The separation process of lithology and fluid reservoir is an important part in the characterization of reservoir. It will explain the physical properties of reservoir rock lithology and fluid content by integrating the geophysics and petrophysical data. This process is difficult to do in the field "B" by using parameters of acoustic impedance and lambda mu rho (LMR), because it still has a fairly high degree of ambiguity. Poisson impedance (PI) has been implemented as a solution to address the problem. In cross-plot between Acoustic Impedance (AI) and Shear Impedance (SI), a rotation of both axes was conducted according to the trend of lithology-fluid to satisfy the equation of PI = AI – cSI. To improve the accuracy of PI calculation, the value of c (optimization factor of rotation) was calculated through the method of TCCA (Target Correlation Coefficient Analysis). The correlation with to be predicted wells data then be done. Analysis of sensitivity parameter was performed on two wells in the field "B". Parameters Zp, Zs and density which obtained from the simultaneous inversion then transformed into PI. PI models clearly showed the separation of rock lithology of hydrocarbon reservoir. Lithology impedance (LI) as a result of the PI-GR correlation was able to separate sand and shale very well. Similarly, the impedance Fluid (FI) as a result of PI-SW correlation was also able to separate the water content in the reservoir with high SW value relative to gas with a low value of SW. Hydrocarbon zone proven at 2360-2400 m. The slicing result of the volumes of Poisson impedance inversion has provided a clear distribution and interpretation of lithology and fluid content reservoir at the field "B" of South Sumatera.
The sandstone reservoir in the “OA” Field is situated in the Northern Bonaparte Basin, which is gas-saturated sandstone. Mineral diagenesis is also causing several reservoir zone areas to become tight sand. The inversion method using acoustic impedance (AI) is less sensitive in distinguishing sandstone and clay rock lithology since they have almost the same impedance. Simultaneous Inversion overcomes this problem by simultaneously inversing partial angle data (near, mid, far) to obtain physical parameters besides acoustic impedance which are expected to be more sensitive in distinguishing lithology and predicting the presence of gas fluids such as shear impedance (SI) and density. These three parameters can be derived as Lame (LMR) parameters. Cross plot analysis shows sensitive physical parameters to predict the distribution of lithology and the presence of gas fluid. Density sensitive in distinguishing lithology which is then inverted, obtaining sandstone cutoff values are 2.3-2.5 (g/cc), tight sand with cutoff 2.5-2.625 (g/cc) and clay stones with cutoff 2.625-2.8 (g/cc). The presence of gas fluid is predicted by inversing the parameter Vp/Vs
which has a cutoff of >1.6 and Lambda-rho cutoff of >25 (Gpa)*(g/cc). Analysis of the parameter distribution map shows the distribution of sandstones and the presence of dominant gas fluids in the northern area of the research zone with relatively clean sandstone, compared to relatively more southern regions.
Korelasi antara log akustik dengan besaran petrofi sik telah dimanfaatkan untuk menghitung distribusivolumetrik porositas dari hubungan linier antara Impedansi Akustik (AI) dengan porositas (ϕ) reservoir.Namun untuk menghitung distribusi saturasi air (Sw) mengalami kendala karena ketidaktersediaan datakecepatan gelombang shear (Vs). Namun kemajuan teknologi saat ini telah memungkinkan mengukurdata log Vs dan ditunjang oleh teknik inversi AVO yang dapat menurunkan atribut seismik Ip(Impedansigelombang-P), Is (Impedansi gelombang-S) dan Poisson’s Ratio (PR) sehingga peluang untuk menghitungSw dari atribut seismik semakin terbuka. Didasarkan pada rumus Gassman, dibangun suatu model analitikantara besaran petrofi sika dengan besaran akustik batuan sehingga untuk kondisi batuan reservoir yangspesifi k, maka ϕ dan Sw akan dapat disebarkan pada skala lapangan, dengan bantuan atribut seismikhasil inversi AVO. Analisa sensitifi tas menguji korelasi antara log akustik dan log ϕ dan Sw di sumurzona-fasies target, lalu kemudian ditentukan zona pancung (cut-off). Hasil kalkulasi ϕ dan Sw divalidasiterhadap data log sumur. Contoh kasus ini diambil dari lapangan gas di Indonesia Timur yang memilikidata lengkap. Paper ini merupakan bagian pengembangan karakterisasi reservoir yang menyajikan suatumetode pendekatan baru untuk menghitung ϕ dan Sw dengan mengintegrasikan atribut seismik dan modelanalitik petrofi sika. Hasil pemodelan yang diperoleh dari metode ini sangat berguna dalam pemodelanreservoar statik.
Lapangan RB termasuk wilayah kerja blok Rangkas yang berlokasi di propinsi Banten memiliki Petroleum System yang sudah terbukti menghasilkan hidrokarbon. Di beberapa tempat terdapat rembesan minyak tetapi masih belum ada kajian yang mendalam mengenai potensi batuan reservoir penghasil hidrokarbon tersebut. Studi ini dilakukan untuk menentukan jenis litologi pada formasi Saraweh berumur Miocene awal dan formasi Cijengkol berumur Oligocene akhir-Miocene awal yang dijadikan sebagai kandidat batuan reservoir dengan melakukan perhitungan nilai impedansi akustik dan porositasnya. Nilai impedansi akustik tersebut dicrossplotkan terhadap parameter litologi gamma ray sebagai indikator litologi. Nilai porositas batuan dihitung berdasarkan hubungan empirik antara nilai impedansi akustik dan neutron-porosity. Hasil penelitian ini menunjukkan bahwa batuan karbonat memiliki nilai impedansi akustik berkisar antara 10000 ((m/s)*(g/cm³)) - 13500 ((m/s)*(g/cm ³)) dan nilai porositas kurang dari 0.20 v/v sedangkan batupasir memiliki nilai impedansi akustik berkisar antara 3500 ((m/s)*(g/cm³)) - 8000 ((m/s)*(g/ cm³)) dan nilai porositas 0.30 v/v-0.38 v/v. Nilai porositas yang dimiliki batupasir cukup baik sehingga dapat dijadikan sebagai kandidat batuan reservoir. Berdasarkan penampang impedansi akustik dan porositas, distribusi reservoir batupasir pada umumnya berkembang dan menebal ke arah utara dan timur sehingga pada area tersebut dapat dilakukan kegiatan eksplorasi lebih lanjut.
The anisotropic phenomenon in wave propagation has been widely recognized on various scales. Knowledge of anisotropic effects is essential for interpretation and processing of seismic data. The existence of anisotropy leads to the moveout of nonhyperbolic even in a homogenous layer. A transversely isotropic medium with a vertical symmetry axis (VTI) is a reasonable approximation of horizontally layered anisotropic medium. The approximation of travel time is important for reducing the residual normal moveout of layered VTI media. The aim of this study is to develop globally optimized generalized moveout approximation in reducing residual normal moveout in VTI media. A comparative analysis was carried out to recent method for given an ellipticity parameter (0 ≤ η ≥ 0.5 ) and wide offset depth to ratio (0 to 4). The result shows that the globally optimized generalized moveout approximation is better in reducing residual moveout at large offsets with a stronger anellipticity parameter than existing methods. This is essential for reducing the accumulation of error especially for deeper substructures.
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