Microbial enhanced oil recovery in a mature sandstone reservoir: Reservoir evaluation of production improvement and water cut reduction in the Oligocene Complex, Gialo Field

Title : Microbial enhanced oil recovery in a mature sandstone reservoir: Reservoir evaluation of production improvement and water cut reduction in the Oligocene Complex, Gialo Field

Abstract:

Microbial Enhanced Oil Recovery (MEOR) has gained attention as an alternative technique for improving oil recovery from mature reservoirs. Despite encouraging laboratory results and several field applications, documented cases showing simultaneous oil production improvement and water cut reduction under stable operating conditions remain limited. This paper presents the reservoir evaluation of a MEOR application performed on a selected production well in the Oligocene Complex of Gialo Oil Field, a mature sandstone reservoir.

Prior to the microbial treatment, the well performance was evaluated using production tests conducted in December 2025 and February 2026 following a routine workover. The recorded oil production ranged from 173 to 260 BOPD, with water cut values between 42% and 52%, establishing the pre-treatment performance range. The MEOR treatment was applied on 21 March 2026, followed by a four-day shut-in period before returning the well to production. No additional production optimization measures, including ESP replacement, choke adjustment, acid stimulation, or other remedial operations, were carried out during the evaluation period.

The reservoir response was monitored through production tests conducted between 6 April and 1 June 2026. A noticeable improvement in well performance was observed approximately two weeks after treatment. Oil production increased to 350–444 BOPD, while water cut decreased to 3–15%. The maximum recorded production reached 444 BOPD at 3% water cut. Subsequent production tests confirmed that the well continued to produce above the pre-treatment performance range with significantly lower produced water volumes.

The observed increase in oil production combined with the reduction in water cut indicates a positive change in reservoir fluid-flow behavior following MEOR application. These reservoir results demonstrate the potential of MEOR to improve oil recovery and reduce water production in mature sandstone reservoirs.

Keywords: MEOR, Enhanced Oil Recovery, Mature Sandstone Reservoir, Gialo Oil Field, Water Cut Reduction, Reservoir Performance Evaluation.

Biography:

Mohamed Mustafa Faituri is a Senior Reservoir Engineer at Waha Oil Company, Libya, with eight years of experience in reservoir engineering. He holds a Bachelor's degree in Petroleum Engineering from the Faculty of Petroleum Engineering, University of Tripoli. His work includes reservoir surveillance, well performance evaluation, production optimization, water production management, and supporting field development activities for mature oil field.