Enhanced Oil Recovery (EOR) Techniques and Helpful Technology
August 6, 2019 Welcome
Oil recovery in hydrocarbon production is a series of efforts aimed at obtaining as much oil & gas as possible from a hydrocarbon-bearing reservoir. Typically, the rate of production varies over the lifecycle of a well; thus, the formation will require additional stimulation to ensure that production volumes remain at sustainable levels for as long as possible.
For optimal oil recovery, various techniques and technologies are employed across several phases depending on the age of the well, formation characteristics, and the cost of operation.
This article will discuss the various oil and gas recovery methods with a special focus on tertiary or enhanced oil recovery.
Types of Oil Recovery
Oil recovery efforts fall into three broad categories – primary, secondary, and tertiary oil recovery (also known as enhanced oil recovery).
Let’s look at these three in closer detail:
Primary Oil Recovery
Primary recovery is employed during the initial phase of oil production. For conventional oil and gas, it begins immediately after drilling operations have been concluded, and a Christmas (production) tree installed at the wellhead. In primary recovery, oil production is chiefly due to the natural formation pressure of the reservoir and basic pumping operations via the production casing. Primary oil recovery techniques recover only about 30% of OIIP.
Secondary Oil Recovery
Secondary recovery follows primary recovery, typically due to a decline in the natural formation pressure of the reservoir. The operator may inject gas or steam flooding into the reservoir through an injection well to force more oil toward the production casing. Secondary oil recovery methods can help operators recover up to 60% of OIIP.
What Is EOR?
Enhanced oil recovery is the process of artificially stimulating a reservoir to recover more oil after secondary recovery techniques have become unable to sustain desired production volumes. EOR is usually employed when the oil left in the reservoir is trapped in hard-to-reach (low-permeability) sections with poor oil-water contact or irregular fault lines.
Tertiary oil recovery techniques are employed extensively in unconventional oil and gas plays across the U.S. as well as brownfields where they help operators recover up to 75% of the oil initially in place (OIIP) and ramp up existing production by up to 300%.
Enhanced Oil Recovery (EOR) Techniques
Enhanced recovery methods for oil and natural gas are employed after secondary recovery techniques are insufficient to sustain profitable production, mostly due to a severe decline in reservoir pressure or unconventional oil and gas plays such as shale or tight sandstone.
The major enhanced oil recovery processes and operations include chemical injection, steam injection, and gas injection. These methods typically require non-standard enhanced oil recovery technology.
Gas injection as an EOR method uses nitrogen gas (N2) or Carbon dioxide (CO2) for the miscible displacement of crude in unconventional reservoirs our mature wells. The principle for recovery is that when the gas dissolves in the oil, it reduces its viscosity, hence improving mobility.
To carry out a gas injection, CO2 is pumped into the formation via injection wells. At high downhole pressures, the gas forms a miscible zone that mops up stranded oil and forces it towards the production casing of the target well. Gas injection is often alternated with water injection using a water injection pump system to further improve the sweep efficiency.
Due to growing concerns about the impact of CO2 (a known greenhouse gas) on global climate change, operators may opt to use high-purity nitrogen gas. N2 is also favored over CO2 due to it is relatively inert properties which prevent downhole combustion. N2 can be generated cost-effectively from atmospheric air using a nitrogen generator skid.
Steam injection enhanced oil recovery (or steam flooding) refers to the injection of water vapor at high pressure and temperature into a well to mop up stranded oil from the reservoir following a decline in the formation pressure.
To carry out steam injection, an operator drills one or more ‘injection’ wells close to the well to be stimulated. Steam is then introduced into the formation via the injection well(s). When it contacts the oil, it lowers its viscosity and increases its kinetic energy, improving mobility toward the production casing. Steam injection is particularly useful for oil recovery in heavy oil reservoirs.
In chemical injection, long-chain polymers are injected into a well via a chemical injection skid to free up oil and gas molecules from remote sections of the reservoir. Chemical injection can be done alongside waterflooding to improve the recovery factor by improving the efficacy of the surfactants for improved mobility of hydrocarbons.
The polymers utilized in the process can be alkaline or micellar substances which enhance the flow of crude (sweep efficiency) by reducing the interfacial tension between the hydrocarbon molecules and water present in the reservoir.
Use IFS Modular Process Skids to Support Your EOR Technology
IFS is a best-in-class manufacturer of process equipment for the oilfield industry. We provide a range of modular process skids to support your enhanced oil recovery operations, with rugged durability suitable for the most challenging oil and gas fields.
To learn more about our products or speak with a professional, please contact us online today!