K-mean cluster analysis for better determining the sweet spot intervals of the unconventional organic-rich shale: a case study

• Autorzy: Akbar M. N. A. , Nugraha S. T.

Identyfikatory

DOI

10.2478/ctg-2018-0014

• Języki publikacji: EN

Abstrakty

EN

The petrophysical analysis is the crucial task for evaluating the quality of unconventional organic-rich shale and tight gas reservoirs. The presence of organic matter and the ultra-tight with over complex pore system have remained a lack of understanding of how to evaluate the extensive parameters of porosity considering organic content, gas saturation, organic richness, brittleness index, and sweet spot interval by only using conventional log. Therefore, this study offers effectively applied techniques and better analysis for interpreting these parameters by maximizing and integrating geological, geochemical, rock mechanical and engineering data. In general, the field data used in this study are from the first dedicated well for source rock exploration in the North Sumatra Basin, Indonesia. The developed method was derived by using conventional log. All interpretation results were validated by laboratory data measurements of routine and special core analysis, petrography, total organic carbon (TOC) and organic maturation, and brittleness index (BI) calculation. Moreover, the high quality of NMR log data was used as well to ensure our developed techniques present good estimations. Briefly about the methods, we started to determine the total and effective porosity based on the density log by including the presence of organic matter and multi-mineral analysis in these estimations. Then, we used the revised water saturation-TOC of water saturation while the TOC was predicted in advance by averaging three results from the correlation of TOC-Density, modified CARBOLOG and Passey’s ΔlogR methods. Equally important, in order to obtain the reliable gas saturation prediction, we used saturation exponent (n), cementation factor (m), and the tortuosity factor (a) parameters which obtained from laboratory measurement of formation resistivity factor and resistivity index (FFRI). In addition, the brittleness index was predicted based on sonic log data. Finally, all parameters needed for determining gas shale sweet spot have been made. Then, we developed a way to evaluate the sweet spot interval by using K-mean clustering. In conclusion, this clustering result properly follows the shale quality index parameters which consist of organic richness and maturation, brittleness index, the storage capacity of porosity and gas saturation. This study shows that these petrophysical applied techniques leads us to interpret the best position of shale interval to be developed with a simple, fast, and accurate prediction way. Furthermore, as a novelty, this method can be used as rock typing method and obviously can reduce uncertainty and risks in organic-rich shale exploration.

Słowa kluczowe

EN

shale gas petrophysics; organic-rich shale; rock typing; cluster analysis; shale gas water saturation; sweet spot

PL

gaz łupkowy; gaz ziemny; złoża łupkowe; nasycenie

• Wydawca: De Gruyter
• Czasopismo: Contemporary Trends in Geoscience
• Rocznik: 2018
• Tom: Vol. 7, iss. 2
• Strony: 200--213
• Opis fizyczny: Bibliogr. 20 poz., rys., tab.

Twórcy

autor

Akbar M. N. A.

• University of Miskolc, Petroleum Geoengineering, Miskolc Egyetemvaros, 3515, Hangary

autor

Nugraha S. T.

• China University of Petroleum-Beijing, 18 Fuxue Road, Changping, Beijing China 102249

Bibliografia

• Akbar A, Nur M., Musu JT. (2017) Rock typing and shale quality index methods based on conventional log a case study for organicrich shale in the North Sumatra Basin. In: 23rd Formation Evaluation Symposium of Japan, Society of Petrophysicists and WellLog Analysts, Japan, 11-12 October (JFES-2017-T).
• Akbar A, Nur M., Musu JT., and Milad B. (2018) Water Saturation Interpretation Model for Organic-Rich Shale Reservoir: A Case Study of North Sumatra Basin. The Unconventional Resources Technology Conference held in Houston, Texas, USA, 23-25 July. URTeC: 2879229, DOI: 10.15530/urtec-201 8-2879229.
• Aranibar A., Saneifar, M., and Heidari, Z. (2013) Petrophysical rock typing in organic-rich source rocks using well logs. the Unconventional Resources Technology Conference held in Denver, Colorado, USA, 12-14 August 2013. SPE 168913/URTeC 1619574.
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Uwagi

Opracowanie rekordu w ramach umowy 509/P-DUN/2018 ze środków MNiSW przeznaczonych na działalność upowszechniającą naukę (2019).