A Case Study on Miscible and Immiscible Gas Injection Pilots in Middle East Carbonate Reservoir in an Offshore Environment

Abstract

Hydrocarbon gas injection is the most widely applied process after waterflooding, and is a promising enhanced oil recovery (EOR) injectant for use in Middle East carbonate oil fields. Gas injection improves microscopic displacement efficiency and generally acts as pressure maintenance; however, unfavorable mobility ratio can negatively impact the ultimate recovery due to viscous fingering and gravity override. This paper describes two gas injection pilots that have been implemented in offshore Middle-East carbonate reservoirs, a secondary and a tertiary gas injection through line drive to assess injectivity, productivity, macroscopic sweep efficiency, flow assurance and operational efficiency in a field that has long water-injection history. A strong monitoring plan, including an observer well, was applied through time-lapse saturation logging, pressure measurements, production testing, tracer campaign, etc. to evaluate the pilot efficiency and address key uncertainties upfront prior to full-field application.This paper describes the pilot performance in the context of full-field development, local and macroscopic displacement efficiency, flow assurance issues, and operational learnings. The gas injection performance is strongly impacted by reservoir heterogeneity, gravity segregation and the existing pressure gradient, and the history match performed indicates near-miscible or miscible behavior depending upon local pressure regimes, which thus govern the ultimate recovery. The history match also shows that for the same pilot, performance can be further improved through water-alternating-gas (WAG) injection, resulting in a viable development scheme for full-field implementation.

A review of development methods and EOR technologies for carbonate reservoirs

“…Hydrocarbon gas flooding is one of the most widely used processes in the petroleum industry, and it is a promising EOR method that can be used in carbonate oil fields in the Middle East (Kumar et al 2017). The injected hydrocarbon gases include methane, rich gas and liquefied petroleum gas (LPG).…”

Modeling minimum miscibility pressure using multiple mixing cells: Comparison of injection of gases enriched with Naphta, LPG, and NGL

“…Measuring the miscibility pressure with appropriate accuracy and appropriate combination for injection in order to carry out increased EOR projects is very important because the pressure and composition used directly affect the project economy [1]- [3]. Therefore, providing a suitable and easy method for calculating minimum miscibility pressure for designing EOR projects is important and efficient [4]- [16].…”

Advances in Raw Material Industries for Sustainable Development Goals

“…Scientists (Hoare & Coll 2018, Kumar et al 2017, Khorsandi et al 2017Alzayer & Sohrabi 2018) note the influence of hysteresis relative permeability on the effectiveness of WAG. It is often expected that the gas phase will show large hysteresis effects (Hoseini et al 2011).…”