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All Journal Indonesian Journal of Electrical Engineering and Computer Science Indonesian Journal of International Law LEMBARAN PUBLIKASI MINYAK DAN GAS BUMI Scientific Contributions Oil and Gas
Bambang Widarsono
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An Investigation Over Rock Wettability And Its Alteration On Some Indonesian Sandstones Bambang Widarsono
Scientific Contributions Oil and Gas Vol 33 No 3 (2010)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.33.3.820

Abstract

Wettability is a reservoir rock property that is not easy to measure and quantify but has a crucial effect on other rock properties such as relative permeability, capillary pressure, and electrical properties. Problem that may occur with regard to this matter is that those properties are often measured on already cleansed core samples as part of the standard procedure. Having undergone the normally utilized heated cleansing process alteration in the rock’s original wettability was often reported. Under such condition, unrepresentative wettability certainly leads to unrepresentative measured data with all of consequences. This article presents a study that uses 363 sandstone samples retrieved from 28 oil and gas fields in Indonesia. The study consists of two stages of analysis. First analysis is performed on data obtained from three wettability tests results while the second one is made with using water-oil relative permeability data, that is usually measured on cleansed core samples. Original wettability data shows that the sandstones varry in wettability from water-wet to oil-wet (48.2% and 30.2% of total samples, respectively). Comparison between data of the two analyses shows that original wettability tends to degrade in strength after cleaning down to neutral wettability, among which neutral wettability appears to be the largest in number (49.1% of total sample). Results also show that weak wettability tends to endure more than stronger ones. The overall results have demonstrated the need for caution in core handling and for measures that can minimize the risk.
Integrating Petrography With Core-Log-Well Test Data For Low Permeability Sandstone Reservoir Characterization: Preliminary Recommendation For Production Optimization Junita Trivianty Musu; Hadi Prasetyo; Bambang Widarsono
Scientific Contributions Oil and Gas Vol 33 No 3 (2010)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.33.3.823

Abstract

Integrating petrographic core information into combined core petrophysics, log, and well test data for understanding facies and environmental deposition in rock characterization has proved itself useful to improving quality and reliability of the required conclusions. This integrated approach has specifically shown its use in the cases of complex reservoirs such ones characterized as low-permeability sandstone reservoirs. It is in this spirit that this paper demonstrates how this virtually cost efficient analysis provides preliminary recommendations for the exploitation of such reservoirs. As case study, two types of producing reservoirs (Bekasap, Bangko, Pematang, and Tanjung Formations) have been taken in 2009. The first type is strongly controlled by depositional environment. It is found in the upper part of Bekasap and Bangko formations (1900 - 2300 ft-ss), deposited in estuarine system, and made of very fine to fine grained sand with low to moderate bioturbation. This mostly feldspathic and lithic greywackes have permeability of up to 200 mD. The second type is strongly dominated by diagenesis process and is mainly found in the Upper Pematang and Tanjung Formations (6200 - 7400 ft-ss). This reservoir type is characterized by its coarse-grained and conglomeratic sandstones resulted from fan- elta and braided channel depositional system. Diagenetic events such as compaction, recrystallization of matrix into microcrystalline clay minerals, precipitation of authigenic minerals in pore system are also well identified from the performed petrographic analysis. This is dominated by sublitharenite and litharenite sandstones exhibit horizontal permeability of up to several dozens mD. The two producing reservoir types have undergone carefully planned exploitation and stimulation operations, and the horizontal drilling and fracturing
Estimation Of Water Saturation In Carbonate Reservoirs Without Resistivity Log Data. Part Ii: Formulation Of A New Model Bambang Widarsono; Heru Atmoko; Ridwan Ridwan; Kosasih Kosasih
Scientific Contributions Oil and Gas Vol 32 No 1 (2009)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.32.1.827

Abstract

This paper is the second part of the two-part report on study for establishing alternative models that are valid for Indonesian carbonate reservoirs. In this second part formulation of the new models is presented. For the study, 407 plug samples taken from various limestone reservoirs in Indonesia were used. Following Lucia’s procedure the samples were classified, grouped, averaged, and their capillary pressure data was formulated to form water saturation models that are essentially functions of porosity and height above free water level. Validity test on the models are performed on two wells in West Java with very encouraging results. With using the Archie model as reference, justified using well test data, the new models prove themselves reliable while the original Lucia models provide far too optimistic estimates. The model validity check shows tha the models are valid for at least Class 1 and Class 2 rocks in accordance with Lucia classification. Study on Class 3 rock is needed in the future
Establishment Of More Reliable Equations For Estimation Of Coalbed Methane Proximate Analysis Data Bambang Widarsono; Kosasih Sartadiredja; Bambang A Widjayanto
Scientific Contributions Oil and Gas Vol 32 No 2 (2009)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.32.2.839

Abstract

Coal bed methane (CBM) data such as ash contents, moisture contents, volatile matters, and fixed carbon – commonly obtained from log analysis - are direct input to calculation of gas accumulation in CBM reservoirs. However, recent studies on some coal samples taken from Rambutan field CBM pilot project have shown that the commonly used log analysis equations are simply inapplicable for the field’s coal samples. Calculation results tend to give far different magnitudes when compared to laboratory results. After a series of re-evaluations and re-measurements on the laboratory results it was convinced that the problem does not lie with the laboratory results but with these ‘conventional’ equations. Therefore modification efforts are spent to find better equations. Comparisons between measured data (coal samples taken from two coal seams in the field) and calculated data show that only equation for ash contents gives accurate results. The other proximate analysis output data - i.e. moisture contents, volatile matter, and fixed carbon – is at considerable odd with their corresponding calculated data. Modification upon the original empirical models is then carried out. The following modifications on the equations have produced analogous but different empirical equations to the original equations. These equations certainly work more reliably for the field’s coals, and these better results underline that future log analyses in the field have to use the modified equations
Seismic-Derived Rock True Resistivity (R) Revisited. Part I: Reformulation Of Combined Gassmann – Shaly Sand Models Bambang Widarsono; Merkurius F Mendrofa
Scientific Contributions Oil and Gas Vol 29 No 2 (2006)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.29.2.867

Abstract

The last decade has observed frantic efforts by geoscientists to extract as much information as possible from seismic data. From the traditional role of establishing subsurface structural geometry, seismic processing and interpretations have evolved into an ever increasing role in providing rock physical properties such as acoustic impedance (AI) and porosity (0). The more common use of 3-D seismic surveys, in both exploration and development stages, have fur- ther underlined the role of seismic data as provider of inter-well rock property data. Further developments in the petrophysics-related seismic interpretation have also shown efforts to ex- tract information related to contents of formation rocks. From the widely acknowledged brightspot analysis for detecting presence of gas-bearing porous rocks in the last decades of the 20 century to the later efforts to extract information regarding fluid saturation in reservoir. Actually, as early as in mid- 1960s have scientists started to investigate the relations between acoustic signals and fluid saturation (e.g King, 1966; Domenico, 1976; Gregory, 1976). However, due to the fact that the then commonly used of 2-D seismic was considered as having insuf- ficient resolution for any practical uses in the field, the efforts remained mainly for academic purposes only. Rapid developments in technology of 3-D seis- mic survey and processing, as well as its more com- mon use at present have prompted attentions back to the investigations aimed at extracting fluid saturation information from seismie data. In 1990s have Widarsono and Saptono (1997) started a series of investigation through laboratory measurements and modeling using core samples. This was followed by more works not only at laboratory level but at larger levels of well and field scales (e.g. Widarsono & Saptono, 2000a, 2000b, and 2001; and Widarsono et al, 2002a, 2000b). Other investigators (e.g. Furre & Brevik, 2000; Wu, 2000; Zhu et al, 2000; and more recently Wu et al, 2005) have also devoted some works to achieving the same goal. Other paths of development have incorporated other supporting tech- niques such as non-linear regression (e.g.Balch et al, 1998) and artificial neural network (e.g. Poupon & Ingram, 1999; Oldenziel et al, 2000).From various investigations using seismic waves as the sole data for fluid saturation extraction, short- comings were soon felt in the form of 'narrow bands' of acoustic signals (ie P-wave velocity, V, and acoustic impedance, AI) that are influenced by varia- tions in fluid saturation. In other words, V, and AI are not too influenced by variation in fluid saturation. This reduces the effectiveness of seismic-derived V and Al as fluid saturation indicators. Efforts were then devoted to link V, and AI to other parameters such as rock true resistivity (R), a parameter known to be very sensitive to variation in fluid saturation. Widarsono and Saptono (2003, 2004) provide laboratory verifications and first field trial with some degree of succes. However, certain assump- tions (i.e. constant/uniform porosity) in the theoreti- cal formulation were still adopted in the above works, which in turn reduced the validity of the resulting formula produced and used. In this paper, the first part of a three-part work, is devoted to reformulating the combination of Gassmann theory and shaly sand water saturation models of Poupon and Hossin. These are to replace the shale-free Archie model used in the above works, which is considered as invalid for most field uses. With this reformulation, it is hoped that a more robust model/formula of resistivity as a function of acoustic impedance (R, = fAI)) is achieved, hence a more reliable resistivity could be extracted from seismic- derived acoustic impedance. Summarily, the objectives of the works a part of them presented in this paper are - To establish a model/method to obtain formation rock true resistivity (R) from seismic-derived acoustic impedance (AI), and To provide correction/modification onto previous works reported in Widarsono & Saptono (2003, 2004).
Fuzzy Logic As A Tool For Estimating Production Potential Of A Sand Layer Bambang Widarsono; Heru Atmoko; Fakhriyadi Saptono; Tunggal Tunggal; Ridwan Ridwan
Scientific Contributions Oil and Gas Vol 27 No 3 (2004)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.27.3.872

Abstract

In production management, a prior knowledge over production potential of a candidate sand layer (geological complexity in Indonesia has led to existence of stratified reservoirs with a set of layers) to be opened is always desirable. The common practice performed during drilling and completion activities of a production well is through the use of well testing and fluid sampling. From the test, fluid dynamic data such as total liquid rate, water cut, and gas cut are produced. A similar set of data is also required for more mature fields for the purpose of monitoring through the running of routine production and/or swab tests.Although the tests, especially flow tests during drilling and completion, are always regarded as the only source of proof about productive layer(s) production potential, an alternative means that can be used to provide estimates is always desired. The main reason is that flow tests are costly so that only layer(s) considered as the most potential are to be assigned for testing. Layer(s) that are considered less potential are left untested, eventhough in some cases they are also set on production during the well's production phase.The idea of establishing a method that can provide illustration over production potentials of all layer(s) always exists. Certainly, there are approaches to serve the purpose such as productivity index (PI) analogy and petrophysical through fractional flow measurement in a core laboratory. However, those approaches are often considered inadequate in accommodating various factors that may influence production potential.To materialize the idea stated above, the pattern recognition approach was taken. This approach was taken in order to model the relationships between various fac- tors in wellbore and production potential without being trapped by the certain complexity that occurs in any mathematical expressions trying to explain the relationships. For the purpose, fuzzy logie (a branch in ArtificialIntelligence) has been used. The choice is actually based on its ability to accommodate both numeric and non-numeric data. Some non-numeric data such as lithology and pore system also have some degrees of influence on production potential. With a tool that enables us to have production potential estimates of reservoir layers, from which layers with the most promising potential are taken to undergo flow tests. Furthermore, as flow test data has been acquired and used as feedback and calibration by the fuzzy model, production potential of layer(s) with less promising or ambiguous prospect can also be predicted.
An Intelligent Approach For Obtaining True Resistivity (𝑅𝑇) From Rock Acoustic Data : A Laboratory Verification Bambang Widarsono; Fakhriyadi Saptono; Heru Atmoko
Scientific Contributions Oil and Gas Vol 26 No 1 (2003)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.26.1.875

Abstract

Rock true resistivity (Rt) is known as more sensitive than compressional-wave velocity (Vp), the principal output of a seismic survey, to variation in water saturation. Therefore, it would be of a great value if there were a way to predict resistivity distribution from seismic signals. This study is essentially an effort to see the possibility of predicting Rt from Vp through a pattern recognition approach. For the purpose, a series of laboratory tests were performed on some Central Sumatran clay-free sandstone samples of various porosity values and at various water saturation levels. For studying the pattern of relationship, artificial neural networks (ANNs) were applied. From the ‘training’ (i.e.pattern recognition) activity performed using the ANNs, it has been show between Vp and Rt in the following ‘blind test’, it has also been shown that the trained relationship can be used to estimate Rt reliably using other data as input. Comparisons between estimated and observed Rt data have indicated good agreement implying the success of the approach taken in the study. This has laid the foundation and justification for further application of the approach on seismic and well-log data.
Application of Artificial Neural Network for Assisting Seismic-Based Reservoir Characterization Bambang Widarsono; Fakhriyadi Saptono; Patrick M Wong; Suprajitno Munadi
Scientific Contributions Oil and Gas Vol 25 No 1 (2002)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.25.1.879

Abstract

 Reservoir rock physical properties, such as porosity and water saturation, always play prominent roles in the development of oil and gas fields. Accurate information regarding their distribution is always desired. For this new approach that uses a purpose, a combination of intelligent computing (artificial neural network or ANN) and rock physics, with a full utilization of core data, well logs and seismic-derived attributes, is proposed. The method is basically an effort to link the required rock physical properties to seismic- derived attributes through the use of rock physics theories. The ANN itself is used to fill the gaps of data array required by the proposed method through its capacity for pattern recognition. The proposed method is applied to a limestone reservoir in East Java. Validation is carried out by comparing the results to the observed data at well locations as well as by geological justification. The application has shown a new potential for supporting reservoir modeling and field development.
Reducing Uncertainty In Log Analysis Due To Presence Of Heavy-Conductive Minerals In Sendimentary Rocks Bambang Widarsono
Scientific Contributions Oil and Gas Vol 23 No 1 (2000)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.23.1.880

Abstract

Presence of heavy-conductive mineral(s) in formation rocks tends to provide negative influence to some log readings especially the resistivity log. With regard to its function in log analysis, any distortion in resistivity log readings will certainly lead to potential misinterpretation on petrophysical properties such as water saturation (S.) Therefore a method dedicated to minimizing the effect is indeed necessary.This paper presents results of a study on presence of heavy-conductive minerals, distributed in structural form, on resistivity reading. Based on analogy and expansion of a structural clay distribution model, a correction method plus its application procedure have been proposed. Since the method is develop using an approach that is considered valid in general term it is, therefore, conceptually applicable to any field cases as long as its theoretical conditions are met. In order to make application of the method easier it has also been presented in form of nomographs.Application of the method on log analysis of two wells in West Java has proved itself well in which corrections on calculated water saturation have yielded values that are more consistent when compared to production test data. The method is also prepared in a manner that it can be easily integrated into standard log analysis practices.
In-Situ Stresses In Rock Masses: A General Review Bambang Widarsono
Scientific Contributions Oil and Gas Vol 23 No 2 (2000)
Publisher : Testing Center for Oil and Gas LEMIGAS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.23.2.881

Abstract

The in situ state of stress is a rock's point-to-point property that must be taken into consideration in every subsurface engineering activity This has been realized to an increasing extent over the past 10 - 20 years. Good quality in situ stress information enhances the quality of engineering designs such ax for mining, petroleum and geothermal production. In turn good engineering designs will support the process of decision making in related industries. However, efforts are required to encourage the use and integration of this information into the engineering activities.This paper is basically a general review over the in situ stress that encompasses various aspects, among others are concept, causes/sources that generate it, influencing factors, the effect of scales, techniques for measuring it, and its distribution throughout the lithosphere. The review is supported by works and conclusions that have been made by various investigators in the past. The relative absence of the use of in situ stress information in petroleum engineering practices in Indonesia is also discussed. This includes the absence of demand upon the information, probable consequence, and the field cases that are likely caused by the absence.Apart from the importance of in situ stress information shown by the review, it has also prompted the need to apply proper use of in situ stress information in relation to the corresponding engineering scales. Inappropriate measurement techniques assigned to an engineering problem, which corresponds to a certain scale, will certainly lead to a serious misprediction over the expected outcome. These all are hoped to provide operators in the industry a complete general view over the in situ stresses their importance.
Co-Authors Anda Lucia Andi Ruswandi Arie Rahmadi Atmoko, Heru Atyanto D Atmoko Aziz M Lubad Bambang A Widjayanto Caryana, Yusep K Danang Sismartono Desi Yensusminar Diana Dwiyanarti Djoko Sunarjanto Endras Pribadi Fakhriyadi Saptono Hadimuljono, Jonathan Setyoko Hazman Hazman, Hazman Herru L Setiawan Herru Lastiadi Herru Lastiadi Setiawan Heru Atmoko Heru Atnioko Heru Atnwko Heru Riyanto Himawan Sutanto Himawan Sutanto, Himawan Humbang Purba Humbang, Purba Ida Ayu Putu Sri Widnyani Jonathan Setyoko Hadimuljono Julikah Julikah Julikah Julikah, Julikah Junita Trivianty Junita Trivianty Musu Kosasih Kosasih KOSASIH KOSASIH, KOSASIH Kosasih Sartadiredja Lucia, Anda Maizar Rahman Mendrofa, Merkurius F Merkurius F Mendrofa Merkurius. F. Mendrofa Mohamad Romli Musu, Junita Trivianty Nurkamelia Nurkamelia, Nurkamelia Ongki Ari Prayoga Panca Wahyudi Pasarai, Usman Patrick M Wong Prayoga, Ongki Ari Pribadi, Endras Rahman, Maizar Ridwan Ridwan Ridwan Ridwan, Ridwan Romli, Mohamad Rosidelly Rosidelly Rosidelly Rosidelly, Rosidelly Rudi Suhartono Ruswandi, Andi Saptono, Fakhriyadi Sartadiredja, Kosasih Septi Anggraeni Setiawan, Herru Lastiadi Sugihardjo Sugihardjo Sugihardjo Suhartono, Rudi Sukarno, Panca W. Suliantara Suliantara Suliantara Suliantara, Suliantara Sunarjanto, Djoko Sunting Kepies Suprajitno Munadi Suprajitno Munadi Tri Muji Susantoro Tri Muji Susantoro, Tri Muji Tunggal Tunggal Tunggal Tunggal, Tunggal Usman Usman Pasarai Usman Usman Wanda Ali Akbar Widjayanto, Bambang A Wong, Patrick M Yensusminar, Desi Yusep K Caryana