Dissertation

Dissertation Presentation on

Design of MEOR Job for one of the Western Onshore Field of ONGC having oil with high paraffin content

19 December 2014 to 19 February 2015

Mohil Giri

M-Tech

Petroleum Exploration

IV Semester

500030842

R770213021

UPES

Dehradun

During oil production, primary & secondary oil recovery methods can account for 25-45 % oil productions leaving behind about 55-75 % of oil as residual oil in the reservoirs. Additional recovery from residual oil can lead to increase in global oil production as well as prolonging the productive life of many oilfields.

Microbial Enhanced Oil Recovery

An enhanced recovery  process in which microorganisms are used in a reservoir  to improve oil recovery. The microorganism can either be injected into the reservoir, or the population of an existing microorganism in the reservoir can be enhanced by injection of nutrients preferred by that microorganism. The microorganisms improve oil recovery by various means: (1) by releasing gases and increasing the pressure  of the reservoir; (2) by breaking the heavier molecules into smaller chain components, resulting in the reduction of viscosity  of oil; and (3) by producing natural surfactants that can improve oil flow by altering the interfacial properties of the system comprising the crude oil, brine and rock

Design of MEOR Job - SOLVENT PREPARATION – The

tubing & wellbore area needs to be cleared of all deposits so that microbes can deposit biofilm on the inner surface of tubing & prevent deposition of wax.

- MICROBIAL CULTURE PREPARATION – Culture of Paraffin Degrading Bacteria, PDS-10 is prepared.

Paraffin : - General formula CnH2n+2. Also referred to as alkanes.o Higher compounds with general formula CnH2n+2 starting at

about C-18 are wax-like . Also called ‘organic deposits’. The paraffin or alkanes that give us problems in the oilfield are those alkanes of C18H38 chain length and higher. The n-alkanes (straight chain) up to chain lengths of C36H74 give the majority of oil field problems.

o Cloud Point is the temperature at which wax crystals first start to form in a crude oil. Wax Appearance Temperature (WAT) & Wax Precipitation Temperature (WPT) are other synonyms. When the wax freezes after reaching the cloud point, it forms crystals formed of paraffin wax known as ‘macro - crystalline wax’.

Paraffin wax deposition

Wax Precipitation Behaviour :- o Temperature – Wax solubility in hydrocarbon fluids decreases as the

temperature is lowered.How? Kinetic Energy or molecular motion, increases with temperature. So the greater the

temperature of a material, the greater the tendency for the material to be thrown apart & thus decrease its density i.e. change from liquid to gas or gas to expand.

So when the temperature decreases, the paraffin molecules of compounds with carbon number more than C 18 in the crude oil tends to be attracted together into a solid state thereby result in the precipitation of wax in the tubing.

o Pressure - Liberation of solution gas from a crude oil as pressure decreases below the bubble point of the fluid results in increase of cloud – point temperature of oil.

How ? When the pressure falls below the bubble point pressure, the gas will come out of

the solution. This gas is generally the short carbon lengths i.e. methane, ethane, propane, butane etc.. This volatilization of short carbon length gases results in decrease in solubility of the paraffin in the oil hence the wax will start to appear and the cloud point will be reached with the decrease in pressure.

Solvent Preparation The paraffin content in oil gets deposited in the wall of tubing on reduction of temperature from reservoir to wellbore, which restricts production through the producing well. So, in order to solubilize this paraffin and clean the well before MEOR job, we treat the well with solvent. The study was done to optimize concentration of solvent mixture that can be used in the field.

Solvent Used

1. Xylene - molecular formula  C8H10 or C6H4(CH3)2

2. LABSA – Linear Alkyl Benzene Sulphonic Acid

. LABSA is used as a dispersant.

3. EGMBE – Ethylene Glycol Mono Butyl Ether .

It is a mutual solvent.

4. Diesel – Diesel is the solvent which is used in large quantity .

Sample No. 1 2 3 4 5 6 7

XYLENE 2.5 %

5 % 7.5 % 5 % 5 % 7.5 % 10 %

EGMBE 5 % 5 % 5 % 2.5 % 7.5 % 10 % 7.5 %

LABSA 1 % 1 % 1 % 1 % 1 % 1 % 1 %

DIESEL 91.5 %

89 % 86.5 % 91.5 %

86.5 % 81.5 %

81.5 %

Laboratory experimental results

In the first 6 mixture composition of solvents the bottom of the beaker filled with oil does not get cleared . So the first 6 solvent compositons are unable to dissolve the paraffin content of oil at 50 °C which is the temperature in the tubing .

In the 7 th solvent composition it was observed that the solvent mixture has successfully cleared the bottom of the beaker filled with oil at 50 °C.

Mechanism of solubilization of paraffin wax crystal

solvent inhibiting structure interfering with agglomeration interfering

with deposition

Paraffin Degrading Bacteria

o Source: Oil contaminated soil of Western Onshore Field of ONGC.

o PDS-10 Geobacillus kaustophilus

Geo = earth or soil Bacillus = small rod Kausto = heat Philus = love

o Thermophilic, Microaerophilic consortium. o PDS-10 Consortium thrives upto 90°C , optimum activity at 50°C

.

o Nutrient media

Carbon source : Glucose and Wax Minimal Salt media Bio-catalyst

o Paraffin degradation efficiency > 82% at 50 °C o Best grows in pH range 5 to 8. o Non-pathogenic o Optimum incubation period : 20 hours

Microbial Culture Preparation

Isolation of bacteria (PDB) – The bacteria is isolated from the oil sands & taken to the facility. It is treated with Luria Bertini (LB) Broth. Then it is grown in Minimal Salt Medium (MSM) & wax (1%) as the sole carbon source.

Minimal Salt Medium (MSM) Composition or Nutrient Media for PDB

(NH₄Cl + MgSO₄.7H₂O + KNO₃) solution is mildly acidic, so we use the buffer solution KH₂PO₄ + K₂HPO₄, which resists the pH change on addition of the mildly acidic solution .

CHEMICAL NAME QUANTITY / LITRE

NH₄Cl 0.5gm

MgSO₄.7H₂O 0.5gm

KNO₃ 0.5gm

KH₂PO₄ 1gm

K₂HPO₄ 1gm

Glucose 10gm

Trace mineral solution 100 ml

Vitamin solution 1ml

Autoclave : - The nutrient media or the MSM composition is put in Autoclave for the sterlization of the nutreint media to kill other bacterias which can contaminate nutreint media.

Laminar Air Flow (LAF) : - This equipment is used for inoculation of microbial culture. LAF has bacteria free environment because of UV rays penetration for 40 minutes, before inoculation.

Incubation Period for the microbes to grow = 20 hours

Temperature = 70 °C

Agitation rate = 180 rpm

pH = 5.8

Microbial Growth is observed in Motic Microscope .

Microbial Growth at 70 °C = 10 6-7 CFU (Colony Forming Unit )

Paraffin Degradation Pathway of Microaerophilic Bacteria Geobacillus Kaustophilus

Oxidation & Reduction of Nicotineamide Adenine Nucleotide

Measurement of Viscosity

Anton Paar Rheometer – Oil is put in the plate & the meas is set upon the oil in the plate. The meas rotates at a fixed shear rate & the temperature of the plate is set which increases from 50 °C to 90°C simultaneously with the rotation of meas.

Temperature (°C)

50 55 60 65 70 75 80 85 900

100

200

300

400

500

600

700

800730

340

156

59.523.3 16.5 14.5 12.4 10.7

115

7344

24.8 14.8 11.5 10.2 9 7.7

Neat Oil Viscosity (cp)PDB Degraded Viscosity (cp)

References SPE 72129, Microbial Enhanced Oil Recovery: Diverse Successful

Applications of Biotechnology in the Oil Field S.A. Bailey, SPE, T.M. Kenney, and D.R. Schneider, SPE, Micro-Bac International, Inc.

SPE 36630, Microbial Pilot Test for the Control of Paraffin and Asphaltenes at Prudhoe Bay, Keith R. Ferguson and Christine T. Lloyd, ARCO Alaska Inc., Dan Spencer and James Hoeltgen, Biostar Technologies.

BIOLOGICAL PARAFFIN CONTROL SYSTEMS SHOW PRODUCTION INCREASES IN ADDITION TO CONTROLLING PARAFFIN BY Mark D. Bishop, Klsakl TDChnology Inc., Dean R. Woodward, P.S.L Inc.

SPE 80529 Microbial Prevention of Wax Precipitation in crude oil by biodegradation mechanism. Ayoub Sadeghazad, NIOC SPE.

SPE 18889 An Investigation Into Practical Removal of Thermal Methods and Chemical Solvents Downhole Paraffin by .- l by T.J. Straub, * Amoco Production Co.; S.W. Autry, U. of Tulsa; and G,E. King, Amoco Produ-lion Co. ‘ SPE Members

SPE 140128 Fully Miscible Micellar Acidizing Solvents vs Xylene, The better paraffin solution. David W. Boswood & Kristopher A. Kreh/ Baker Hughes.

SPE 64995 Paraffin Solvation in the Oilfield K.M. Barker, SPE, M.E. Newberry, SPE, Y.R. Yin, SPE/Baker Petrolite.

THANK YOU