Thermal Recovery (aka Thermal Injection) is a process of injecting the heat into the reservoir to reduce oil viscosity or thin it and significantly enhance its ability to flow through the reservoir. It also reduces tension between rocks and liquids, which in turn improves oil mobility and results in easier flow. In addition, heated oil vaporizes, thus forming thinner oil via condensing. Thermal Recovery is the most widely used method worldwide for heavy oil projects and accounts for more than 60% of the global EOR production.
There are several variations of thermal recoveries, such as:
- Cyclic steam injection is also known as the Huff & Puff method, steam is injected into a well and then left in the well for a period of time, to heat the oil and make it flow more easily. The recovery rate of this method is less efficient than others and can only extract around 20% of the oil in place. It is a common practice to produce in cyclic steams for a few cycles and then use the steam flooding method. Each cycle, inject-soak-produce can last between a few weeks to months.
- Steamflood or Steam Drive is the process of constant injection of steam to the reservoir through an injection well, to heat heavy oil and improve its viscosity. In addition, as steam condenses into hot water, the additional water drive pushes the oil toward producing wells. This technique results in the recovery rate of 25%-70% of the oil in place. Normally, steam is generated by using natural gas to heat the water.
- Steam-assisted gravity drainage (SAGD) is a steam injection in a more advanced approach, whereby two stacked (one above the other) horizontal wells are drilled in the reservoir, approximately 5 meters apart from each other. Pressurized steam injected into the upper well to heat the oil and make it more viscous, thus forcing heavy oil to drain into the lower well, from where it is produced to the surface. This method is mostly used in very heavy oil fields or oil sands. This technique results in the recovery rate of around 50 % of the oil in place.
- Fireflood or in-situ combustion used primarily in oilfields with high saturation and porosity, this method of thermal recovery generates heat inside the reservoir. In shallow depth formations, gas burners are used to provide fire burns in the formation. In deeper reservoirs, fire burns are generated by injecting air or other gas mixture with a very high concentration of oxygen. Fire reduces the viscosity of oil by the hot gases produced by the fire flames, pushing the heated oil to producing wells. Hence, the fire flooding produces two effects: 1) thinning oil and 2) a force to move oil. Sometimes water can be injected as well, which then becomes steam inside the reservoir, creating an additional force to move the oil. Combustion can be achieved by three various methods: 1) Dry forward, 2) Wet and 3) Reverse Combustion. In Dry Forward combustion fire moves in the same direction as the injected air - towards a producing well. During Wet Combustion, water is injected behind the fire burn and then transferred into steam by the hot rocks that were heated by the fire front. This method is also known as COFCAW a combination of forwarding combustion and waterflooding. In Reverse Combustion, fire front moves in the opposite direction to the air injected. Fireflooding or in-situ combustion technique results in a recovery rate of 30%-40% of the oil in place.
In all the methods, thermal energy is generated at the surface. The source of water and power is critical. Footprint, design, complexity, and costs of surface facilities and down-hole systems are dependent on the method utilized. Fields where steam flooding is used, produced water requires recovery and separation, so it can be used as feed water for boilers. Natural gas is required to heat the water and generate steam. However, today, solar energy could be used to heat water to serve the same purpose. It is has been in use successfully for many years now in Oman. The decision of power generation is driven by many factors such as availability of natural gas, weather patterns (number of sunny days) and costs.
Although steam injection and fireflooding are the most commonly used, selection of particular technique is driven by the depth of the reservoir, formation thermal properties and fluid (crude) properties. Hence, one of the key decisions to be made during any thermal recovery project planning is understanding how fast the additional drive can be transferred to the reservoir at the most cost-effective way.
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 rates. For gas wells, the 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 the price of oil is a key factor for an operator when decisions are made on what EOR 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 for a few years to come.
Screening criteria on of which EOR method to deploy require a detailed analysis of a particular 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 equipment packages associated with it in terms of weight, space, treatment facilities and power generation. 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 the others. Below are a guide and major characteristics of available EOR methods.
Worldwide, EOR contributes to less than 2% of global crude production. CO2- EOR is the largest and most widely used EOR method, followed by Thermal injection and Gas Injection.
After long years of production, the recovery rate in most of the fields in the GCC 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 the fields do 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 in the GCC, it is becoming more challenging to meet the demand for natural gas to cater to 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 the best project economics. In addition, the 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.
Supply & Demand Dynamics
Supply & Demand Dynamics
Global demand for thermal recovery services is comparatively significant and the most common method used worldwide for heavy oil projects, accounting for more than 60% of the global EOR production. Due to the relatively low costs involved, this method is the preferred method for heavy oil EOR. Thermal recovery, as part of EOR option, will continue to dominate the EOR production for many years to come. Traditionally, thermal recovery EOR has been used extensively in North America, Indonesia and Venezuela with smaller applications in Oman, Brazil and China.
In the GCC, heavy crude fields in Oman, Kuwait, Iraq and Bahrain and their current recovery rate will create the demand. Solar EOR is expected to boost t lead further developments in this domain.
Cost & Price Analysis
Cost & Price Analysis
EOR production is considered as a project in itself and requires a large number of equipment and packages. Studies, pilot projects, engineering design, equipment procurement, feedstock planning, drilling, and other materials, play an important role in EOR projects. Upfront capital costs in EOR projects are significant.
Cost-wise, thermal recovery services are composed of a number of various components, such as feed gas or solar energy, water, boiling and separation equipment, injection and closed-loop cycle infrastructure.
Almost every EOR project is bespoke and requires a large number of studies, pilot projects, and simulation. As a result of this, equipment and packages are not standard and may require bespoke engineering and manufacturing every time, which in turn reduces the diversity of available suppliers, increases costs and lead times.
The most critical levers that would influence the costs and procurement decisions are
- A comprehensive FEED study
- Analysis of the supplier market and their capabilities.
While there are numerous engineering companies providing the services of FEED studies, companies who specialize in the EOR studies and consultancies are in a better position to produce a more valuable and meaningful FEED - as they have large exposure to varus EOR projects.