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1

Different methods for shale volume determination

100%

Wandycz P.

Geology, Geophysics and Environment

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2014

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tom Vol. 40, no. 1

140

EN

One of the most important steps in well log analysis is proper evaluation of shaly formations. Clay minerals may cause a lot of problems with calculating porosity or water saturation (Jarzyna 1997). There are several different methods that allow us to determine the volume of shale in the geological formation. It is a fact that choosing correct technique is often a problem which many well log analysts must struggle with (Bassiouni 1994). This paper shows the results that interpreter might obtain using different types of methods for quantitative determination of shale content. Well logs used for the calculation of the shale volume come from Borehole A-1, which is located in west central Poland in Greater Poland Voivodeship. The first method for the determination of the shale volume was the Gamma Ray technique. This method allowed to calculate the amount of shale using only one log as an input (Ellis & Singer 2008). Both nonlinear and linear equations were applied to calculate the volume of shale. The second technique used is the Neutron-Density Method (Techlog Manual 2011), where two logs were used as an input data source, Neutron Porosity log (NPHI) and Bulk Density (RHOB). The third and the last method for calculating the volume of shale in Borehole A-1 was Resistivity technique, with deep resistivity log (Schlumberger 1998). The results obtained with each technique were compared to each other and then combined together. The last step allowed to calculate the final volume of shale (Schlumberger 1998). Since each technique gave different results, and it was impossible to choose the correct one, the combination of methods had to be applied for the calculation of shale volume. The errors for every method have a tendency to increase, not to reduce, the apparent shale volume (Schlumberger 1998), therefore a "minimum combination" was applied, meaning that the minimum values of all the variables (calculated shale volumes) were used as an input. Results of the "minimum combination" method give the most probable information about the volume of the shales within the analyzed geological formation.

2

Wspomnienie o moim Ojcu

88%

Wandycz P.

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tom R. 11, nr 1

4--8

3

Correlation analysis of petrophysical parameters within the main dolomite sedimentation zones on the Grotów peninsula

63%

Wandycz P. , Święch E.

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tom Vol. 22

45--54

EN

The study area in geological sense is located on the Grotów peninsula within Gorzów Block in north-western part of Poland, on the border of Fore-Sudetic monocline and Szczecińska Through. In that area two generalized sedimentary zones were recognized: carbonate platform (barrier and platform plain) and slope of the carbonate platform (edge of the slope with bay plain). The aim of this study is the analysis of the relationships between petrophysical parameters of the carbonate reservoir rocks. This research was conducted on the base of mercury porosimetry for 318 rock samples. The analysis showed that not all pore space is available for the accumulation of hydrocarbons. Availability of pore space for accumulation strongly depends on the average capillary, and the amount of pores with diameter higher than 1 μm. In general, slope of the carbonate platform has better conditions for accumulation of hydrocarbons.

4

Determination of seismic wave attenuation based on acoustic full waveforms

63%

Święch E. , Wandycz P.

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tom Vol. 22

55--63

EN

The loss of elastic energy to the medium can be quantified by the quality factor Q. Acoustic full waveforms log from Winna Góra1 borehole were used to estimate P-wave quality factor. Data used in this paper were analyzed with usage of GeoWin software. Interpretation of acoustic full waveforms was performed for the one pair of waveforms. The most important part in the interpretation of data is manual picking of P wave arrival, calculation of semblance function, and picking anomalies of P wave on amplitude spectrum. Using data from interpretation of acoustic full waveforms, we calculated quality factor. Based on provided analysis it is concluded that the highest attenuation ( so the lowest Q) is observed in Rotliegend strata.

5

Effect of the near surface layer for the microseismic monitoring – 2D modelling

51%

Pasternacki A. , Wandycz P. , Maćkowski T.

Geology, Geophysics and Environment

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2016

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tom Vol. 42, no. 1

111

EN

Microseismic monitoring is usually used to map hydraulic fracture or stress changes in the reservoir, which is stimulated (Maxwell et al. 2010, Duncan & Eisner 2010). Examining the wave traveling through the reservoir can provide many important information on medium properties (Grechka et al. 2011) and can be used either to assess the stimulated reservoir or improve microseismic imagining. Microseismic monitoring network can be deployed either on surface or in borehole. Noise level observed on the surface network is usually 10 times higher than one observed in the receivers placed in borehole but still the detection the microseismic events by the surface array is possible (Eisner et al. 2010). In this study, we present the results of the synthetic modeling to show qualitatively and quantitatively the influence of the near-surface layer and the effect of the attenuation in this layer for the assessment of the strength of the signal recorded by receivers placed on the surface or just below it. For the purpose of this research, authors performed 2D seismic modeling using Tesseral software. We performed several different models, each of them in two variants. First variant included the impact of the impedance contrast of the near surface layer; in the second variant we suppressed that effect. Layer composition in models differed both in number and their properties (velocity and quality factor). In each model, we used one type of source located in 3 different places. Monitoring array was vertical and constrained with 100 geophones. First receiver was placed on the surface, and the spacing between phones was 1m. Data obtained with this procedure were then analyzed using Matlab software. For each model, we compered the relative amplitudes of the different events in both variants, and then assessed the impact of the impedance contrast in the near surface layer. Performed modeling proved that the influence of the near surface layer is significant. We observe that the amplitude ratio between the first receivers in two variants of each model ranges from 1.5 to almost 2, regardless of the depth of the source. Signal enhancement is the function of the impedance contrast, and does not depend on the attenuation in the near surface layer. However, attenuation does not influence the enhancement of the signal, very low quality factor in the shallow layers highly influences the strength of the arriving waves.

6

Comparison of solutions for microseismic focal mechanism estimation

51%

Wandycz P. , Święch E. , Pasternacki A.

Geology, Geophysics and Environment

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2016

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tom Vol. 42, no. 1

137--138

EN

One of the major advantages of microseismic data, recorded during hydraulic fracturing of prospective shale intervals is ability to use both P and S wave in the analysis, not only to determine epicentral locations of events but also to describe source itself. The information about the mechanisms of located microseismic events allows better understanding of in situ stress and strain conditions and the local subsurface geomechanical properties and forces (Kamei et al. 2015). As Duncan stated in his work, a proper characterization of the observed events mechanisms is the key to understand radiation pattern of the signals in the investigated area (Duncan & Eisner 2010). Moreover, an understanding of the nature of the rock failure supports reservoir simulation models and stimulated reservoir volume estimates (Kratz & Thorton 2016). Proper assessment of event strike, dip and rake provides the geometry of the fracture plane assuming double couple focal mechanism, while full moment tensor inversion provides information about shear and tensile nature of the calculated mechanisms. The common method to obtain reliable focal mechanisms of observed microseismic events is decomposing of the full moment tensor. Seismic moment tensor is powerful tool which provides a general mathematical solution of sources that can be used to distinguish between various types of microseismic events. The method comes to reliably estimation of the six independent components of a full moment tensor by lestsquares inversion (Eaton & Forouhideh 2010). The motivation for this analysis was to determine microseismic focal mechanisms based on P – wave peak amplitude, P and S – waves peak amplitudes and S – wave peak amplitude only to estimate the differences and uncertainties between these three different solutions. Furthermore authors decided to check how the mechanisms changes with different geometries of downhole monitoring array. In this study only synthetic data computed in MiVu GeoTomo software using raytracing method and simple layered velocity model were used. The mentioned velocity model was constructed based on well logs data delivered by PGNiG from measurements done in Northern Poland where active exploration of shale gas takes place. In this analysis authors focused only on double couple (DC) and compensated linear vector dipole (CLVD) mechanisms which are two most common types of microseismic focal mechanisms occur during hydraulic fracturing of shale deposits. Performed analysis proved that the best and most consistent results with the lowest uncertainties reflected in the condition number parameter can be obtained by using both P and S peak amplitudes.

7

Rozkład parametrów petrofizycznych w zróżnicowanych typach przestrzeni porowej dolomitu głównego brzeżnej strefy platformy wielkopolskiej

51%

Semyrka R. , Semyrka G. , Wandycz P.

Wiadomości Naftowe i Gazownicze

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2014

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tom R. 17, Nr 9 (197)

9--13

EN

Distribution of petrophysical parameters in diverse types of pore space in the Main Dolomite marginal zone of the Wielkopolska platform Abstract Microfacial analysis along with detailed sedimentological analysis enabled authors to describe different sub-facies in the studied area and to distinguish depositional environments of the Main Dolomite. Both quantitative and qualitative petrophysical parameters differ within sub-facies of the Main Dolomite. Moreover reservoir rocks of main dolomite have low and very low porosity. The fracture porosity is dominant, intergranular/fracture porosity (dual porosity) has lower meaning, intergranular type is rare. Complexity of the reservoir space of the Main Dolomite creates optimal conditions for its pore space volume and possible migration and accumulation processes of hydrocarbons, thereby they exhibit very promising perspectives for petroleum prospection.

PL

Analiza mikrofacjalna wraz ze szczegółową analizą sedymentologiczną umożliwiły wydzielenie na omawianym obszarze środowisk depozycyjnych dolomitu głównego, oraz określenie odrębnych subfacji. W ich obrębie utwory dolomitu głównego charakteryzują się zróżnicowanymi ilościowymi i jakościowymi parametrami petrofizycznymi. Dominują tu skały zbiornikowe o niskiej i bardzo niskiej pojemności, typu głównie szczelinowego, podrzędnie szczelinowo – porowego i sporadycznie porowego. Złożoność przestrzeni zbiornikowej dolomitu głównego stwarza warunki optymalne dla jego pojemności oraz możliwej migracji i akumulacji płynów złożowych, a tym samym stwarza obiecujące perspektywy w prospekcji naftowej.