Oral-History:Harry O. McLeod, Jr.
About Interviewee
Harry O. McLeod, Jr. has devoted his career to evaluating well behavior and making continuous improvements to project technology. At Phillips, he implemented trials of new stimulation treatments; at Exxon, he made an impact focusing on artificial-lift and hydraulic-fracturing systems; and at Dowell, he developed a formation analysis technique for evaluating wells when using acid treatments. Later, at Conoco, with others, he designed a fracturing model used to eliminate screenouts by using control measures.
Further Reading
Access additional oral histories from members and award recipients of the AIME Member Societies here: AIME Oral Histories
About the Interview
Harry O. McLeod, Jr.: An interview conducted by Fritz Kerr for the Society of Petroleum Engineers, June 27, 2013.
Interview SPEOH000101 at the Society of Petroleum Engineers History Archive.
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Interview Video
https://streaming.spe.org/oral-history-harry-o-mcleod-jr
Interview
INTERVIEWEE: Harry O. Mcleod, Jr.
INTERVIEWER: Fritz Kerr
OTHERS PRESENT: Mark Flick
DATE: June 27, 2013
PLACE: Houston, Texas
Background, Education, and Entry into the Petroleum Engineering Profession
FLICK:
All right. So Harry, I’m going to ask you the first questions. So tell me who you are. Give me your name.
MCLEOD:
Oh.
KERR:
Name and then spell it, please.
MCLEOD:
I’m Harry McLeod, Junior. McLeod is spelled M-C-L-E-O-D.
FLICK:
Very good. Where do you live, Harry?
MCLEOD:
I live here in Houston near Gessner and Hammerly.
FLICK:
And currently, you’re retired. But what did you do before that?
MCLEOD:
I retired in 1997 from Conoco. I was a senior staff engineer. No, excuse me, a senior engineering professional.
FLICK: [Laughs].
MCLEOD: [Laughs].
FLICK:
Okay, that’s good. All right, that’s it for me. Very good. Now, I’ll turn it over to Fritz.
MCLEOD:
Okay.
KERR:
Nice to meet you, Harry.
MCLEOD:
Thank you, Fritz.
KERR:
So just tell us in your own words how did you get interested in the petroleum engineering industry?
MCLEOD:
Well, I got involved in the industry about the time I was born because my grandfather worked for Texaco, my father worked for Cities Service, a subsidiary of Cities Service at that time. So I grew up in the oil field in Louisiana and Texas.
FLICK:
And Fritz will pause because we don’t want to jump right in for editing purposes so…
MCLEOD:
Okay.
FLICK:
It will feel awkward but it’s for editing.
MCLEOD:
Okay.
KERR:
But if you want to jump back in with more information, that’s the other reason why we pause. Part of it is our editors like to have at least a bit of space in between. But if something comes to mind then just go right with it. Okay?
MCLEOD:
Okay. Well, from early on, I knew that I would be going to college. That was implanted in my mind by my father who was not able to complete college during the Depression. And so he put in my head that I should either be an engineer or an accountant because those were the good jobs back then. And so growing up, I sort of had it lined out somehow I was going to attend college. And then going through school, I enjoyed Math and Science. I never did really know what an engineer did.
In high school, I worked on a pipeline maintenance crew for my dad’s company cutting right of way and repairing oil leaks and pipelines, digging up pipelines and reconditioning the pipe surface and coating it with a material to prevent corrosion. And one day while digging in a deep ditch and scraping rust off of a pipeline, I saw an engineer come out on the scene and he was putting out little metal anodes to kind of protect the pipe from corroding in this low spot in this area. And so I kind of liked the way that he looked coming out in his clothes and boots and everything, and that kind of impressed me. So I started thinking about what an engineer would be like.
We moved from Oil City, Louisiana to Longview, Texas, kind of the heart of the East Texas oil field. And in Longview, they had a library there which I was not privileged to have in Oil City, Louisiana. Oil City was a former boom town area back in the 1920s but then it lost its population. And when I lived there, it had about a thousand people. But the oil activity was still around that area. But when we moved to Longview, we found this library and my mother would drop us off on Saturday mornings to spend time in the library. And so I began to read more books at that time.
And one of the books I read was about kind of an Alger [Horatio Alger], whatever that guy was, a story about a young man working hard and becoming successful. And this story was about a mining engineer. That captured my imagination. So through high school, I thought I was going to be a mining engineer and go to Russia and mine gold or go to South America and mine silver or whatever. So I started looking for mineral engineering schools and looked at El Paso School of Mines, Missouri School of Mines, the Colorado School of Mines and sent off for the catalogues. And so the pictures in the Colorado School of Mines really kind of attracted me. So the mountains and the meadows and everything else looked like a cool place to go to school.
So I applied there and found out they had a scholarship for each state of the union. So I applied for the scholarship for the State of Texas and was awarded that. So that’s how I went off to the Colorado School of Mines. And it was the first time I’d ever been out away from home more than 50 or 100 miles. And so it was quite an exciting experience and I really enjoyed the atmosphere and the challenges that first year.
My Freshman Spring Semester, I decided to switch from mining to geology. And I had been down in some real mines in Colorado. It was dark and damp and muddy. And when they were drilling, it was very dusty so I was used to being on the surface in the sunlight. And so I decided to switch to geology. There was a very enthusiastic, interesting professor of geology that taught a course there called Dr. Leslie Leroy. And he captured my imagination. And so I thought, “Well, that would be great. I could do all this on the surface and climb mountains and go hiking and things like that as a geologist.”
And then the next semester, I got involved in a course, what Dr. Keating called Crystallography. And that just about ate my lunch. And I said, “Well, if this is what I got to learn as a geologist then maybe I better look at something else.” And in English, Technical English that semester, we had to do a technical report on something in the mineral industry. And I chose something called cathodic protection. And this went back to that engineer that came out to that pipeline back then installing anodes to protect pipeline from corroding. And so I decided, “Well, that might be interesting to learn something about that.” So I did and I wrote my dad about it and he sent me back about a two-page report that he wrote for me to use as a reference. And then we had to give a talk in class about what we learned. And so I said, “Well, gee, that’s interesting.” So I decided to go in to petroleum engineering. So I continued on through that for the next three years to graduation.
Changes He Saw in the Petroleum Industry During His Career
KERR:
That’s fantastic. That’s fantastic. So Harry, tell me, what are some of the biggest changes that you saw throughout your career in the petroleum engineering industry?
MCLEOD:
Well, the biggest changes I saw, first of all… the first one was in computing, calculation. When I started in college, it was a slide rule to do mathematical computations and it’s not precise but it’s precise enough for engineering that has a lot of assumptions in it. And so I went through college with a slide rule. I worked as an engineer with a slide rule up until about 1975.
Although I did study computer programming at OU, the big thing about computing at that time is that you punched out computer cards and then ran them through a machine to allow the computer to do the computations. But when you worked for a company, you didn’t really have hands-on use of the computer. That was a big building and you had specialists that handled the cards and gave you printouts.
And then about 1975 or ’74, we began to use terminals where we could actually do programming ourselves and be tied in electronically to the computers. At the same time, in the 70’s, they developed these electronic calculators and they developed programmable calculators where you could input operations so that you didn’t have to push every button every time you wanted to multiply a number. And so about that time, 1975, I went to work for Conoco and we really stopped using the slide rule about that time although we still used the slide rule for about ‘75 to ‘77 in the different courses and short courses that we used.
And then just before up to about 1980, we began to use programmable calculators. At the same time, there were still these computer departments but then you didn’t have access like you do today with the desktop computers. The desktop computer just revolutionized what we could do as engineers because you could both program, you could connect to bigger terminals, you could do computations.
Let me give an example. We did fracturing design when I first joined Conoco. We used a slide rule. We had equations that we ran through with a slide rule that would take about a week to design a fracturing treatment. And then we began to go to the programmable calculator where we could now drop that down to about a day or half a day. And then when the desktop computer came out and we were able to develop easier to use design programs, we could do it in two hours. So I went from one part of my career from one week to do something to two hours. And probably today, it probably still is going to take about two hours. But the programs are much more complex than they were in the ‘70s or ‘80s.
The second thing, of course, is the switch to horizontal drilling that has a tremendous impact. Now, I retired before the full impact of horizontal drilling became evident. They were doing horizontal drilling in the ‘80s and a lot of extended reach drilling.
Nowadays, they can drill a mile or two in a horizontal direction. The significance of this was that in my day, you had a vertical wellbore and you might have 20 feet of perforations and then the oil and gas would flow in to that 20-foot long interval. But now, you’ve got two miles of interval that are exposed to the formation so the tremendous increase in productivity.
Now, when you have just a short wellbore and you have perforations in that wellbore, you’ve got very restricted entry into the wellbore to come to the surface. And it’s very significant how much formation damage affects the flow into the perforations, into the wellbore. But when you’ve got two miles or a mile or two miles, you really don’t have to worry about formation damage as much. So it’s a complete transformation of how we develop oil fields.
Discusses His Work in Drilling Completions, Well Stimulation, Fracturing, and Horizontal Drilling
KERR:
Your expertise is in drilling and completions. That was your area of discipline. That’s correct?
MCLEOD:
Well, it’s really completions.
KERR:
Completions. Okay. So talk to us just generally speaking about completions, drilling and completions as the discipline, as known in the… within the SPE and why is that important, why was that important in your career and why is it important now?
MCLEOD:
Well, I worked in the area of completions and more specifically, in well stimulation. Earlier, I talked about the fact that you had just a short section of wellbore and so it was very easy to plug off the perforations that allowed the flow from the formation sand into the wellbore and up to the surface. And there was so much damage that could happen during drilling, during perforating, during circulating out the fluid in the wellbore. And so with stimulation, you could either remove that damage by dissolving the plugging material with acid or you could fracture the formation by opening up a plane of flow from the formation into the wellbore. And that fracturing bypassed a lot of the early damage that you had during completion. So I focused at first in my work on both acidizing and fracturing.
KERR:
Great. Can you elaborate on your particular contributions to fracturing and horizontal drilling?
MCLEOD:
Well, my contributions really had nothing to do with drilling. I was involved in hydraulic fracturing and acidizing, and this all took place before horizontal drilling became a big factor in the industry. I started out with Phillips Petroleum Company in a training program for a year and then I went into the military service in the army for two years, came back to Phillips and then was assigned to Pauls Valley, Oklahoma where there was a water flood unit that was owned by several oil companies. It was actually the first unitized water flood in Oklahoma.
And so they were allowed to do a lot of different types of oil production and stimulation at that time because they were supported by so many different oil companies in that particular field or that reservoir. So I was involved in both water flood injection, quality control, and remedial acidizing to improve the injectivity of water into the formation. And then on the other end, on the producing wells, a lot of times when the water flood response would reach the well, they would get kind of a little spurt of improved production and then nothing.
And so there was some sort of damage taking place and it was common to go in and do fracturing treatments with sand and oil or sand and gelled acid, something like that to bypass the damage around the wellbore in the well and so stimulate flow into the wellbore. So I was allowed to do different types of fracturing treatments at that time – gelled acid, gelled oil. And it was very empirical at that time. They really didn’t have the design techniques, the understanding of the fracturing process that exists today. And so we would inject, break down the formation with oil or something like that and then start injecting frac sand mixed in with the oil into the formation.
Those treatments were anywhere from 5,000 to 20,000 gallons. But nowadays, it’s over a million gallons and maybe a million pounds of sand to go in to one fracture. So that is a significant change over the years. During that time, there was some move to start using water as a fracturing fluid. Prior to that, the industry and people were afraid of water damaging the formation in some way if you injected a lot of it into the formation and then try to produce oil back. But I think it was Dowell that came up with what they called Riverfrac which was injecting sand into water at a high rate. And so we thought we’d give that a try. And so norm—
KERR:
Let me stop you there. We have to reset it from time to time.
MCLEOD:
Oh, okay.
Discusses Dowell, Riverfrac and Waterfracking
KERR:
Okay. So tell me again about the Riverfrac. So back up just a couple of seconds from where you were talking about Riverfrac and maybe describe that a little because I’ve never heard of that.
MCLEOD:
Okay. Well, River Fracking is a brand name I think used by Dowell at that time. And what they would do, they would bring in a lot of water to a big pond so they could transport a lot of water. And then they would have blenders where they would mix sand into the water and they had high pressure pumps that could really pump at high rates and pick up the water and carry it into the formation in these fractures to place sand way out there. And these fracs were coming about to use more volume, I think up around 50 to 100 thousand gallons at that time, which is still small compared to today. But nowadays, they kind of do similar treatments like that in the shale formations that they’ve developed using water and sand fracturing along these horizontal wellbores.
But back then, that was kind of a first. And also, we’d heard that people were fracturing down the casing so that you could get higher rates. If you go down to tubing, you’re restricted often to 5 to 10 barrels per minute which you could not really pump very much fluid. But then with Riverfracs or Waterfracs, they could get up to 20, 30, 50 barrels per minute. And they could… at that high rate, they really did a better job of transporting sand out into the fracture.
So we did a couple of those. One, we could break down and crack down casing at a safe pressure. The second one we tried, our supervisor said, “We don’t want to go above a certain pressure limit. We’re afraid of breaking down, splitting the casing.” So we didn’t do that one. But that was a procedure that was picked up by the industry later on and they designed casing to be able to take those kind of pressures. And so there was a lot of fracturing down casing later on in the industry.
Discusses His Involvement with the Society of Petroleum Engineers
KERR:
Very interesting. Let’s just switch gears just for a second and talk about your experience with The Society of Petroleum Engineers. Tell us, what did the SPE organization do for you? And then I’ll ask it again but be thinking about what did they do for you in your career? And then after that, we’ll talk briefly about your volunteer work with the SPE and what you were able to give back through them?
MCLEOD:
I first became involved in the SPE at the Colorado School of Mines. It was AIME at that time. So there was no SPE. It was a branch or division of American Institute of Mining and Metallurgical Engineers. So there was a chapter there at OU. I mean, at Colorado School of Mines. And so I participated in that but not to a great extent. I really did not get started with the SPE or its predecessor until I started working for Phillips Petroleum Company in Pauls Valley, Oklahoma.
I became a member of that organization in 1956. And, of course, I started receiving the Journal of Petroleum Technology at that time along with other trade publications like the Oil and Gas Journal and World Oil. And that began to expose me to what was going on in technology in the industry.
I think my training in petroleum engineering up to that point was not that great. It was more in terms of operations and procedures. And there was not a great detailed understanding of how the reservoir performed. And it was more learning the different tools and procedures to complete and bring wells into production. So the SPE began to open my eyes to what was being learned at that time, but it didn’t become very significant until I went to graduate school at The University of Oklahoma.
I was in Pauls Valley, Oklahoma for two years and I was not married at that time and Pauls Valley was 5000 people and I didn’t think I could take another winter in Pauls Valley. So I had served in the army, had access to the GI Bill, so I went back to the University of Oklahoma on the GI Bill. And that’s where really the modern technology at that time really came to fore as I studied graduate courses in petroleum engineering. And also it’s where I wrote and presented my first paper. It was my first graduate work at the University of Oklahoma.
I was doing research on the formation of natural gas hydrates at high pressures. When I say high pressure, that means pressure above 5000 pounds per square inch, from 5000 up to 10,000 pounds per square inch. There were some high-pressure wells that when you got water mixed in with natural gas, it developed a solid substance called a natural gas hydrate, and that could plug off tubing or choke at the wellhead and people had to add things to the gas and to the water to prevent that happening but they needed to know what temperatures and what pressures would cause natural gas hydrates to form.
And so I did research with a high-pressure [unintelligible] mixing natural gas and water under controlled temperature and pressure to see when these white solids would form and when they would melt. It was kind of like ice but instead of ice melting at 32 degrees, natural gas hydrates would melt at 40 or 50 or 60 degrees. So you could have these solids form at temperatures that were at high pressure sort of room temperature type temperatures. But anyway, I presented that research at a meeting in Denver, Colorado, I guess, in 1960 as my first presentation of a paper at an SPE meeting. And that was probably the first annual SPE meeting I ever attended. And I was just blown away at all the information that you could find at an SPE meeting.
Discusses Professional Technical Papers He Has Written for His PhD, SPE, Dowell, and the University of Tulsa. Discusses Innovations and Papers that Resulted from SPE Lecture Series, Short Courses, and Technical Presentations
KERR:
So tell us, Harry, about some of the papers that you authored, what their content was, why it was attractive to you, or why you were asked to, or why you did write the papers? Can you tell us a little bit about that?
MCLEOD:
SPE gave me the opportunity to author papers, primarily when I first was in graduate school. As I said, the study of natural gas hydrates is my first experience. And then it took me so long to complete my Master’s work that I was already halfway into a PhD program before I got that finished. So I was fortunate to get fellowship from Mobil Oil Corporation at that time and continue on toward a PhD. I still worked at natural gas processing under Dr. John Campbell at the University of Oklahoma. So my doctoral work was on the absorption of natural gas liquids from natural gas. There was great interest at that time of different processes of extracting hydrocarbons like butane and propane out of natural gas.
And when it was produced, it was all one continuous phase of gas. But if they cool it down, refrigerate it, they could separate out liquid hydrocarbons like butane and propane. And at that time, butane and propane were worth much more than natural gas. Natural gas was cheap. The industry almost gave it away at that time but they could earn a much better return on the recovery and sale of butane and propane. So they looked at different ways of extracting these hydrocarbons out of a natural gas stream.
The area I was working in was in fixed bed absorption of these liquids out of natural gas. And they would… first things that were used were activated carbon granules. They would flow the natural gas through the carbon and butane and propane and it would be absorbed on to the carbon particles and then a hot stream would come along to desorb the hydrocarbons and then send them into a cool chamber to recover them. And so that was a process of getting even more butane and propane out of a drier natural gas.
So that was what my research was on and I eventually presented a paper on that at the SPE meeting about, I think, 1965. And so that was my second presentation at an annual SPE meeting. I went to work for a division of Exxon for two years after graduate school and got my first really baptism in production research. I left there after two years and went with Dowell.
But Dowell is a service company and the service company’s driving force was to develop new technology and services that they could market to the producing companies. It was part of this marketing process. It was important that the people that work for Dowell, particularly in research, to publish papers and to show that the service company could provide valuable technology and services to the producing industry. That’s still true today, even more so than back then. And so, part of the goal of working in research at Dowell is to develop technology that could be of use to the industry and then to publish that at SPE meetings.
And my first work in Dowell was in overcoming water blocking as a form of restricting production in gas wells, and then later on involved also in acidizing to help clean up acid faster from gas wells in particular. And at that time, we were adding surfactants and then I worked more with adding alcohol like methanol and ethanol to acid to help recover the spent acid faster from particularly low permeability formations.
That resulted in different papers and Dowell would send me to SPE meetings to present those papers over two or three times that that happened. At the same time, it wasn’t all just national meetings. There was a very active SPE chapter in Tulsa, Oklahoma. I think it was called the Golden Trend Chapter at that time but they had monthly meetings at some hotel in Tulsa. And I was involved on the program committee of SPE there. And so I would arrange for speakers to come to our luncheons and present a technical paper.
We had several research labs there in Tulsa, so that was a good resource. Not only were there monthly luncheons, there were also… there were also evening meetings that they had every so often where SPE would provide what we now call distinguished lecturers to come to Tulsa to present a technical talk along with dinner. And so that would expose people in the industrial community there in Tulsa to new technology.
Another thing they started at that time in about the early 70s were these short courses. There was a big interest in continuing education. And about that time, I left Dowell to join the staff of the University of Tulsa. And this is where the short courses were held, there in the facilities at the University of Tulsa. And I was on that program committee providing facilities for the speakers to come in and teach or present their technology.
One of those speakers was Mike Fetkovich with Phillips Petroleum Company. And one good thing the speakers provided was really kind of extended papers or extended write-ups that would go along with their technical presentations. And the one that Mike Fetkovich had a significant impact upon my career, he talked about the production of things that affected flow into a wellbore. He had different techniques of evaluating a well performance. And one idea he had… at that time, they had an interest in what they call non-Darcy flow of gas into a wellbore. Some of us think of that as turbulent flow. Well, it’s really not turbulence but we like to use the term turbulent because turbulence is dramatic. Everybody can understand turbulence with the way that air blows through trees and fluids flow through pipelines. And turbulent flow causes additional pressure drops whether flowing through pipes or flowing through formations.
At that time, they developed some techniques using Forchheimer’s equation to describe this non-Darcy flow into a wellbore. And so with normal, what we call viscous flow or slow flow, you may have a pressure drop of 10 PSI, whereas non-Darcy flow is high speed. You maybe have 50 PSI pressure drops. They would observe this in the field that they had these exceptional pressure drops that restricted flow into the wellbore and a gas well. But they really couldn’t define it very well.
And Mike pointed out that the way that they looked at the wellbore was like it was just an open hole and that you had flow coming in to this open hole that was maybe eight inches in diameter. But actually, flow didn’t flow right into an open hole. You had casing there and you had perforations. The way that people looked at a perforated gas well at that time was kind of controlled by what Muskat had presented. And he said that if you had four shots per foot of perforations that were six inches in length, that that’s essentially the same as an open-hole production capability.
And Mike said that anyway, when they used the Forchheimer’s equation to describe non-Darcy flow into a wellbore, it just couldn’t account for the exceptional pressure drops that they saw and said the predictions that they had using Forchheimer’s equation into an open wellbore were a certain number but what they observed in the field was like a hundred times more than what they observed. Then that kind of stuck with me and that stayed for several years. At that time, I was teaching a Well-Completion Course at the University of Texas… University of Tulsa. I was very involved in looking at the effect of perforations and the case toll on well performance. And so there were quite a few papers that were coming out that time looking at what does a perforation look like. They tested perforating and developed the fact that when they use a shape charge which is like the old bazooka in World War II, that’s where that came from where there was a focused shape charge that blew a hole through the casing and the cement and into the formation. And there was work being done at that time to evaluate how gas or oil can flow into those perforations and then into the wellbore. And they realized that there was… the force of that perforation created a zone around the perforated hole that was really crushed formation sand and that restricted flow into the wellbore.
And so because of that information, the industry developed perforating guns that would shoot the well underbalanced. In other words, the pressure in the wellbore would be 2000 PSI below the formation pressure. And so when they shoot these holes, the gas pressure would flow forcefully into the wellbore and clean up that crushed sand. And so that worked out to be very significant later on in my career when I left the University of Tulsa and went to Conoco. The first effort was in acidizing and looking at what kind of damage acidizing removed. Eventually, we began to focus on the effect of perforations on formation damage and well performance.
And because of the call I received from an engineer in Conoco that was having problems with a perforated well… he was experiencing a real high pressure drop into the wellbore right around the wellbore. In other words, it was restricted by what was going on in perforations. And so I asked him to send me some information about it. At that time, we were very much influenced by the work of Kermit Brown and Joe Mach on Nodal Analysis which is a way of evaluating well performance using wellhead pressures and flow rates.
Now, I had just returned from a short course that Joe Mach had taught Conoco personnel. And at that time, the way they used Nodal Analysis was they were defining a pressure drop into the wellbore in gravel packed wells that the gas had to flow into perforations. The perforations were filled with gravel and that high velocity flow through the gravel pack perforation gave an exceptional pressure drop. And especially if you had foreign material and they’re blocking the flow, you get really high pressure drops and it would restrict the production of the gas well.
So they developed this Nodal Analysis technique to calculate the pressure drop through the gravel pack perforations. They would calculate the pressure drop from the reservoir limit into the wellbore, the pressure drop across the gravel pack perforations into the wellbore. And then they had techniques to calculate the pressure drop from the bottom of the wellbore up to the surface where you had a pressure gauge at the surface to give you that information.
So with a knowledge of the reservoir pressure and knowledge of the pressure at the surface, the information of the gas flow rate, they could show where the pressure drops took place throughout this whole system. But they didn’t have any way to account for a pressure drop in the perforations in a gas well at that time and that question came up in the short course we were attending. So fortunately, this call that I received from the engineer stimulated thought about what was going on.
So the previous information from Mike Fetkovich back at the University of Tulsa in the 70s, my work with teaching perforating and courses there, and the fact that they were able to describe non-Darcy flow through gravel pack perforations, it all came together and then I realized the key to what Fetkovich had said. He said the calculated non-Darcy pressure drop at that time was a hundred times… the actual flow pressure drop was a hundred times more than what the radial use if the Forchheimer equation predicted. Well, it became clear that they had always been assuming the non-Darcy flow into an open wellbore.
But actually, there was flow into perforations. The inflow area in a wellbore is a hundred times… I mean, it’s 10 times more than the surface area of the perforation. And the thing about non-Darcy flow, the effect is an order of magnitude more. So instead of just 10 times more pressure drop, you get a hundred times more pressure drop. And that matched exactly what Fetkovich had observed years before. So I had used radial flow equations and non-Darcy flow equations into a perforation to predict the performance of perforated gas wells. And that just completely changed the way that we go about designing perforating and completion of natural gas wells at that time.
Discusses in More Detail His Involvement in SPE
KERR:
So Harry, go ahead and tell us a little bit about this next segment of your involvement with SPE.
MCLEOD:
Okay. I became more involved in SPE during the time I was on the staff at the University Of Oklahoma… University of Tulsa. And when I was teaching well completion and stimulation at the University Of Tulsa, SPE came out with a new meeting. They called it the Formation Damage Control Symposium that was first held in New Orleans, Louisiana in 1973.
And I was fortunate enough to be sent there by the dean of engineering at the University Of Tulsa. And that was in my area of expertise at that time in well stimulation and well completion design. And that was a transformative meeting for me because it brought together all of these experts in well completion and well stimulation in the industry for the first time. And I met a lot of what I call the leaders of that time.
I was particularly impressed by Roland Krueger and George Maly with Union Oil Company. They were very active in research and gravel packing and well completion and stimulation and control of formation damage. I was able to learn from them, particularly from some of the work that George Maly was doing and quality control on site and well completion operations.
Some of the work that he did, I was able to incorporate in improving the quality control and acidizing operations. Also, I met people like John Gidley with Exxon, Wally Penberthy with Exxon, Al Abrams with Shell Development Company. There were quite a few people. And the great thing about it was I would never have the opportunity to visit with these people particularly ideas about what was going on in certain oil field operations. So that just expanded my knowledge and view of what was possible in developing technology in the industry, particularly in well completion and stimulation. And I continued to attend that symposium on formation damage control throughout my career and presented several papers at that symposium which usually was held in Lafayette, Louisiana every two years.
KERR:
Very good. I like the way you elaborated on that. So you had a long career?
MCLEOD:
Yes.
Discusses His Crowning Achievements in His Career
KERR:
Can you pinpoint one or maybe two things that you feel were maybe a crowning achievement for yourself?
MCLEOD:
Well, the most significant achievement, I think, I made was when I spoke about using the equations for non-Darcy flow into a perforation and evaluating gas well performance and also in designing perforated completions to achieve maximum productivity. A lot of that really came about because my prior primary effort at first at Conoco was in improving acid stimulation, both acid fracturing and matrix acidizing, matrix acidizing being what we call wellbore cleanup to inject acid into the wellbore dissolving plugging particles to reduce the pressure drop of flow into the wellbore during production.
And it became clear that when you have a limited inflow into the wellbore through just short vertical sections and through tiny perforations into the wellbore, that the controlling factor was the kind of damage or plugging you had around these perforations. One way to treat that was with acidizing and you had to be able to calculate or determine the performance of flow into these perforations in order to successfully plan acidizing treatments.
And a lot of times before this period of time, acidizing was kind of a formula. In other words, if a well kind of was not performing well, people would say, “Well, give it a shot of acid to dissolve whatever was restricting flow.” And that was about it. It was empirical. It was trial and failure. And so they’d experiment with different acid types and different concentrations and different volumes of acid and look at it before and after. A lot of times, acid would improve production but it may not last very long.
Matrix acidizing stimulated thought about what was causing it to succeed and what was causing it to fail. John Gidley wrote a paper about an extensive study of acid results where he said that only about 56% of matrix acid treatments resulted in success, success being defined by the fact that the increased production would pay for the acidizing treatment which is really not that great a success. What you really want is to improve production and have sustained production increase.
So that was a question in the industry, is what can we do to improve matrix acidizing? And it was particularly important in the Gulf Coast wells where most of the wells were gravel packed. And when you gravel pack wells, you’re trying to keep formation sand which is weak from flowing into the wellbore and loading up the well and stopping production. So gravel packing has been used a long time. It was used first probably in water wells where you drill shallow sands and you had to hold the sand back so that water could flow into it.
So the oil industry used that same technique of using metal screens, placing fine gravel around the screens to hold back formation sand but yet let oil and gas flow into the wellbore. Then later on, they wanted to do gravel packing in several different zones. And so you had to case the well, you had to perforate the well, and then you had to pump gravel into those perforations to allow fluid to flow without sand flowing.
So when that happens as you started doing these cased hole gravel packs, you had still a lot of restriction of flow into the wellbore through those gravel pack perforations. And that’s where they used a lot of matrix acidizing to go in and clean up the plugging material in those gravel packed perforations. There was a theory at that time that a lot of the decrease in production through those gravel packed perforations was due to fine movement through the formation into the gravel and it would plug up the gravel.
That never made sense to me. It seemed like if fine particles could flow through the formation which had smaller pores and get into the gravel, it ought to flow right on through the gravel and up out of the well. So this control of fine particle movements didn’t make sense. And it finally dawned on me that there was something else blocking formation flow into gravel packed perforations. We did a field study with a young engineer in Lafayette where we studied completion procedures and well performance after gravel packing. And we found out where wells were perforated and then flowed prior to gravel packing that they had better performance. And so I went back to an earlier understanding of perforations and realized that when you perforate formation sand that’s unconsolidated, you’re still going to crush the formation sand around this perforated hole.
The gravel packing analysis was significant when we first realized that it was the crushed formation sand that was moving into the gravel that restricted production. And once this crushed formation sand moved into the gravel, the pore sizes then were smaller, smaller such that then any fine particles coming out of the formation would be trapped in there. So fine movement and plugging could be a problem but only because the crushed sand is a result of perforating that invaded the gravel.
We mentioned that in one of our papers at Mike Minarovic and I wrote and presented. And then about six months to a year later, Schlumberger had carried on a joint project with Shell that actually did a laboratory study showing that if you didn’t remove that crushed formation sand, that that crushed formation sand would invade and plug off the gravel perforations, so that changed the way people looked at gravel packing.
First of all, they realized that you had to get that crushed formation sand out of the perforations before you put gravel into the perforations to stabilize the hole there. And so people began to use these large case, tubing conveyed perforating guns where you could perforate these formations. There was enough competency there that a lot of these wells you could underbalance and flow that crushed sand out. And then when you went into the wellbore and injected gravel, then you didn’t have that impediment to flow that you had before.
And not only that, they began to see there was so much restriction still flowing in to those perforations, that if they could frac by that wellbore and do a frac pack… And Bob Hannah with BP was the one that developed that. We actually… people knew that if you could do that, that would change things. We actually did a frac pack at Conoco early on, I think before Bob actually presented his paper. Our results were not as successful.
So he did a technique that changed the way that a lot of high rate gravel packs perform with his improved design and operation. Also, later on, horizontal wells with open-hole gravel packs eliminated the problem of being concerned about formation damage in gravel pack perforations. So going to high angle wells and running screens and open wellbore completions were a significant move forward.
Discusses His Thought Process When Solving Engineering Problems
FLICK:
Harry, you have encyclopedic knowledge on stuff and you work a lot in theoretical as well as realistic, real-world stuff. What’s your thought process? Do you visualize this in your mind? Do you make a lot of sketches? How do you… what’s your creative process?
MCLEOD:
Yeah. The way I go about thinking about problems and petroleum production involves imagination and visualizing flow. At the University of Oklahoma, there was some work done, I think, by Chenevert. And he actually did flow of oil and gas through visual cells where you had sand packed between glass plates or plastic plates and flowing oil and gas through there. So then you could see how oil and gas flowed as it flowed through a porous media and also thin sections of just taking a slice of a formation and looking at the pore spaces and what was in there, having pictures of what you’re dealing with. And that had an impact on looking at acidizing because in previous times of acidizing sandstones, it’s just going through a nice, clean sand. But sand is composed of a lot of different minerals and acid reacts with those minerals. And I would visualize acid flowing through pores, dissolving particles. And also, I knew from the lab that some of these reactions would cause precipitates that would plug.
And so my way of thinking was to try to imagine I was in that pore space going along with the acid. Also seeing how fluids travel down tubing to the formation. And I could see that there were places where acid would pick up contaminates on the way from the surface to the formation. And so you could… I could see acid picking up rust and pipe dope and other things. It would carry down to the formation, start plugging it up.
So this process of visualization really helped me. Not only did I use visualization but I had a flow equation in the industry that could define that when you flow through formation into a perforation, you could calculate the pressure drop that was required to give you a certain flow rate. So it’s a combination of visualization and then using appropriate equations to describe flow that was the main part of my thinking process.
Discusses His Contributions to Artificial Lift and Hydraulic Fracturing
KERR:
So talk to us about your particular contributions in artificial lift and hydraulic fracturing.
MCLEOD:
I’ve worked with artificial lift when I was at the unit in Oklahoma with Philips and not very much but I was exposed to gas lifting, hydraulic pumps, sucker rod pumping, REDA, electric pumps, and things like that so that I knew there were various ways of taking oil that flowed into the wellbore and lifting it to the surface.
After graduate school, when I went to work with Exxon, one of my first assignments was looking at the artificial lifting of heavy oil. And the problem when you have really viscous oil, it’s so difficult to pump that up into the wellbore because of the high friction losses of pumping very viscous oil. And so some of my work involved is there a way to reduce that friction loss of flow of heavy crude up and through the tubing. One thing that kind of arrived… came to me out of the teaching I did at OU in fluid flow was that if you have a low viscosity fluid that you could put around the viscous oil, that you would have less friction of flow up the tubing.
So I developed an analysis of that which I never was able to carry beyond that because I’ve switched to another project but that did have some influence on the development of using viscous oil with an annular water ring that Othar Kiel developed at Exxon, and we shared an office together. One interesting thing about the oil industry is you learn and you influence one another and ideas just percolate in your mind from all the things that people have shared over the years. So even though the work I did didn’t result in any real contribution, it influenced some work that became commercially successful. There’s no paper ever presented about that but it just shows that different technologies influence other technologies just through the scientific processes that occur.
KERR:
So Harry, tell us about your experience and your contribution in hydraulic fracturing?
MCLEOD:
I was very involved in hydraulic fracturing when I first joined Conoco in Houston and I and others were instrumental in teaching the hydraulic fracturing school. About this time, the industry began to work using cross-linked fracturing fluids to get really viscous fluid to create wider fractures. The more viscous the fluid, the wider the fractures were because you had higher pressures in fluid flow down the fractures.
And this really tied back to the earlier work and using viscous oil in fracturing when I was working with Othar Kiel. But now, they’re using water-based fluids that have polymers that are cross linked, viscosified with cross linkers. And those did a great job at transporting sand or proppant out into the fracture. But because they had such efficient transport, the sand would start concentrating because fluid would leak off into the formation. When you get up to a certain concentration of about 20 pounds per gallon in the fracture, it just starts slowing down and eventually stops and screens out.
And we were having that difficulty in Conoco down at South Texas and we really couldn’t figure out what to do. Fortunately, one of our engineers came up with a real novel technique. Dennis Kaspereit came out with a way of modeling this flow and leak off which is kind of a percent rate of loss. He used a technique from financial evaluation to describe fluid flow carrying sand in a fracture. And he came up with some equations and then we took the equations that he developed and worked with them and changed them around to where we could take treatments where the sand screened out and the treatment stopped and we could back out the fluid loss coefficient from the time of screen out. And then we found out that our fluid loss was higher than what people expected from laboratory experiments of fluid loss additives and the fluid loss of cross-link formations.
And then another engineer, Oz Osborne, and I worked together to see what would cause these high fluid loss coefficients and then it became clear that in high temperatures and shear, that the cross linkers and the fluids were breaking down. So we partnered with Western at that time to study the effect of high temperatures. We were able to modify the fluids to change the fluid loss additives that we were using.
At that time, people felt, well, cross-link fluids have such low fluid loss, you don’t need solid particulate fluid loss additives added. But we found out we had to start taking fine silica of solid particulate to control leak off from these fluids. And then with these equations that Kaspereit developed, we could better design treatments to where we knew exactly how the sand would concentrate as it moved out into the fracture and we could design the volumes and the pads that went ahead of the sand-laden fluid and prevent sand-out.
So in that area, we were experiencing about 90% screen-out of fracturing treatments using those cross-link fluids and we were able to reduce that to 5%. So that was a significant advance. It wasn’t just the design, it was also the fact that we went out on site and monitored the mixing of sand and fluid and also the quality of the water, the pH of the water, the control of cross linking. And we had people actually stationed at the blender which is the heart of the fracturing operation where you add the gelling agents and the sand to blend this up.
And if you don’t monitor the sand, you get a spike in concentration, that could screen you out too soon. So we developed quality control techniques on site that gave us a much better, smoother operation coupled with the design then we significantly improve the success of fracturing treatments in South Texas.
KERR:
What helps you get up in the morning, go to work every day and makes your job fun? And do you have any stories that the audience might kind of help us get to know you a little bit better, who you are, what makes you tick type of thing?
MCLEOD:
The thing that motivated me is that I just love ideas. I love to understand processes that go on. I love a mystery. I love mystery books. And so there’s a lot of things since I was going in the industry that are mysteries about why wells behaved a certain way and this was the fun of being involved with other people in SPE, in symposiums, and forums. Forums came along where you could get together with people and discuss ideas and say why is it that things act a certain way and that’s very stimulating. I’d go to these forums and I’d get so high just from sharing the ideas that after it was over, I would have a period of depression as I came down off this high of being attracted to ideas and thoughts, so…
Discusses Fond Memories He Has of Working in the Petroleum Engineering Industry
KERR:
Do you remember a moment or two, aside from the symposiums and the interacting with likeminded folks, was there anything that the audience would like to learn that was just like fun? I mean, like a fun adventure within your career that you have a fond memory of?
MCLEOD:
Well, one of my fondest memories or say many fond memories was travelling to different divisions of Conoco interacting with engineers on the site. I was able to see sights perhaps that I wouldn’t see on my own. Going offshore was exciting for me, to get on the first tension-leg platform in the Gulf of Mexico and experiencing the movement of that floating platform that was anchored by steel tubes down to the bottom, flying out in planes and landing… or helicopters to land on the deck of these platforms out there, travelling overseas.
The Society of Petroleum Engineers sent me overseas a couple of different times as a distinguished lecturer. And so the most amazing thing was to see the cultures and how other people lived and how they worked. In Dubai, we were there at the Dubai Petroleum Camp which was a subsidiary of Conoco. We were teaching a school there. And next door, there was a large group of Pakistani and Indian laborers working on building a water tower.
And here in the States, everything was so mechanized with cranes and everything else and there they had just a small cement mixer. And they would mix it up and carry it up in buckets and dump it in forms on top. It’s very slow but I guess they didn’t pay the people very much but it amazed me the finished product was every bit as good as what was done in the States with cranes and pumps. And we do it so fast and efficiently here but they could compete there with simple techniques and yet come up with a very fine product at the end.
So that was fascinating to observe. I got into trouble in Dubai. One of the secretaries there was a devout Muslim woman and she was so very helpful to us in preparing for the school. And I had been back in the States watching Kojak on a TV film and he had a habit of calling people sweetheart when they did a really good job. And I told this lady, “You’re a real sweetheart,” and she thought… she was really insulted. She thought that I meant she was my lover or something and so words don’t mean the same thing around the world. You got to be careful how you use certain idioms.
KERR:
That’s wonderful.
MCLEOD:
In developing technology, a real important process is how people with different disciplines come together and share ideas that affect the other’s work. I had a wonderful opportunity of working in different areas where I interacted with chemists and geologists and reservoir engineers and drillers. And so sharing their knowledge across these technical lines were so significant particularly in acidizing. I had to understand the petrology and mineralogy that came from the geologist. I had to understand the chemistry that came from people that worked with the chemistry of acidizing. I had to understand the way to describe flow that came from people that were reservoir engineers. When you start transferring all that and trying to understand how these fit together, you are able to come up with new ways of doing things and understanding things that were mysteries before.
Discusses the Achievements of Which He is Most Proud
KERR:
That’s really good. Okay. And you also wanted to say something, Harry, about the aspect of your career that you have a little pride in. What’s one of your… we talked about a crowning achievement a minute ago but what makes you the most proud about what you’ve done?
MCLEOD:
The things I’m most proud of is how I worked with younger engineers, as I developed expertise and I was given more opportunity to work with younger engineers and they brought so much enthusiasm and interest into working together. The first one really to do that was Michael Minarovic with our Lafayette office and we had dinner one time. We were talking about a problem. We were trying to work together. And he said if I had something come up that I could involve him in working on a project or study together, he’d really like to do that. And that really encouraged me. I was at the twilight of my career and so we did. I was interested in doing some field studies where he could do the on-ground work to gather information and we could work together in analyzing it. And this was really where we came up with the knowledge of how crushed sand around perforations really impeded the success of gravel packing. And that was a tremendous moment.
And that followed up with another young engineer, Mark Passion to do a similar study on oil well, gravel pack completions and oil wells. And we developed some technology of doing more thorough study of the data that was in normal well completion operations where you could take that data and understand what was happening to the formation and to the completion through each stage of the completion process and add new information to how we go about doing these operations.
And besides, the young engineers also had the opportunity to work with older, experienced engineers. One of the most satisfying times was when I worked with Oz Osborne who I had known at Dowell when I worked there and he joined our group in Conoco. And Oz had a lot of practical information and knowledge. He never had presented a paper but he had a lot to share. And I encouraged him in writing a paper with me and presenting it for the first time at an SPE meeting. And he did a beautiful job and that was really great.
KERR:
Fantastic. Thanks.
