About Gefei Liu, PVI

Please visit my LinkedIn profile to learn more about me. http://www.linkedin.com/profile/view?id=115784500&trk=hb_tab_pro_top

Face Time with New Graduates

On August 22, 2018, I was honored to participate in the BP/CAPA 2018 Career Development Forum organized by the BP Asian Network (BPAN) and Chinese American Petroleum Association (CAPA). The theme was the challenges and opportunities in the digitalization revolution.

Gefei Liu, president of PVI, participated in the 2018 Career Development Forum in Houston, organized by BP Asian Network (BPAN) and CAPA

My first time as a panelist turned out to be a very good experience. I was encouraged by the CAPA organizers and co-panelists, especially the attendees, some old friends, mostly fresh graduates and students. The message I passed to the audience can be summarized into three points:

  • You are always your own CEO, no matter if you work for someone or have a business of your own. Give your best, and go all in. Nobody regrets giving his or her best.
  • Think big and start small as illustrated by the old Chinese saying, “A journey of thousand miles starts with the first step.”
  • A little kindness goes a long way. Being kind will help you succeed in the workplace, your business and life. “People will forget what you said and what you did, but people will never forget how you made them feel.”

Despite the lingering heatwaves in Houston, this forum was like fresh breeze in the air. I felt that it was a special day, because I had meaningful interactions with old and new friends. After all, life is about inspiring and being inspired.

Small Business, Bit Impact.

“I know you always want to have an MBA degree.” My brother called me from Kentucky in August. “There is this program specially designed for small business owners like you. Try it. It is free if admitted.”

This 10-minute conversation with my dear brother caused me a 4-month commitment to the Goldman Sachs 10,000 Small Business Program this fall. After an on-line application, an on-site interview and one week of Hurricane Harvey, I was admitted to this program (Houston site) in the middle of September 2017.

We have 20 scholars, as called by the organizer, in this session. The purpose of the program is to teach busy businessmen to grow their business. Unlike degreed programs, which are costly, length and faculty-focused, the Goldman Sachs 10,000 Small Business Program is a gift, fast paced and peer-focused. It is not only free, but they also provide breakfast and lunch. My classmates are all business owners, but I am the only one in petroleum engineering area. I guess that this does not matter, as all business share the similar process.

One day, a lady instructor showed us a slide loaded with the information of US firms. To my surprise, there are nearly 30 million companies in US. She continued to the next slide showing the number of employees of these companies. It was even more shocking: among those 29+ million companies in US, more than 80% are no-employee firms. Ever wonder how many US firms hiring more than 500 people? The answer is 18,219. So, for those of you who are working for big companies, you should feel privileged, because only 0.06% of all the US companies hire more than 500 people.

However, if you are working for companies with only a few or a couple of hundred employees or you are running one of similar sizes, please do not be discouraged, because together, we are the largest employer in the US economy.

A few weeks into the program, I have been inspired by the creative way of their teaching. We paired up to do presentation and discuss. We used super-sized Post-It to brainstorm our ideas on new opportunities. We are encouraged to generate ideas for other business owners. I already got some ideas how to generate ideas within our company. Keep learning and keep practicing, I told myself.

Goldman Sachs 10,000 Small Business Program

Goldman Sachs 10,000 Small Business Program

A Memento from the Past: Keep Calm and Carry On

The wear and tear of our clothing is not caused by wearing them, but by washing them in washing machines instead. Many of my tennis shirts which I have been wearing for more than a decade have faded in color here and there and the fabric has thinned out over time. Still, I have no problem wearing these shirts on the tennis courts.

Every fall, the SPE Gulf Coast Section (GCS) holds an annual tennis tournament where they give out t-shirts to every registered player. I have been an active participant of this event and have collected close to 20 shirts over the years. The designs have varied in some way, but have maintained the same style, a cartoon on the back depicting the theme of the year.

Among these t-shirts is the one I got from the tennis tournament held in 1998. Every time I see this shirt, I cannot help but let out a long sigh. Last month, I decided that this particular T-shirt should be treated as a relic, a piece of history that should be hung up in a museum. So I got it framed and hung it up on our office wall.

SPE_Tennis_T-shirt

That year, I was a mechanical/software engineer with Maurer Engineering, developing drilling software for DEA-44 (Drilling Engineer Association’s horizontal drilling joint-industry project). $12/bbl must have been the lowest oil price in 1998 right before SPE held their tennis tournament on October of that year. I don’t recall SPE ever making a T-shirt showing the record high oil price in the 2000s. Every time I wear this 1998 shirt to play tennis, my friends and I get a good laugh from it since most of them are involved with the industry and have all been a part of the oil-price roller coaster ride. The heydays of the drilling industry have helped us grow, and we have survived (or at least try to do so) in an era like the one we’re living through now.

In early 2015 I told my team members that the low oil price was an opportunity for us to shift our focus to development. Now, being already the 3rd quarter of 2016, we are still stumbling on the downturn. But then again, who in this industry isn’t? Robert Louis Stevenson once said, “Judge each day not by the harvest you reap, but by the seeds you plant.” This is probably not our time for reaping, but for planting seeds instead.

I used to carry this oil price on my back, but now I have placed it on the wall, knowing that some things are bound to be out of my control. I do my best within my means, and I have to make peace with those things I have no control over.

A Small World in a Big Airplane

 

More than 6000 miles away from Houston and 30,000 feet above the ground, I shared a row of seats with a Turkish man who happened to have visited our office 6 years ago. Can anyone tell me what the chance of this occurring is?

After the Abu Dhabi International Petroleum Exhibition and Conference (ADIPEC), I took a flight from Abu Dhabi to Istanbul. During that 4-hour flight, I began sketching some interface designs for our next version of casing wear software. The man seated right next to me was quietly reading a book. After a while, he asked me, “Are you developing a casing design software?” He had obviously seen me write “casing wear” and thought it was “casing design.” I felt pleasantly surprised with his question. “Casing” is a frequently used word in the drilling industry. It is a steel pipe that is assembled and inserted into a wellbore and typically held into place with cement. Outside the petroleum world, it has a very different meaning. Generally, if someone asks me a question about a casing design, not only does that tell me that he is in the industry and familiar with it, but also that he is in the drilling side and familiar with drilling software.

Finding something in common is a good way to break the ice. We began to chat enthusiastically. He was Turkish, but had received an education in the U.S. and was now working with Schlumberger as a drilling engineer. I gave him my business card and he spent a little bit longer than usual looking at it.  He then murmured, “I know you guys…I have been to your office. Don’t you have a software package called MUDPRO?” (MUDPRO is our mud reporting software). Dale Carnegie once said, “A person’s name is to that person the sweetest sound in any language.” This same rule applies to names of family members, friends or even one’s own software products! I felt touched. He explained to me that he has a friend, who owned a mud company. The owner of the mud company visited our office in Houston 6 years ago and he happened to be with him during this trip. It must have been the logo on my business card that reminded him of the meeting, which I had not been a part of.

“What a small world!”  We exchanged mutual feelings.

Chatting with him not only made the flight shorter, but also memorable.

I would never have anticipated this meeting, but an unnoticed event years ago led to this very occasion. “Don’t judge each day by the harvest you reap, but by the seeds that you plant,” said Robert Louis Stevenson, a Scottish novelist from the 19th Century.

Though we are not guaranteed to have harvests every day, we can plant seeds as often as we wish, even every day. The world gets smaller as we plant more seeds daily.

How to Prevent a Flat Tire on the Way to the Airport

Recently, I have been thinking about writing another article. It seems as though whenever I take a trip, it is my most productive time when it comes to writing. Trips lead to many occurrences, which are a good source for topics.

My journey to Abu Dhabi to attend ADIPEC (Abu Dhabi International Petroleum Exhibition and Conference) had just started, but it had already generated a couple of interesting ideas. On my way to the airport, I suddenly realized that I forgot to check if my passport was in my bag. I pulled my car to the shoulder of the highway. Before I stopped the car, I heard a loud noise coming from the front tire. I secretly wished that I had just hit an abandoned tennis ball. I stopped the car, opened my trunk, and checked my bag.

My passport was there, as it was supposed to be, but my right front tire was flat. Long story short, I spent the next hour driving my disabled car to a parking lot, calling AAA and my wife, who drove me to the airport. I caught my flight in time, leaving the whole ordeal to my wife. Even when looking at the photo I took of my car, I can still smell the burnt rubber.

I always thought that events like this were unlikely to happen. Or if it did happen, it would most likely happen to someone else.

I should have checked my travel essentials ahead of time. Or perhaps I should have picked a more secure place to stop, or even better, I should have a little bit of faith on myself in getting my travel documents in place. I just chose a wrong time to pull my car to a wrong place. “A little bit preparing saves lots of trouble. I could almost hear my flat tire complaining.

Incidentally, the book I read on my flight, called “The Power of Persuasion” by Robert Levine, talks about the illusion of invulnerability overoptimism. Here are some research examples from the book:

  • People who feel at risk for health problems are more likely to gather disease prevention information.
  • Smokers who minimize their own risk of disease are less likely to try quitting.
  • People in high earthquake risk areas who downplay danger are more likely to live in poor structures.

The book just listed a few.  Real world examples are everywhere. For instance, within our drilling community, if we use an analogy of the above sayings, it would go something like this:

  • Drilling engineers who feel the risk of drilling issues arising are more likely to prepare for potential problems.
  • Engineers who minimize potential problems are less likely to prepare for or identify them.

As the geneticist David Searls observed, “The tendency for an event to occur varies inversely with ones preparation for it.” I learned my lesson the hard way.

Return to Square One: A Round Trip without Reaching the Destination

Due to business, I had to make a trip to Saudi Arabia via Paris. It was uneventful from Houston to Newark, where I made connection. I boarded on the flight, the meal was delicious and I took a Benadryl, hoping I could get some sleep on the way to Paris.

While I dreamt, I heard the announcement, “Ladies and gentlemen, as we start our descent…” I woke up and was delighted to imagine that I would be in Paris in a few minutes. Looking at the lights below, I tried to locate the Eiffel Tower. Then, a suspicious feeling arose, it was too soon for us to arrive; we should land in Paris during the day time. Then I heard my neighbor, who had also just woken up, saying, “Why are we landing in Newark?”

Finally, a flight attendant told us that 3 hours after the airplane took off, as we were just above the Atlantic Ocean, they found some issues with one of the engines. The captain decided to return home. The following is our flight trajectory that night.

Although I am a frequent business traveler, this was my first time experiencing this. I had a meal in the air, took a nap, and then I was back to square one. After all, the airline company must have had its own justification to fly back, and it is better to be safe than sorry.

As a result of this incident, except extra fuel cost, the airline company had to pay for our hotel and meals during delays. Apparently, everyone in this trip lost 6 hours; moreover, it brought about much inconvenience. No one would enjoy these types of surprises. However, the big picture is that the decision on flying back may have saved hundreds of lives. I am certain that airlines are making efforts to ensure flight safety and punctuality.

Drilling operations are like flight missions. There is a destination we want to reach, which we call total depth (TD). We assemble drill pipes, tools and bit. We circulate drilling fluid, control the hook load and weight on bit (WOB) to penetrate. But things could go wrong: pipe may get stuck, circulation lost, or bit dulled. Like this trip, those problems are unpredictable.

What we can do is to engineer the operation more carefully to identify potential problems prior to drilling. With our best effort, we keep the problems under control, and then we can be at ease with the outcome.

Despite the cancelled flight, I had brief but good sleep in a hotel by the airport. The next night, I caught another flight. After dinner, I took another Benadryl. This time, I woke up in Paris!

Eccentric Annulus in a Cement Job

Finding a good picture of an eccentric annulus was challenging until Dennis (Global Sales Manager of PVI) and I walked down a street in downtown Calgary yesterday. I took a picture of this interesting sewerage cover. Dennis immediately guessed what I wanted to do with it, “Picture for your blog article about eccentricity?”

Eccentric Annulus

Picture 1: Eccentric Annulus

Many drilling engineering textbooks and modeling software assume concentric annulus because it is easy to model the fluid dynamics in it. Unfortunately, the most natural state of pipe in a well is almost always close to one side of the wellbore, if not touching, especially in a deviated well. Casing centralizers keep casing from contacting the wellbore wall. Even with centralizers installed, the casing between centralizers will still deform (sag) and could contact the wellbore.

An eccentric annulus has the same cross-section area as the concentric annulus. However, the flow through the eccentric annulus exhibits various forms. The following picture shows the velocity profiles in annuli with various degrees of eccentricity. The percentage represents casing standoff. A standoff of 100% means a perfectly centered pipe while a standoff of 0% represents the situation that the casing is in contact with the wellbore.

Velocity Profiles

Picture 2: Velocity Profiles

The eccentric annulus has many unique characteristics such as less frictional pressure drop than that in concentric annulus. As the standoff gets lower, less energy is required to move the fluid, and mud removal becomes a problem in the narrow side.

To easily view the numerically simulated results of the fluid mixture in the annulus, we are going to unwrap the annulus into a 2D picture. In this picture, the middle represents the narrow side and the 2 edges represent the wide side.

Picture 3 shows the mud concentration with various standoffs.

Mud Concentration for Various Standoff

Picture 3: Mud Concentration for Various Standoff

A well-centered pipe in a wellbore will lead to a more uniform axial velocity profile and shorter fluid interface length. As standoff approaches 0, the narrow side flow could even be blocked, leaving fluid not displaced.

Casing Wear Series – 3: Prevention

Computer casing wear modeling reduces risks and can identify potential problems prior to its occurring. Necessary modifications on casing designs and drilling parameters could be made before the pumping starts once we can predict the location and magnitude of wear.

Figure 1 shows the 3D visualization of magnitude and location of wear in a previously set casing.

Figure 1. 3D Visualization of Casing Wear
Figure 1. 3D Visualization of Casing Wear

The knowledge we have acquired through decades of studies, lab testing, post-job analyses and computer modeling provides a good foundation for the following casing wear preventive measures:

  • Minimize dogleg severity and expect real dogleg at least 1.5 times higher than the planned value.
  • Use casing friendly tool joint materials.
  • Reduce rotor speed and use downhole motor.
  • Increase ROP.
  • Select proper mud type and add lubricants to reduce wear and friction.
  • Use drill pipe protectors.
  • Use thick wall casing in the anticipated wear section area.
  • Use software to reduce risks.

Please go to www.pvisoftware.com/white-paper/Casing-Wear-Causes-Prediction-and-Prevention.pdf to download the complete Casing Wear white paper.

Casing Wear Series – 2: Prediction

1. Wear Mechanism

The casing wear model applied in CWPRO (casing wear prediction software developed by PVI) assumes that the metal volume worn away in a wear groove section is proportional to the frictional energy transmitted to the casing by a rotating tool joint as shown in Figure 2 in the Casing Wear Series – 1: Causes.

transmitted-frictional-energy-formula-1

The transmitted frictional energy is defined in this formula:

Where:

E  = Frictional Energy, lb-ft

μ  = Friction factor, dimensionless

SF= Side force on tool joint per foot, lbf/ft

SD = Sliding distance traveled by the tool joint against casing wall, in

The volume of casing wall removed per foot in time t hours is mathematically expressed in the equation:

equation-The--volume-of-casing-wall-removed-per-foot-in-time-t-hours

Where:

WV = Casing wear volume per foot, in3/ft

WF = Wear factor, E-10psi

SFdp = Side force on drill pipe per foot, lbf/ft

Dtj = Tool joint OD, in

N = Rotary speed, rpm

t = Rotating time, hr

The definition of wear factor is the ratio of friction factor to specific energy, which is the amount of energy required to remove a unit of steel. The unit for wear factor is E-10psi-1; therefore, when a wear factor is reported as 8, the actual value used in casing wear calculation is 8E-10psi-1.

Quite a few experiments were conducted to find the casing wear factors under different mud systems, tool joint materials, casing interior and drill string protectors. Among them, Maurer Engineering Inc. conducted joint-industry project DEA-42. It was reported that more than 300 laboratory tests were performed under DEA-42 to determine the wear factors for various drilling conditions.

For a typical water-based mud, WF can vary as follows:

Normal or low: 3 – 7

Medium: 8 – 13

High: 14 – 20

WF above 20 can be considered as very high and may cause severe casing damage.

2. Wear Geometry

A typical wear groove is shown in the following figure.

Figure 1. Casing Wear Groove | PVI drilling software

Figure 1. Casing Wear Groove

The relationship between wear depth and casing wear volume is:

equation-relationship-between-wear-depth-and-casing-wear-volume

Where:

WV = casing wear volume per foot, in3/ft

h = wear depth, in

r = tool joint outer radius, in

R = casing inner radius, in

S = R - (r - h), in

P = (R + r + S) / 2, in

equation-relationship-between-wear-depth-and-casing-wear-volume-cos

3. Software

Based on the R & D results from the past two decades, PVI developed CWPRO, software that enables us to understand the casing wear phenomenon and accurately predict casing wear before the drilling operation or perform a post-drilling analysis.

CWPRO is a comprehensive casing wear prediction software with built-in torque and drag function. For every incremental drilling interval, the amount of energy transferred from drill pipe to casing is calculated. Accumulative wear and wear depth are first obtained and then the burst and collapse strength of the worn casing can be assessed.

Being a time-dependent incident, casing wear deepens as we drill deeper. Figure 2 shows the sequence of drilling and corresponding wear profile along the previously set casing.

Figure 2. Time-dependent Casing Wear | PVI drilling software

Figure 2. Time-dependent Casing Wear

Casing Wear Series – 1: Causes

During the drilling phase, the most costly component is the casing. On top of the expensive casing materials and the costs likely to be encountered in cutting, pulling and replacing a worn or damaged string, casing wear creates more serious problems for operators due to its potential catastrophic incidents such as oil spills, blow outs or loss of the well.

To analyze the forces behind casing wear, we need to study the torque and drag (T&D) of the drill pipe during drilling operations. The basic mathematical and physical model of T&D has not changed significantly since Johancsik et al. published their paper on T&D prediction. Pipe movements such as drilling ahead or tripping create drag, while rotation produces torque. The magnitude of T&D is determined by the combination of these two movements.

Since the so-called vertical well virtually does not exist (the whirring action of the bit always creates a micro-helical shape of the well path), the contact of the drill pipe and its tool joint with the casing ID is unavoidable. The gravitational force acting on the drill pipe is always trying to pull the pipe to the lower side of the wellbore, while the axial tension on the drill pipe (in a build-up section) tends to push the pipe to the upper side of the wellbore. Depending on the pipe weight, dogleg severity, and axial force along the pipe, the drill pipe either touches the upper or lower side of the wellbore.

Typical T&D analysis starts by dividing the pipe into small elements. Calculation begins from the bottom element of the pipe, where weight on bit (WOB) and torque on bit (TOB) are expected. For each element, force and torque are balanced and the T&D at the top of the element are calculated. From bottom to top, calculations are performed for each pipe element, until it reaches the rig floor. This step-by-step calculation also determines the direction and magnitude of the side force, which pushes the drill pipe against the wellbore as shown in Figure 1.

Figure 1. Snapshot of Side Force along a Drill Pipe

Figure 1. Snapshot of Side Force along a Drill Pipe

Under this side force, the rotating tool joint on the drill pipe against the casing inside, gradually removes steel from the casing wall and forms a crescent-shaped wear on the casing as shown in Figure 2.

Figure 2. Rotating Tool Joint Wears Crescent Grooves in Casing

Figure 2. Rotating Tool Joint Wears Crescent Grooves in Casing

The seriousness of friction between two contacting surfaces is dependent on the nature of the rubbing surfaces and the mud.

The tool joint coating plays a bigger role here compared to the casing wall. The industry has seen tool joint coating evolve from “casing killer” (rough tungsten carbide) to “casing friendly” as shown by many high-tech hardbanding materials.

Tungsten carbide is applied on the tool joint. While it is a very good protector of the tool joints, it aggressively wears the casing so much that the mud type and its additive will not help much in reducing casing wear if rough tungsten carbide is present.

Once a casing friendly tool joint coating has been selected, the mud type and its additives play an intermediate role in casing wear. Water-based mud causes twice as much casing wear as the oil-based alternative. Lubricant reduces friction and severity of the wear.

Generally speaking, high dogleg will create a high side force and severe casing wear. The wear profile resembles the shape of dogleg severity. Higher RPM and lower ROP make more rotation time between the tool joint and casing and will cause aggressive wear.

The following conditions contribute to casing wear:

  • Well path and dogleg
  • Drill pipe weight
  • Tool joint coating
  • Mud and additives
  • RPM and ROP