Chemical Classification of Sediments in JVX -Well, Greater Ughelli Depobelt Niger Delta Basin, Nigeria

This study evaluate the Chemical classification of sediments in JVX well, Greater Ughelli Depo belt Niger Delta Basin. Samples collected from different intervals were analyzed using geochemical proxies. Agbada Formation was suggested for the sampled intervals due to the presence of shaleand sand intercalations. lithofacies units gotten from sampled intervals are Sand, Shale and Shaly sand facies . The sands are milky in colour, translucent to opaque, medium to coarse grain, subangular to subrounded and are moderately sorted while the shales are Grey in colour,fissile with the presence of lignite streak and calcareous materials.The geochemical studies of the sediments revealed that SiO2 is the dominant oxide followed by Al2O3 and Fe2O3 which constitutes over 90% while others like CaO, K2O, TiO2, Na2O and MgO constitute 10%. The sediments were classified as Fe-shale, Fe-sand and Quartz arenite. Samples that plotted in the quartz arenites region suggests an intense degree of weathering and reworking. The SiO2/Al2O3 ratios for the sediments in the well are appreciably high indicating that the samples have been heavily weathered, evidenced from the enrichment of quartz and depletion of feldspars. Also, the relatively high concentrations of Fe2O3 and TiO2 is an indication of iron-titanium minerals such as haematite and anatase retiles.

Geochemical Maturity and Paleo-Weathering Indices of Sedimentary Succession in JV Field Greater Ughelli Depo-Belt Niger Delta Basin

This study evaluates the geochemical maturity and paleo weathering indices of X well JV-Field, Greater UghelliDepo belt Niger Delta Basin, using reflected light microscope and geochemical proxies. The data obtained identified three lithofacies units as Sand, Shale, and Shaly sand facies .The application of source area weathering using Chemical index of alteration (CIA) and Chemical index of weathering (CIW) values for the sampled intervals ranges from (48.6-94.9%) and (60.6-96.7%), and have median values of (83.2 and 90.3) % respectively which is an indication of high weathering at the source. The values are variable and it may be as a result of multiple provenances of the sediments which have variable proportions of source area weathering and related processes or may be due to low concentrations of the alkalis and alkaline earth elements. However, all the samples excluding one with depth (12430ft) show CIA and CIW values greater than 70% indicating high (intensive) weathering either at the source or during transportation before deposition .From the high alteration indices value recorded from the sampled intervals, it can be inferred that the sediments are geochemically and texturally mature.

The Application of Maine Petrophysical Method; Adding Resources by Explore the Opportunity in Low Resistivity Pay Reservoir

Manifestation of Low Resistivity Pay (LRP) Existences in ONWJ Area because of Fine Grained, Superficial Microporosity, Laminated Shaly Sand and Electronic Conduction. Water saturation petrophysical analysis for LRP Case due to those reason above can be solved by electrical parameter determination with Type Curve. But to overcome the LRP caused by Laminated Shaly Sand, the use of high resolution resistivity logs that are close to the resolution of thin bed reservoir is a must. Alternative solutions, conventional high resolution resistivity logs, namely Micro Spherical Focused Log (MSFL) are used to interpret thin bed reservoirs that have the hydrocarbon potential. This intergrated petrophysical analysis is called MAINE Petrophysical Method The Petrophysical MAINE method is the development of the TECWAL (Type Curve, Core and Water Analysis) method which leaves question marks on Laminated Shaly Sand Reservoir and the possibility of variations in the Electrical Parameter and Water Saturation Irreducible (SWIRR) dependent on Rocktype. The Basis of the MAINE Method is the Worthington Type Curve with some assumptions such as Each rocktype has a different value of Bulk Volume of Water (BVW) and BVW can be used to determine the SWIRR value of each rocktype and Each rocktype has different electrical parameter m and n. In the process, the use of J-Function and Buckles Plot is applied to help determinet Rocktype and BVW values. The rocktype will be the media in distributing the value of Electrical Parameter generated by the Type Curve and the value will be used in water saturation calculation. In Laminated Shaly Sand Reservoir, Rocktyping will be analyzed more detail using the High Resolution Conventional Log, Micro Spherical Focused Log (MSFL). The expected final result of this analysis is the more reliable Water Saturation (SW) and the integration of water saturation values in the Buckles Plot which can help in determining the transition zone in order to avoid mistakes in determining the perforation zone. Through the MAINE Petrophysical Method, there is a decrease in water saturation from an average value 86% to 66% or a decrease 23%. This result is quite significant for the calculation of reserves in the LRP zone. By integrating this method with the Buckles Plot, it can help the interpreter to determine the perforation interval in order to avoid water contact or the transition zone

Workflow for Shaly-Sand Reservoir Model Calibration by Integrating Multi-Scale Data

The calibration of shaly-sand reservoir is challenging since the nature of geological complexity of the reservoir. This complex structure involves multiple scales that should be acknowledged during geologic and reservoir modeling activities. This paper is intended to show multi-scale response of shaly-sand reservoir, by integrating well, sector, and reservoir data. Reservvoir modeling is used as a tool to understand the concept and behaviour of shaly sand reservoir under multiple scenarios of shale geological setting and shale configuration. The research is based on day-to-day findings in PHE ONWJ working area where drilling activities often encounter zones with very low water saturation or high pressure, even though the infill drilling is performed nearby depleted zones. This work demonstrates the needs of multiscale integration to analyze shaly-sand reservoir response. The geology of shaly-sand reservoir indicates "compartment" behavior. The interbedded shale layers disconnect the continuity of several layers. The global scale data, e.g. average reservoir pressure, cannot accurately capture the local responses and discontinuities. Therefore, huge amount of oil reserves becomes undetected and undeveloped. Reservoir characterization based on Field X in PHE ONWJ area is used as a benchmark in modeling a generic reservoir model. The model utilizes several shale configuration and shale characteristics in order to mimic shaly sand reservoir behavior during a single primary production cycle. Whilst general production resultsis not the main concern of the current publication, The main goal of the publication is to observe pressure behaviour after several years of primary production. The research provides a new insight on how field development plan should be prepared accordingly should there be a conviction of shaly sand reservoir from test data. Developing shaly sand reservoir should require multiple plans for higher number of infill well as well as its placement and economic aspects.

A New Method To Estimate Resistivity Distribution Of Shaly Sand Reservoirs Using New Seismic Attributes

A subsurface resistivity model is important in hydrocarbon exploration primarily in the controlled-source electromagnetic (CSEM) method. CSEM forward modelling workflow uses resistivity model as the main input in feasibility studies and inversion process. The task of building a shaly sand resistivity model becomes more complex than clean sand due to the presence of a shale matrix. In this paper, a new approach is introduced to model a robust resistivity property of shaly sand reservoirs. A volume of seismic data and three wells located in the K-field of offshore Sarawak is provided for this study. Two new seismic attributes derived from seismic attenuation property called SQp and SQs are used as main inputs to predict the volume of shale, effective porosity, and water saturation before resistivity estimation. SQp attribute has a similar response to gamma-ray indicating the lithological variation and SQs attribute is identical to resistivity as an indicator to reservoir fluids. The petrophysical predictions are performed by solving the mathematical step-wise regression between the seismic multi-attributes and predicted petrophysical properties at the well locations. Subsequently, resistivity values are estimated using the Poupon-Leveaux (Indonesia) equation, an improvised model from Archie’s to derive the mathematical relationship of shaly sand’s resistivity to the volume and resistivity of clay matrix in shaly sand reservoirs. The resistivity modeled from the predicted petrophysical properties distributed consistently with sand distribution delineated from SQp attribute mainly in southeast, northeast, and west regions. The gas distribution of the net sand modeled by 5% and 90% of gas saturation scenarios also changed correspondingly to SQs attribute anomaly indicating the consistent fluid distribution between the modeled resistivity and SQs attribute.

ENHANCED ASSESSMENT OF FLUID SATURATION IN THE WOLFCAMP FORMATION OF THE PERMIAN BASIN

Conventional resistivity models often overestimate water saturation in organic-rich mudrocks and require extensive calibration efforts. Conventional resistivity-porosity-saturation models assume brine in the formation as the only conductive component contributing to resistivity measurements. Enhanced resistivity models for shaly-sand analysis include clay concentration and clay-bound water as contributors to electrical conductivity. These shaly-sand models, however, consider the existing clay in the rock as dispersed, laminated, or structural, which does not reliably describe the distribution of clay network in organic-rich mudrocks. They also do not incorporate other conductive minerals and organic matter, which can significantly impact the resistivity measurements and lead to uncertainty in water saturation assessment. We recently introduced a method that quantitatively assimilates the type and spatial distribution of all conductive components to improve reserves evaluation in organic-rich mudrocks using electrical resistivity measurements. This paper aims to verify the reliability of the introduced method for the assessment of water/hydrocarbon saturation in the Wolfcamp formation of the Permian Basin. Our recently introduced resistivity model uses pore combination modeling to incorporate conductive (clay, pyrite, kerogen, brine) and non-conductive (grains, hydrocarbon) components in estimating effective resistivity. The inputs to the model are volumetric concentrations of minerals, the conductivity of rock components, and porosity obtained from laboratory measurements or interpretation of well logs. Geometric model parameters are also critical inputs to the model. To simultaneously estimate the geometric model parameters and water saturation, we develop two inversion algorithms (a) to estimate the geometric model parameters as inputs to the new resistivity model and (b) to estimate the water saturation. Rock type, pore structure, and spatial distribution of rock components affect geometric model parameters. Therefore, dividing the formation into reliable petrophysical zones is an essential step in this method. The geometric model parameters are determined for each rock type by minimizing the difference between the measured resistivity and the resistivity, estimated from Pore Combination Modeling. We applied the new rock physics model to two wells drilled in the Permian Basin. The depth interval of interest was located in the Wolfcamp formation. The rock-class-based inversion showed variation in geometric model parameters, which improved the assessment of water saturation. Results demonstrated that the new method improved water saturation estimates by 32.1% and 36.2% compared to Waxman-Smits and Archie's models, respectively, in the Wolfcamp formation. The most considerable improvement was observed in the Middle and Lower Wolfcamp formation, where the average clay concentration was relatively higher than the other zones. Results demonstrated that the proposed method was shown to improve the estimates of hydrocarbon reserves in the Permian Basin by 33%. The hydrocarbon reserves were underestimated by an average of 70000 bbl/acre when water saturation was quantified using Archie's model in the Permian Basin. It should be highlighted that the new method did not require any calibration effort to obtain model parameters for estimating water saturation. This method minimizes the need for extensive calibration efforts for the assessment of hydrocarbon/water saturation in organic-rich mudrocks. By minimizing the need for extensive calibration work, we can reduce the number of core samples acquired. This is the unique contribution of this rock-physics-based workflow.

Identifikasi Karakteristik Reservoar Berdasarkan Data Akuistik Impedan dan Log Neutron Porositas Studi Kasus: Lapangan Boonsville, USA

<p>Penelitian ini berjudul Identifikasi Karakteristik Reservoar Berdasarkan Data Akuistik Impedan Dan Log Neutron Porositas Studi Kasus: Lapangan Boonsville, USA. Penelitian ini dilatarbelakangi oleh perlunya menemukan lokasi prospek hidrokarbon dalam upaya menjaga ketahanan energi. Tujuan dari penelitian ini antara lain untuk mendapatkan nilai <em>cutoff AI</em> <em>clean</em> <em>sand stone</em> pada formasi Caddo dan Vineyard berdasarkan hasil <em>crossplot</em> <em>log AI</em>, <em>density</em>, dan gamma ray dan untuk menentukan lokasi/zona yang di prediksi mengandung hidrokarbon pada formasi Caddo dan Vineyard berdasarkan hasil analisis inversi<em> AI</em>, porositas, dan analisis kualitatif data log. Metode yang digunakan dalam penelitian ini adalah metode seismik inversi impedansi akustik (<em>AI</em>). Metode seismik inversi<em> AI</em> digunakan untuk mendapatkan parameter fisis batuan yaitu impedansi akustik sehingga persebaran zona reservoar tempat tersimpannya cadangan hidrokarbon dapat diprediksi. Hasil sebaran<em> AI</em> pada volume seismik dapat digunakan untuk memprediksi sebaran porositas. Prediksi sebaran porositas pada volume seismik didapat dari hasil regresi linier antara nilai<em> AI</em> dengan data <em>log</em> porositas pada sumur B Yates 18 D. Hasil penelitian didapatkan nilai <em>cutoff AI clean sand stone</em> pada formasi Caddo sebesar 38000 - 55500 (ft/s) (gr/cc) dan pada formasi Vineyard sebesar 33000 - 37500 (ft/s) (gr/cc). Pada Top Caddo memiliki 4 zona yang diprediksi mengandung gas dengan reservoar berupa <em>clean sand stone</em>. Pada Top Vineyard ditemukan 3 zona yang diprediksi juga mengandung gas dengan reservoar berupa <em>shaly sand</em>.</p>

Foraminiferal Biozonation of Late Eocene - Early Oligocene sediments of BC-1 well, Onshore, Western Niger Delta Basin, Nigeria

Foraminiferal analysis was carried out on forty (40) ditch cutting samples from BC-1 well in the Onshore, Western Niger Delta at depth intervals of 5590 ft. - 8300 ft. Lithologic description of the samples together with the gamma ray log analytical data indicated the presence of four lithostratigraphic units composed of shale, sandstone, sandy shale and shaly sand corresponding to the continental Benin and paralic Agbada Formations. A total of twelve (12) species defined into eleven (11) genera, six (6) subfamilies and eleven (11) families were recovered. Benthonic and planktonic foraminiferal species constitute approximately 82 % and 18 % respectively. The calcareous benthics make up 44.4 % while the arenaceous benthics representing 37.7% of the total foraminiferal assemblages. Foraminiferal index marker species - Globorotalia opima nana, Nonion oyae, Cassigerinella chipollensis and Spiroplectammina wrightiirevealed that the age of the studied well is from Late Eocene - Early Oligocene epoch. This indicated that both the planktonic and benthonic foraminiferal recovered from the well contained the transition between the Priabonian and the Rupelian age. Three (3) informal foraminiferal zone were established - Nonion oyae zone, Cassigerinella chipollensis zone and undiagnostic zone. The zones compares with foraminiferal markers species whose stratigraphic ranges are well established in the Niger Delta and globally. Keyword: Lithostratigraphic units, Agbada Formation, Eocene, Oligocene and Biozone.