Introduction of Gas Lift || Petroleum Engineering

Introduction of Gas Lift

Gas Lift System

Gas lift is one method of artificial lift. For gas lift, gas is injected continuously or intermittently at selected locations, resulting in a reduction in the natural flowing gradient of the reservoir fluid, and thus reducing the hydro static component of the pressure difference from the bottom to the top of the well. The purpose is to bring the fluids to the top at a desirable wellhead pressure while keeping the bottom hole pressure at a value that is small enough to provide good driving force in the reservoir. The pressure drawdown must not violate restrictions for sand control and water or gas coning.

Two other considerations must enter the design. First, large amounts of gas injected into the well will affect the separation facilities at the top. Second, there exists a limit gas-liquid ratio (GLR) above which the pressure difference in the well will begin to increase because the reduction in the hydrostatic pressure will be offset by the increase in the friction pressure.

The positioning of the gas lift valves and their number is a matter of wellbore hydraulics optimization. For continuous gas lift, an “operating valve” will be used to inject the appropriate amount of gas at the desirable tubing pressure at the injection point. Other valves may be placed below the injection point and may be put into service during the life of the well as the reservoir pressure declines or if the water-oil ratio increases.

For  intermittent gas lift, both a single injection point and multiple injection points can be employed. First a liquid slug must be built in the tubing above the bottom valve. Then, the valve opens, displacing the liquid slug upwards. The valve remain open until the slug reaches the top, and then the valve closes. It reopens when a new liquid slug builds in the bottom of the well.

For multiple injection points, the bottom valve opens as described for the single injection point operation, but as the liquid slug moves upward, valves below the slug open. The valves close after the slug reaches the top. The actuation of the valves for intermittent gas lift can be done with a timing device or can depend on the pressure.

Valves can open and close based on the value of the casing or the tubing pressure. Other valves may be operated on the basis of the fluid level. 

Notes:- Data  is collect from different university notebook and main purpose of this articles is to help peoples.

Article Written by

Raktim Ranjan Borah 

Vice-President & Event Organizer

Petroleumbuddy websites & initiatives

Sucker Rod Pumping: A Brief Discussion || Petroleum Engineering

Sucker Rod Pumps 

Sucker Rod method is one type of Artificial lift method which we used lift oil from bottom hole to surface with the help of mechanical energy. It is efficient, simple and easy for the technicians to operate on field. It can pump. A well down to very low pressure to maximize oil production rate. This method is applicable to slim holes, multiple completions, high temperature and viscous oils. This system is also easy to change to other wells at a minimum cost.

Sucker rod pumping system consists of a pumping unit at surface and a plunger pump submerged in the production liquid in well. The prime mover is either an electric motor or an internal combustion engine. The power from the prime mover is transmitted to the input shaft  of a gear reducer by a V-Belt drive. The output shaft of the gear reducer drives the crank arm at lower speed. The rotary motion of the crank arm is converted to an oscillatory motion by means of the walking beam through a Pittman arm. The horse's head and the hanger cable arrangement is used to ensure that the upward pull on the sucker rod string is vertical at all times. Thus, no bending moment is applied to the stuffing box. The polished rod and stuffing box combine to maintain a good liquid seal at the surface. Thus, force fluid to flow into the “T” connection just below the stuffing box.

Conventional pumping units are available in a wide range of sizes, with stroke lengths varying from 12 to almost 200 in. The strokes for any pumping unit type are available in increments. Walking beam ratings are available in allowable polished rod loads and vary from approximately 3,000 to 35,000 lb. Counterbalance for conventional pumping unit is accomplished by placing weight directly on the beam or by attaching weight to rotating crank arm.

The major disadvantages of beam pumping include excessive friction in crooked/deviated holes, solid sensitive problems, low efficiency in gassy wells, limited depth due to rod capacity and bulky in offshore operation.Beam pumping trends include improved pump-off controllers, better gas separation, gas handling pumps and optimization using surface and bottom hole cards.

Sucker Road Pumps and Its different parts:-

   

Notes:- Data is collect from different university notes and experience  basic. Main purpose is to help peoples.

Article Written By 

Raktim Ranjan Borah 

Vice President & Event Organizer 

Petroleumbuddy websites and Initiatives 

Jet Perforation Overview || Petroleum Engineering

Jet Perforation 

Firing is initiated electronically or  mechanically by a detonation via the detonating cord which in terms sheds off primary explosive. The Primary Explosive detonated secondary main explosives. The explosive pressure on metal liner caused it collapsed inwardly (Towards inside). Along it axis forming a high velocity jets of fludize metal.

       Liners are form from a mixture of copper, Lead, Zinc, tin & tungsten. First thing fludize metal comes out happens only,  15-16 microsecond.  Whole process of jet perforation takes only 100 microseconds. 

The tip of the particle, jet moves at a velocity of 25,000-30,000 ft per seconds which is equal to 8,000-10,000 metre per seconds. The develop pressure is in order of 5 to 15 mega pascals psi.

Under this conditions of material in its path flow parasitically under impact, the jet crushes the reservoir rock and displaces both the rock and fluid, radically from its axis. The entire perforating process from initial to completion last only few micro seconds.

Although the formation rock crushed and compacted it is not fused together.

Depth of perforation

Depth of perforation  is only 2 inch - 20 inch 

Entrance hole diameter 

Entrance hole diameter is between 0.2 to 1 inch.

Common Terms used in Jet Perforations 

Total Penetration 

Inner line from casing + cementing + Reservoir penetration depth or you can say total impact depth

Formation Penetration

From outer wall of formation zone to  total formation depth.

Notes:- Information is collected from our university notes. This is useful for any students and industry persons.

Article written & composed by-

Ritu Raj Medhi

President & Founder

Chief Technical & Editorial Officers

Petroleumbuddy Initiatives

     

The Explosive Train & Perforating Gun Types || Production Engineering || Petroleum Engineering

The Explosive Train

Explosive train is a series connection of explosives.It used in petroleum industry for perforation job. If you not aware of what is perforation and  overview of perforation in petroleum industry then click this link ......

When initiated high explosives reacts supersonic in a process called detonation, By comparison, low explosives reacts sub-sonically in a process called deflagration.  

Component of The Explosive Train   

1.  An initiator or detonator that is used to start process.
2. A detonating cord which is used to transmit detonation.
3. Shaped Charge ( Used to perforate up to the formation )

Perforating Gun Types

• Retrievable Hollow steel career Guns 
• Semi Expandable
• Fully Expandable 

Advantages and disadvantages of perforating gun types

1. Retrievable Hollow Steel and Career Guns

Advantage of Retrievable HSCG  

1. High Reliability because all component are pro acted within the carrier.
2. Heavier and Stronger which permit rough treatment handling running procedure.
3. Generally high pressure and temperature rating,
4. Very little debris left in the well after perforation.
5. Explosive force is retained within the carrier to eliminating casing deformation.
6. Port Plug provides positive medication of five.

Disadvantages of Retrievable HSCG

1. Many have trouble running in and out through tubing retrievable guns in buckle tubing.(Buckle Casing :- In deviated wells)
2. Many have smaller charge components (Space required for retrievable)
3. Due to more weight, manpower is needed while lowering. Example-

Small Standoff	More Charge
Large Standoff	Less Charge

         

2. Semi Expandable

Advantages of Semi expandable -

1.  High reliability( Not as much as RHSCG )
2. After Detonation, Metal Strip and some component can be retrieved  which is turn reduced the debris in the well.
3. With a metal strip or wire carrier, Ceramic or Glass Charge cases can be used reduces the debris particle size and decreasing the chemical reaction rate.

Disadvantage of Semi Expandable

1.  More Debris remains inside the well.
2. Metal Strip Jumps. In the well fishing operation is used because difficult to put up.
3. Deeper penetration , more amount of charge.

3. Fully Expandable

Advantage of Fully Expandable of perforating gun

1.  Generally cheaper, easier to assemble at the well site.
2. Lighter and more flexible.
3. It offers more penetration compared to the retrievable Guns.
4. We can not Large sized shape charge as it is open.

Dis Advantages of Fully Expandable.

1. Can or may be deform casing of well when detonation.
2. It leaves, substandard amount of debris in the well.
3. Less reliability because component are directly exposed to the well fluid condition.
4. It sometimes doesn't detonate because it is wetted  by the reservoir due to leak in casing.
5. There is no positive indication of perforation from the surface (Only seen after removable)

Notes:- Data is collected from different university class notes and E&P company. Article is usefull for student and industry person

Article Written By:-

Ritu Raj Medhi

Founder & President 

Chief Technical & Editorial Officers

Petroleumbuddy websites and initiatives

  

Explosive that we used in Well Perforation Job || Petroleum Engineering

Explosive & Perforation

we used different types of explosive in well perforating job. Explosive are used to create impact on casing , cementing and reservoir. So that we can make suitable  hole & connection from reservoir to well-bore. And with the help of this hole formation fluid pass from reservoir to well bore sites.

We used mainly two types of explosive and these are - 1. Low explosive and 2. High explosive

Types of explosive we used

we used two types of explosive and these are 

1. Low Explosive 
2. High Explosive

1. Low Explosive

Here velocity is 500-1500 meter per second for example - Gun powder is an example of low explosives. Generally not used in perforation. We used low explosive in side well coring operation. Low explosives is mainly used for collecting rock sample from reservoir. 

2. High Explosives

Velocity of high explosive is from 3000 to 10,000 metre per second. First high explosive discovered in 1846. High explosive can be Uncontrolled high explosive and control high explosive. 

Chemical explosives material having at extremely high reaction rate that create very high combustion pressure, unlike low explosive that have much lower  reaction rate and are furthered categorized as -

• Primary High Explosive
• Secondary High Explosive

Primary High explosives are very sensitive can be detonated very easily and are generally used only in precaution and electrical detonators. Secondary High Explosives are less sensitive and require a high energy are less sensitive and require a high energy shoke wave to achieve detonation and are also suffer handle. Secondary High explosives are used in almost all elements of bullistics chain, other than the detonation, such as detonating cord and shape charge. 

High Explosive Classification 

We can classify high explosive into two categories. These are prime high explosive and secondary high explosive.

1. Primary High Explosive

It is generally high density compounds of metals and nitrogen, that instantaneous detonate when subjected to energy ( High Explosive )

    These lead azide is most common commonly used in Oil Industry, advantage is:- High Resistant to temp ( up to 600 degree F )

Some example of primary high explosive are -  Lead Azide  and Styfnate. 

2. Secondary High Explosive

Not very sensitive at all. So we carry it.

Explosive	Chemical Formula	Density	Velocity (ft/second)	Pressure (PSI)
RDX	C3H6N6O6	1.8g/cc	28700 ft/second	5 * 10^6 PSI
HMX	C4H8N8O8	1.9g/cc	30000 ft/second	5.7* 10^6 PSI
HNS	C4H6N6O12	1.74 g/cc	24300 ft/second	3.5 * 10 ^6 PSI
PYX	C17H7N11016	1.77 g/cc	24900 ft/second	3.7 * 10^6 PSI

Full form of some secondary high explosives

1. RDX = Royal Demolition Explosive 
2. HMX = High Melting Explosive
3. HNS = Hexa Niteo Stibene

We use both primary high explosive and secondary high explosive. We mixed them and with the help primary high explosive and secondary high explosive,  we do well perforation job.

Primary high explosive acts as a Ignition of secondary high explosive. We burn or burst secondary high explosive with  primary high explosive. Because primary high explosive is very sensitive, and we can burst them easily with very less energy.

We can try to give more information in future articles.

Notes:- We collect this information from various university notes and various E&P Company websites.

Well activation overview || Petroleum Engineer

Well Activation Introduction

Well activation involves reducing hydro static head in the well. After well completion well required activating so that formation fluid will come from reservoir to well head and well is produce crude oil. We have to create negative overburden pressure in the well head, thereby inducing formation fluid into well bore. Displacing the workover fluid with lighter fluid may be sufficient to enable to well flow. However when higher draw-down is required to activate the well, one of the activation method is used. We will discuss 5 types of well activation method here.

Different Method Of Well Activation

We will discuss 5 types of well activation method briefly in this article, these are-

1. Displacement Method
2. Compression Application.
3. Application of Nitrogen.
4. Aerisation Techniques.
5. Swabbing 

 

1. Displacement Methods

• Main aim to reduce the density of completion fluid so that production will occur
• It is step by process so we can control formation fluid
• Aim is to reduce the pressure of the bottom of the well bore.
• High density fluid is displaced by some low density fluid.
• It is step by step by step process. If we decrease suddenly the fluid density, then (completion fluid density then) uncontrol influx of Hydro Carbon Occurs.
• 0.2-0.3 density sg is reduced in each step
• It is done until well is activated

 

2. Compression Application 

We compressed Gas and injected into well ( In annular space we inject high pressure gas ) – U Tube effect occur. Ps – pwf is sufficient to produce hydrocarbon.

Main aim to reduce the pressure of the bottom of the well bore. It is also step by step process.

• Compression application is not a single step process.
• Compression gas injected in to annulus.
• Packer is not put in annulus, So that we inject compression fluid.
• Gas Buddle mixes with fluid in tubing.
• Density of fluid decreases.
• Ps – pwf is sufficient to produce the well.
• Applied repeatedly until and unless well is activated.

3.  Application  of Nitrogen

 

Gaseous N2 is obtained at  350 kg per cm2. The high pressure is sufficient to displace half almost of the well. So it reduce time and man power.

Generally liquid Nitrogen is brought and pumped using “ Cryogenic pump” and converted to gaseous nitrogen.

Aim is the same as previous method

In this method we used oil tubing

Large bubble are formed.

4. Aerisation Technique

Entire liquation column density reduced, no piston effect – bubbling effect takes place, aerisation is responsible for density reduced.

Air is used. When we used air , generally gas bubble become bigger.

If displace or aerisation is not successful, N2 is used.

Under condition air compress is released. This process leads to form bubble and hence density reduced.

 

5. Swabbing

Pipe is suddenly released during tripping or pipe is suddenly withdraw,

1. Surging Pressure:- 

When drilling fluid filled , pipe is suddenly released during tripping. More pressure is generated inside the well.

2. Swabbing pressure:-

 Pressure is reduced during pulling the drill pipe, then it leads influx of fluid.

Swabbing well activation is done by swabbing tool.

 

We discuss this well activation process with further information in next articles.

 

Notes: -  I collect this article information from various university notes. Some information also collected from schlumberger and other e&p company sites.