Types of Directional Drilling Profiles

There are four basic well profiles considered while planning a directional well. Here we are only going to have basic preview of these profiles and the design considerations will be covered in the coming posts.

TYPE I WELLS
Type I wells are made up of a kick off point, one buildup section and a tangent section up to the target. They are also called Build and Hold Trajectory or L Profile Wells (as it is L - shaped). These wells are drilled vertically from the surface to kick-off point at a relatively shallow depth. From the kick off point, the well is steadily and smoothly deflected until a maximum angle and the desired direction are achieved (BUILD). Then, if desired, casing is run and cemented. Further, the established angle and direction are maintained (HOLD) while drilling upto the target depth.

Usually this method is employed when drilling shallow wells with single producing zones.

TYPE II WELLS
Type II wells are made up of a vertical section, a kick- off point, a build-up section, a tangent section, a drop-off section and a hold section upto target. They are also called S Profile Wells (as they are S - shaped). Like Type I Wells, the Type II wells are drilled vertically from the surface to the kick-off point at a relatively shallow depth. From the kick off point, the well is steadily and smoothly deflected until a maximum angle and the desired direction are achieved (BUILD). The angle and direction are maintained until a specified depth and horizontal departure has been reached (HOLD). Then, the angle is steadily and smoothly dropped (DROP) until the well is near vertical. Finally the angle and direction is maintained till we reach the target depth.
A disadvantage of the Type II is that it will generate more torque and drag for the same horizontal departure.
Usually this method is employed to hit multiple targets or to avoid faulted region or to minimize the inclination in the zone which will be fractured during completion or for sidetracking.

TYPE III WELLS
Type III wells are made up of a vertical section, a deep kick off and a build up to target. They are also called Deep Kick off wells or J Profile wells (as they are J - shaped). They are similar to the Type I well except the kickoff point is at a deeper depth. The well is deflected at the kickoff point, and inclination is continually built through the target interval (BUILD). The inclinations are usually high and the horizontal departure low.
This type of well is generally used for multiple sand zones, fault drilling, salt dome drilling, and stratigraphic tests. It is not used very often.

TYPE IV WELLS
Type IV wells are made up of anyone of the above profiles plus a horizontal section within the reservoir. They are also called Horizontal wells or Horizontal Directional Wells. A horizontal well is a well which can have any one of the above profiles plus a horizontal section within the reservoir.
The horizontal section is usually drilled at 90 degrees and therefore the extra maths involved is quite simple as we only need the measured length of the horizontal section to calculate the total well departure and total measured depth.
The hole total TVD usually remains the same as the TVD of the well at the start of the horizontal section. However, if the horizontal section is not drilled at 90 degrees or there are dip variations within the reservoir, then the total hole TVD will be the sum of the TVD of the horizontal section and the TVD of the rest of the well.
Horizontal drilling is used to produce thin oil zones with water or gas coning problems, used to increase productivity from low permeability reservoirs by increasing the amount of formation exposed to the wellbore, used to maximize production from reservoirs which are not being efficiently drained by vertical wells and to connect the portions of the reservoir that are productive.

RELATED TOPICS

Read More

Wireline Log Quality Control Reference Manual by Schlumberger

This Log Quality Control Reference Manual (LQCRM) is the third edition of the log quality control specifications used by Schlumberger. It concisely provides information for the acquisition of high-quality data at the wellsite and its delivery within defined standards. The LQCRM also facilitates the validation of Schlumberger wireline logs at the wellsite or in the office.

Produced by: Schlumberger

Download link is below post in First comment

Don't forget to leave your comment

Read More

Oil and gas firms in UK expect jobs growth

Companies in the UK oil and gas sector expect to create up to 39,000 jobs over the next two years.

A survey of 100 companies, commissioned by the Bank of Scotland, found expectations of employment growth had increased since last year.
A clear majority (69%) of executives in the companies were optimistic about their growth prospects in 2014/2015.
A total of 38% of those responding said a shortage of skilled workers would be their greatest challenge.
International expansion was cited as a priority by 64% of those taking part. Key areas for investment were Africa, North America and the Middle East.

Half of the companies said they were already planning to use their expertise by investing abroad

'Expand internationally'

The survey found 46% of companies were already planning further growth in foreign markets over the next 24 months.

The research was carried out by BDRC Continental and companies were chosen to reflect a range of size, location and service type.

A similar study carried out last year indicated companies in the sector would recruit an additional 34,000 people over two years.

Bank of Scotland commercial area director Stuart White, said: "The findings of this report are excellent news for the economy, demonstrating the employment-generating nature of the oil and gas industry now and in the future.

"With most of the UK's oil and gas firms clustered in Aberdeen and the north-east, Scotland should reap the largest share of these new jobs, however other parts of the UK will benefit from expansion plans.

"The report also highlights the growing challenges posed by the lack of a skilled workforce."

Mr White said new specialist apprenticeship schemes could help address the shortfall.

"The results also demonstrate the global nature of the industry as more firms look to expand internationally and tap into the markets with the largest levels of recoverable reserves," he explained.

"With 44% of income already generated internationally, this is not a new trend, and reflects the reach UK firms have as the industry benefits from the expertise gained in the challenging North Sea environment."

'Key strength'

A Scottish government spokesman said: "This is an increase of 5,000 on the estimate made only last year.

"It is also very encouraging to see a strengthening of the international expansion of these companies, and this is a trend which is expected to continue.

"The skills and knowledge developed in Scotland as a result of the development of the North Sea are a key strength for Scotland.

"We are committed to working with the oil and gas sector to maintain competitiveness, facilitate the transfer of skills and knowledge to other sectors and utilise Scottish-based skills in world markets."

The Labour MP for Aberdeen North, Frank Doran, said that, while the report was good news for the industry and Scotland, there were long-term issues facing the sector, including price volatility.

Speaking on BBC Radio's Good Morning Scotland programme, he questioned whether an independent Scottish government would have the expertise and resources to run the industry efficiently.

He added: "I don't know where the Scottish government is going to get the talent, particularly given the wages and the salaries which are paid in the oil and gas industry, which are way beyond what the public sector is prepared to pay,

"That is one of the unanswered questions - where are the civil servants going to come from?"

Source : BBC News

Related News

Read More

Petroleum Engineering Handbook Vol.1

The Petroleum Engineering Handbook has long been recognized as a valuable, comprehensive reference book that offers practical day-to-day applications for students and experienced engineering professionals alike. This new edition, the first since 1987, has been greatly expanded and consists of seven volumes.

Drilling technology has evolved substantially over the years, from slide rules and hand calculations to advanced computer science and numerical analysis. This volume, the first drilling content to be included in the Petroleum Engineering Handbook, is intended to provide a snapshot of the drilling state of the art at the beginning of the 21st century.

Written by: H. B. Bradley

Contents: Drilling geoscience • Drilling fluids • Drilling fluid mechanics • Well control • Bit selection • Directional drilling • Casing and wellhead design • Cementing • Drilling problems • Well planning • Underbalanced drilling • Emerging technologies • Marine drilling • Data acquisition and interpretation • Coiled tubing

Download link is below post in First comment

Don't forget to leave your comment

Read More

Standard Handbook of Petroleum and Natural Gas Engineering Edition 2

This new edition of the Standard Handbook of Petroleum and Natural Gas Engineering provides you with the best, state-of-the-art coverage for every aspect of petroleum and natural gas engineering. With thousands of illustrations and 1,600 information-packed pages, this text is a handy and valuable reference.
Written by over a dozen leading industry experts and academics, the Standard Handbook of Petroleum and Natural Gas Engineering provides the best, most comprehensive source of petroleum engineering information available. Now in an easy-to-use single volume format, this classic is one of the true "must haves" in any petroleum or natural gas engineer's library.
* A classic for the oil and gas industry for over 65 years!
* A comprehensive source for the newest developments, advances, and procedures in the petrochemical industry, covering everything from drilling and production to the economics of the oil patch.
* Everything you need - all the facts, data, equipment, performance, and principles of petroleum engineering, information not found anywhere else.
* A desktop reference for all kinds of calculations, tables, and equations that engineers need on the rig or in the office.
* A time and money saver on procedural and equipment alternatives, application techniques, and new approaches to problems.

ًWritten by: William C. Lyons, Ph.D., P.E.

Contents

Preface. RESERVOIR ENGINEERING. Basic Principles, Definitions, and Data. Formation Evaluation. Pressure Transient Testing of Oil and Gas Wells. Mechanisms and Recovery of Hydrocarbons by Natural Means. Material Balance and Volumetric Analysis. Decline-Curve Analysis. Reserve Estimates. Secondary Recovery. Fluid Movement in Waterflooded Reservoirs. Estimating Waterflood Residual Oil Saturation. Enhanced Oil Recovery Methods. References. PRODUCTION ENGINEERING. Properties of Hydrocarbon Mixtures. Flow of Fluids. Natural Flow Performance. Artificial Lift Methods. Stimulation and Remedial Operations. Surface Oil Production Systems. Gas Production Engineering. Corrosion and Scaling. Environmental Considerations. Offshore Operations. References. PETROLEUM ECONOMICS. Estimating Oil and Gas Reserves. Classification of Petroleum Products. Methods for Estimating Reserves. Non-Associated Gas Reservoirs. Production Stimulation.Determining the Value of Future Production. The Market for Petroleum. Economics and the Petroleum Engineer. Preparation of a Cash Flow. Valuation of Oil and Gas Properties. Risk Analysis. References. Appendix: Units and Conversions (SI). Index.

Download link is below post in First comment

Don't forget to leave your comment

Read More

Basic Well Log Analysis for Geologists

Reader's Review
This is a very fine introduction to petroleum well log analysis. It is written very clearly and designed from the ground up as a text, not just a list of examples.

Written by : Asquith, George B.

The principles are well stated and the logging curves that were available at publication date are all discussed in seperate chapters. Actual interpretation which involves suites of logs is presented clearly in later chapters, each technique having its own chapter. There follows a quarter of the book's volume on case studies which is good, but the previous three quarters are what sets this book above most other log analysis texts. Asquith also has a text devoted exclusively to shaley sand analysis where the reader may want to go for further treatment of this aspect of log analysis. I believe there is a more recent version of this book than the 1982 version I have and that version likely will have a few more recently applied types of logging curves incorporated into it.

Download link is below post in First comment

Don't forget to leave your comment

Read More

Schlumberger: Largest oilfield services company

Schlumberger Limited is the world's largest oilfield services company Schlumberger employs approximately 123,000 people representing more than 140 nationalities working in more than 85 countries.Its

 principal offices are in Houston, Paris, and the Hague.

History

Schlumberger was founded in 1926 by French brothers Conrad and Marcel Schlumberger as the Société de prospection électrique (French: Electric Prospecting Company). The company recorded the first-ever electrical resistivity well log in Merkwiller-Pechelbronn, France in 1927. Today Schlumberger supplies the petroleum industry with services such as seismic acquisition and processing, formation evaluation, well testing and directional drilling, well cementing and stimulation, artificial lift, well completions, flow assurance and consulting, and software and information management. The company is also involved in the groundwater extraction and carbon capture and storage industries.

Sclumberger Brothers

The brothers had experience conducting geophysical surveys in countries such as Romania, Canada, Serbia, South Africa, the Democratic Republic of the Congo and the United States. The new company sold electrical-measurement mapping services, and recorded the first-ever electrical resistivity well log in Merkwiller-Pechelbronn, France in 1927. The company quickly expanded, logging its first well in the U.S. in 1929, in Kern County, California. In 1935, the Schlumberger Well Surveying Corporation was founded in Houston, later evolving into Schlumberger Well Services, and finally Schlumberger Wireline & Testing. Schlumberger invested heavily in research, inaugurating the Schlumberger-Doll Research Center in Ridgefield, Connecticut in 1948, contributing to the development of a number of new logging tools. In 1956, Schlumberger Limited was incorporated as a holding company for all Schlumberger businesses, which by now included American testing and production company Johnston Testers.[citation needed]

Over the years, Schlumberger continued to expand its operations and acquisitions. In 1960, Dowell Schlumberger (50% Schlumberger, 50% Dow Chemical), which specialized in pumping services for the oil industry, was formed. In 1962, Schlumberger Limited became listed on the New York Stock Exchange. That same year, Schlumberger purchased Daystrom, an electronic instruments manufacturer in South Boston, Virginia which was making furniture by the time the division was sold to Sperry & Hutchinson in 1971. Schlumberger purchased 50% of Forex in 1964 and merged it with 50% of Languedocienne to create the Neptune Drilling Company. The first computerized reservoir analysis, SARABAND, was introduced in 1970. The remaining 50% of Forex was acquired the following year; Neptune was renamed Forex Neptune Drilling Company. In 1979, Fairchild Camera and Instrument (including Fairchild Semiconductor) became a subsidiary of Schlumberger Limited.

the headquarter of Schlumberger, Houston

Schlumberger established the first international data links with e-mail in 1981. In 1983, Schlumberger opened their Cambridge Research Center in Cambridge, England and in 2012 it was renamed the Schlumberger Gould Research Center after the company's former CEO Andrew Gould.

The SEDCO drilling rig company and half of Dowell of North America were acquired in 1984, resulting in the creation of the Anadrill drilling segment, a combination of Dowell and The Analysts' drilling segments. Forex Neptune was merged with SEDCO to create the Sedco Forex Drilling Company the following year, when Schlumberger purchased Merlin and 50% of GECO.[citation needed]

In the 1970s, the company's top executives in North America were relocated to New York City.

In 1987, Schlumberger completed their purchases of Neptune (North America), Bosco and Cori (Italy), and Allmess (Germany). That same year, National Semiconductor acquired Fairchild Semiconductor from Schlumberger for $122 million.[12] In 1991, Schlumberger acquired PRAKLA-SEISMOS, and pioneered the use of geosteering to plan the drill path in horizontal wells.[citation needed]

Schlumberger acquired software company GeoQuest Systems in 1992. With the purchase came the conversion of SINet to TCP/IP and www capability. In the 1990s Schlumberger bought out the petroleum division, AEG meter, and ECLIPSE reservoir study team Intera Technologies Corp. A joint venture between Schlumberger and Cable & Wireless resulted with the creation of Omnes, which then handled all of Schlumberger's internal IT business. Oilphase and Camco International were also purchased.[citation needed]

In 1999, Schlumberger and Smith International created a joint venture, M-I L.L.C., the world's largest drilling fluids (or mud) company. The company consists of 60% Smith International, and 40% Schlumberger. Since the joint venture was prohibited by a 1994 antitrust consent decree barring Smith from selling or combining their fluids business with certain other companies, including Schlumberger, the U.S. District Court in Washington, D.C. found Smith International Inc. and Schlumberger Ltd. guilty of criminal contempt and fined each company $750,000 and placed each company on five years probation. Both companies also agreed to pay a total of $13.1 million, representing a full disgorgement of all of the joint venture's profits during the time the companies were in contempt.

In 2000, the Geco-Prakla division was merged with Western Geophysical to create the seismic contracting company WesternGeco, of which Schlumberger held a 70% stake, the remaining 30% belonging to competitor Baker Hughes. Sedco Forex was spun off, and merged with Transocean Drilling company in 2000.[citation needed]

In 2001, Schlumberger acquired the IT consultancy company Sema plc for $5.2 billion. The company was an Athens 2004 Summer Olympics partner, but Schlumberger's venture into IT consultancy did not pay off, and divestiture of Sema to Atos Origin was completed that year for $1.5 billion. The Cards division was divested through an IPO to form Axalto, which later merged with Gemplus to form Gemalto, and the Messaging Solutions unit was spun off and merged with Taral Networks to form Airwide Solutions. In 2003, the Automated Test Equipment group, part of the 1979 Fairchild Semiconductor acquisition, was spun off to NPTest Holding, which later sold it to Credence.[citation needed]

In 2004, Schlumberger Business Consulting was launched. Based in Paris, it is the company's management consultancy arm. 

In 2005, Schlumberger purchased Waterloo Hydrogeologic,[unreliable source?] which was followed by several other groundwater industry related companies, such as Westbay Instruments, and Van Essen Instruments. Also that year, Schlumberger relocated its U.S. corporate offices from New York to Houston.

In 2006, Schlumberger purchased the remaining 30% of WesternGeco from Baker Hughes for US$2.4 billion.[citation needed] Also that year, the Schlumberger-Doll Research Center was relocated to a newly built research facility in Cambridge, Massachusetts to replace the Ridgefield, Connecticut research center. The facility joins the other research centers operated by the company in Cambridge, England; Moscow, Russia; Stavanger, Norway; and Dhahran, Saudi Arabia.

In 2010, the acquisition of Smith International in an all stock deal valued at $11.3 billion was announced. The sale price is 45.84-a-share price was 37.5 percent higher than Smith closing price on 18 February 2010. The deal is the biggest acquisition in Schlumberger history.The merger was completed on August 27, 2010. Also announced in 2010 were Schlumberger plans to acquire Geoservices, a French-based company specializing in energy services, in a deal valued at $1.1 billion, including debt.

Click Here to know More about Schlumberger

Read More

Drilling Problems: Pipe Sticking

During drilling operations, a pipe is considered stuck if it cannot be freed and pulled out of the hole without damaging the pipe and without exceeding the drilling rig’s maximum allowed hook load. Differential pressure pipe sticking and mechanical pipe sticking are addressed in this section.

Differential-Pressure Pipe Sticking
Differential-pressure pipe sticking occurs when a portion of the drillstring becomes embedded in a mudcake (an impermeable film of fine solids) that forms on the wall of a permeable formation during drilling. If the mud pressure, pm , which acts on the outside wall of the pipe, is greater than the formation-fluid pressure, pff , which generally is the case (with the exception of underbalanced drilling), then the pipe is said to be differentially stuck (see Fig. below). The differential pressure acting on the portion of the drillpipe that is embedded in the mudcake can be expressed as

....................(10.1)

The pull force, Fp, required to free the stuck pipe is a function of the differential pressure, Δp; the coefficient of friction, f; and the area of contact, Ac, between the pipe and mudcake surfaces.

....................(10.2)

From Bourgoyne[1],

....................(10.3)
where

....................(10.4)

In this formula, Lep is the length of the permeable zone, Dop is the outside diameter of the pipe, Dh is the diameter of the hole, and hmcis the mudcake thickness. The dimensionless coefficient of friction, f, can vary from less than 0.04 for oil-based mud to as much as 0.35 for weighted water-based mud with no added lubricants.

Eqs. 10.2 and 10.3 show controllable parameters that will cause higher pipe-sticking force and the potential inability of freeing the stuck pipe. These parameters are unnecessarily high differential pressure, thick mudcake (high continuous fluid loss to formation), low-lubricity mudcake (high coefficient of friction), and excessive embedded pipe length in mudcake (delay of time in freeing operations).

Although hole and pipe diameters and hole angle play a role in the pipe-sticking force, they are uncontrollable variables once they are selected to meet well design objectives. However, the shape of drill collars, such as square, or the use of drill collars with spiral grooves and external-upset tool joints can minimize the sticking force.

Some of the indicators of differential-pressure-stuck pipe while drilling permeable zones or known depleted-pressure zones are an increase in torque and drag; an inability to reciprocate the drillstring and, in some cases, to rotate it; and uninterrupted drilling-fluid circulation. Differential-pressure pipe sticking can be prevented or its occurrence mitigated if some or all of the following precautions are taken:


-Maintain the lowest continuous fluid loss adhering to the project economic objectives.
-Maintain the lowest level of drilled solids in the mud system, or, if economical, remove all drilled solids.
-Use the lowest differential pressure with allowance for swab and surge pressures during tripping operations.
-Select a mud system that will yield smooth mudcake (low coefficient of friction).
-Maintain drillstring rotation at all times, if possible.

Differential-pressure-pipe-sticking problems may not be totally prevented. If sticking does occur, common field practices for freeing the stuck pipe include mud-hydrostatic-pressure reduction in the annulus, oil spotting around the stuck portion of the drillstring, and washing over the stuck pipe. Some of the methods used to reduce the hydrostatic pressure in the annulus include reducing mud weight by dilution, reducing mud weight by gasifying with nitrogen, and placing a packer in the hole above the stuck point.

Mechanical Pipe Sticking
The causes of mechanical pipe sticking are inadequate removal of drilled cuttings from the annulus; borehole instabilities, such as hole caving, sloughing, or collapse; plastic shale or salt sections squeezing (creeping); and key seating.

Drilled Cuttings. Excessive drilled-cuttings accumulation in the annular space caused by improper cleaning of the hole can cause mechanical pipe sticking, particularly in directional-well drilling. The settling of a large amount of suspended cuttings to the bottom when the pump is shut down or the downward sliding of a stationary-formed cuttings bed on the low side of a directional well can pack a bottomhole assembly (BHA), which causes pipe sticking. In directional-well drilling, a stationary cuttings bed may form on the low side of the borehole (see Fig. below). If this condition exists while tripping out, it is very likely that pipe sticking will occur. This is why it is a common field practice to circulate bottom up several times with the drill bit off bottom to flush out any cuttings bed that may be present before making a trip. Increases in torque/drag and sometimes in circulating drillpipe pressure are indications of large accumulations of cuttings in the annulus and of potential pipe-sticking problems.

Borehole Instability: This topic is addressed in Sec. 10.6; however, it is important to mention briefly the pipe-sticking issues associated with the borehole-instability problems. The most troublesome issue is that of drilling shale. Depending on mud composition and mud weight, shale can slough in or plastically flow inward, which causes mechanical pipe sticking. In all formation types, the use of a mud that is too low in weight can lead to the collapse of the hole, which can cause mechanical pipe sticking. Also, when drilling through salt that exhibits plastic behavior under overburden pressure, if mud weight is not high enough, the salt has the tendency of flowing inward, which causes mechanical pipe sticking. Indications of a potential pipe-sticking problem caused by borehole instability are a rise in circulating drillpipe pressure, an increase in torque, and, in some cases, no fluid return to surface. (Fig. below) illustrates pipe sticking caused by wellbore instability.

Key Seating: Key seating is a major cause of mechanical pipe sticking. The mechanics of key seating involve wearing a small hole (groove) into the side of a full-gauge hole. This groove is caused by the drillstring rotation with side force acting on it. (Fig. Below)illustrates pipe sticking caused by key seating. This condition is created either in doglegs or in undetected ledges near washouts. The lateral force that tends to push the pipe against the wall, which causes mechanical erosion and thus creates a key seat, is given by

....................(10.5)

where Fl is the lateral force, T is the tension in the drillstring just above the key-seat area, and ϴdl is the abrupt change in hole angle (commonly referred to as dogleg angle).

Generally, long bit runs can cause key seats; therefore, it is common practice to make wiper trips. Also, the use of stiffer BHAs tends to minimize severe dogleg occurrences. During tripping out of hole, a key-seat pipe-sticking problem is indicated when several stands of pipe have been pulled out, and then, all of a sudden, the pipe is stuck.

Freeing mechanically stuck pipe can be undertaken in a number of ways, depending on what caused the sticking. For example, if cuttings accumulation or hole sloughing is the suspected cause, then rotating and reciprocating the drillstring and increasing flow rate without exceeding the maximum allowed equivalent circulating density (ECD) is a possible remedy for freeing the pipe. If hole narrowing as a result of plastic shale is the cause, then an increase in mud weight may free the pipe. If hole narrowing as a result of salt is the cause, then circulating fresh water can free the pipe. If the pipe is stuck in a key-seat area, the most likely successful solution is backing off below the key seat and going back into the hole with an opener to drill out the key section. This will lead to a fishing operation to retrieve the fish. The decision on how long to continue attempting to free stuck pipe vs. back off, plug back, and then sidetrack is an economic issue that generally is addressed by the operating company.

To Be Continued in the second Part. Leave your Comments
Read More HERE

Read More

The Chemistry and Technology of Petroleum FOURTH EDITION

The Chemistry and Technology of Petroleum offers a 21st century perspective on the development of petroleum refining technologies.
The Chemistry and Technology of Petroleum traces the science of petroleum from its subterranean formation to the physicochemical properties and the production of numerous products and petrochemical intermediates.

Written by: James G. Speight

No. of Pages: 217

Presenting nearly 50 percent new material, The Chemistry and Technology of Petroleum emphasizes novel refining approaches that optimize efficiency and throughput.

Download link is below post in First comment

Don't forget to leave your comment

Read More

Perforations Part 1

Overview
Perforating is a critical part of any well completion process. The perforating process generates holes -perforation tunnels- in steel casing surrounding cement and the formation.

In the past, perforation was regarded simply as holes in steel casing made .By different methods. But perforation is not just a simple hole drilling process.Perforated completions play a crucial role in economic oil and gas production. Long term well productivity and efficient hydrocarbon recovery.

2.2. History of Perforation in Brief 

1. Prior to the early 1930's, casing could be perforated in place by mechanical perforators. These tools consisted of either a single blade or wheel-type knife which could be opened at the desired
level to cut vertical slots in the casing.
2. Bullet perforating equipment was developed in the early 1930's and has been in continuous and widespread use since that time.
-The major drawbacks with this method were that the bullet remained in the perforation tunnel, penetration was not very good, and some casings could not be perforated effectively.
3. After World War II the Monroe, or shaped – charge, principle was adapted to oil well work, and the resulting practice is now commonly referred to as jet perforating.
-The principle of the shaped charge was developed during World War II fo armor piercing shells used in bazookas to destroy tanks. This new technology allowed the oil producers to have some control over the perforating design (penetration and entry hole size) to optimize productivity. 2.3. Gun systems
2.3.1. Overview

In order to allow oil and gas to flow into the well, conduits need to be made into the formation. To do this, a gun is positioned across the producing formation and is detonated to create perforations through the casing and cement.
The guns used for this purpose are known as perforating guns.
2.3.2. Perforating guns are divided into two primary categories:
- Capsule guns
- Carrier guns
2.3.3. The perforating gun performance is affected by the
- Gun size
- Clearance
- Entrance hole diameter
- Shot density
- Gun phasing
- Perforating length
- Temperature rating

After firing the gun and while retrieving, unwanted solids enter into the wellbore or formation through perforating tunnels. These are called the perforating debris. Perforating debris can create problems in highly deviated or horizontal wellbores and can also create problems with the completion hardware.
Sources of debris are not only gun system, but also from the casing, cement and formation.
Gun hardware contributing to debris are:
- Gun body
- Shaped charge liner slug and jet
- Shaped charge cas
- Shaped charge retaining system (that holds the charge inside the gun).
2.3.4.1. Shaped charge liner
Perforating debris sources can be controlled if properly engineered.

Shape charge liner used in deep penetrating charges is made of powder metal, which eliminates the carrot and slug associated with liner penetration into the formation during charge detonation. Big hole charges us solid liners in order to produce large hole into the casing. However pf4621 power flow liners, produce big holes and yet leave no slugs into perforating tunnels, this new technology charge can replace the ultrapack charges. Attempts are made to contain the debris in the gun,
collect it after perforating or minimize the quantity expelled.
To address this problem of controlling the debris,
two methods are used. These are:
- Zinc casing method
- Patented packing method
Additional techniques that contribute to reduced perforating debris include powder metal liners and non-plastic charge retention systems. These recent innovations help in limiting problems arising from perforation debris.
2.3.4.1.1. SHAPED CHARGE THEORY
The ultimate goal of perforating is to provide adequate productivity. Test laboratories evolved over the years to provide means of predicting and improving well performance. Today, the performance of the charges is determined according to the procedures outlined in the API RP 43 (standard procedure for evaluation of well perforators) fifth edition, published in 1991. From Figure B1 it can be seen that the penetrating power of a cylinder of explosive is greatly increased by a cavity at
the end opposite to the detonator. Furthermore, placing a thin metallic liner in the cavity increases penetration. A typical shaped charge consists of four main components: a case, a high order explosive powder, primer and a liner, as shown in Figure shown

The case simply holds all the components together.

- The explosive (RDX, HMX and HNS) is a complex mixture designed to allow packing and shipping in the case.
- The primer is a purer mixture of explosive which is more sensitive to the detonation of the detonating cord.
- The liner is used to form a jet which physically does the perforating.
- The detonating cord, which is initiated by a blasting cap, detonates each charge.
The selection of explosive material is based on the well temperature and anticipated exposure time at that temperature (Figure B3). RDX, HMX and HNS are all explosives used in oil well shaped charge manufacture. For deep penetrating charges, the liner is made from a mixture of powdered metals pressed into the shape of a cone. High precision inthe pressing operation is required and it must be done in an extremely uniform and predictable manner. For Big Hole charges, the liner is
drawn from a solid sheet of metal into hemispherical, parabolic, or more complex shapes.
For each of the two types of charges, there is a trade-off between entrance hole size and penetration. The sequence of events in firing is illustrated in Figure B4 from top to bottom.
The detonator initiates the cord which detonates at a rate of approximately 7000 m/s (23,000 ft/sec.) The pressure impulse from this detonation initiates the primer in the charge and the
explosive begins to detonate along the length of the charge.
The high pressure wave 30x106 kPa, 4,500,000 psi) strikes the liner and propels it inward. The liner collapses from apex to skirt imparting momentum with a velocity approaching
2500 m/s (8000 ft/sec). At the point of impact on the axis the pressure increases to approximately 50x106 kPa (7,000,000 psi) and from this high pressure region, a small amount of material is
propelled out at velocities in excess of 7000 m/sec (23,000 ft/sec). As the liner collapses further down the cone, more and more material must be propelled by less and less explosive such that the
impact pressure is substantially less. Thus the tip of this so-called jet is travelling 20 times faster than the rear portion and gives the elongated shape to the jet. The penetration depth depends on this stretching action. As the liner walls collapse inward, the resultant collision along the axis divides the flow into two parts, as in Figure B5. The inner surface of the liner material forms
the penetrating jet which is squirted out along the charge. The outer surface of the liner, which was in contact with the explosive, forms a rear jet or slug which moves forward slower than the forward jet. In the zone of collision, where division of the material forming the jet and slug takes place, there is a neutral point which moves along the axis as the liner collapse process continues. The very fast jet impacting a casing generates a pressure of approximately 70x106 kPa (10,000,000 psi). At this pressure the steel casing flows plastically and the entrance hole is formed. A similar behavior occurs with formation material as the jet penetrates. In addition, crushing and compacting of the formation material around the perforation may also occur. The entire process from detonation to perforation completion takes from 100 to 300 microseconds. The jet material arriving last at the target, making the end of the perforation, comes from the skirt or base. As discrete portions of the jet strike at this end of the hole, they penetrate, expending their energy in the process.
Portions of the jet continue the penetration process, until the entire jet is expended.
The perforation occurs so fast that, essentially, no heat is transferred. Indeed, it has been demonstrated that a stack of telephone directories can be penetrated without singeing a single page. It follows that no fusing of formation material occurs during penetration. However, crushing and
compacting of formation material is to be expected, and will be reviewed later.

2.3.4.1.2. SHAPED CHARGE DESIGN

Liner aspects, such as geometry, angle, material, and distance from base to apex, as well as stand off, and explosive density are more important than the amount of explosive (Figure B7a). Only about 20% of the available explosive energy goes into the useful jet. It has been proven that properly designed charges can out perform poorly designed charges that have twice the explosive load.

This is important in situations where a higher explosive load causes casing damage. Once a charge is designed for entrance hole and penetration efficiency, manufacturing quality control and
consistency become significant in shaped charge performance. Perforation efficiency is accomplished with maximum penetration, uniform crushed zone, and minimal plugging due to slug debris. This is achieved by designing a liner that will provide a uniform jet diameter and velocity with little to no deviation from the conical liner axis. For example, it is critical that the liner thickness and density be precise around the cone at any given point away from the apex. Figure 7b is an example of a less desirable jet due to poor quality control.

Related Links

Read More