2001) and a full revision of other author's technical reviews. The plot is generated through the information obtained from a full reservoir characterization to acquire petrophysical evaluations and Pressure Transient Analysis (PTA) to find the product of the effective porosity and the average flow capacity of each of the fields tested in order to plot them against the recovery factor; this analysis considered more than 200 carbonate fields from more than 40 countries around the world. When plotting the data involved, it is clear to see that they are grouped in different zones for its reclassification as Naturally Fractured Reservoirs, where we added a subcategorization of type II reservoirs (type II A and type II B) and also the influence of vugs in type I reservoirs and the gas and condensates region; all attributed to the dynamic behavior associated to the type of fluid, the acting drive indices, the depositional environments and the rock texture. The results obtained were fully coupled to a probability distribution and have shown to be consistent with the observed behavior, being a useful tool for determining the actual type of NFR, the expected production rates, the range of possible recovery factors to be achieved and the characterization of reservoirs. Likewise, the proposed plot can be applied to the analysis of sectors in the same reservoir or formation to try to identify the variations regarding the type of NFR by zones, blocks or compartments according to the location of each well in the field, considering their respective recovery factors concerning its cumulative production and original reserves.

Wietrzenie mrozowe wybranych skał tatrzańskich w świetle badań laboratoryjny = Frost weathering of selected Tatra rocks in the light of laboratory tests

The aim of the work described here was to determine the rate of frost weathering for selected types of rock, and the manner in which this proceeds. The authors attempts to answer questions regarding progress with the disintegration of a given type of rock over time; the size and shape of weathered grains; the role played by fissures in rock and rock texture; and further relevant properties like compressive and tensile strength, porosity and water absorption. The rock samples used in laboratory testing were collected in the catchment area of the Chochołowski Stream in the Western Tatra Mountains of Poland. The seven types of rock analysed were white and brown granite, organodetric limestone, fine-grained conglomerate, dolomite breccia, quartzite sandstone and amphibolite. Samples were subjected to simulated frost weathering via the impact of repeated thermal cycles across a temperature range of -5 to +10°C. The simulation was carried out at the Low Temperatures Laboratory of the Institute of Geography and Spatial Management of Kraków’s Jagiellonian University, using a CI/1400/LT/2D cooling device. As testing was in progress, changes in the states of samples were determined through the measurement of dry and saturated mass and water absorption, as well as the speed at which an ultrasonic wave passed through. By reference to results for these measures, it was possible to calculate the frost weathering index after Matsuoke, i.e.:Rf= (Vp0-Vpk)/(Vp0*k) [cykle -1],where Vp0 is wave speed at cycle 0 (in km/s), Vpk is wave speed at cycle k (km/s) and k is the number of cycles. Rock dissolution tests and measurements of the products of weathering were also carried out. Values obtained for the index were used to rank the rocks tested for their resistance to frost weathering, as was the percentage of material in the initial mass that became subject to rock weathering. The least-resistant rock proved to be dolomite breccia, and the most-resistant amphibolites and quartzite sandstones. The rankings of other rocks varied in line with the indicative parameter referred to. The testing of physical properties suggested several reasons for high resistance to frost weathering among the analysed types of rock from the Western Tatras, i.e. the limited (<5%) open porosity noted for all types, limited water absorption, high compressive and tensile strength, compactness and homogeneity, low densities of fissures in samples in their initial state, almost complete filling of pores with matrix (e.g. in sandstone and conglomerate), re-filling of cracks (e.g. in limestone), and a significant component of resistant quartz. No effect of rock texture on resistance to frost weathering could be observed, but the presence of carbon matrix and carbonate rock fragments is important. The latter dissolve steadily, creating more favourable conditions for physical weathering (e.g. of amphibolites and conglomerates). The occurrence of mineral veins within rocks determines disintegration routes (e.g. in conglomerates). Given that rocks were subjected to an average of 850 repeated thermal cycles in the laboratory, the simulation achieved was of approx. 50 years of frost weathering under natural conditions in the study area. Experiments of this kind thus offer insight into processes running very slowly under natural conditions.