OIL RECOVERY TECHNIQUES

VARIOUS METHODS OF OIL RECOVERY

BY:-GEIKARAN PATEL ROLL NO:-U10CH025

Methods of Recovery

• Oil extraction and recovery• Primary Recovery• Secondary Recovery• EOR- Enhanced Oil Recovery- Tertiary

Primary Recovery• Drilling- The oil well is created by

drilling a hole into the earth with an oil rig. A steel pipe (casing) is placed in the hole, to provide structural integrity to the newly drilled wellbore. Holes are then made in the base of the well to enable oil to pass into the bore. Finally a collection of valves called a "Christmas Tree" is fitted to the top, the valves regulating pressures and controlling flows.

Grounds for Primary Recovery• If the underground pressure in the oil

reservoir is sufficient, then this pressure will force the oil to the surface. Gaseous fuels, natural gas or water are usually present, which also supply needed underground pressure. In this situation, it is sufficient to place a complex arrangement of valves (the Christmas tree) on the well head to connect the well to a pipeline network for storage and processing.

• Usually, about 20% of the oil in a reservoir can be extracted using primary recovery methods.

Secondary Recovery• Secondary or enhanced oil recovery

(EOR) methods are needed because only a small fraction of the oil in a reservoir can be produced by primary means (the reservoir's natural drives).

• Initial recovery ranges from only about 5 per cent (Lloydminster-area heavy oils) up to about 20 per cent (better quality oils like those produced in the province's southwest and southeast). These methods must, naturally, also be both economic and effective, or companies may not bother trying to coax more oil from the reservoir.

• Over the lifetime of the well the pressure will fall, and at some point there will be insufficient underground pressure to force the oil to the surface. If economical, as often is, the remaining oil in the well is extracted

• using secondary oil recovery methods (see: energy balance and net energy gain).

• Secondary oil recovery uses various techniques to aid in recovering oil from depleted or low-pressure reservoirs. Sometimes pumps, such as beam pumps and electrical submersible pumps (ESPs), are used to bring the oil to the surface. Other secondary recovery techniques increase the reservoir's pressure by water injection, natural gas reinjection and gas lift, which injects air, carbon dioxide or some other gas into the reservoir.

• Together, primary and secondary recovery generally allow 25% to 35% of the reservoir's oil to be recovered.

Examples of Secondary Recovery• Water Flooding: Water flooding is

utilized primarily as a secondary recovery technique, where the primary drive mechanism used to produce the oil (dissolved gas) is depleted. Water is recovered from the water table and injected into the reservoir, displacing the oil towards the target production wells. Because of the limited amount of dissolved gas remaining in solution, pumps are used to bring the oil to surface.

• Sand Franc (beam pump, electrical submersible pump): Sand Fracas are used where porosity development or permeability is low (the formation is tight). This treatment is done under high pressure, the formation is fractured, and a sand/gel mixture is pumped into the fractures. Once the fractures are allowed to settle, trapping the sand, the well is produced with a significant increase in production, because the pathways towards the well-bore have been opened up. Almost like changing a single lane highway into a six lane highway

Tertiary Recovery• Tertiary oil recovery reduces the oil's viscosity to increase oil production.• Thermally enhanced oil recovery methods (TEOR) are tertiary recovery

techniques that heat the oil and make it easier to extract. Steam injection is the most common form of TEOR, and is often done with a:

1) cogeneration plant. In this type of cogeneration plant, a gas turbine is used to generate electricity and the waste heat is used to produce steam, which is then injected into the reservoir. This form of recovery is used extensively to increase oil production in the San Joaquin Valley, which has very heavy oil, yet accounts for 10% of the United States' oil production.[

citation needed] .

2) In-situ burning is another form of TEOR, but instead of steam, some of the oil is burned to heat the surrounding oil. Occasionally, detergents are also used to decrease oil viscosity as a tertiary oil recovery method.

• 3) carbon dioxide flooding.• Tertiary recovery allows another 5% to 15% of

the reservoir's oil to be recovered.• Tertiary recovery begins when secondary oil

recovery isn't enough to continue adequate production, but only when the oil can still be extracted profitably. This depends on the cost of the extraction method and the current price of crude oil. When prices are high, previously unprofitable wells are brought back into production and when they are low, production is curtailed

Other Tertiary Recovery Methods• Cyclic Steam Stimulation• This method, also known as the Huff

and Puff method, consists of 3 stages: • 1)injection,• 2)soaking • 3) production. • Steam is first injected into a well for a

certain amount of time to heat the oil in the surrounding reservoir to a temperature at which it flows. After it is decided enough steam has been injected, the steam is usually left to "soak" for some time after (typically not more than a few days). Then oil is produced out of the same well, at first by natural flow (since the steam injection will have increased the reservoir pressure) and then by artificial lift. Production will decrease as the oil cools down, and once production reaches an economically determined level the steps are repeated again.

• The process can be quite effective, especially in the first few cycles. However, it is typically only able to recover approximately 20% of the Original Oil in Place (OOIP), compared to steam flooding which has been reported to recover over 50% of OOIP. It is quite common for wells to be produced in the cyclic steam manner for a few cycles before being put on a steam flooding regime with other wells.

• The mechanism was accidentally discovered by Shell while it was doing a steam flood in Venezuela and one of its steam injectors blew out and ended up producing oil at much higher rates than a conventional production well in a similar environment.

Steam Flooding• Steam Flooding• In a steam flood, sometimes known as a

steam drive, some wells are used as steam injection wells and other wells are used for oil production. Two mechanisms are at work to improve the amount of oil recovered. The first is to heat the oil to higher temperatures and to thereby decrease its viscosity so that it more easily flows through the formation toward the producing wells. A second mechanism is the physical displacement employing in a manner similar to water flooding, in which oil is meant to be pushed to the production wells. While more steam is needed for this method than for the cyclic method, it is typically more effective at recovering a larger portion of the oil.

• A form of steam flooding that has become popular in the Alberta tar sands is steam assisted gravity drainage (SAGD), in which two horizontal wells are drilled, one a few meters above the other, and steam is injected into the upper one. The intent is to reduce the viscosity of the bitumen to the point where gravity will pull it down into the producing well.

polymer flooding

DescriptionPolymer augmented water flooding consists of adding water soluble polymers to the waterbefore it is injected into the reservoir.Mechanisms That Improve Recovery EfficiencyMobility control (improves volumetric sweep efficiency).LimitationsHigh oil viscosities require a higher polymer concentration. Results are normally better if the polymer flood is started before the water-oil ratiobecomes excessively high.Clays increase polymer adsorption.Some heterogeneity is acceptable, but avoid extensive fractures. If fractures are present,the cross linked or gelled polymer techniques may be applicable.

ChallengesLower infectivity than with water can adversely affect oil production rates in the early stagesof the polymer flood.Acryl amide-type polymers loose viscosity due to sheer degradation, or it increases insalinity and divalent ions.Xanthus gum polymers cost more, are subject to microbial degradation, and have agreater potential for wellbore plugging.Screening ParametersGravity >18º APIViscosity <200 cpComposition not criticalOil saturation >10% PV mobile oilFormation type sandstone/carbonateNet thickness not criticalAverage permeability >20 madTransmissibility not criticalDepth <9,000 feetTemperature <225ºF

Microbial injection

Introduction

• Currently global energy production

from fossil fuels is about 80-90% with oil and gas representing about 60 %

• During oil production, primary oil recovery can account for between 30-40 % oil productions

• While additional 15-25% can be recovered by secondary methods such as water injection leaving behind about 35-55 % of oil as residual oil in the reservoirs

• This residual oil is usually the target of many enhanced oil recovery technologies and it amounts to about 2-4 trillion barrels (Hall et al., 2003)

What is microbial enhanced oil recovery (MEOR)?

Use of microbes to improve oil recovery, established by Beckman 1926

How much additional oil can be produced? Up to 60% oil in place after primary recovery

MEOR Mechanisms

Bioproduct Effect Acids Biomass Gases (CO2, CH4, H2) Solvents Surface-active agents Polymers

Modification of reservoir rock Improvement of porosity and permeability Reaction with calcareous rocks and CO2 production Selective or non selective plugging Emulsification through adherence to hydrocarbons Modification of solid surfaces Degradation and alteration of oil Reduction of viscosity and oil pour point Desulfurization of oil Reservoir repressurization Oil swelling Viscosity reduction Increase permeability due to solubilization of carbonate rocks by CO2 Dissolving of oil Lowering of interfacial tension Emulsification Mobility control Selective and non-selective plugging

Microbial Enhanced Oil Recovery (MEOR)

Microbial Enhanced Oil Recovery (MEOR) is a technology using micro-organisms to facilitate, increase or extend oil production from reservoir.

Average size of microbe is one micron, 10,000th of cm. More than 27,000 species of bacteria have been identified.

The bacteria, which can be mobile or non-mobile, have three basic shapes: round (cocas), rod (bacillus) and spiral (spiralled).

Microbes are the most primitive earth's single celled organisms.

Their basic role in life is to recycle the components of living organisms, converting them to the nutrient chemicals used by plants in photosynthesis & chemosynthesis.

Enhanced Oil Recovery Research

Saskatchewan’s Heavy Oil Production

20.4 billion barrels currently in place

Solvent Injection and SVX

Saskatchewan Research Council: Experimental Apparatus

• A suite of projects to gain knowledge of enhanced oilrecovery in light and tight oil reservoirs, and heavy oil• Considering the certainty of decline, these will hopefullyprovide solutions before solutions are even required• Projects designed to help us with water, be it from anenvironmental standpoint, or usage in water flood

CONCLUSION

According to production rates from graph of oil recovery methods we can say that thermal method is more efficient than other methods and chemical method is less efficient

REFERENCES

• Petroleum Technology Research Centre Saskatchewan articles

• Dr. Maria Antoinette Baronet- fall 2001, class notes Pete module-1

• Oil and Gas recovery by Squab• Microbial oil recovery by I.A Jimson, Rudy S.N and

Sugared E.G