iptc-23177-ea

IPTC-23177-EA Overview

  • Title: Cased-Hole Saturation Tool is Crucial for Optimizing Production and Reducing Uncertainties in a Naturally Fractured Carbonate Reservoir, Offshore, Libya

  • Authors: Abdurahman Grada, Hamza Ahmed, Anis Elgihani, Abduallah Almalti (SLB); Abdulrraziq Imhimmid, Kareema Mansour, Nureddin Mohamed, Mnani Mohamed (Mellitah Oil and Gas Company)

  • Conference: International Petroleum Technology Conference, Dhahran, Saudi Arabia, February 2024

  • Copyright: 2024, International Petroleum Technology Conference

Abstract

  • Location: Bouri Field, offshore Libya, identified as an offshore saturated oil-bearing structure characterized by a fractured carbonate reservoir.

  • Challenges: Gas and water intrusion complicate oil recovery, with a critical concern around the Gas-Oil Contact (GOC) which affects production targets.

  • Objectives: Utilize cased-hole saturation logging tools to optimize production and assess well performance, particularly for 17 wells affected by high water cuts and decreasing pressure.

  • Findings: A systematic approach led to identifying new contacts, revealing a rise in Oil-Water Contact (OWC) in certain areas while gas expanded in others.

Introduction

  • Field Characteristics: The Bouri field has a highly faulted carbonate reservoir with extensive fractures affecting fluid dynamics.

  • Production History: Early production began in the late 1980s, with increasing concerns related to water cuts affecting overall output.

  • Evaluation Process: Comprehensive analysis of well performance and reservoir characteristics led to the selection of key wells for saturation logging to mitigate water issues.

Workflow

  • Well Focus: The paper emphasizes one well (B4-35) for detailed analysis, which has resulted in the production of substantial oil and water, affected by various workover operations through the years.

Production Performance Analysis

  • Historical Performance: B4-35 has experienced declining oil rates due to increased water cuts (60%-80%) and operational difficulties from organic blockage within the well.

  • Workovers: Several attempts (acid washes, diesel treatments) were executed to revitalize production, highlighting a continuous decline in output over the years.

  • Comparison with Offset Wells: Assessments revealed different cumulative productions based on geological placements and operational histories.

Saturation Logging Tool Interpretation

  • Saturation Imaging: Utilizing versions of saturation logging at various speeds provided insights into hydrocarbon depletion and water encroachment across established reservoir layers.

  • Recent Findings (2023): Strong indicators of water saturation in Unit 4 and signs of gas expansion in Unit 5, with recommendations to maintain monitoring practices to address critical water cuts up to 60%.

Recommendations

  • Monitoring: Annual use of saturation tools is recommended to refine operational strategies preemptively before reaching critical water cut, thereby enhancing recovery efficiency.

  • Well Management: Adjustments to the operational strategy by isolating unproductive watered-out sections are necessary to sustain production levels and optimize resource usage in Bouri field.