MAJOR PROJECT REPORT

on

In-Situ Combustion: Air Compressor Operations

UNDER THE MENTORSHIP OF

Mr. R. P. Soni

Professor, Petroleum Engineering and Earth Science Department (UPES)

SUBMITTED BY

Mohit Upadhyay

Enrolment Number: R870211015

E-mail address: Mohit.Upadhyay@stu.upes.ac.in

Dr. Pushpa Sharma Dr. D. K. Gupta

Professor Head of Department

Course Coordinator Deptt of Petroleum Engineering & Earth Sciences

B. Tech. APE – Upstream UPES

University of Petroleum and Energy Studies, Dehradun

April 2015

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CERTIFICATE

This is to certify that this project report entitled, “In-Situ Combustion: Air Compressor Operations” is submitted by Mohit Upadhyay (R870211015) to University of Petroleum& Energy Studies, for the award of the degree of Bachelor of Technology, and is a bonafide record of research work carried out by him under my supervision.

Mr. R. P. Soni Professor, Department of Petroleum Studies &Earth Sciences

College of Engineering Studies University of Petroleum & Energy Studies

Dr. Pushpa Sharma Course Co-ordinator

B. Tech. Applied Petroleum Engineering with specialisation in Upstream (2011-15) College of Engineering Studies

University of Petroleum & Energy Studies

Dr. D. K. Gupta Head of Department

Department of Petroleum Studies &Earth Sciences College of Engineering Studies

University of Petroleum & Energy Studies

Place: Dehradun Date: April 28, 2015

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DECLARATION BY AUTHORS

This is to declare that the project is a genuine piece of work by its author. No part of the report is

plagiarized from other sources. All information included from other sources have been duly

acknowledged. I aver that if any part of the same is found to be plagiarized, the responsibility shall be

mine solely.

Mohit Upadhyay

Roll No. R870211015

SAP ID: 500017293

Place: Dehradun

Date: April 28, 2015

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ACKNOWLEDGEMENT

I would like to thank Mr R. P. Soni for his constant support and keen interest in the subject without

which this project was not possible. Being our professor, he has closely observed us and has always

pushed us towards going an extra mile to get the job done and meet our stringent timelines.

I am grateful to Dr Srihari, Pro Vice Chancellor, UPES and Dr Kamal Bansal, Dean, College of Engineering

Studies for their firm support. I am also grateful to Dr D. K. Gupta, Head of Department, Department of

Petroleum Engineering & Earth Sciences for his constant motivation to reach our goals. I would also like

to thank our course coordinator, Dr Pushpa Sharma for the motivation she has always been to me. The

kind of independence and space she gives the students in the completion of this report is beyond words.

I would also like to thank my friends, family and the Almighty for their support.

Mohit Upadhyay

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CONTENTS

CERTIFICATE .................................................................................................................................................. 2

DECLARATION BY AUTHORS ......................................................................................................................... 3

ACKNOWLEDGEMENT ................................................................................................................................... 4

CONTENTS ..................................................................................................................................................... 5

LIST OF FIGURES ............................................................................................................................................ 6

LIST OF TABLES .............................................................................................................................................. 7

ABSTRACT ...................................................................................................................................................... 8

INTRODUCTION ............................................................................................................................................. 9

LITERATURE REVIEW ................................................................................................................................... 10

1. Air Compression Plant ......................................................................................................................... 10

2. Compressors ....................................................................................................................................... 11

3. Lubricants ............................................................................................................................................ 19

4. Ancillary System .................................................................................................................................. 22

5. Control and Safety System .................................................................................................................. 23

CASE STUDY ................................................................................................................................................. 24

1. FIELD DESCRIPTION ............................................................................................................................. 24

2. PROBLEM STATEMENT ........................................................................................................................ 24

3. MAJOR ISSUES IDENTIFIED .................................................................................................................. 24

4. DISCUSSION ......................................................................................................................................... 26

5. CARBON DEPOSITION on INTER COOLERS .......................................................................................... 27

6. LUBRICANT SELECTION ....................................................................................................................... 28

7. CONCLUSION ....................................................................................................................................... 28

APPENDIX .................................................................................................................................................... 29

A.1. Case Study – Parameters ................................................................................................................. 29

A.2. Comparison of Lubricants ................................................................................................................ 31

REFERENCES ................................................................................................................................................ 32

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LIST OF FIGURES

Figure 1: In-situ Combustion .......................................................................................................... 9

Figure 2: Air Compression Plant Design ...................................................................................... 10

Figure 3: Principle Compressor Types ......................................................................................... 12

Figure 4: Typical Application Ranges .......................................................................................... 12

Figure 5: Reciprocating Compressor ............................................................................................ 13

Figure 6: Ideal Reciprocating Compressor Cycle ......................................................................... 14

Figure 7: Centrifugal Compressor ................................................................................................ 15

Figure 8: Comparison of Compressor Efficiencies ....................................................................... 16

Figure 9: Comparison of Compressor Power Requirements ........................................................ 16

Figure 10: Gear Efficiency versus Reduction Ratio ..................................................................... 20

Figure 11: Temperature Limits for Mineral and Synthetic Lubricants ......................................... 21

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LIST OF TABLES

Table 1: Reciproicating vs Centrifugal Compressor ..................................................................... 17

Table 2: Field parameters.............................................................................................................. 30

Table 3: Various Lubricants.......................................................................................................... 31

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ABSTRACT

In-situ combustion is an enhanced oil recovery method utilised to recover heavy

oil. This involves extensive use of air compressors at injection wells. Mehsana

asset (Gujarat) has seen successful implementation of this technique to obtain

large amount of incremental oil. However, there were certain challenges during

the implementation phase. One such issue was failure of air compressors. This

report investigates the reason behind such occurrences, proposes possible

solutions and analyses the actual solutions adopted by ONGC in order to shed

light on future, hopefully successful, implementation of in-situ combustion

elsewhere.

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INTRODUCTION

It is often stated that the era of easy oil is bygone. As the quest to produce more oil from new

locations picks up, it becomes even more important to produce more and more oil from the

existing wells. Enhanced Oil Recovery is a method that aims to maximise the ultimate recovery

from a well. One of the most well known techniques under EOR is ‘In-situ Combustion’.

In-situ combustion is a thermal enhanced oil recovery (EOR) method, adopted to recover heavy

oil. The method involves reducing viscosity by heating oil in the reservoir. This is achieved by

ignition in the well, using a heater or ignitor and air injection to sustain the front. The ‘burning

front’ moves from injection well towards the producer well.

It is also known as ‘fireflood’ method.

Figure 1: In-situ Combustion

The main focus of this project is on air compression plant and the potential issues associated with

air compressors. The intent is to find a viable solution for a problem encountered in an ISC project,

through a case study.

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LITERATURE REVIEW

1. Air Compression Plant

Partha S. Sarathi states in “In-Situ Combustion Handbook – Principles and Practices” that air

compression systems are critical to the success of any ISC field project.

“The role of an air compression plant in an ISC project is to economically and continuously provide

clean, dry, high-pressure air at the required rate to support and sustain combustion, while meeting

environmental and safety requirements.”

The components of an air compression plant are as follows:

(1) Compressor(s) with a power source (2) Control system

(3) Intake air filter (4) Inter and after coolers

(5) Separators (6) Filters

(7) Dryers (8) Fuel and lube oil storage tanks

(9) Interconnections piping (10) Exhaust emission control equipment

(11) Air distribution system

Figure 2: Air Compression Plant Design

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2. Compressors

Air compressor is a device that converts power (from motor or engine) to potential energy. There

exist two basic mechanical methods for air compression:

1. by reducing air volume (Intermittent flow)

2. by increasing velocity or kinetic energy and consequently converting kinetic energy into

potential energy (Continuous flow)

The energy in the compressed air can be used for various applications, such as air injection during

in-situ combustion. The governing relationship for compressors is PVγ = constant (adiabatic

compression). These can operate for various discharge pressures: Low-pressure air compressors

(LPAC’s) have discharge pressure of 150 psi or less, Medium-pressure air compressors (MPAC’s)

have discharge pressure of 151 to 1000 psi and High-pressure air compressors (MPAC’s) have

discharge pressure above 1000 psi.

The major working components in a compressed air system are: inlet air filters, inter-stage

coolers, after coolers, air dryers, moisture drain traps, receivers, piping network, filters, regulators

and lubricators. These are meant to maintain the quality and conditions of air entering and exiting

the compressor. Inter-stage coolers reduce the temperature of air before it enters the next stage

of compression as temperature of air increases due to compression. After coolers are heat

exchangers that remove moisture in air by reducing the temperature. Lubricator is a reservoir of

oil and it is fed in mist form into the air steam so that it reaches the point of use to lubricate all

moving parts.

Petroleum Conservation and Research Association’s (PCRA) “Energy Saving in Compressed Air

System” states that air compressors can be classified as positive displacement and dynamic

compressor, on the basis of design and principle of operation. Positive displacement compressors

increase the pressure of the gas by reducing the volume whereas, dynamic compressors increase

air velocity, which is then converted to increased pressure at the outlet. The principle types of

compressors are shown in Figure 3. The typical operation ranges of various types of compressors

are shown in Figure 4.

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Figure 3: Principle Compressor Types

Figure 4: Typical Application Ranges

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The most prominently used compressor types in in-situ combustion are: centrifugal and

reciprocating compressors. However, certain large scale projects may use rotary compressors as

well, either to boost the discharge pressure or as first stage compressors. Therefore, these

compressor types have been explained below.

Reciprocating Compressor: This is the most widely used compressor type in oil industry. The basic

construction of a reciprocating compressor is illustrated in Figure 5.

Figure 5: Reciprocating Compressor

The cylinder assembly consists of:

1. Piston

2. Cylinder

3. Cylinder heads

4. Valves - suction and discharge

Reciprocating compressors can be single-acting (compression occurs on one end of the piston) or

double-acting (compression occurs on both ends of the piston). The ideal reciprocating compressor

cycle is shown in Fig. 6 below.

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Figure 6: Ideal Reciprocating Compressor Cycle

The flow output remains nearly constant over a range of discharge pressures. Moreover, the

compressor capacity varies with the speed, piston displacement and volumetric efficiency.

Volumetric efficiency varies with cylinder clearance, compression ratio and the properties of the

gas being compressed.

Displacement refers to the actual volume displaced by the piston (in cubic feet per minute.

Clearance volume is the volume remaining in the cylinder at the end of a discharge stroke.

Volumetric efficiency is the ratio of actual cylinder capacity to piston displacement (in percentage,

%).

The compressor generates a pulsating output. Reciprocating compressors cannot handle liquids

and solid particles. Such particles, if entrained in gas, can destroy cylinder lubrication and cause

excessive wear.

Centrifugal compressor: The energy is transferred due to change in centrifugal forces acting on the

gas, flowing radially. The load determines the flow to be handled and the compressor develops

pressure within itself. The basic construction is illustrated in Figure 7.

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Figure 7: Centrifugal Compressor

The compressor has high capacity per unit of installed space and weight, good reliability and

require lesser maintenance than reciprocating compressors. However, their performance

characteristics are highly dependent on the gas conditions. The diameter depends on volumetric

flow rate at inlet. The number of stages is related to compression ratio. The rotating speed varies

inversely with the desired peripheral speed. Depending on application, power can range from 500

hp to above 50000 hp. API has produced an industry standard, API Standard 617 to govern the

design and manufacture of centrifugal compressors. Further, the compressors can be single stage

or multi stage.

The following is a comparative study of the aforementioned compressor types, in order to justify

the prevalent use of reciprocating compressors in ISC operations.

The efficiencies and power requirements of both the compressors have been depicted in Figure 8

and 9 respectively.

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Figure 8: Comparison of Compressor Efficiencies

Figure 9: Comparison of Compressor Power Requirements

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The advantages and disadvantages of reciprocating and centrifugal compressors are listed in Table

1 below.

S. No. RECIPROCATING COMPRESSOR CENTRIFUGAL COMPRESSOR

1 Greater flexibility – capacity and pressure

range

Very unstable at low flow rates

2 Compression efficiency increases with higher

compression ratios (above 1.3)

Compression efficiency is less than reciprocating compressor at compression

ratios above 1.3

3 Less power requirement (at compression ratio

above1.3)

Require more power at higher compression ratios

4 Less susceptible to changes in operating

conditions

Has a narrow operating regime

5 Requires less skilled manpower

Requires skilled manpower to operate due to narrow operating range

6 Major mechanical problems are rare and easy

to repair

Mechanical issues take longer to be dealt with

7 Higher initial installed costs

Lower installed initial cost

8 Lower mechanical efficiency due to more

moving parts

Higher mechanical efficiency

9 Lower capacity

Greater capacity per unit of floor space occupied

10 Higher operating and maintenance costs

Maintenance costs are one-third of a reciprocating compressor

Table 1: Reciproicating vs Centrifugal Compressor

Courtesy: In-Situ Combustion Handbook, Partha S. Sarathi

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As shown, centrifugal compressors usually have lower capital, operation and maintenance costs.

Despite these advantages, the following shall highlight the main reason for adopting reciprocating

compressors in ISC operations.

1. At the start of ISC operations, the injection pressures are high and injection rates are

lower. After ignition, as the combustion front begins to move away from injector well,

the injection pressures decrease with an increase in injection rates. So, flexibility in

operating pressure and throughput is desired. Reciprocating compressors are the only

type that can be used at various capacity and pressures, without compromising the

efficiency.

2. In certain cases (pilot or experimental projects), the volume of air to be injected is less

than 1 MMSCFD. Whereas, the operating range of centrifugal compressors is 14.4

MMSCFD to 216 MMSCFD. Therefore, reciprocating compressors are preferred.

3. Centrifugal compressors require gas turbines on electrical motors. On the other hand,

reciprocating compressors can be natural gas driven. And, in most field locations, there

is vast availability of natural gas. This is another reason for reciprocating compressors

being used.

4. Other reasons are – requirement of less skilled manpower, less costly downtime, easy

availability of spares and superior compression efficiency.

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3. Lubricants

Lubricant is a substance which is meant to reduce friction in working parts of a machine,

such as oil or grease. Malcolm H. Knapp explains in “The use of Synthetic Lubricants in

Air Compressors” that there are certain requirements on lubricants in displacement type air

compressors. Lubricants are needed to provide cooling; reduce wear, gas leakage, frictional

power loss, corrosion; and flushing of dirt particles.

Lubricants are characterised on the basis of their properties, such as viscosity, viscosity

index (VI), pour point and flash point. Viscosity Index is a measure of viscosity change

with temperature. Higher VI‟s indicate less thinning at high temperatures. Pour point is the

lowest temperature at which the first drop of lubricant occurs. Flash point refers to the

temperature at which the vapours of the lubricant result into an ignitable mixture in air.

Pour point is supposed to be at least 10° below the lowest startup temperature. Flash point

should be high – typically above 200°C.

Lubricants are generally composed of a majority of base oil and certain additives that

impart desired characteristics. Sometimes, a mixture of base oils may also be used. The

lubricant base oil is also referred to as „mineral oil‟. According to the American Petroleum

Institute (API), the base oils are classified as follows:

1. Group I – contains < 90% saturates and sulphur > 0.03%. The viscosity index

(VI) lies between 80 and 120.

2. Group II – contains > 90% saturates and sulphur < 0.03%. The viscosity index

(VI) lies between 80 and 120.

3. Group III – contains > 90% saturates and sulphur < 0.03%. The viscosity index

(VI) is above 120.

4. Group IV – contains polyalphaolefins (PAO). VI lies between 130 and 170.

5. Group V – others such as, esters and naphthenics.

“Synthetic lubricants are a broad range of compounds derived from chemical synthesis

rather than from refining of petroleum oils or oils of animal or vegetable origin.” A

mixture of lube oil base stock (LOBS) and certain additives is prepared for specific

requirements. The base stock can be classified into three major classes:

1. Synthesised Hydrocarbons

2. Organic Esters

3. Polyglycols

4. Miscellaneous (silicon-containing fluids)

A.Jackson states in his paper “Synthetic versus Mineral Fluids in Lubrication” that the

title comparison between the two types of lubricants has no meaning. Synthetic

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lubricants are preferred almost unanimously in all industrial applications. The several

benefits of synthetic lubricants over mineral lubricants are listed below.

1. Improved energy efficiency: The synthetic lubricants provide reduced viscosity

and hence, reduced hydrodynamic friction. Also, the high temperature wear

performance is better than mineral oils.

Figure 10: Gear Efficiency versus Reduction Ratio

(Courtesy: SAE, 1981)

2. Wider operating temperature range: Lower pour point, higher VI, better oxidative

stability and lower volatility contribute to synthetic lubricants‟ wider operating

temperature range (-70 to 450°F).

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Figure 11: Temperature Limits for Mineral and Synthetic Lubricants

3. Increased design ratings: Several industrial machines, tools and components are

limited in their ratings by the amount of heat generated (or high temperatures

reached) due to friction. Synthetic lubricants have allowed machines to be either

up-rated to a higher throughput or replaced by a smaller unit.

4. Reduced Maintenance: This is due to reduced oil consumption, extended service

life, higher VI and cleanliness of synthetic lubricants over mineral oils.

5. Better reliability and safer operations.

The synthetic lubricants tend to swell certain types of packing and elastomers. It is,

therefore, suggested to use packing and elastomers which are compatible with synthetic

lubricants.

“The advantage of synthetics over mineral oils comes from the ability to synthesize

selected molecular structures which are beneficial in lubrication.” Hence, synthetic

lubricants are widely accepted to be used in various industrial applications.

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4. Ancillary System

It is usually prescribed by the compressor vendor and special care needs to be taken in its

installation. Some ancillary equipments are as follows:

1. Interstage coolers

2. Lubrication system

3. Scrubber

4. Air dryers

5. Filters

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5. Control and Safety System

Typically, air compressors have a number of control and safety equipments installed. This is

because compressors are the most valuable and integral part of an air compression facility.

Pressure, temperature and vibrations are usually monitored and controlled by the system.

Automatic warning and shutdown systems are preferred as they require minimal human

surveillance. Also, the cost of installing a particular type of control system must be balanced with

the probable loss in revenue in case of system failure or compressor shutdown.

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CASE STUDY

1. FIELD DESCRIPTION

‘Astro’ asset produces heavy oil in areas like Site – A2 and Site – A1, having API gravity between

15ᵒ and 18ᵒ. The oil viscosity ranges from 50 to 450 Cp at reservoir conditions. Reservoir pressure

and temperature were measured to be 100 kg/cm2 and 70ᵒC at 990 m. Owing to the permeability

of 3-8darcy and a high water cut, the primary recovery was found to be below 13%. Artificial lift

was adopted on certain wells but it resulted in even higher water cut (95-100%). Therefore, it was

deemed necessary to adopt another suitable approach in order to achieve a higher ultimate

recovery. One such method was in-situ combustion technique.

Other details are as follows:

(1) Rate of lubricant consumption – 5 litres per day

(2) Ambient temperature ~ 45°C

(3) Air cooled intercoolers

2. PROBLEM STATEMENT

Bursting of 3rd stage after coolers at Site - A1 field, thrice, in a span of a few years was reported.

Fortunately, there was no casualty at any of the three incidents. However, the plant was shut

down after the third incident. This led to down time and hence, economic loss for ONGC.

3. MAJOR ISSUES IDENTIFIED

(1) Operating temperatures as high as 180°C have been recorded.

This can potentially damage the internals of compressor as well as other components of

the plant. The overall efficiency is reduced and hence, it results in a need to redesign the

system. Also, very high temperatures can make the lubricants unstable (depending on

kinematic viscosity). Lubricants are known to deposit carbon, when unstable, which can

ignite at high temperatures. The situation is, therefore, deemed hazardous.

(2) Accumulation of carry over lubricants and deposition of carbon from lubricants over the

components of compressor cylinder.

Any accumulation directly chokes the flow lines and valves. Further, it induces a

reduction in heat exchange efficiency if the deposition is on the exchanger. The

corresponding units may not be designed to handle the abnormally high temperatures,

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resulting from lack of proper heat exchange. Thus, there are high chances of plant

shutdown if the situation persists.

(3) Choking of valves – at the discharge of compressor and inlet of after cooler.

Choking leads to adverse pressure rises inside the compressor, which the equipments

may not be designed to handle. Also, the higher the pressures, smaller the operational

window is. Hence, the compression plant becomes more critical and difficult to mitigate.

(4) Superheated air between heat exchanger and the suction of after cooler.

The heat exchanger, apart from conduction and convection, can release heat by

radiation. Air surrounding the exchanger is directly affected by this radiation. This air is

sucked in by the after cooler and thus, the overall temperature of the system increases.

(5) Auto-ignition of carbon deposited, leading to the incidents.

During investigation, it was found that carbon was deposited in the cylinder case of high

pressure compressors used. Since there was an explosion, this carbon is considered to

be a major factor in the same. This report also presents a quantitative analysis of carbon

deposition.

(6) Difference between flash point of lubricant Servopress C 100 (192°C) and highest

recorded temperature (180°C) is very less, only 12°C.

Flash point is the temperature at which the vapours of lubricant can get ignited on its

own. Small difference or margin is usually not preferred. Similarly, it is desirable to

choose a lubricant with higher margin.

(7) Similar compressors, used in Site - A2 had no such issues or incidents.

This is a major fact that explains why re-designing the compressor would be futile.

Compressors used in A1 and A2 are both similar, in terms of their operating

temperatures, pressures and capacities. So, any design related or mechanical issues in

one should be equally prominent in the other. Unlike, A1, Ste – A2 had no reported

issues of bursting. Therefore, the necessity to change the compressor can be easily ruled

out.

The possible solutions are listed below:

(1) Regular inspection of equipments in use.

To mitigate the causes and prevent the system from failing owing to the issues listed

above.

(2) Replacing air coolers with water-cooled systems.

This addresses the lack of heat exchange due to deposition and also, the case of

superheated air.

(3) Replacing lubricant used in compressor.

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To deal with the root cause of this problem. Since carbon is found to be the main

reason, it is only natural to reduce remove (or try to prevent) its deposition.

The following sections shall discuss the possible solutions in detail.

4. DISCUSSION

(1) Regular inspection and maintenance of the plant.

Advantages:

(a) Increased service life of the equipments in use.

(b) Better knowledge of changes or variations in operational conditions.

(c) Less chances of carbon deposition leading to auto-ignition.

Disadvantages:

(a) Need for regular down time, to inspect the units.

(b) Additional costs and manpower required.

(c) Reduction in overall throughput from plant, due to frequent shut downs.

Verdict:

The solution is simple and can be very effective, if implemented rigorously but it would

be unwise to adopt any solution at the expense of efficiency. Also, the additional costs

shall be incurred, which would potentially prevent the management from implementing

it. However, with the availability of proper standby units at hand, this solution may be

adopted.

(2) Replacing air-cooled coolers with water-based cooling system.

Advantages:

(a) Improved efficiency of heat exchange due to higher specific heat capacity of water.

(b) No issues of superheating, as in the case of air coolers.

Disadvantages:

(a) Need for water treatment plant, as water available in the area is not suitable for

being used in the system directly.

(b) Water cooling towers need to be set up.

(c) Water desalination plant and descaling units shall be necessary.

Verdict:

This solution may be acceptable in areas where water available is suitable for such

cooling systems. However, it would lead to additional costs and prolonged down time,

to set up water treatment facilities. Therefore, this solution stands unfavourable from

an economic point of view.

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(3) Replacing lubricant used in compressor cylinder, with higher flash point and less carbon

deposition tendency.

Advantages:

(a) Most cost-effective as only new lubricant needs to be purchased.

(b) In sync with the observations made – carbon deposited from lubricants was

reported to be the main cause.

(c) Requires minimal maintenance.

(d) No added down time.

(e) Improves the efficiency of compressors by reducing carbon deposition.

Disadvantages:

(a) The vendor (Dresser Rand, compressors) needs to agree with the new lubricant

under consideration.

Verdict:

This seems to be the most promising prospect, owing to negligible cost in comparison to

other proposed solutions. With the investigation report in hand, it should be easy for

the operator to get a nod from the vendor.

Hence, this solution is accepted.

5. CARBON DEPOSITION on INTER COOLERS

It was found that the major reason behind those incidents was deposition of carbon compounds.

Since the compression system comprised of lubricants as the only possible source of carbon

deposition, it becomes important to analyse the amount of carbon that might be deposited by

lubricants.

A general assumption has been made: 0.5 grams per litre per day is the rate of carbon deposition.

According to the available data, 5 litres/day lubricant was supplied.

Therefore, carbon deposition in 1 day = 0.5 * 5 = 2.5 grams.

Similarly, carbon deposited in 1 year = 2.5 * 365 = 912.5 grams.

Considering the extreme environmental conditions and the mechanical efficiency of system, it can

be safely assumed to be around 1 kg/year.

In any air compression system, this much amount of carbon is enough to cause an explosion due

to its ignition. Hence, lubricant shall be considered as the root cause.

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6. LUBRICANT SELECTION

A number of synthetic lubricants were surveyed. The intent was to select a lubricant having:

(1) Higher flash point

(2) Lower carbon deposition tendency

(3) Higher viscosity index

(A detailed analysis of lubricant properties and lubricant types can be found in Literature Review

section on Lubricants).

The lubricants compared were:

(1) IOCL Servopress C 100

(2) Shell Corena S2 P100

(3) HP Enklo 68

(4) IOCL Servocress 100

(5) APAR Powerpress 100

Servocress 100, from Indian Oil is found to be the most suitable lubricant for the

aforementioned compression system because of the following reasons:

(1) Highest viscosity index (210)

This implies that Servocress would be more stable than the rest at high temperatures,

i.e., 180°C.

(2) Appropriate kinematic viscosity (90 – 110 cSt @ 40°C)

The ISO VG of initially used lubricant was 100 (Servopress C100). This parameter refers

to the viscosity of lubricant and its compatibility with compressor. Therefore, it is

advised not to change this characteristic.

(3) Acceptable safety margin (35°C) between flash point and highest recorded temperature,

180°C.

This margin reduces the probability of auto-ignition. As carbon ignition was found to be

the main cause for explosion, mitigating this margin is of prime concern.

(A detailed comparison/data sheet of the lubricants considered is provided in Appendix A2).

7. CONCLUSION

A similar issue was reported at the Mehsana asset (ONGC) in 2006.The solution proposed above,

that is, use of Servocress 100, was implemented. Moreover, there have been no reported issues

with the plant for the past 9 yearsand the plant is still functioning efficiently. Hence, the

practicality of the solution is proven in the field as well.

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APPENDIX

A.1. Case Study – Parameters

Parameters/Plant A1 A2

Flow rate (m3/day/train) 7.0 lac 2.0 lac

LP Comp (nos) 5+1 5

HP Comp (nos) 5+1 5

LP compr Make Ingersoll Rand Atlas Copco

LP compr Model C235MX3 HL7-3

LP compr Type 3 stage Centrifugal 3 stage Centrifugal

LP comprLub oil

Used

Servoprime-32

From IOC

Servoprime-32 From IOC

LP compr Suction

Pr. (kg/cm2)

Atmospheric Atmospheric

LP compr Discharge

Pr. (kg/cm2)

9.2 8.0

HP compr Make Dresser Rand Energy Industries

HP compr Model 3HHE-VL FE650-D4

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HP compr Type 3 stage Reciprocating 3 stage Reciprocating

HP comprLuboil

a) Crankcase

b) Cylinder

Servosystem 220

Servopress C 100

Servoultra 40

Servoultra 40

Oper. Disch. Pr.

1st/2nd/3rd stage

22/58/120

kg/cm2

25/55/123

kg/cm2

Op. Disch. Temp.

1st/2nd/3rd stage

150/150/148

degree C

180/150/147

degree C

Water Injection Pump Make National Oil Well National Oil Well

Water Injection Pump (nos) 6+1 3

Total Water injection capacity 5400 m3/d 3600 m3/d

Peak Power Requirement 50 MW 14 MW

Table 2: Field parameters

A1 field (additional parameters):

(1) Multi layered – late Eocene age

(2) OOIP – 54 MMt

(3) Pay thickness – 2 m to 10 m

(4) Monocline structure – 1ᵒ to 5ᵒ dip

(5) Active edge water drive

(6) Average depth – 1000 m

(7) Non-sealing fault

31 | P a g e

A.2. Comparison of Lubricants

S. No. NAME KINEMATIC VISCOCITY

@ 40°C, cSt VISCOSITY INDEX

FLASH POINT, °C

SAFETY MARGIN, °C

1 IOCL Servopress C 100

90 - 110 90 192 12

2 Shell Corena S2 P100

100 NA 240 60

3 HP Enklo 68 62 - 68 90 210 30

4 APAR Powerpress 100

90 - 110 95 210 30

5 IOCL Servocress 100

90 - 110 210 215 35

Table 3: Various Lubricants

32 | P a g e

REFERENCES

1. A. Doraiah, Sibaprasad Ray, Pankaj Gupta. “In-situ combustiontechnique to enhance heavy-oil recovery at Mehsana, ONGC-A success story”. SPE Middle East Oil & Gas Show and Conference. Bahrain, Kingdom of Bahrain.

2. Gas Processors Suppliers Association: Engineering Data Book.(2004). Tulsa,

Oklahonma: GPSA.

3. M. H. Knapp, M. Freifeld. “The use of synthetic lubricants”. Internationsl Compressor

Engineering Conference. Paper 79. Web:<http://docs.lib.purdue.edu/icec/79>

4. A. Jackson. “Synthetic versus mineral fluids in lubrication”. (1987). Mobil Central

research laboratory. Princeton, NJ.

5. A. C. Bhandari, Amit Chauhan, S. K. Khadia. “Management of in-situ combustion

project in Santhal field of Mehsana asset”. (2010). New Delhi, IN.

6. HP Lubricants –Product Data Sheet. HPCL.

7. Shell Corena Data Sheet. Shell Petroleum Company.

8. Servo Lubricants data Sheet. IOCL.

9. ASTM Fuels & Lubricants Handbook, Hydrocarbon Chemistry, pg 169-184, section 7.