CFT will screen your reservoirs for chemical EOR potential first using waterflood screening processes developed by waterflood experts at Mid-Con Energy. The initial screening examines primary production, secondary production, the reservoir response to waterflood, injection history, usable wellbores, remaining oil saturations, residual oil saturations, tertiary recoverable oil volumes, and economics. In addition, several factors critical to successful chemical EOR flood are included in the screening process:
- Available water supply (produced water is preferred)
- Reservoir temperature less than 60oC or 140oF
- Reservoir brine salinity < 230,000 ppm eq. NaCl
- Limited fracture permeability
Reservoir brine and oil samples are collected and brought to the laboratory. First, fluid properties are measured upon delivery to our laboratories. Next, microemulsion studies are conducted to find a surfactant formulation that 1) will lower interfacial tension, 2) remain compatible with produced water or injection water, and 3) is stable in the reservoir brine. Once an optimum formulation is developed, a suitable polymer that remains stable with the chemical formulation and brine water is added to the chemical system. The polymer improves conformance and sweep efficiency. Lastly, a combination of column and core floods are carried out to optimize chemical concentrations and determine the required volumes.
Understanding reservoir behavior is critical for any flood, whether it is a waterflood or chemical EOR flood. Our approach is to quickly assess reservoir behavior in the field prior to starting expensive and time consuming subsurface reservoir studies. The objectives of Interwell Tracer and Single Well Tracer Tests are to understand the key factors impacting economic success of a chemical flood and include sweep efficiency and target oil volumes.
CFT offers Interwell Tracer Testing (IWTT) which is an established and often under-utilized field test for assessing sweep efficiencies, reservoir barriers, reservoir and well connectivity, time to breakthrough, and fracture networks. The basic principle is to inject non-reactive stable tracers into injection wells and monitor produced water at nearby producing wells for tracer breakthrough. The tracer concentrations used are low and our standard tracers are non-reactive with oil, have very low solubility in oil, and will not adsorb onto the reservoir rock. IWTT is frequently used by our parent operating company for optimizing waterflood developments and improving injection efficiency.
CFT is also providing Single Well Tracer Tests (SWTT) to characterize residual oil saturations after waterflood. This technology has been practiced for over 30 years and is vital to understanding target oil volumes for EOR recovery processes whether it is chemical EOR or a miscible CO2 flooding. The SWTT test is performed on a single producer well and consists of first injecting partitioning tracers, followed by producing these tracers back to determine the residual oil saturations (see this PDF for reference) . In addition, SWTTs can be performed before and after a small-scale EOR test to determine the quantity of residual oil or “trapped oil” mobilized by the EOR process. This is commonly done for chemical EOR or miscible CO2 floods. CFT has a SWTT portable lab with pumping, mixing systems, and analytical equipment.
The combination of both the SWTT and IWTT provides critical and often superior information of the prospects of a successful chemical or CO2 flood at lower costs than subsurface and laboratory studies alone. The goal is to quickly de-risk EOR at lower costs and at an accelerated time frame.
Multi-well piloting is the last step prior to full field deployment. Objectives of the multi-well pilot include achieving operational know-how, assessing the effectiveness of the chemical EOR process to put additional barrels of oil in the tank, and assessing technical and economic feasibility of the project.
The principal barriers to EOR deployment is technical risks and high costs associated with facilities and equipment. CFT’s goal is to reduce technical risk with the IWTT and SWTT and aggressively lower costs for small scale multi-well field piloting. Custom facilities from CFT are available that will enable timely and cost-effective pilot deployment in the field. By significantly lowering facilities costs, small independent oil & gas companies will be able to mitigate investment risks and be enabled to test the effectiveness of chemical EOR to profitably produce addition barrels of oil.
Logistics are critical to successful chemical EOR from the delivery of quality chemicals to the field to ensuring proper chemical mixing and injection. CFT will work with our client or partner to develop quality assurance and quality control processes at minimal complexity. Learnings from Mid-Con Energy’s chemical EOR pilots will be broadly shared across the community and will bring considerable value to CFT’s clients and partners.