Monthly Archives: August 2014

Looking for The Right Key

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“Many people are confused with complexity and shy off from it. Strangely, complexity arises from simple rules, but people are finding it difficult to grasp. However, you need to move out of this situation soon before it gets out of control. Do what ants do: they diverge to look for new sources of food and then converge once a new path has been identified. Look for new ideas till you identify a new path or a new pattern to help you find the right key for the right lock that opens up the right door.”

        - Ali Anami

As the 21st century passes, the oil industry continues to look for new ways to innovate and increase its productions. It continues to search for reserves in more complex environments, especially in deep water. Already many fields are slated for development in both shallow and deep offshore wells and new solutions and technology are needed to meet these goals.

As a reservoir depletes, the pressure and production rates decline and lost circulation or differential sticking problems can prevent the drilling operations from increasing their production. Underbalanced drilling (UBD) is a practical method to drill in such depleted or low-pressure areas. One of the many benefits of underbalanced drilling is that it can prevent or reduce near wellbore permeability damage; as a result, it enhances the production, delaying water, gas or oil leaks due to the lower pressure drop that is required for the same flow rates.

The advantages of Underbalanced Drilling are:
  • Improves drilling performance
  • Increases penetration rate (ROP)
  • Extends bit life
  • Minimizes differential sticking of pipe
  • Diminishes lost circulation
  • Reduces formation damage
  • Simplifies early production while drilling
  • Allows formation evaluation and tests while drilling
  • Higher productivity completions
  • Picks total depth (TD) from inflow performance
  • Closed, pressure-controlled system

In order to design and achieve a successful underbalanced drilling project many important elements must be taken in consideration and there are 4 steps that have to be applied to determine the options and requirements for UBD: This is particularly important for underbalanced drilling operations offshore from floating vessels, where critical issues can increase significantly.

  1. Determine Bottom Hole Pressure (BHP) requirements.
  2. Identify the drilling fluid options.
  3. Establish the well design and perform flowing modeling.
  4. Select the surface equipment.

An advance software model has been developed which incorporates these elements, including multiphase flow calculations, gas and liquid injection rate optimization, hydrostatic gradient and frictional pressure loss calculations, cuttings transport, reservoir fluid influx (oil, gas, or water), and operational procedures such as tripping and liquid unloading.

Just like the rest of PVI's software, UBDPRO is the right tool when it comes to increasing a well’s productivity. It’s all about looking in the right direction (for the right key) and making the efforts to obtain it.

UBDPRO - Underbalanced Drilling Hydraulics

Hot Game with Hot Model

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A couple of days ago, at 3:30pm, the hottest time of the day, my friend Francisco and I played a match of outdoor tennis for an hour and half, under the unforgiving sun of August and high humidity of Houston.
For the first 30 minutes, I felt great. Then, my legs were not coordinating with my mind. I only won 4 games in 2 sets. But I was proud of myself to be able to survive the heat.
We took breaks and chatted between games. During one of the breaks, while holding his hot iPhone, he shook his head and told me: “You know what, my phone quits working!” Then he read to me the message on his cellphone screen, which said:

HTHP Classification

Fig.1: HTHP Classification

We started laughing and felt good about ourselves: we were running directly under the sun and the iPhone was sitting in the shadow of the pavilion.

Heat does amazing things to our bodies, helping us warm up or exhaust us. It was my intention to test the strength of my body when exposed under the sun. It was not my best experience, but it served a purpose.

In petroleum industry, the days of easy, cheap oil are over, making it harder to meet demands without any complicated and expensive projects. As operators continue to drill in deeper and more extreme formations, we are facing extreme temperatures, which create detrimental effects to drilling operations.

More often than not, we encounter high temperature and high pressure (HTHP) conditions, which are defined with the following picture.

HTHP Classification

Fig.2: HTHP Classification

HPHT is currently defined as 20,000 psi and 450°F and ultra-HPHT is typically considered anything above.

When drilling a well, we use drill pipes and other tools including downhole motors, which have rubber parts. The combination of high temperature and pressure, and other tough conditions has a dramatic effect on reducing the drilling tools’ ability to withstand the HPHT conditions. When exposed to high temperatures for extended periods, the rubber parts may deteriorate, causing operational failures. High temperatures also have implications for flow assurance (wax, hydrates, or viscosity), stress analysis, drilling tool temperature tolerance, completion fluid density and cementing, etc.

If we can predict downhole temperatures, we can evaluate the risk involved. The downhole temperature changes as we start the mud circulation bring heat from formations at the bottom of the hole upward and release the heat to cool down the formation in the upper section of a well. Here is a snap shot of a temperature profile in a wellbore, using CTEMP, PVI’s Wellbore Circulation Temperature Model.

CTEMP - temperature profile along the wellbore

Fig. 3: CTEMP - Temperature Profile Along the Wellbore

Predicting the temperature and knowing our limits are necessary for tennis games and drilling operations.

From The Pencil to Engineer Is Human

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“Design is a way of life, a point of view. It involves the whole complex of visual communications: talent, creative ability, manual skill, and technical knowledge. Aesthetics and economics, technology and psychology are intrinsically related to the process. Design is the evolution of useful things.”

- Paul Rand, also known as the American Modernist.

When Paul Rand made this comment he was referring to two books written by Henry Petroski: The Pencil and To Engineer Is Human, in which basically he talks about how we can take everyday objects and turn them into better useful objects. For instance, how pins were turned into paper clips; how Styrofoam containers evolved; how Post-it Notes came about and even how a simple rock can be turned into something very useful. The list goes on and on, and it is easy to understand the connection between Petroski’s points of view with Rand’s ideas on invention, innovation and ingenuity.

When it comes to the evolution of useful things, the oil and gas industry has many examples, but just let’s take this moment to talk about one of them: cementing and its development process.

Cement fills and seals the annulus between the casing string and the drilled hole. It has three general purposes:

  • Zone isolation and segregation
  • Corrosion control
  • Formation stability and pipe strength improvement.

Cement forms a very strong and impermeable seal from a thin slurry. The properties of the cement slurry and its behavior depend on the components and the additives in the cement slurry.

The cement is produced from limestone and either clay or shale by being roasted at 2600 to 3000°F. This high temperature fuses the mixture into a material called clinker cement. Once the roasting step is done, the rough clinker product is ground to a size specified by the grade of the cement. The final size of the cement particles has a direct connection with how much water is required to make the slurry without producing an excess of water at the top of the cement or in pockets as the cement hardens.  However, not all cements, including those made from the same components, will have the same reaction when mixed with water. Generally, the differences are in the quality of the grind of the cement, impurities in the water and in the additives added during the cement manufacturing process.

The design and test of the slurry are essential parts of every cementing job and without an efficient lab database cementing companies can face many problems, but thanks to the evolution of technology PVI has developed the right tool for this: CEMLab (Cement Lab Data Management).

CEMLab - Cement Lab Data Management

Since its first release in the fall of 2012, CEMLab has evolved into a powerful web-integrated and highly functional software product. CEMLab formulates slurries, calculates the amount of all ingredients, generates weight-up sheets and lab reports and allows engineers to have quick access to all their slurry formulation, and testing statuses anytime from anywhere.  These are just a few of the many features that make up CEMLab. Just like from the books “The Pencil” to “To Engineer Is Human” we get to see how an object can be designed and turned into something more useful and successful, CEMLab has been turned into a useful, successful and sophisticated lab tool.

Flying Among The Clouds

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Louis D. Brandies once said:

“Most of the things worth doing in the world had been declared impossible before they were done. Impossible means that you haven’t found the solution yet.”

A little over 100 years ago there were things that were considered impossible to do and that there was no way they could ever be achieved. For instance, to be able to fly among the clouds, but was it really an impossibility? Time proved that it wasn’t.

Just like flying among the clouds was impossible to do once, there are many things that thanks to the advancement of technology now are possible. For instance, a few decades ago horizontal or extended-reach drilling was considered impossible as well as casing wear prediction. In these environments, casing design is critical to a safe and successful drilling operations and well production, and unexpected casing wear can result in significant costs or even the loss of the well itself. This is the problem that drilling companies want to prevent.

So the question is: Is there any tool or software to calculate and predict casing wear severity? Yes there is! It’s called CWPRO.

2D wellbore schematic in CWPRO

This casing wear model uses the number of drill string rotations and contact force between the drill pipe and casing to calculate wear. The contact force is calculated using the dogleg severity inside the well. The maximum dogleg severity frequently determines the location and extent of the most severe casing wear. CWPRO helps operators and service companies identify, control and prevent potential problems. In overall the goal of CWPRO is to more accurately quantify casing wear risks and to ensure that the integrity of the casing is maintained during drilling operations.

Like mentioned before, there are many things that were considered an impossibility not too long ago like for instance, flying among the clouds. Likewise, thanks to software like CWPRO, predicting casing wear is no longer impossible; it is a fact.