SUMMER TRAINING REPORT AT WELL STIMULATION SERVICES (WSS) Oil and Natural Gas Corporation Limited, Ahmedabad PROJECT: STIMULATION JOBS FOR OIL AND INJECTOR WELLS 2015 MEHUL JAIN Summer trainee, ONGC, Ahmedabad asset University College of Engineering, RTU, KOTA
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SUMMER TRAINING REPORT
AT WELL STIMULATION SERVICES (WSS)
Oil and Natural Gas Corporation Limited, Ahmedabad
PROJECT: STIMULATION JOBS FOR
OIL AND INJECTOR WELLS
2015
MEHUL JAIN Summer trainee, ONGC, Ahmedabad asset University College of Engineering, RTU, KOTA [Type the company name]
1/12/2015
ACKNOWLEDGEMENT
The training here at Oil & Natural Gas Corporation (ONGC), WSS, Ahmedabad in Stimulation jobs has been a great experience, both educative and enjoyable at the same time. I would like to thank the entire WSS team for their support and co-operation throughout the training period 15.05.2015 to 15.07.2015.
I wish to express my indebted gratitude and special thanks to Mr. S.P.Nainwal, GGM-Head of Well Stimulation Services (WSS), Oil & Natural Gas Corporation Limited (ONGC) for giving me an opportunity to gain an insight into the working of an industry.
I would specially like to thank Mr.P.Dinesan, Sr. HR Executive for allowing me to do my project here at WSS.
I express my deepest thanks to my guide Mr. K.W.S Rajendra (GM, Location Manager WSS) And Mr. S.K. Singh (DGM, Production) for his vital encouragement and guidance to carry out my industrial training work at WELL STIMULATION SERVICES.
I would like to thank Mr. Suyog Yadav (Asst. Executive Engineer) For his guidance throughout the training period.
Mehul Jain
Student of B.Tech. (Petroleum)
University College of Engineering,
Rajasthan Technical University, Kota
Trainee
Comp: Oil & Natural Gas Corporation Limited
Ahmedabad
Well Stimulation Services
Oil and Natural Gas Corporation Limited
Ahmedabad Asset
Certificate
This is to certify that Mr. Mehul Jain from University College of Engineering,
RTU, Kota has successfully completed his project work on ‘Well Stimulation
Jobs for Oil and Injector Wells’ at the Well Stimulation Services (WSS),
ONGC, Ahmedabad as a part of his Curriculum. The Project was carried out
from 1st June 2015 to 15th July 2015.
The project is a part of the fulfillment of the B.Tech. degree in Petroleum
Engineering from University College of Engineering , RTU, Kota.
Mr. Suyog Yadav Mr. S.K. Singh
(Asst. Executive Engineer) DGM- Production
Project Coordinator Project Guide
INDEX
Sr. No. Contents
1. Overview of Well Stimulation Services in ONGC
2. Introduction to Well Stimulation
3. Hydraulic Fracturing
4. Acidization
5. Coiled tubing Services
6. Nitrogen Services
7. Sand Control Services
8. Hot Oil Services
9. Case Study
OVERVIEW OF WELL STIMULATION
SERVICES ONGC
Well Stimulation Services in ONGC started with the creation of central
stimulation team (CST) in year 1975 to cater the stimulation needs of western
region.
The CST was transformed into Well Stimulation Services (WSS), Ahmedabad in
1982.
ONGC entered into a technical collaboration with NOWSCOW, Canada for
transfer of state of the art equipment and technology that were required for
well stimulation.
After the base at Ahmedabad other Well Stimulation Service bases were
subsequently created to cater the needs of different regions.
The Ahmedabad base was made the mother base and the other bases were
developed under its guidance. ONGC now has bases at:
Ahmedabad(1982,mother base)
Sivsagar(1982)
Rajahmundry(1982)
Karikal(1990)
Gandhar(1995)
Bokaro(2001)
Jorhat(2004)
The services provided by WSS can broadly be categorized under two heads
namely 1) Stimulation Services and 2) Allied Production Services. Hydraulic
fracturing, Acidization and solvent / surfactant treatment falls under
stimulation category, whereas Coiled Tubing Services, Sand Control Services,
Nitrogen Services, Hot Oiler Services, Casing Tubing Cleaning, Microbial EOR
etc falls under allied production services.
At present, ONGC own a fleet of highly sophisticated WSS units of different
make and type which are distributed across all the WSS onshore work centers.
These units are;
o Coil Tubing Unit
o Nitrogen Pumper
o Hot Oiler
o Sand Blender
o Sand Dumper
o Multi Purpose Pumping Unit (MPPU)
o Frac Pumper
o Acid Pumper
o Acid Tanker
WSS AHMEDABAD
WSS Ahmedabad was established in 1982, it has expertise in carrying out
different types of stimulation jobs. The head office of WSS Ahmedabad is
located at Chandkheda, Ahmedabad which houses the offices of Head WSS, IN
charge HR-ER, IN charge TSG, IN charge Material Management, IN charge
finance and IN charge procurement and contracts. It has two bases located at
Saij and Sertha. The Saij base takes care of Hydraulic fracturing, Hot oil
circulation and Acidization jobs. It also houses the Maintenance section and
the Chemistry lab, while Sertha base is involved in carrying out Coiled tubing
applications, Nitrogen jobs and Sand control jobs.
WSS Ahmedabad caters to the needs of both Ahmedabad asset and
Mehsana asset it also provides services to Mumbai offshore as and when
required apart from this it also provide support to other bases for special jobs.
The services rendered and capabilities of WSS Ahmedabad are as follows:
1. Hydraulic fracturing
Pumping horse power 9000 HP
Pumping pressure 12000 psi
Pumping rate 60 BPM
Design by 3D FracPro simulator
Experience of more than 1700 jobs
First ever FracPack job in India
2. Acidization
Acid storage capacity 50m3
Pumping pressure 10,000psi
Job design using MACIDES
Experience of more than 5000 jobs
Development of customized acid formulation for sand stone reservoirs
Deep penetrating acid system
Retarded mud acid system
Reduced strength mud acid
Emulsified acid system
Chemical diversion system
Alcoholic mud acid system
Nitrified acid system
3. Coiled tubing applications
Coiled tubing size :1 1/4 ̓ ̓, 1 1/2 ̓ ̓
Depth: 5000 meters
Injector capacity up to 80,000lbs
Online monitoring of tubing fatigue
Experience of more than 7000 jobs
CTU operations carried out by WSS Ahmedabad
Well Bore Clean Outs
Zone Isolation for Water Control
Well Stimulation
Well Activation
Velocity String Completion
Well Intervention In Horizontal/High Angle/Multilateral Wells
Well Subduing And Fishing
Well Plug And Abandonment
Cement Drilling
Dewaxing
4. Sand control
Job design and execution of different sand control techniques
GP for 5 1/2 ̓ ̓ and 7 ̓ ̓ casing
High rate water pack
Pre pack completion
Fracpack
High density slurry packing
Experience of more than 1400 jobs
First gravel packing of horizontal well
Longest gravel pack (>200mts)
First ever fracpack
5. Nitrogen services
Liquid nitrogen storage capacity :100 m3
Pumping rate : 8.5-170 m3/min
Pumping pressure : 10,000psi
Experience of more than 17000 jobs
Nitrogen applications
Well fluid displacement
Nitrification of fluids for acidization
Foam cleanout in sub-hydrostatic wells
Pressure testing/purging of gas plant,pipe lines and equipment
Foam fracturing
6. Hot oil circulation
Ciculation fluid temperature: 90 ͦ c
Pumping rate : 140 lpm
Heat transfer : 7MMBTU/Hr
Experience of more than 4500 HOC jobs
7. Laboratory services
o Equipments
High temperature, high pressure viscometer
Core flow setup
Sieve analyser
Corrosion test apparatus
API crush test machine
o Chemical formulation for specific field requirements
Hydraulic fracturing
Acidiztion
o Development for field application
High temperature frac fluid
Breaker for low temperature reservoir
8. Maintenance services
o Workshop facilities
Preventive maintenance
Breakdown maintenance
Capital overhauling
Under chassis repair
o Expertise in
Transmission system
Engine
Hydraulic systems
Instrumentation
Pump and compressor
Heat exchengers
o Equipment population
60 primemovers cummins/Detroit/caterpillar
60 transmission Allison and fuller
20 reciprocating pump OPI and SPM
35 centrifugal pumps
250 hydraulic pumps and motors
5 cranes
6 heat exchangers
INTRODUCTION TO STIMULATION
History:-
Stimulation can be traced to the 1860s, when liquid (and later, solidified)
nitroglycerin (NG) was used to stimulate shallow, hard rock wells in
Pennsylvania, New York, Kentucky, and West Virginia. Although extremely
hazardous, and often used illegally, NG was spectacularly successful for oil well
“shooting.” The object of shooting a well was to break up, or rubblize, the oil-
bearing formation to increase both initial flow and ultimate recovery of oil.
This same fracturing principle was soon applied with equal effectiveness to
water and gas wells.
In the 1930s, the idea of injecting a nonexplosive fluid (acid) into the ground
stimulate a well began to be tried. The “pressure parting” phenomenon was
recognized in well-acidizing operations as a means of creating a fracture that
would not close completely because of acid etching. This would leave a flow
channel to the well and enhance productivity. The phenomenon was
confirmed in the field, not only with acid treatments, but also during water
injection and squeeze cementing operations. But it was not until Floyd Farris of
Stanolind Oil and Gas Corporation (Amoco) performed an in-depth study to
establish a relationship between observed well performance and treatment
pressures that “formation breakdown” during acidizing, water injection, and
squeeze cementing became better understood. From this work, Farris
conceived the idea of hydraulically fracturing a formation to enhance
production from oil and gas wells.
The first experimental treatment to “Hydrafrac” a well for stimulation was
performed in the Hugoton gas field in Grant County, Kansas, in 1947 by
Stanolind Oil. A total of 1,000 gal of naphthenic-acid and- palm-oil- (napalm-)
thickened gasoline was injected, followed by a gel breaker, to stimulate a gas
producing limestone formation at 2,400 ft. Deliverability of the well did not
change appreciably, but it was a start. In 1948, the Hydrafrac process was
introduced more widely to the industry in a paper written by J.B. Clark of
Stanolind Oil. A patent was issued in 1949, with an exclusive license granted to
the Halliburton Oil Well Cementing Company (Howco) to pump the new
Hydrafrac process.
What is stimulation?
Oil well stimulation is the general term describing a variety of operations
performed on a well to improve its productivity. Stimulation operations can be
focused solely on the wellbore or on the reservoir; it can be conducted on old
wells and new wells alike; and it can be designed for remedial purposes or for
enhanced production. Its main two types of operations are matrix acidization
and hydraulic fracturing. Matrix acidization involves the placement of acid
within the wellbore at rates and pressures designed to attack an impediment
to production without fracturing or damaging the reservoir (typically,
hydrofluoric acid is used for sandstone/silica-based problems, and hydrochloric
acid or acetic acid is used for limestone/carbonate-based problems). Most
matrix stimulation operations target up to a ten foot radius in the reservoir
surrounding the wellbore. Hydraulic fracturing, which includes acid fracturing,
involves the injection of a variety of fluids and other materials into the well at
rates that actually cause the cracking or fracturing of the reservoir formation.
The variety of materials includes, amongst others: water, acid, special polymer
gels, and sand. The fracturing of the reservoir rock and the subsequent filling
of the fractured voids with sand ("proppant") or the creation of acid channels
allows for an enhanced conduit to the wellbore from distances in excess of a
hundred feet.
Why is stimulation required?
Hydraulic fracturing and acid fracturing in practically all types of formations
and oil gravities, when done correctly, have been shown to increase well
productivity above that projected in both new and old wells. From an economic
standpoint, oil produced today is more valuable than oil produced in the future.
Fracturing candidates may not necessarily "need" oil well stimulation, but the
economics may show that such a treatment would payoff.
To understand why remedial stimulation (matrix acidization) is necessary, one
has to consider the conditions at work, deep down inside the reservoir. Before
the well is ever drilled, the untapped hydrocarbons sit in the uppermost portions
of the reservoir (atop any present water) inside the tiny pore spaces, and in
equilibrium at pressures and temperatures considerably different from surface
conditions. Once penetrated by a well, the original equilibrium condition
(pressure, temperature, and chemistry) is permanently changed with the
introduction of water or oil-based drilling fluids loaded with suspended clays,
and the circulation of cement slurries. The interaction of the introduced fluids
with those originally present within the reservoir, coupled with pressure and
temperature changes can cause a variety of effects which, in turn, can plug the
numerous odd-shaped pores causing formation damage. Some of the types of
damage include: scale formation, clay swelling, fines migration, and organic
deposition.
Petroleum engineers refer to the level of formation damage around the wellbore
as skin effect. A numerical value is used to relate the level of formation damage.
A positive skin factor reflects damage/impedance to normal well productivity,
while a negative value reflects productivity enhancement. Formation damage,
however, is not limited to initial production operations. Remedial operations of
all kinds from well killing to well stimulation itself, can cause formation
damage. Nor is fines and scale generation limited to the reservoir. They can also
develop in the wellbore in casing and tubulars, and be introduced from surface
flowlines and incompatible injection fluids. These fines and precipitates can
plug pores and pipe throughout an entire oil field.In short, any operation
throughout a well's life can cause formation damage and impede productivity.
Hydraulic Fracturing
What is fracturing?
If fluid is pumped into a well faster than the fluid can escape into the formation,
inevitably pressure rises, and at some point something breaks. Because rock is
generally weaker than steel, what breaks is usually the formation, resulting in
the wellbore splitting along its axis as a result of tensile hoop stresses generated
by the internal pressure. the simple idea of the wellbore splitting like a pipe
becomes more complex for cased and/or perforated wells and nonvertical wells.
However, in general, the wellbore breaks—i.e., the rock fractures—owing to the
action of the hydraulic fluid pressure, and a “hydraulic” fracture is created.
Because most wells are vertical and the smallest stress is the minimum
horizontal stress, the initial splitting (or breakdown) results in a vertical, planar
parting in the earth.
The breakdown and early fracture growth expose new formation area to the
injected fluid, and thus the rate of fluid leaking off into the formation starts to
increase. However, if the pumping rate is maintained at a rate higher than the
fluid-loss rate, then the newly created fracture must continue to propagate and
grow.This growth continues to open more formation area. However, although
the hydraulic fracture tremendously increases the formation flow area while
pumping, once pumping stops and the injected fluids leak off, the fracture will
close and the new formation area will not be available for production. To
prevent this, measures must be taken to maintain the conductive channel. This
normally involves adding a propping agent to the hydraulic fluid to be
transported into the fracture. When pumping stops and fluid flows back from
the well, the propping agent remains in place to keep the fracture open and
maintain a conductive flow path for the increased formation flow area during
production.
The propping agent is generally sand or a high strength, granular substitute for
sand. Alternatively, for carbonate rocks, the hydraulic fluid may consist of acid
that dissolves some of the formation, leaving behind acid-etched channels
extending into the reservoir.
Stages in Proppant Fracturing job
Spearhead
Sometimes, the formations can be difficult to breakdown and under such
scenario spearhead is pumped to reduce formation breakdown pressure. In this
stage, typically 5 - 10 bbl of HCl acid is pumped ahead of pad. -half the volume
at matrix acidization rates and the remaining at higher rates.
Pad
Pad stage breaks down the blocked perforations and initiates fracture. Proper
volumes of fluids are required to be pumped since small pads may not develop
sufficient width for placement of proppant thereby potentially causing screen-
outs. Excessive pad may delay closure for a significant period of time, allowing
proppant convection out of zone. The pumping rates must exceed formation
leak-off limits in order to propagate the fracture.
Proppant Stages
The proppant stages immediately follow the pad in which fracturing fluid mixed
with proppant is pumped into the formation to generate length and width of the
fracture.
Initially proppant slurry of low concentration is pumped since perforations and
formation near well bore may not accept higher concentrations of proppant early in
the treatment if the wedge is not large enough. The proppant concentration is
gradually increased in steps of 1 to 2 ppg once the perforations and formation near
well bore are eroded.
Flush
In this stage, clean fluid is pumped to displace the proppant to within a short distance
of the perforation and remove it from the well bore. Often low friction, economical
fluid is used.
Energized Treatments
These specialized treatments make use of N2/CO2 and are used in sub-
hydrostatic formation to aid in load fluid recovery.
Why fracture?
Hydraulic fracture operations may be performed on a well for one (or more) of
three reasons:
• To bypass near-wellbore damage and return a well to its “natural” productivity
• To extend a conductive path deep into a formation and thus increase
productivity beyond the natural level
• To alter fluid flow in the formation.
Fracturing Fluid Systems
The basic function of fracturing fluids is to transmit pressure to the formation and
transport proppant into the fracture. Based on formation types and base lithology,
presence of additional mineral components, formation fluid nature, objective of
fracturing, pumping configuration planned and above all the economics, various
fluids-both Newtonian and Non-Newtonian- are used as fracturing mediums. Some of
them are Water-Based, Hydrocarbon–Based, CO2 assisted Fluids, Emulsion–Based,
N2 Foams, Methanol based etc.
Various type of additives used in fracturing fluids are Gelling agents/ Gellants,