Downhole oil water separation technology
Encyclopedia
Downhole oil–water separation technology (DOWS) is an emerging technology
that separates oil
and gas
from produced water
at the bottom of the well, and re-injects most of the produced water into another formation which is usually deeper than the producing formation, while the oil and gas rich stream are pumped to the surface. DOWS effectively removes solids from the disposal fluid and thus avoids injectivity impairment caused by solids plugging. Simultaneous injection using DOWS minimizes the opportunity for the contamination of underground sources of drinking water (USDWSs) through leaks in tubing and casing during the injection process.
, it separates oil and water in the wellbore
the oil rich stream is brought to the surface while the water rich stream is pumped into an injection formation without ever coming to the surface. A DOWS system includes many components but the two primary components are an oil/water separation system and a pumping/injection system used to lift oil to surface and inject the water into a deeper formation. Two basic types of DOWS system have been developed, one type uses hydrocyclones to mechanically separate oil and water and the other relies on gravity separation
that takes place in the wellbore. Three basic types of pumping/injection system are used with the DOWS technology these include electrical submersible pumps, progressive cavity pump
s and sucker rod pumps. Hydrocyclone separators are usually used with the electrical submersible pumps because of higher drawdown
created with effective injection of water into the lower zone.
2. Reduction of environmental Impact of oil and gas operations: Standard injection well
operations pose a significant but manageable risk of environmental pollution. The highest risks occur due to surface spills during re-injection of the separated brine. By reducing the amount of brine
brought to the surface and re-injected the environmental risks associated with re-injection wells can be reduced.
3. Pollution of underground sources of drinking water: produced water in most cases contains brines, dissolved impurities are not allowed to get to the surface hence they do not pass through intervals containing underground sources of drinking water (USDW) and again the water does not require re-injection from the surface to pass through intervals of USDWs. Therefore, the risks posed by large volumes of these fluids passing USDWSs both exiting and re entering the well upon injection are minimized.
4. Because DOWS are underground equipments, surface brine disposal operations, which may comprise of pump
s, pipe
s, tank batteries, and other storage facilities, may also be reduced in size and extent if not altogether eliminated.
5. DOWS system is used for re-injection hereby beefing up the drawdown pressure which can result in increased production rate.
Emerging technologies
In the history of technology, emerging technologies are contemporary advances and innovation in various fields of technology. Various converging technologies have emerged in the technological convergence of different systems evolving towards similar goals...
that separates oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
and gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
from produced water
Produced water
Produced water is a term used in the oil industry to describe water that is produced along with the oil and gas. Oil and gas reservoirs have a natural water layer that lies under the hydrocarbons. Oil reservoirs frequently contain large volumes of water, while gas reservoirs tend to have smaller...
at the bottom of the well, and re-injects most of the produced water into another formation which is usually deeper than the producing formation, while the oil and gas rich stream are pumped to the surface. DOWS effectively removes solids from the disposal fluid and thus avoids injectivity impairment caused by solids plugging. Simultaneous injection using DOWS minimizes the opportunity for the contamination of underground sources of drinking water (USDWSs) through leaks in tubing and casing during the injection process.
Overview
A DOWS system is installed at the bottom of an oil wellOil well
An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
, it separates oil and water in the wellbore
Wellbore
A wellbore is any hole drilled for the purpose of exploration or extraction of natural resources such as water, gas or oil where a well may be produced and a resource is extracted for a protracted period of time....
the oil rich stream is brought to the surface while the water rich stream is pumped into an injection formation without ever coming to the surface. A DOWS system includes many components but the two primary components are an oil/water separation system and a pumping/injection system used to lift oil to surface and inject the water into a deeper formation. Two basic types of DOWS system have been developed, one type uses hydrocyclones to mechanically separate oil and water and the other relies on gravity separation
Gravity separation
Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: ie the components of the mixture have different specific weight. All of the gravitational methods are common...
that takes place in the wellbore. Three basic types of pumping/injection system are used with the DOWS technology these include electrical submersible pumps, progressive cavity pump
Progressive cavity pump
A progressive cavity pump is a type of positive displacement pump and is also known as a progressing cavity pump, eccentric screw pump or even just cavity pump. It transfers fluid by means of the progress, through the pump, of a sequence of small, fixed shape, discrete cavities, as its rotor is...
s and sucker rod pumps. Hydrocyclone separators are usually used with the electrical submersible pumps because of higher drawdown
Drawdown (hydrology)
In water-related science and engineering there are two similar but distinct definitions in use for drawdown.*In subsurface hydrogeology, drawdown is the change in hydraulic head observed at a well in an aquifer, typically due to pumping a well as part of an aquifer test or well test.*In surface...
created with effective injection of water into the lower zone.
Advantages
1. Lower cost of oil production: DOWS reduces more than 70% of the water that was supposed to be produced thereby reducing the total cost of lifting, treating, re-injecting and disposal of produced water, the cost of production of oil is greatly reduced.2. Reduction of environmental Impact of oil and gas operations: Standard injection well
Injection well
An injection well is a vertical pipe in the ground into which water, other liquids, or gases are pumped or allowed to flow.-Waste disposal: One application is waste water disposal, in which treated waste water is injected into the ground between impermeable layers of rocks to avoid polluting fresh...
operations pose a significant but manageable risk of environmental pollution. The highest risks occur due to surface spills during re-injection of the separated brine. By reducing the amount of brine
Brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...
brought to the surface and re-injected the environmental risks associated with re-injection wells can be reduced.
3. Pollution of underground sources of drinking water: produced water in most cases contains brines, dissolved impurities are not allowed to get to the surface hence they do not pass through intervals containing underground sources of drinking water (USDW) and again the water does not require re-injection from the surface to pass through intervals of USDWs. Therefore, the risks posed by large volumes of these fluids passing USDWSs both exiting and re entering the well upon injection are minimized.
4. Because DOWS are underground equipments, surface brine disposal operations, which may comprise of pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
s, pipe
Pipe
Pipe may refer to:* Pipe , a hollow cylinder following certain dimension rules* Smoking pipe* Pipe or butt, a cask measurement* Pipe , a type of metal casting defect...
s, tank batteries, and other storage facilities, may also be reduced in size and extent if not altogether eliminated.
5. DOWS system is used for re-injection hereby beefing up the drawdown pressure which can result in increased production rate.