well perforation overview:

We placed casing in the well. After all necessary production equipment install and necessary condition maintained, the well is ready to produce crude. But well can't produce crude automatically. So we have to hole.

So Well perforation can be defined as it is a process of making communication hole through cement, casing and some distance of reservoir. Basically Perforation is a process of making hole, so that reservoir fluid can flow from reservoir to well automatically.

Perforation can be done before production tubing or after putting production tubing. There are different method available for well perforation. These are:-

Bullet Perforation
Jet perforation method

Basic well Perforation:

1. Bullet Perforation:-

Metallic bullet hits and do Perforation. Old Techniques Perforation. In this perforation method we use 100 to 1000 steel bullets or projectile, we use explosive charge to fire bullets, bullets did not create big impact on reservoir. So permeability of reservoir remains very low and debris remains at the end of tunnel. Very old method, So we use jet perforation now a days.

2. Jet perforation:-

Now a days we use jet perforation method, in this method we use explosive charge to create tunnel. here we use perforation gun assembly and that can be easily installed on wire-line tubing such as slicked line coiled tubing unit etc. High explosive produce high pressure and temperature , this high shaped charger penetrates casing, liner, cement and reservoir. It create huge impact and by this process we can expect huge formation zone. High reservoir permeability can be expected.

Basic perforation methods:-

Generally three types of perforation method available.

Conventional casing Gun
Through tubing Gun
Tubing conveyed gun

1. Conventional Casing Gun:-

It trance into the well on electric wire line with or without wire-line pressure control equipment. Hollow cylinder gun and power is given by electrical line.

2. Through Tubing Gun:-

Through tubing gun trance into the well after the tubing has been install via wire-line pressure control tubeline.

3. Tubing Conveyed Gun:-

It trance on the bottom of the tubing string and detonated using mechanical, electrical, or pressure activated equipment

well perforation based on delivery systems:-

Generally three well perforation delivery systems available, these are 1. Retrievable, 2. Semi Expandable and 3. Fully Expandable.

1. Retrievable:-

It consist of cylindrical hollow string charge carrier. Detonated will occur in hollow-cylinder. As we give energy detonate occur and perforation done less than 2 second, Metal is retrievable, very small amount of material left in button of the well bore in compare to others.

2. Semi Expandable:-

It effect casing because it hit some of the direction, semi burst of cylinder.

3. Fully Expandable:-

All body is burst, Hit all direction. If you not done this operation precautionary then may be it damaged casing. No debris left.

Factors to be consider during design a perforation

The relative important of hole size, penetration depth, and shot density
The anticipated radial extend of the formation damage during drilling.
The reservoir pressure permeability and the damage from completion fluid.
The length of the perforated intervals, the size of the completion string component and need to perform specialize operation (Sand control, Well stimulation)
The safety issue related to the well sight conditions.
The expected pressure, temperature and timing for perforating operation.

Explosive used in Well perforation Job

In well perforation job, we used different types of explosive. And we can categorize explosive in two category.These are 1. Primary High Explosive and 2. Secondary High Explosives.

1. Prime High Explosive.

Primary high explosive that we used are perforating job are

Lead Azide
Styfnate

It is generally high density compounds of metals and nitrogen, that instantaneous detonate when subjected to energy high source.

The purpose of primary high explosive is to initiative less powerful and extremely sensitive then secondary high explosive.

This Lead Azide is most commonly used in oil Industry.

2. Secondary High Explosive:-

Not sensitive at all. We used RDX, HMX, HNS, and PYX explosive for well perforation Job.

written by,

Ritu Raj Medhi

Founder& President

Petrobuddy initiative

Notes:- We collected data from different university notes and schlumberger websites.

Sunday, June 21, 2020

Well Perforation overview || Production Engineering - Petroleum Engineering