Although many issues can be raised in screening EOR processes, this session focuses on interpreting laboratory results for use in pilots and field study because there are still a lot of uncertainties in the area. The difficulty is compounded when the reservoir itself is complex, e.g. fractured, stratified, compartmental, etc. Multiple phases may form in the labs and not the reservoir or vice versa. While chemical flooding has the advantage of a large variety of injection fluids as compared with other processes, it also increases screening for the best chemicals.
In chemical flooding, much of the de-risking and uncertainty reduction is done through laboratory experiments. Early phase research and development includes a variety of investigations including phase behavior studies, interfacial tension measurements, wettability changes, core flood analyses, PVT analyses, slim tube experiments, sand pack screens, etc. Collaboration between chemical vendors, service companies, research institutes, universities, and operators allows for the agreement upon key performance indicators in the experiments that will help provide confidence in correct product development and eventual implementation. Equally important is the interpretation of how laboratory generated data can be used for modelling parameters and successful field scale up. Continued research is required to optimise the current technologies leading to a better fundamental understanding of the processes, lower risks and improved economics.
A key challenge in chemical EOR studies is how to combine laboratory-scale process mechanisms and reservoir-scale geologic description in a reservoir simulation model that accurately represents field-scale performance. In order to reflect the chemical EOR recovery with dynamic modelling and design the optimum injection strategy, the lab data need to be scaled up in the model to correctly capture phenomena at various scales. However, it is impractical to collect all the data needed to do full-physics reservoir simulation. In addition, the reservoir characterisation needs for chemical EOR studies can be different from standard reservoir studies. This session will review the current practices of subsurface modeling techniques used in FDP studies, and discuss the appropriateness of current techniques to capture the chemical EOR performance in the reservoir.
While EOR projects can improve production, they are complex and costly. Using a pilot test to assess an EOR project can be crucial to evaluate the economic potential of the selected method. Designing and realising a pilot is an important step between models, laboratory experiments and a commercial implementation. Poor pilots will yield little information, while successful ones will facilitate and hasten transition to full field. A pilot requires careful planning: objectives need to be clearly defined, a plan designed to address specific risks/uncertainties needs to be created, data acquisition and monitoring strategies must be developed, facilities and operational procedures must be adequate, and finally, results should be interpretable for full field implementation.
Implementing a full field chemical flood is a critical decision for a CEOR project team. Given the capital requirements and challenges, a team should have significant understanding of the reservoir and confidence in the response through laboratory studies, field tests, simulation, and operating history. Many recent full field implementations have been successful. However, some projects have not performed up to expectations. The lessons learned and common success characteristics identified from both successful and unsuccessful full field implementations can better prepare the operator to improve recovery and reduce project risk.
In this session, we will discuss risks associated with chemical EOR pertaining to the screening process up to full field implementation. Also, we will discuss how we can mitigate and manage the risks. This subject is mainly focused on the environmental impact and potential risk related to both onshore and offshore EOR chemical application. Onshore and offshore application can create differential tremendous challenges to ecosystem/bio system and give impact to environmental system. As such, handling requirements are vital to ensure chemical handlings are properly cured prior to discharging it overboard. Amongst ecotoxicological properties testing are biodegradability, bioaccumulation, and acute toxicity. This is essential to identify hazardous level/severity of the produced chemicals.
There are many facts to consider before implementing an EOR project, particularly in aging facilities which require brown field rejuvenation. Most of the identified EOR field candidates have reached at least 15 years production and with the introduction of chemical EOR additional risks and uncertainties are brought to the well. Taking into account the fact that many of the current/existing wells were not designed to cater to CEOR, it brings to light the importance of not ignoring the best practice techniques to ensure well integrity and ensure performance (productivity and infectivity). The relatively high capital expenditure and operating costs for EOR must be taken into account. As such, continue looking for ways to reduce well cost and implement simple completions that can meet well objective(s) while minimising well risks. Additionally, we need to consider and mitigate the side effects of chemical flooding such as, fine migration and formation of asphathane.