Papers by Bambang Widarsono
Scientific contributions oil and gas/Scientific Contributions Oil & Gas, Mar 30, 2022
Integrated Approach to Investigate the Potential of Asphalt/Tar Sand on Buton Island, Indonesia
Scientific Contributions Oil & Gas, Jul 31, 2023
Scientific contributions oil and gas/Scientific Contributions Oil & Gas, Dec 1, 2023
Oil production from the extraction of Buton Asphalt (Asbuton) becomes for oil production is an at... more Oil production from the extraction of Buton Asphalt (Asbuton) becomes for oil production is an attractive subject in bitumen to study considering that the use of exploration. Currently, Asbuton usage is currently still relatively limited for asphalt needs with absorption of to meeting only 0.9% of national asphalt needs, of course this is a contradiction considering Asbuton demand. This restriction is significant given the considerable deposits reach, totaling 667 million tons. Another factor is additionally the high price of crude oil encouraging the use of has stimulated interest in bitumen as an alternative to crude oil, especially, specifically in the context of heavy crude oil. The bitumen reserves contained in Asbuton are capable of meeting oil refinery needs of 50,000 BOPD or the equivalent of 4.3% of domestic refinery capacity requirements for a substantial period of 20 years. There are two options for bitumen equivalent to 50,000 BOPD. Therefore, this study aimed to enhance understanding of the potential contribution of Asbuton to future crude oil production the 2 production options from Asbuton, namely all production comes from included full-scale open pit mining or as well as a combination of production from open pit mining (40%) and in situ extraction (60%). The Techno-economic analysis was prepared with the assumption that the Asbuton production area is was integrated into part of the Oil and Gas Working Area with, operating under a Cost Recovery Production Sharing Contract (PSC) scheme. The development of Bitumen production from The results showed that Asbuton provides feasible economic indicators with NPV = viability, as evidenced by such as $ 973 million NPV and IRR = 15.2% IRR. During the contract period, the government received gained revenue of $ 14.7 billion and the contractor was projected to receive $ 12.0 billion. This economic feasibility study is expected to enrich further our understanding over Buton asphalt utilization in support of crude oil production in the future.
All Days, Aug 31, 2006
Reservoir rock heterogeneity is an ever-present occurence in most reservoirs. One among reservoir... more Reservoir rock heterogeneity is an ever-present occurence in most reservoirs. One among reservoir properties that are the most affected by its presence is permeability. In most cases, reservoir rock heterogeneity causes permeability anisotropy or variations in permeability with directions. As most theoretical bases used in many aspects in petroleum engineering (e.g. waterflooding, well completion, well productivity, well stimulation, and reservoir simulation) are developed under an assumption of homogeneous reservoir rocks, this permeability anisotropy certainly imposes a special problem that needs to be dealt with. Indonesia's geological setting is characterized by its high level of complexity. Permeability anisotropy in Indonesian reservoirs varies very widely, and careless approach in picking values representing the level of heterogeneity for individual reservoir may lead to various problems. This paper presents results of a study on permeability anisotropy - in this case vertical-to-horizontal anisotropy - in Indonesian reservoirs through the use of core analysis results. The study involves 14,634 core samples, of which 6,689 are pairs of vertical and horizontal plug samples and 1,256 are full-diameter core samples. They are taken from 259 wells representing 157 fields in all 15 Indonesia's productive sedimentary basins to date. The core samples cover a wide lithology spectrum from sandstones to various limestones. The study that is carried out through a series of classifications and comparisons has indeed shown the complexity as expected, even though differences can still be distinguished among groups of classification. Evidence has also been observed that results for sandstones and limestone/carbonates core samples as two lithology groups are significantly different even though there are also differences among either group. One very important lesson that can also be drawn from this study is a reconfirmation upon the common opinion suggesting the requirement of a careful study for individual reservoir before adopting K[V]/K[H] values for the reservoir of interest. Introduction Permeability variation always draw attention of any engineer and geoscientists whenever they come to the task of characterizing and producing reservoirs as good and efficiient as they can. In homogeneous reservoirs, permeability is considered the same in all directions. On the contrary, in heterogeneous reservoirs, permeability tends to differ with direction. The more heterogeneous a reservoir the higher variation in permeability it tends to show. In this case, permeability may be different in all directions making it difficult to obtain the overall picture of permeability distribution in reservoir. In lesser degree of heterogeneity, the permeability in vertical direction is still considerably different than the permeability horizontal direction but with similar permeability in all horizontall directions (transversely anisotropic). Nevertheless, the net impact of such changing permeability in different directions is especially marked on all aspects that involve flows of reservoir fluids such as natural recovery efficiency, well testing, enhanced oil recovery, and completion scheme.
Scientific Contributions Oil & Gas, Apr 1, 2022
The in situ state of stress is a rock's point-to-point property that must be taken into considera... more 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.
Ketidaktepatan dalam Pemakaian Model Saturasi Air dan Implikasinya
Lembaran Publikasi Minyak dan Gas Bumi, 2008
Saturasi air adalah besaran yang sangat penting dalam perhitungan akumulasi hidrokarbon di tempat... more Saturasi air adalah besaran yang sangat penting dalam perhitungan akumulasi hidrokarbon di tempat dan cadangan. Saturasi air pada umumnya diperoleh melalui penerapan model saturasi air saat dilakukan analisis log open hole konvensional. Disebabkan oleh peran pentingnya data tersebut, berbagai model saturasi telah dikembangkan sesuai dengan kebutuhan. Dengan banyaknya jumlah model saturasi air maka pertanyaan yang masih selalu terdengar di kalangan praktisi adalah: model yang mana yang harus dipakai? Tulisan ini tidak bermaksud untuk memberikan jawaban yang konklusif tapi lebih sebagai usaha untuk mengaktualkan kembali problema yang telah dapat dianggap klasik ini. Dalam tulisan ini dibuktikan kembali diskrepansi estimasi saturasi air yang dapat terjadi dengan menggunakan lima model saturasi air. Demikian pula ditunjukkan efek dari diskrepansi tersebut pada estimasi akumulasi hidrokarbon. Hasil utama dari studi literatur dan hipotetikal ini adalah perlunya mengobservasi beberapa hal penting dengan tujuan untuk mereduksi diskrepansi dan ketidakpastian akibat kesalahan dalam pemilihan model saturasi air. Kata kunci: saturasi air, model saturasi air, pemilihan model, ketidakpastian, cadangan.
Perubahan Sifat Kebasahan Fluida dan Sifat Kelistrikan Batuan Reservoir: Isu Lama, Persoalan Aktual
Lembaran Publikasi Minyak dan Gas Bumi, 2008
A Laboratory Study to Improve Acid Stimulation in Sandstones
A laboratory study is performed before acid stimulation in order to test the reaction between com... more A laboratory study is performed before acid stimulation in order to test the reaction between commercial mud acid and the sandstone samples taken from a field in Malaka Strait that will be planned for acid stimulation. In laboratory, experimental study of acid response test has been designed to simulate the acid stimulation operation. Before acid response test, an integrated petrographic analysis such as thin section, SEM with EDX and XRD has been performed to determine mineralogy, pore geometry of the samples. The results that sample with highest percentage of siderite tend to show poor acid performance. After acid injection, an integrated petrographic analysis was also conducted to see the effect of acid to the mineralogy and pores interconnection of the sandstone samples. The results show heavy presence of silica gel that blocks pore throat and causes low permeability. The dissolution of siderite as iron bearing mineral during acid test has caused the pH of the environment become higher, causing the precipitation of dissolved silica. This prompts to another important conclusion drawn from the study, which is the need to anticipate the possibility of pH increase during acid injection.
Indonesian Journal of International Law, Jan 2, 2007
Beberapa tahun terakhir telak terjadi pemtntnan drastis produksi minyak burnt Indonesia secara na... more Beberapa tahun terakhir telak terjadi pemtntnan drastis produksi minyak burnt Indonesia secara nasional dengan laju pemtntnan sekitar IQ% per tahun. Pada kurun waktu yang sama pzda situasi produksi dan cadangan gas bumi nasional jttstru menunjukkan perkembangan yang menggembirakan. Lajtt produksi dapat dipertahankan dan cadangan bakkan menunjukkan pertumbuhan yang baik dari tahun ke tahun. Analisis atas sejarak produksi dan cadangan, kegiatan eksplorasi, dan perbandingan antara penetmtan minyak dan gas bumi pada tahun-tahun belakangan ini mendasari kesimpulan bahwa gas bumi dapat menjadi sumber energi dan pendapatan nasional alternatif terhadap minyak di masa yang akan dafang.Meskipun demikian terdapat beberapa tantangan yang dihadapi dalam eksploitasi gas bumi terutama dalam kaitatmya dengan penerapan teknologi, infra-struktur, penegakan kukum, keresahan sosial, peraturan yang terlalu kef at, dan insenttf. Tantangan-* tantangan tersebut harus diatasi jika tingkat produksi gas, dan juga minyak, yang berkesinambungan ingin dicapai.
Establishment Of More Reliable Equations For Estimation Of Coalbed Methane Proximate Analysis Data
Scientific Contributions Oil & Gas, Mar 17, 2022
Coal bed methane (CBM) data such as ash contents, moisture contents, volatile matters, and fixed ... more 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
Scientific Contributions Oil & Gas, Apr 8, 2019
Informasi tentang permeabilitas air-minyak dari batuan reservoar memainkan peranan yang penting d... more Informasi tentang permeabilitas air-minyak dari batuan reservoar memainkan peranan yang penting dalam kegiatan pemodelan yang berhubungan dengan pemodelan reservoar dan peramalan produksi. Permeabilitas relatif dalam skema imbibisi-skema yang merupakan tema dari tulisan ini-berpengaruh besar atas berbagai proses dinamis di reservoar. Proses injeksi air dan masuknya air dari akuifer ke reservoar merupakan dua contoh yang membutuhkan data tersebut. Studi ini menggunakan model permeabilitas relatif Corey sebagai model permeabilitas relatif imbibisi yang digunakan. Data laboratorium dari 340 percontoh-batupasir dan batugamping-dengan berbagai permeabilitas dan wetabilitas yang diambil dari berbagai lapangan minyak di Indonesia digunakan. Kegiatan pemodelan yang dilakukan menunjukkan perlunya untuk menambahkan dua faktor empiris yang berhubungan dengan wetabilitas batuan dan hambatan diluar pembasahan ke dalam model. Peran kedua faktor tersebut dalam model senyara nyata meningkatkan kemampuan dari model, dan nilai-nilai yang dianggap paling baik untuk kedua faktor juga dihasilkan sesuai dengan jenis wetabilitas dan kategori permeabilitas batuan. Perbandingan antara hasil pemodelan sebelum dan sesudah modifi kasi menunjukkan perbaikan dalam validitas dari keluaran.
Hubungan antara Porositas dengan Kedalaman untuk Reservoir-Reservoir Batupasir di Indonesia Barat
Lembaran Publikasi Minyak dan Gas Bumi, 2008
Porositas batuan sebagai data penting bagi kegiatan produksi minyak dan gas (migas) memiliki hubu... more Porositas batuan sebagai data penting bagi kegiatan produksi minyak dan gas (migas) memiliki hubungan yang unik, meskipun bervariasi, dengan kedalaman. Secara umum porositas mengecil dengan bertambahnya kedalaman, dan pengetahuan ini menjadi suatu aset yang sedikit banyak dapat digunakan untuk berbagai aplikasi di industri migas antara lain untuk mengontrol keakuratan porositas hasil evaluasi log sumuran. Pertanyaan yang selalu hadir adalah apakah hubungan antara porositas dan kedalaman yang ada di literatur cukup valid untuk kasus-kasus di Indonesia. Tulisan ini menyajikan usaha untuk mencari validitas bagi hubungan porositas – kedalaman yang ada di literatur. Sebagai data penguji diambil porositas 157 percontoh batuan dari 15 lapangan minyak yang berasal dari 6 cekungan di Indonesia bagian Barat. Hasil utama dari studi ini adalah tidak validnya hubungan porositas – kedalaman yang ada dan bukti bahwa tingginya tingkat sementasi dan heterogenitas dari batuan-batuan reservoir di Indonesia. Hasil penting lainnya adalah sebuah hubungan matematis porositas – kedalaman yang sedikit banyak dapat dianggap mewakili untukreservoir-reservoir di Indonesia Barat.
An Improvised Method for Determining Reservoir Rock Porosity Cut-off with Support of Laboratory Mercury Injection Data
All Days, Sep 20, 2011
Porosity cut-off is a major key parameter in evaluation of reservoir dimensions. Through the use ... more Porosity cut-off is a major key parameter in evaluation of reservoir dimensions. Through the use of this parameter formation rocks regarded as ‘reservoir(s)’ are distinguished from ‘non-reservoir’ ones. This makes determination of this parameter to have a direct impact on estimations of reservoir volumes and in turn volumes of hydrocarbon accumulation. Error in the determination may influence commerciality of the hydrocarbon accumulation. Traditionally, determination of porosity cut-off values is made through relationship between rock porosity and permeability. Although some suggested the use of supporting data such as clay volume and porosity types or computational methods such as artificial neural network, this method is often regarded as unsatisfactory due to different intrinsic features between the two. Relationship between rock pore throat size – obtained from mercury injection on core samples – and permeability is on the other hand more direct in nature. This study actually attempts to integrate this more theoretically consistent relationship into the old porosity – permeability relationship. The integration is essentially made through multi-variable regression analysis using data from eight (4 sandstone and 4 limestone) oil and gas fields in Indonesia. Results from the study have shown significant improvement in porosity – permeability relationship resulting in more reliable porosity cut-off estimates. The method, which procedure is presented in this article is hoped to have helped petrophysicists in reducing and overcoming high uncertainties in estimating porosity cutoff.
Scientific Contributions Oil & Gas, Mar 29, 2022
Recent years has witnessed decline in national oil production at an alarming rates of higher than... more Recent years has witnessed decline in national oil production at an alarming rates of higher than 10% annually. On the other hand, national gas reserves and production situation is much better even though problems such as unanticipated production shortfall of existing fields and commerciality of new reserves have still to be faced. Analysis on history of production and reserves and comparison between oil and gas discoveries in recent years may lead into a conclusion natural gas may serve as an alternative source for energy and national income in years ahead. However, challenges such as technology, infra-structures, law enforcement, social unrests, tight regulations, and incentives are still day-today reality. These challenges need to be addressed appropriately if sustainable gas, and also oil, productions are to be achieved.
Seismic-Derived Rock True Resistivity (R) Revisited. Part I: Reformulation Of Combined Gassmann – Shaly Sand Models
Scientific Contributions Oil & Gas, Mar 29, 2022
The last decade has observed frantic efforts by geoscientists to extract as much information as p... more 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).
Scientific Contributions Oil & Gas, Mar 14, 2022
Rock wettability plays a very important role in affecting various rock physical properties such a... more Rock wettability plays a very important role in affecting various rock physical properties such as relative permeability and capillary pressure. Common practice at present is that carbonate rocks are assumed to be preferentially oil wet in nature. This assumption may prove fatal since the need of true knowledge over the real wettability for one's carbonate reservoir is often neglected, and wettability aspect in reservoir modeling is in turn based on assumption. To prove over reliability of the assumption a study is carried out using information from 350 core samples taken from Baturaja Formation. The choice for the Baturaja limestone is basically based on the fact that it is a mature productive rock formation and its extensive spread into three of the most productive sedimentary basin in Indonesia, Northwest Java Basin, South Sumatra Basin, and Sunda Basin. The study proves that the assumption of the generally oil wet limestone does not apply for Baturaja limestone. The Baturaja limestone tend to exhibit, quantitatively, equality in their tendency towards oil wettability and water wettability and leave some proportion to neutral or mix wettability as well. However, when a more detailed comparison is made results show that qualitatively the limestone are indeed more inclined to oil wettability than water wettability even though this finding is insufficient to support a conclusion that the Baturaja limestone are specifically oil wet. Other finding from comparison with past studies also shows that limestone may behave in the way sandstones do. Both limestone and sandstones may vary in the same way and no assumption over their preferential wettability is justified without direct measurements. Wettability alteration as the result of hot core cleaning following the widely accepted standard procedure is also strongly indicated. It is therefore concluded that the practice has to be abandoned for a better and reliable laboratory testing results.
Scientific Contributions Oil & Gas, Feb 15, 2022
Irreducible water saturation (S wirr) plays a very significant role in the estimation of hydrocar... more Irreducible water saturation (S wirr) plays a very significant role in the estimation of hydrocarbon in place and reserves. Inaccurate S wirr and lack of knowledge for judging its accuracy may result in erroneous and misleading reserve estimates along with its consequences. This study is basically aimed at understanding of S wirr characteristics of reservoir sandstones in some fields in western Indonesia. For the study, data obtained from 1,334 core samples-taken from 78 fields in 10 sedimentary basins-is used. Observations and investigations are made in sedimentary basin, field, and formation scales. The main finding is that rock wettability plays a very significant factor in determining S wirr characteristics, in a manner more than what rock pore types and configuration do. Its variation-be it contrasting or difference in strength-influences the S wirr characteristics in its relation to rock permeability. It is also found that geological similarity and geographical proximity do not have effects on S wirr characteristics unless they directly affect the rock's overall wettability. This occurs not only at higher scale of sedimentary basin but also at lower levels of field and rock formations. The study also produces permeability-S wirr correlations for both sedimentary basins and rock formations levels. The overall results of this study is an understanding that gross simplification in assuming reservoir general wettability has to avoided in order to prevent erroneous picture over a field's most representative S wirr characteristics.
Development Of A Supplementary Technique For Determining In Situ Stress Magnitude Using Acoustic Wave Propagation
Scientific Contributions Oil & Gas, Mar 29, 2022
In accordance with the increasing awareness of the importance of in situ stress information in th... more In accordance with the increasing awareness of the importance of in situ stress information in the design of various geotechnical and other petroleum related subsurface engineering in Indonesia, a complete knowledge of the insitu stress is a fundamental requirement. Basically, complete information of the insitu state of stress means both the trends and magnitudes of the principal in situ stresses. Some stress determination techniques can provide a complete stress tensor (e.g. differential strain analysis, DSA, method), some provide an incomplete tensor (e.g. sleeve fracturing method), and some provide merely the directions of the principal stresses. The Shear wave (S-wave) splitting technique presented by Widarsono et al (1998), following the earlier works made by Yale and Sprunt (1989), obviously falls in the last category. In some cases, which usually do not require in situ stress information regarding the magnitudes as an input parameter, principal stress directions still provide useful information. Nevertheless, the expanding use of in situ stress information requires, as stated above, a complete information, which means the stress magnitudes as well as directions. Designs of hydraulic fracturing, wellbore stability, and prevention of sand problems are among examples for which information about in situ stresses is required.In relation to the requirement outlined above, the effort which results are presented in this paper was devoted to presenting efforts to predict in situ stress magnitude by using ultrasonic wave propagation. This paper mainly presents efforts to find relations between acoustic propagation and in situ stress magnitude with an ultimate goal to provide the S-wave splitting technique presented in Widarsono et al (1998) with a means for estimating stress magnitudes.
Scientific Contributions Oil & Gas, Mar 14, 2022
Fluid contact(s) in reservoir sets the lower limit above which an accumulation of hydrocarbon (i.... more Fluid contact(s) in reservoir sets the lower limit above which an accumulation of hydrocarbon (i.e. oil or gas) has the maximum level of mobility under a specific circumstance. This mobile hydrocarbon determines the reservoir's production feasibility. In this light, an accurate knowledge over position of fluid contact contributes to accuracy in the estimation of initial hydrocarbon in place and its corresponding reserves. Determination of fluid contact in reservoir may utilize any available sources of information but well pressure survey data is usually regarded as the primary source of information. Despite the importance, the data is sometimes not in ideal condition usually marked by absence in clear change of pressure gradient and/or data scatter for various reasons. The use of Hough transform-as introduced by Kang and Xue (2009)-for supporting fluid contact detection can solve the problem. In this study, the method that is usually used for, among others, recognizing regular shapes in images has been successfully applied for fluid contact detection. The study uses three sets of data with different level of difficulty, and the technique proves to work well for the all cases. The study also shows that the Hough transform can be used reliably in a simple way without employing the full weight of it.
Scientific Contributions Oil & Gas, Feb 22, 2022
Wettability is a reservoir rock property that is not easy to measure and quantify but has a cruci... more 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.
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Papers by Bambang Widarsono