Petrophysical Analysis of the Upper Shale Member and the Upper Sand Member of the Zubair Formation in the Zubair Oilfield, Southern Iraq

Rayan Al-Atab; Fahad M. Al-Najm; Basim H.  Soltan

Article Details

Petrophysical Analysis of the Upper Shale Member and the Upper Sand Member of the Zubair Formation in the Zubair Oilfield, Southern Iraq

Authors:

Rayan Al-Atab | Fahad M. Al-Najm | Basim H. Soltan

Publisher:

Iraqi Geologists Union (Union of Iraqi Geologists)

Journal:

The Iraqi Geological Journal Vol.58 Issue 2E, pp.40-57

Document Type:

Article

Publication Date:

11/2025

Document Language:

English

Document ID (Org No.):

2001836926

pISSN:

2663-8754

Keywords:

Abstract:

 The Zubair Formation is a major hydrocarbon-bearing unit in southern Iraq, consisting of five distinct members. This study focuses on evaluating the petrophysical properties of its two upper members—the Upper Shale Member and the Upper Sand Member—within the Zubair Oilfield. The objective is to assess the spatial variability and quality of the petrophysical properties across these members using open-hole well log data. Four wells were selected for analysis, each located in a different structural domes: Hammar, Shuaiba, Rafidhiya, and Safwan. Petrophysical analysis was conducted using integrated log interpretation software to calculate key parameters, including shale volume, total porosity, effective porosity, hydrocarbon saturation, bulk volume hydrocarbon, effective bulk volume hydrocarbon, movable oil saturation, and water saturation in the invaded zone (Sxo). Non-reservoir intervals were filtered based on gamma ray values >70 API, porosity <0.05, and hydrocarbon saturation <0.30. The results show that the best petrophysical properties in both members are observed in the Hammar Dome (Z1). In the Upper Shale Member, the poorest properties were recorded in the Shuaiba Dome (Z2). In contrast, the lowest values were observed in the Safwan Dome (Z4) within the Upper Sand Member. An apparent north-to-south decline in petrophysical quality was identified in the Upper Sand Member, but not in the Upper Shale Member. The widespread presence of heavy, tar-like hydrocarbons across all wells may indicate a regional reservoir characteristic. These findings contribute to a better understanding of petrophysical variability in the upper Zubair Formation and can support further geological or reservoir modelling efforts.

Article Details

Petrophysical Analysis of the Upper Shale Member and the Upper Sand Member of the Zubair Formation in the Zubair Oilfield, Southern Iraq

Authors:

Rayan Al-Atab | Fahad M. Al-Najm | Basim H. Soltan

Publisher:

Iraqi Geologists Union (Union of Iraqi Geologists)

Journal:

The Iraqi Geological Journal Vol.58 Issue 2E, pp.40-57

Document Type:

Article

Publication Date:

11/2025

Document Language:

English

Document ID (Org No.):

2001836926

pISSN:

2663-8754

Southern Iraq

Zubair Oilfield

Zubair Formation

Upper Sand Member

Upper Shale Member

Petrophysical Properties

Issues

Article Details

Petrophysical Analysis of the Upper Shale Member and the Upper Sand Member of the Zubair Formation in the Zubair Oilfield, Southern Iraq

Authors: Rayan Al-Atab | Fahad M. Al-Najm | Basim H. Soltan

Publisher: Iraqi Geologists Union (Union of Iraqi Geologists)

Journal: The Iraqi Geological Journal Vol.58 Issue 2E, pp.40-57

Document Type: Article

Publication Date: 11/2025

Document Language: English

Document ID (Org No.): 2001836926

pISSN: 2663-8754

Southern Iraq

Zubair Oilfield

Zubair Formation

Upper Sand Member

Upper Shale Member

Petrophysical Properties

Issues

Authors:

Rayan Al-Atab | Fahad M. Al-Najm | Basim H. Soltan

Publisher:

Iraqi Geologists Union (Union of Iraqi Geologists)

Journal:

The Iraqi Geological Journal Vol.58 Issue 2E, pp.40-57

Document Type:

Article

Publication Date:

11/2025

Document Language:

English

Document ID (Org No.):

2001836926

pISSN:

2663-8754