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Prediction of litho-porosity using incompressibility and rigidity, offshore Niger delta, Nigeria

Nwokoma Esomchi, Agbasi Okechukwu Ebuka, Dinneya Obinna Christian

Geoinformatica Polonica

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2022

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T. 21

31--42

EN

The computed velocity ratio and Poisson’s ratio were used to calculate the pore fluid and lithology content. The gas sand, oil sand, and brine sand were identified using velocity ratio and Poisson’s ratio analyses. The velocity ratio and Poisson’s ratio study supported the gas sand anticipated by the rock physics analysis using lambda-mho and mu-rho. The velocity ratio and Poisson’s ratio analyses were used to better define the wet sand anticipated by the lambda-mho and mu-rho rock physics analyses. Lithology and pore fluid determination are very essential for the exploration and production of hydrocarbons. The wet sand from the rock physics analysis of lambda-mho and mu-rho was predicted to comprise oil sand and brine sand. The value of lambda-mho is between 21.74 and 25.67; for mu-rho is between 16.34 to 23.21; for Poisson’s ratio is between 0.25 to 0.29; and for Vp/Vs ratio is between 1.74 to 1.83. These confirm the presence of oil sand in all the seven (7) reservoirs studied in two (2) wells. All the reservoirs fall between the Agbada region (10212.50 – 11741.00 ft) and have a very good net pay zone ranging from 41.50 ft to 193.00 ft in the Niger Delta region, Nigeria. The obtained velocity ratio and Poisson’s ratio were used to calculate the pore fluid content. The gas sand, oil sand, and brine sand were identified using velocity ratio and Poisson’s ratio analysis. The velocity ratio and Poisson’s ratio studies supported the gas sand anticipated by the rock physics analysis using lambda-mho and mu-rho. The velocity ratio and Poisson’s ratio analyses were used to better define the wet sand anticipated by the lambda-mho and mu-rho rock physics analyses. The moist sand anticipated by the rock physics studies of lambda-mho and mu-rho was oil sand and brine sand.

PL

Do obliczenia zawartości płynu porowego i zbadania litologii zastosowano współczynnik prędkości i współczynnik Poissona. Piaski gazonośne, roponośne i solankonośne zidentyfikowano na podstawie analizy współczynnika prędkości i współczynnika Poissona. Badania w oparciu o współczynnik prędkości i współczynnik Poissona potwierdziły występowanie piasku gazonośnego, na co wskazywała analiza właściwości fizycznych przy użyciu lambda-mho i mu-rho. Analizy współczynnika prędkości i współczynnika Poissona zastosowano dla lepszego zdefiniowania piasku mokrego przewidzianego przez analizy właściwości fizycznych skały za pomocą lambda-mho i mu-rho. Określenie litologii oraz zawartości płynu porowego jest bardzo ważne w procesie poszukiwania i pozyskiwania węglowodorów. W wyniku analizy właściwości fizycznych skały za pomocą lambda-mho i mu-rho przewidziano, że piasek mokry zawiera piaski roponośne i solankonośne. Wartość lambda-mho waha się pomiędzy 21,74 a 25,67; a wartość mu-rho wynosi 16,34 – 23,21; współczynnik Poissona ratio wynosi 0,25 – 0,29; a Vp/Vs waha się pomiędzy 1,74 a 1,83. Potwierdza to obecność piasku roponośnego we wszystkich siedmiu (7) złożach badanych w dwóch (2) odwiertach. Wszystkie złoża znajdują się w regionie Agbada (10212,50 – 11741,00 stóp) i mają bardzo dobrą strefę opłacalności netto – 41,50 do 193,00 stóp w rejonie delty Nigru (Nigeria). Otrzymane współczynniki prędkości i Poissona wykorzystano do wyliczenia zawartości płynu porowego. Piaski gazonośne, roponośne i solankonośne zidentyfikowano na podstawie analizy współczynnika prędkości i współczynnika Poissona. Badania za pomocą współczynników prędkości i Poissona potwierdziły występowanie piasku gazonośnego, przewidzianego przez analizę właściwości fizycznych skały, przy użyciu lambda-mho i mu-rho. Współczynniki prędkości i Poissona wykorzystano dla lepszego określenia piasków mokrych, przewidzianych przez analizy właściwości fizycznych skały, przy użyciu lambda-mho i mu-rho. Najwięcej piasków przewidzianych przez badania nad właściwościami fizycznymi skały, przy użyciu lambda-mho i mu-rho stanowiły piaski roponośne i solankonośne.

2

Towards reliable velocities of permanent GNSS stations

Bogusz J., Klos A., Gruszczynska M., Gruszczynski M.

Reports on Geodesy and Geoinformatics

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2016

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Vol. 100

17--26

EN

In the modern geodesy the role of the permanent station is growing constantly. The proper treatment of the time series from such station lead to the determination of the reliable velocities. In this paper we focused on some pre-analysis as well as analysis issues, which have to be performed upon the time series of the North, East and Up components and showed the best, in our opinion, methods of determination of periodicities (by means of Singular Spectrum Analysis) and spatio-temporal correlations (Principal Component Analysis), that still exist in the time series despite modelling. Finally, the velocities of the selected European permanent stations with the associated errors determined following power-law assumption in the stochastic part is presented.

3

Erroneous GNSS Strain Rate Patterns and their Application to Investigate the Tectonic Credibility of GNSS Velocities

Araszkiewicz A., Figurski M., Jarosiński M.

Acta Geophysica

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2016

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Vol. 64, no. 5

1412--1429

EN

The paper concerns investigation of the credibility of tectonic interpretation of GNSS strain rates. The analysis was focused on stable regions, where the crustal deformations are small and the reliability of GNSS velocities is questionable. We are showing how the unreliable motion of stations affects calculated strains around them. We expressed distribution of local principal strains by a sinusoidal function and used them to investigate the significance of strain distortion. Then we used this method to investigate real motions of GNSS stations. As a test object we used Polish GNSS stations belonging to the ASG-EUPOS network. Station velocities were estimated on the basis of the 4.5 years of observations. The results let us identify stations that disturb the obtained local GNSS strain rate field. After verification and exclusion of some stations, the new GNSS strains show a much greater internal compatibility and also better fit to the directions of lithosphere stresses.

4

Lithospheric structure of the Arabian Shield from joint inversion of P- and S-wave receiver functions and dispersion velocities

Al-Amri A. M.

Acta Geologica Polonica

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2015

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Vol. 65, no. 2

227--243

EN

New velocity models of lithospheric thickness and velocity structure have been developed for the Arabian Shield by three tasks: 1) Computing P-Wave Receiver Functions (PRFs) and S-Wave Receiver Functions (SRFs) for all the broadband stations within the Saudi seismic networks. The number of receiver function waveforms depends on the recording time window and quality of the broadband station. 2) Computing ambient noise correlation Green’s functions for all available station pairs within the Saudi seismic networks to image the shear velocity in the crust and uppermost mantle beneath the Arabian Peninsula. Together they provided hundreds of additional, unique paths exclusively sampling the region of interest. Both phase and group velocities for all the resulting empirical Green’s functions have been measured and to be used in the joint inversion. 3) Jointly inverted the PRFs and SRFs obtained in task 1 with dispersion velocities measured on the Green’s functions obtained in task 2 and with fundamental-mode, Rayleigh-wave, group and phase velocities borrowed from the tomographic studies to precisely determine 1D crustal velocity structure and upper mantle. The analysis of the PRFs revealed values of 25 - 45 km for crustal thickness, with the thin crust next to the Red Sea and Gulf of Aqaba and the thicker crust under the platform, and Vp/Vs ratios in the 1.70 – 1.80 range, suggesting a range of compositions (felsic to mafic) for the shield’s crust. The migrated SRFs suggest lithospheric thicknesses in the 80-100 km range for portions of the shield close to the Red Sea and Gulf of Aqaba and near the Arabian Gulf. Generally, the novelty of the velocity models developed under this paper has consisted in the addition of SRF data to extend the velocity models down to lithospheric and sub-lithospheric depths.

5

Alternatywny sposób obliczeń prędkości średnich w otworach wiertniczych

Miluk A.

Prace Naukowe Instytutu Nafty i Gazu

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2010

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nr 170 wyd. konferencyjne

539--542

PL

W pracy przedstawiono najnowsze rozwiązanie stosowane przy obliczeniach prędkości średnich dla danych wibratorowych. Jest to sposób na dokładniejsze odwzorowanie prędkości średnich, zwłaszcza na płytszych głębokościach, poprzez uwzględnienie w oblicze- niach wpływu strefy małych prędkości na przebieg promienia sejsmicznego. Następnie zostały omówione różnice wynikające z odmiennych podejść do zagadnienia średnich prędkości.

EN

The paper presents the most recent solution for checkshot computation in case of vibroseis acquisition. This is the way to get better results of average velocity in borehole, especially for shallower depths. Computation assumes effect of low velocity layer on ray tracing. In the next step, differences between various checkshot algorithms are presented.

6

On plane waves in an isotropic linear thermoelastic solid with initial stresses

Singh B.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 4

957-963

EN

The plane wave propagation in a homogenous isotropic, thermally conducting elastic solid under normal initial stresses is studied with two thermal relaxation times. Three types of plane waves, quasi-P, thermal and quasi-SV waves, are shown to exist. The dependence of the velocities of these plane waves on the direction of propagation is shown graphically for different combinations of normal initial stresses.