Enhanced Oil Recovery (EOR) is a set of activities and techniques designed to reduce oil saturation and increase the oil recovery rate. In general, oil production is divided into 3 stages: primary, secondary and tertiary (improved). The tertiary method is also called as Enhanced Oil Recovery (EOR).
EOR is used when the primary (natural flow) and secondary (water and gas injection) methods are no longer effective and normally leave around 60-80% of oil unrecovered. Using EOR can help to recover more oil and help to achieve higher recovery rate. For gas wells, primary production method is normally enough to produce around 80% of the reserves. Hence, EOR is used in crude oil production.
EOR techniques are very costly and price of oil is a key factor for an operator, when decisions are made on what technique to implement. What could be technically feasible might be expensive and not economical. In addition, there is always a dilemma between exploration (to find more oil) and EOR and sometimes exploration risks are too high, thus companies choose EOR approach instead. In addition, the pace of new oil discoveries and its size has been declining; hence producing more oil from existing fields is a dominant thinking.
Screening criteria on of which EOR method to deploy require a detailed analysis of field and its location, reasons of lower recovery rate following primary and secondary methods, is conducted to understand the strategy and what EOR approach to apply. Due to a number of reasons, both technical and commercial, EOR makes economic sense in larger fields.
Offshore EOR makes it even more challenging and costly, due to the fact that existing infrastructure was not designed to accommodate it, in terms of weight, space, treatment facilities and power. In addition, due to well placement offshore and the distance between the wells, any EOR campaign will require more time to have a noticeable effect. On average an EOR project takes 1-7 years till it is fully deployed. Laboratory testing and pilot projects are prerequisites of any full scale EOR development and can take up to 4 years to complete.
EOR is divided into 4 distinctive categories as shown below.
Each EOR technique has its own use in and it is hard to be definitive with any particular EOR technique, as every method unique enough to work better in some cases than in others. Below is a guide and major characteristics of available EOR methods.
Worldwide, EOR contributes to around 3MM B/D of production, which is less than 5% of global crude production. Thermal injection is the largest and mostly widely used EOR method.
After long years of production, the recovery rate in most of the GCC fields is coming to a point, whereby focusing on EOR considerations become more and more important - most oil fields in the region have been under primary and secondary production for decades. Although most of the fields did not require any EOR yet, some of the EOR projects in the GCC are one of the world's biggest and challenging, whereby the most advanced technology is used. Those include steam injection and polymer flooding in Oman, gas injection in UAE and CO2 pilot projects in UAE, Saudi Arabia and Qatar, with more steam injection projects on the way in Kuwait. Oman is the regional leader in EOR projects and has implemented thermal, chemical and gas injections projects. It is estimated that by 2020, EOR production in Oman will be around 22% (PDO).
As a result of growing population and efforts to maintain and increase oil production, here in the GCC, it is becoming more challenging to meet the demand for natural gas to cater for power generation, gas re-injection projects and steam generation. Hence, focus on other EOR methods, such as chemical and CO2, will be evident in the years to come.
CO2 EOR projects are gaining more traction, not only because of its favorable economics, but also as part of sustainable practices, as well as preserving natural gas used for gas injection, for power generation purposes and alike. There have been a number of research centers established in UAE, Qatar and Saudi Arabia to make progress in applying CO2 EOR in the region. NOCs in the region are taking proactive steps to establish a knowledge base and expertise ahead of time.
EOR is challenging and time consuming and ineffective screening may result in lower-than-expected recovery rates. It is a common practice to conduct small trial projects to understand which EOR technique delivers best project economics. In addition, environmental impact and effects of chemicals could be best understood in smaller projects.
Some of the giant fields in GCC will not require EOR for the next 20-30 years. However, certain fields may need one in the next 3-5 years. The chart below represents the projected growth in EOR production worldwide. Growth in EOR production in GCC is evident and represents a notable proportion of GCC oil production.
CO2 EOR and Thermal Injection (steam flooding) are expected to dominate the growth in GCC.