Driller’s method and wait and weight method (engineer’s method) are widely used to circulate wellbore influx while maintaining bottom hole pressure constant. There are a lot of opinions regarding which method is the best for well control operation therefore this article will discuss about pros and cons of both methods.

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Driller’s Method

The driller’s method requires two circulations to kill the well. The first circulation is to circulate influx out of the well with original mud weight. The second circulation is to kill the well with kill weight fluid. During the first circulation, the bottom hole pressure remains constant due to maintain drill pipe pressure constant while circulating. For the second circulation, in order to maintain constant bottom hole pressure, casing pressure is held constant while circulating kill mud to the bit. Once the kill mud passes the bit, the drill pipe pressure will be held constant until the kill weight mud is on surface and there is no sign of influx in the annulus.

Wait and Weight Method

The Wait and Weight method requires only one circulation. The influx will be circulated out while the kill weight mud is displaced into the well simultaneously. While pumping the kill fluid from surface to the bit, drill pipe pressure schedule must be strictly followed. After that the drill pipe pressure is maintained constant until the kill mud returns back to surface.  Some people call the Wait and Weight method as “Engineer’s Method” because there are more calculations compared to the Driller’s method.

Comparison between Driller’s Method and Wait and Weight Method

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Shut-In Procedure while Tripping with a Subsea BOP Stack

by DrillingFormulas.Com on August 31, 2014

After we publish this article “Hard Shut-In Procedure while Drilling with a Subsea BOP Stack”, there are some people asking us about what about the shut-in procedure while tripping with a subsea stack. So today we will focus on this topic.

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For the shutting in procedure with subsea stack, there are 3 steps which are stab valve, space out, and shut in and the details for the procedure are below.

 1st step: stab valve

  • Stab the full opening safety valve into the string and then make it up to the drillstring. Close the valve.

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Enchova Central Blowout Oilfield Disaster

by DrillingFormulas.Com on August 26, 2014

Learning from the past oilfield disaster will help you realize about well control, safety management, etc which you can apply to mitigate the future catasrophe. Today, we would like to share the information about Enchova Central which blown out years ago. This is very good information for everybody.

The Enchova Central platform, which was the place where two big catastrophies occurred was situated in the Campos Basin close to Rio de Janeiro and was administered by Petrobras. The initial incident was on August 16, 1984, when there was fire and an explosion. Most of the people and personnel at the time of the incident were saved with a helicopter or lifeboat. However, 42 workers lost their life in this catastrophe.

It was the most consequential and grave occurrence when there was an issue in the functioning of the lowering mechanism of a lifeboat due to which there was a malfunction with the bow hook. Consequently, the lifeboat was left hanging vertically till there was a rupture in the stern support and following this the lifeboat drowned 10 to 20m to the sea, which resulted in the death of 36 personnel. Around 6 personnel lost their lives on trying to jump 30 or 40m from the platform to the sea.

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Hard Shut-In Procedure while Drilling with a Subsea BOP Stack

by DrillingFormulas.Com on August 21, 2014

Nowadays, deepwater drilling is one of the important parts of drilling in the world and there are a lot of ongoing deepwater operations. Our team will start focus on subsea well control and this topic is about hard shut in procedure while drilling with a subsea stack. This is quite similar to surface stack but it is quite tricky how you space out the well properly because the BOP is way down below approximately thousand feet from sea surface.

Shut-In Procedure while Drilling with a Subsea BOP Stack

There are 3 steps which are space out, shut down and shut in and the details for the procedure are below.

1st step: Space Out

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Introduction To Underbalanced Drilling VDO Training

by DrillingFormulas.Com on August 17, 2014

Underbalanced drilling becomes very famous in several places of the world because there are some advantages over normal drilling operations. Today we would like to share the basic underbalanced drilling 101 for everybody who is interested in this topic. It is presented by Shell and we also add full VDO transcript for anybody who cannot catch the information from this presentation.

Underbalanced Drilling 101 Full VDO Transcript
underbalanced-drilling-101

This presentation introduces the concept and equipment used in underbalanced drilling operations. The key differences between underbalanced drilling and conventional overbalanced drilling are at both the conceptual and the technical level. At the conceptual level the subsurface drilling conditions needs to be investigated further, the rotating drill bit cuts away rock to deepen the well. The drill cuttings are lifted to the surface by the circulating drilling fluid.

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Can Women Work in the Oilfield (Oil and Gas Industry)?

by DrillingFormulas.Com on August 14, 2014

Women nowadays are dominating the world of men especially when it comes to jobs. They work side by side with males in a man’s industry, which is considered as a great achievement. Back in the days, women should stay at home, serve her husband, cook for the family, care for the children and do the household chores. This happened for many decades until some brave ladies stood up and fought for women’s rights. They showed that women can do almost anything and they can perform the work of a man. In fact, there are women who work in the oilfield, which is a tough job. People, mostly men and unbelievably some women, don’t want to accept that Eve’s daughters can work hard and do laborious jobs too.

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Good thing these days men have embraced this fact and offer wider opportunities to the ladies. There are several male jobs that are now handled by women. These jobs include being a CEO, lawyer, doctor, rescuer, military work, police, a taxi driver, a construction worker, an electrician, a race car driver, engineer, oilfield worker and the list goes on. Some of these jobs were once performed by men and are not allowed for women.

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Fracture Gradient Reduction Due to Water Depth

by DrillingFormulas.Com on August 10, 2014

Fracture gradient is one of the critical information which drilling engineers need to know in order to design drilling programs. For the well control stand point, the fracture gradient directly affects on how much influx volume can be successfully contained in the wellbore. If the wellbore pressure is over the fracture pressure, formations would be broken down and this situation will result in loss of drilling fluid into formations. Additionally, it might lead to well control situation because of loss of hydrostatic pressure. Fracture gradient is quite straight forward for land operation because it will not be reduce due to water column. However, the fracture gradient will be reduced in deepwater environment. In this article, we will discuss why water depth can cause the reduction in fracture gradient.

Fracture Gradient Reduction Due to Water Depth

Basically, the fracture gradient is related to fluids occupying in pore spaces of rock and weight of rock which are called overburden pressure. Generally, the overburden of a typical sedimentary is about 1.0 psi/ft (19.2 ppg). Rocks will be fractured when the wellbore pressure exceeds the confining stresses acting on it. If we make a general assumption that the overburden pressure causes the minimum confining stress of the rock. Then the formation fracture gradient will not be 1.0 psi/ft if the location is offshore.

Note: this assumption is made in order to help you get more understanding on how and why water depth can decrease the formation fracture gradient.

Why does the water depth reduce fracture gradient?

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Ekofisk Bravo Blowout Oilfield Incidents

by DrillingFormulas.Com on August 6, 2014

Ekofisk Bravo blowout incident happened when performing workover operation. If you study in the oilfield industry about well control incidents, there are several cases when the well was unable to control during workover operation. This is what personnel working in this industry needs to learn and fully aware of the hazard which could be occurred and this can affect lives, environment, etc. This is one of the reason why we always emphasize the important of well control in every operation.

The Ekofisk Bravo Platform Blowout

The Ekofisk Bravo Platform is located towards Ekofisk field’s north and is one of the two prime wellhead production facilities of Ekofisk. However, on April 22nd, 1977, it went through a major blowout which is regarded as the biggest oil spills till date at the North Sea.

Ekofisk Bravo 1

The Ekofisk B blowout took place when workover was being carried out at B-14 production well where they were busy pulling about 10,000 feet of production tubing. Before the task, the production Christmas tree valve stack was removed. Besides, the BOP was not installed. However, the well kicked and wrongly installed while the downhole safety valve failed, which caused immediate blow out of the well with wild release of gas & oil. However, fortunately the crew onboard was evacuated safely through lifeboats and was later transferred to the supply vessel. Miraculously, no one was injured.

This event led to wastage of approximately 28,000 barrel/day, later resulting into overall discharge of 202,380 bbls. Around 30-40% oil was assumed to be evaporated and the overall spill estimate by the Norwegian Petroleum Directorate was to be considered around 80,000 bbls & 126,000 bbls.

Ekofisk Bravo 2

Finally, after 7 days, the well was capped in April 30th, 1977. However, higher air temperature & rough seas helped the break-up of the most of the oil. Further investigations concluded that there was no major damage to the environment & shoreline pollution. Besides, there was no major damage to the platform.

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Free Cross Over Generator Excel Spreadsheet for Oilfield Use

by DrillingFormulas.Com on August 4, 2014

You may have a problem regarding ordering the cross over to use on the rig because there are so many threads used for the operation. For example if you have just only three threads (3-1/2” IF, 4-1/2” IF, 7” BTC) for the operation. These are a total of 18 the possible crossovers that you may need as listed below.

3-1/2″ IF PIN X 4-1/2″ IF BOX

3-1/2″ IF PIN X 7″ BTC BOX

4-1/2″ IF PIN X 3-1/2″ IF BOX

4-1/2″ IF PIN X 7″ BTC BOX

7″ BTC PIN X 3-1/2″ IF BOX

7″ BTC PIN X 4-1/2″ IF BOX

3-1/2″ IF PIN X 3-1/2″ IF PIN

3-1/2″ IF PIN X 4-1/2″ IF PIN

3-1/2″ IF PIN X 7″ BTC PIN

4-1/2″ IF PIN X 4-1/2″ IF PIN

4-1/2″ IF PIN X 7″ BTC PIN

7″ BTC PIN X 7″ BTC PIN

3-1/2″ IF BOX X 3-1/2″ IF BOX

3-1/2″ IF BOX X 4-1/2″ IF BOX

3-1/2″ IF BOX X 7″ BTC BOX

4-1/2″ IF BOX X 4-1/2″ IF BOX

4-1/2″ IF BOX X 7″ BTC BOX

7″ BTC BOX X 7″ BTC BOX

You will get lost easily, won’t you??

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As you can see, it is quite tricky to determine all possible required cross over especially when you have a lot of connections. Therefore we create an Excel file to help you do this task. We call this file as “Cross Over Generator”.

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Block and Drilling Line Calculation

by DrillingFormulas.Com on July 29, 2014

This article will focus on block and drilling line calculations as block efficiency, drilling power input/output, etc. Additionally, there are some examples which will help you understand how the formulas work.

Block-and-Drilling-Line-Calculation-cover-page

Block and drilling line efficiency formula is described below;

Block and Drilling Line Calculation 1

Power Output (Po) = Fh x Vtb

Power Output (Pi) = Ff x Vf

Block and Drilling Line Calculation 2

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