Geophysics and Geophysical Exploration (지구물리와물리탐사)

Korean Society of Earth and Exploration Geophysicists (한국지구물리·물리탐사학회)
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Formation Estimation of Shaly Sandstone Reservoir using Joint Inversion from Well Logging Data

복합역산을 이용한 물리검층자료로부터의 셰일성 사암 저류층의 지층 평가

  • Choi, Yeonjin (Korea Maritime and Ocean University, Department of Energy & Resources Engineering) ;
  • Chung, Woo-Keen (Korea Maritime and Ocean University, Department of Energy & Resources Engineering) ;
  • Ha, Jiho (Korea Institude of Geoscience and Mineral Resources (KIGAM) Pohang Branch) ;
  • Shin, Sung-ryul (Korea Maritime and Ocean University, Department of Energy & Resources Engineering)
  • 최연진 (한국해양대학교 에너지자원공학과) ;
  • 정우근 (한국해양대학교 에너지자원공학과) ;
  • 하지호 (한국지질자원연구원 포항지질자원실증연구센터) ;
  • 신성렬 (한국해양대학교 에너지자원공학과)
  • Received : 2018.08.03
  • Accepted : 2019.02.28
  • Published : 2019.02.28
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Abstract

Well logging technologies are used to measure the physical properties of reservoirs through boreholes. These technologies have been utilized to understand reservoir characteristics, such as porosity, fluid saturation, etc., using equations based on rock physics models. The analysis of well logs is performed by selecting a reliable rock physics model adequate for reservoir conditions or characteristics, comparing the results using the Archie's equation or simandoux method, and determining the most feasible reservoir properties. In this study, we developed a joint inversion algorithm to estimate physical properties in shaly sandstone reservoirs based on the pre-existing algorithm for sandstone reservoirs. For this purpose, we proposed a rock physics model with respect to shale volume, constructed the Jacobian matrix, and performed the sensitivity analysis for understanding the relationship between well-logging data and rock properties. The joint inversion algorithm was implemented by adopting the least-squares method using probabilistic approach. The developed algorithm was applied to the well-logging data obtained from the Colony gas sandstone reservoir. The results were compared with the simandox method and the joint inversion algorithms of sand stone reservoirs.

물리검층은 시추공을 이용하여 저류층의 여러 물성을 측정하는 것으로, 암석물리모델 관계식을 이용하여 공극률, 유체포화도 등의 저류층 특성을 파악하는데 활용되어 왔다. 물리검층자료의 분석은 저류층의 조건과 특성에 맞는 적당한 암석물리모델을 선정하고, Archie식이나 시만독스법 등을 활용하여 얻은 결과를 비교함으로써 가장 신뢰성 있는 저류층 물성을 결정하게 된다. 이 연구에서는 기존에 제시된 사암 저류층에서의 물리검층자료 복합역산 알고리즘을 바탕으로, 셰일성 사암 저류층의 물성을 평가하기 위한 복합역산 알고리즘을 개발하였다. 셰일의 양을 변수로 하는 암석물리모델 관계식을 제안하였으며, 야코비 행렬을 구성하고 민감도 분석을 수행하여 물리검층자료와 모델변수의 관계를 파악하였다. 확률론적 방법을 이용한 최소제곱법을 적용하여 복합역산을 수행하였다. 개발한 알고리즘은 Colony 가스사암 지역에서 얻은 물리검층자료에 적용하였으며, 그 결과를 기존에 활용되는 시만독스법과 사암 저류층에서의 복합역산 결과와 비교해 보았다.

Keywords

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Fig. 1. Rock physics modeling of P-wave velocity for (a) cleans and, (b) shaly sand reservoir model.

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Fig. 2. Rock physics modeling of conductivity for (a) (a) clean sand and (b) shaly sand reservoir models.

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Fig. 3. Rock physics modeling of density for (a) clean sand and(b) shaly sand reservoir models.

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Fig. 4. Flowchart for joint inversion procedures.

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Fig. 5. Absolute values of eigenvectors in the model space.

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Fig. 6. Stratigraphic summary of the Colony sand units (modified after Alberta Geological Survey (2015)).

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Fig. 7. Well log data of Colony gas sand.

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Fig. 8. Estimation of reservoir properties using the simandoux method.

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Fig. 9. Measured and calculated data for the joint inversion in the shaly sand reservoir model.

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Fig. 10. Estimation of reservoir properties using the joint inversion in the shaly sand reservoir model.

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Fig. 11. Measured and calculated data for joint inversion in sand reservoir model.

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Fig. 12. Estimation of reservoir properties using the joint inversion in the sand reservoir model.

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Fig. 13. Estimation of reservoir properties for the Colony gas sand.

Table 1. Rock and fluid parameters in a reservoir for rock physics modeling.

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Table 2. Average reservoir properties at each zone using the simandoux method.

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Table 3. Rock and fluid parameters for the joint inversion in the shaly sand reservoir.

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Table 4. Average reservoir properties at each zone using the joint inversion in the shaly sand reservoir.

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Table 5. Average reservoir properties at each zone using the joint inversion in the sand reservoir.

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Table 6. Average porosities and water saturations at each zone.

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