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Tan Z.-L.,Geoscience Center | Fu H.-B.,Geoscience Center | You J.-J.,Geoscience Center | Chen L.-Y.,China National Logging Corporation | Miao K.,GWDC Well Testing Company
Well Testing | Year: 2016

High skin factor of XX-6 DST3 reduced deliverability greatly. According to which is the main factor to influence deliverability of the pollution or degasification skin factor, and through the integrated analysis of well testing and well logging data of XX-6, XX-3 and XX-10, skin factor caused by pollution is the main factor leading to low deliverability of XX-6 but not by degasification based on theory of that the damage factor caused by pollution didn't change during the first shut-in and the second shut-in period of XX-6 DST3. It is suggested to perforate the upper formation of M-II formation and to test M-II and J-0-1 formation together, which would increase deliverability of XX-6 greatly. The study is meaningful to understand skin factor intensively and extend the application area of well testing data. © 2016, The Editorial Department of Well Testing. All right reserved. Source


Torok A.,Budapest University of Technology and Economics | Licha T.,Geoscience Center | Simon K.,Geoscience Center | Siegesmund S.,Geoscience Center
Environmental Earth Sciences | Year: 2011

A novel approach of studying dust, black crust and host limestones by using various techniques is presented in this paper. Samples were collected from limestone monuments located in rural, urban and industrial areas in Germany and Hungary. The paper focuses on differences in the mineralogical composition, major and trace element distribution of materials and their total polyaromatic hydrocarbons (PAH) concentration having different exposure to air pollutants. High concentration of gypsum was found in laminar and dendritic black crusts and even in the dust of both urban and rural areas, despite the low concentration of SO2 in rural atmospheric environments. The black crusts show a typical microfabric with distinct layers of various gypsum-calcite mineral associations, silt-sized mineral fragments and black particle content. In dust, newly formed gypsum crystals were found along with mineral fragments, and siliceous and, less frequently, carbonaceous fly ash particles. High concentration of lead was found both in the samples of urban and rural areas of Germany and Hungary. Lead mostly accumulates in dust and also in the black crust. Highest lead concentrations were found not on the surface of the black crust, but close to the crust/limestone boundary according to LA-ICPMS analyses. It indicates that despite the ban of leaded petrol, lead is still present in the dust and the in the soiled zones of the built environment. Similarly to lead, no significant difference in the total PAH content of dust and crust samples were found in the two countries. Dusts are equally enriched in PAH in both countries, whereas black crusts contain fewer amounts. Most of the aqueous extracts of the samples were saturated with respect to sulphate, which also indicate the presence of gypsum, whilst in some German samples unsaturated conditions were detected. In summary, by using a combination of these analytical techniques, it was possible to distinguish rural and urban samples and to outline the role of dust in bringing pollutants to the stone surface. It is suggested that the analysed dust and stone samples indicate not only present, but also the past, pollution fluxes and as a consequence stones similar to sediments or surface waters can be used as environment indicators. © 2010 Springer-Verlag. Source


Tan Z.,Geoscience Center | Song L.,Geoscience Center | Huang D.,Geoscience Center | Yu T.,Petrochina
Well Testing | Year: 2012

DST5 pressure derivative curve of the first well in D field shows that "pressure depletion' probably exists during the test, so many impermeable boundaries are selected as the outer boundary in well test interpretation. But seismic and geology data show that there wer-en't any bounded boundary. Impermeable boundary model is denied based on the three aspects of PPD function, pressure coefficient and the study of seismic and geology. The reason that false "pressure depletion" appears is analyzed from initial flow time.lithology and physical property. The research result shows that current well testing data cannot prove pressure depletion appears but a false "pressure depletion" phenomenon. Well testing interpretation should be integrated with other subject. For such formation,longer initial flow period,lower mud density and down-hole shut-in method should be chosen to avoid appearing false "pressure depletion". Source

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