The seismic far-offset data plays important role in seismic subsurface imaging and reservoir parameters derivation, however, it is often distorted by the hockey stick effect due to improper correction of the Vertical Transverse Isotropy (VTI) during the seismic velocity analysis. The anisotropy parameter η is needed to properly correct the VTI effect. The anisotropy parameters of ε and δ obtained from log and core measurements, can be used to estimate the η values, however, the upscaling effects due to the different frequencies of the wave sources used in the measurements must be carefully taken into account. The objective is to get better understanding on the proper uses of anisotropy parameters in the the velocity analysis of deepwater seismic gather data. To achieve the objective, the anisotropy parameters from ultrasonic core measurements and dipole sonic log were used to model the seismic CDP gathers. The upscaling effects is reflected by the big difference of measured anisotropy values, in which the core measurement value is about 40 times higher than the log measurement value. The CDP gathers modelling results show that, due to the upscaling effect, the log and core-based models show significant differences of far-offset amplitude and hockey sticks responses. The differences can be minimized by scaling-down the log anisotropy values to core anisotropy values by using equations established from core – log anisotropy values cross-plot. The study emphasizes the importances of integrating anisotropy parameters from core and log data to minimize the upscaling effect to get the best η for the VTI correction in seismic velocity analysis.
The Lower Kutei Basin which contains several giant oil and gas fields is located on the East Kalimantan, Indonesia. This paper discusses the identification and mapping of oil-filled reservoirs and their depositional facies by integrating seismic stratigraphy, attributes, and AI (Acoustic Impedance) inversion methods. The log data cross-plots show that AI can be used to distinguish oil-sands from wet sands and shale, and to derive the total porosity of the sands. However, AI and amplitude values are greatly affected by the oil, porosity and tuning effects, hence they cannot be used to identify the facies containing the oil-bearing sands. Therefore, to map the facies containing the oil-filled sands, the AI map is combined with the variance and sweetness maps. It can be seen clearly from the variance and sweetness maps that the oil-sands suggested by the AI map are contained in a narrow and elongate meander-like geometry which is typical of channel facies. The variance and sweetness maps suggest that there are two channels in the study area. To determine which channel is thicker, spectral decomposition RGB map was made. The result suggests that the right channel is more prospective as it associates with thicker sand deposits. The combination of variance, sweetness and RGB maps strongly indicate that the channels in the study area are in upper-slope environment, and the thicker oil-sands are located in the eastward of the study area.
Permeability is a key to determine the quality of reservoir. Reservoir quality can be defined as the ratio between permeability and porosity of a rock. Besides, permeability is not influenced by porosity solely, there are other factors which affect the value of the permeability of a rock. One of them is affected by the pore structure, which includes turtuosity, surface area, and grain size. To determine how much these factors affect the permeability of a rock, it takes an elastic parameters that can be an indicator of the quality reservoir e.g pore space stiffness and critical porosity.Primary data such as petrophysics, XRD data, and permeability are used as input data to determine the quality of reservoir. By using Zimmerman's equation and Nur's model, we will get the value of pore space stiffness and critical porosity at each point. The combination of rock quality equation derived from Kozeny Carman's with elastic parameters as indicators produces qualitative rock quality identification. Results of this study is able to show that the pore space stiffness and critical porosity can represent turtuosity, surface area, and grain size of a rock which lead to the determination of rock quality. The method proposed in the present study demonstrated an excellence reservoir quality prediction based on the relation between petrophysical parameters with elastic parameters.Abstrak: Permeabilitas menjadi parameter yang sangat penting dalam penentuan kualitas reservoir. Kualitas reservoir dapat didefinisikan sebagai perbandingan antara permeabilitas dengan porositas. Salah satu faktor utama yang mempengaruhi permeabilitas adalah porositas, namun masih terdapat faktor-faktor lainnya yang mempengaruhi besarnya nilai permeabilitas. Salah satunya dipengaruhi oleh stuktur pori batuan, yang merupakan fungsi dari turtuosity, surface area, dan besar butir. Untuk mengetahui seberapa besar faktor tersebut mempengaruhi permeabilitas suatu batuan, maka dibutuhkan suatu parameter elastik yang dapat menjadi indikator penentu kualitas reservoir. Dalam penelitian ini, parameter elastik yang digunakan adalah pore space stiffness dan critical porosity. Data-data primer seperti data log, data XRD, serta parameter reservoir khususnya permeabilitas digunakan sebagai data input untuk pemodelan kualitas reservoir. Parameter elastic pore space stiffness dan critical porosity diperoleh dari perhitungan menggunakan persamaan Zimmerman dan model Nur. Hasil penelitian ini berhasil menunjukkan bahwa pore space stiffness dan critical porosity mampu merepresentasikan nilai turtuosity dan besar butir suatu reservoir. Kata kunci: permeabilitas, kualitas reservoir, pore space stiffness, critical porosity PENDAHULUANMayoritas sumber energi di Indonesia masih bergantung pada bahan bakar fosil, tetapi kenyataannya bahan bakar fosil merupakan sumber daya yang tidak bisa diperbarui dan produksinya terus menurun. Dengan didasari masalah tersebut, upaya yang bisa dilakukan yaitu melakukan kegiatan eksplorasi di cekungan kawasan timur Indonesia dengan target reservoi...
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