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Clay volume (Vcl) calculations are a crucial part of formation evaluation, which significantly influence the determination of other petrophysical properties such as porosity (Φ), water saturation (Sw), and permeability (k). Therefore, it is essential to precisely calculate Vcl. The Vcl can be derived indirectly from well logs and directly from laboratory data such as X-ray diffraction (XRD). From Staatsolie’s XRD data, it was revealed that the well log-derived Vcl (Log_Vcl) is overestimated in the reservoir intervals and underestimated in the shale intervals of the heavy-oil Eocene reservoirs in the Tambaredjo Northwest (TNW) field. The current Vcl model relies on the Gamma Ray (GR) and Neutron-Density (N-D) methods for determining Vcl in their reservoirs. However, previous studies suggested using the average Vcl (VCLAV) results from both methods for improved accuracy. For the GR method, the Gamma Ray Potassium Thorium Curve (GRKT) is used when available, otherwise resorting to the Total Gamma Ray. The chosen equation for GR adjustment is the Larionov Young Rock equation. Recent Technical Assessments on the Vcl calculations of onshore reservoirs have provided valuable insights to enhance the aforementioned calculations. These assessments recommend: To assess the choice of the Vcl GR correction model and explore other Vcl methods, a “Vcl equation assessment tool” was used. Additionally, this tool allowed a sensitivity analysis that could guide towards modifications on known equations. From the wells with XRD data in the TNW field, 9 (nine) were selected because the samples were systematically taken through the Eocene zones of interest. The Vcl modeling favored Stieber’s model for reservoirs, while the Linear model better matched shales. To maximize accuracy, a combined equation has been proposed. For the final Vcl calculation, a 50/50 blend (VCLAV) of Vcl Gr and Vcl N-D was utilized. Implementing this approach in neighboring wells resulted in a notable improvement in Vcl, ranging from 2–5%. This enhancement led to an increase in net pay and a boost in the estimated Petroleum initially in place (PIIP).

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Integrating Well Log and X-ray Diffraction Data to Improve Clay Volume Calculations in Unconsolidated Eocene Heavy-Oil Reservoirs of the Onshore Tambaredjo North West Field in the Guiana-Suriname Basin

  • 会议论文

  • 发表日期：

    2025年

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  • Idoe Ferhaad,
  • Acosta Elias,
  • Gajadien Shaskia

摘要

Clay volume (Vcl) calculations are a crucial part of formation evaluation, which significantly influence the determination of other petrophysical properties such as porosity (Φ), water saturation (Sw), and permeability (k). Therefore, it is essential to precisely calculate Vcl. The Vcl can be derived indirectly from well logs and directly from laboratory data such as X-ray diffraction (XRD). From Staatsolie’s XRD data, it was revealed that the well log-derived Vcl (Log_Vcl) is overestimated in the reservoir intervals and underestimated in the shale intervals of the heavy-oil Eocene reservoirs in the Tambaredjo Northwest (TNW) field. The current Vcl model relies on the Gamma Ray (GR) and Neutron-Density (N-D) methods for determining Vcl in their reservoirs. However, previous studies suggested using the average Vcl (VCLAV) results from both methods for improved accuracy. For the GR method, the Gamma Ray Potassium Thorium Curve (GRKT) is used when available, otherwise resorting to the Total Gamma Ray. The chosen equation for GR adjustment is the Larionov Young Rock equation. Recent Technical Assessments on the Vcl calculations of onshore reservoirs have provided valuable insights to enhance the aforementioned calculations. These assessments recommend: To assess the choice of the Vcl GR correction model and explore other Vcl methods, a “Vcl equation assessment tool” was used. Additionally, this tool allowed a sensitivity analysis that could guide towards modifications on known equations. From the wells with XRD data in the TNW field, 9 (nine) were selected because the samples were systematically taken through the Eocene zones of interest. The Vcl modeling favored Stieber’s model for reservoirs, while the Linear model better matched shales. To maximize accuracy, a combined equation has been proposed. For the final Vcl calculation, a 50/50 blend (VCLAV) of Vcl Gr and Vcl N-D was utilized. Implementing this approach in neighboring wells resulted in a notable improvement in Vcl, ranging from 2–5%. This enhancement led to an increase in net pay and a boost in the estimated Petroleum initially in place (PIIP).