Experimental investigation of simultaneous water and CO₂ (SWACO₂) injection for oil recovery in immiscible and near‐miscible conditions: A comparative study

Abstract

A simultaneous water and CO2 injection to a dead crude oil has been performed on sandstone cores to evaluate oil recovery under secondary immiscible, secondary near‐miscible, tertiary immiscible, and tertiary near‐miscible injection modes. It is demonstrated that secondary SWACO2 injection as well as tertiary flood is an effective method for oil/residual oil recovery from oil‐saturated/water flooded porous media. In near‐miscible condition, oil recovery is higher than in immiscible condition because there is another active pore‐scale production mechanism in near‐miscible injection besides volumetric displacement mechanism. In secondary near‐miscible SWACO2 injection, the ultimate oil recovery increases by increasing SWAG ratio from 0.2 to 0.4 but due to some limits, e.g., topological effects, prohibiting contact of injected gas with residual oil in pores, altering SWAG ratio from 0.4 to 0.6 showed no essential effect on ultimate oil recovery. Secondary SWACO2 injection can recover higher fraction of oil than tertiary SWACO2 injection. This higher oil recovery results from the oil being more accessible by injected gas due to less water‐shielding effects. The results of this work can be helpful to better recognition and selection of gas‐based oil recovery methods to be implemented in depleted reservoirs.

Comprehensive Water–Alternating-Gas (WAG) injection study to evaluate the most effective method based on heavy oil recovery and asphaltene precipitation tests

“…There are wide range of investigations to increase sweep efficiency of CO 2 injection. WAG injection, Simultaneous-Water-and-Gas (SWAG) injection, and direct CO 2 thickeners are some of these investigations [15][16][17][18][19][20][21]. These processes have major problems with poor sweep efficiency of oil in low pressure reservoirs [22].…”

On determination of interwell connectivity under immiscible gas injection process: Modified capacitance‐resistance model

“…Experimental and numerical modelling has been used to study production mechanisms in gas injection processes such as pressure maintenance, oil swelling, and gravity drainage . Although immiscible gas flooding and lab/field scale applications are well known in the petroleum industry, few studies have been published on the CRM applications in gas‐oil systems. Salazar‐Bustamante et al combined the decline curve model with the CRM in a fractured reservoir under a gas flood.…”