2025 Spring Meeting and 21st Global Congress on Process Safety

(97a) Compositional Simulation Gas Injection to Unlock the Potential of Tight Carbonate Reservoir of Middle East

Authors

Adel Elsharkawy - Presenter, Kuwait University
Reem AlAbbas, Kuwait Oil Company
Mohammed Al-Murayri, Kuwait Oil Company
The Middle East country reservoir poses significant production and injection challenges due to its tight, low permeability (<10 md) and heterogeneous carbonate makeup characteristics. Oil recovery is still less than 1% due to the injectivity/productivity challenge, despite trials of various strategies such as matrix acidizing, radial drilling, hydraulic fracturing. Gas injection is identified as a viable technology to overcome this reservoir's difficult traits. The gases can either expand and push gases through the reservoir, mix with, or dissolve within the oil, thereby decreasing viscosity and increasing oil production. This work elaborates on novel practical strategies for the evaluation of gas injection so that the available gases become miscible to unlock the potential of low reservoir pressure and the challenging characteristics of a tight reservoir. In addition, this work also presents the techno-economic benefits of oil recovery and reservoir performance in miscible and immiscible gas flooding compared to water flooding.

The minimum miscibility pressure (MMP) is a crucial factor in the design of a miscible gas flooding project. However, the MMP measurement was not available from the laboratory. Therefore, multiple approaches and procedures were used to estimate MMP and swelling effects for different injected gases. The current reservoir pressure is 2500–3000 psi, compared to the initial 3400–3700 psi at 6800 ft. Therefore, enrichment with different agents (C2, C3, and C4) is required with CO2 and available separator hydrocarbon gases to achieve multi-contact miscibility at this low reservoir pressure. First, the equation of state (EoS) was tuned with available laboratory data. Next, MMP and swelling factor were estimated from high-resolution 1D slim tube compositional simulations using various gases, as well as enriching with C2, C3, and C4 components. Next, a 3D sector model was extracted from a full-field history-matched simulation model. Additionally, compositional simulations were carried out in a high-resolution 3D sector model by considering optimized parameters from water and gas floods.

It was found that the hydrocarbon separator gas and CO2 are found to be near-miscible, while their multi-contact miscibility can be achieved by enriching with 18–19% lean gas. Conversely, N2 gas remains immiscible under the reservoir's low pressure and challenging conditions. Water flooding shows poor performance and requires ~ 10-15 years longer than continuous gas injection to achieve 1 PVI. CO2 or hydrocarbon gases in near-miscible and miscible states can boost oil recovery by 6.5–7% and 10–14% OOIP, respectively. WAG injection shows low oil recovery compared to continuous gas injection due to poor water injectivity. Therefore, continuous miscible gas injection of CO2 or separator hydrocarbon gas (A) with 18–19% C3 enrichment is recommended to unlock the potential of this reservoir due to its techno-economic viability in terms of oil recovery, GOR (gas oil ratio), GUF (gas utilization factor), and economics.