Chapter 1 - Workover Introduction

1.01 Lesson 1.01: Workover Introduction - Part 1 (22 min.) Sample Lesson
1.02 Workover Introduction - Part 2 (25 min.) Quiz: 1.02 Workover Introduction - Part 2

Chapter 2 - Obstructions to Production

2.01 Obstructions to Production - Part 1 (17 min.)
2.02 Obstructions to Production - Part 2 (21 min.)

Chapter 3 - Influence of Workovers on Surface Facilities

3.01 Influence of Workovers on Surface Facilities - Part 1 (26 min.)
3.02 Influence of Workovers on Surface Facilities - Part 2 (14 min.)
3.03 Influence of Workovers on Surface Facilities - Part 3 (22 min.) Quiz: 3.03 Influence of Workovers on Surface Facilities - Part 3

Chapter 4 - Fracture Driven Interactions: Causes and Potential Controls

4.01 FDI: Causes and Potential Controls - Part 1 (19 min.)
4.02 FDI: Causes and Potential Controls - Part 2 (26 min.)

Chapter 5 - Paraffin, Asphaltenes and Scales

5.01 Paraffin, Asphaltenes and Scales - Part 1 (20 min.)
5.02 Paraffin, Asphaltenes and Scales - Part 2 (15 min.)
5.03 Paraffin, Asphaltenes and Scales - Part 3 (19 min.)

Chapter 6 - Capillary and Wettability Effects

6.01 Capillary and Wettability Effects - Part 1 (14 min.)
6.02 Capillary and Wettability Effects - Part 2 (16 min.)

Well Production & Productivity / Chapter 1 - Workover Introduction

Lesson 1.01 Lesson 1.01: Workover Introduction - Part 1

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Transcript

01. Lesson 1.01: Workover Introduction - Part 1

This is the introduction to the workovers and recompletions course.

02. Quick View Workover Course Abstract

What we're going to try to do here just in a real quick overview is introduce some of the common topics that you run into on workovers. Look at the well integrity of the well that you're going to be working on and determine if it can receive a workover safely. The training here is field-based. It comes from experiences of a great many people that I have met and talked with over the 50 years that I've been in the business. And what we're going to try to do here is to look at some of the better practices in workovers. The diagnostics section, the evaluation, and of course selecting a method of workovers from a great many options here. And this is one thing I want to stress that there are many ways to do most workovers. This will show a few of these, but it's up to you to decide what is the best approach based on the economics, the potential left in the well, the risk that you will involve opening the well to do a workover, and of course, looking at the success rate of some of the workovers that we've been able to monitor. Now, some of the safety topics are going to be addressed here, but we leave that to the companies. The companies should set their own standards and that is what you have to adhere to.

03. Wellwork (Workovers)

In-well work; this is part of the base management of production. The wellwork itself can help you achieve a 15 - 50% improvement in the total recovery of this well. Now, what we're doing is we're looking for candidates for workovers that maybe have not performed up to expectation, have had unexplained drops in production that is not seen in the normal decline. And also, we're looking for ways where new technologies might be applied to get better production or a longer life out of the well. So what we're going to do here is try to look for support information, and that really remains the better way of spotting potential additions to production. But, understand here that effective wellwork really requires good diagnostics and planning. And then of course, you move to another sector. You've got to have people with the skill set to do this workover and you need the proper equipment that is right for your area of operation.

04. Quick Quiz: What is the “Best” workover approach?

Now, a quick quiz. Standing by the wellhead, how do you find what's going on? I mean, you're 1 - 5 miles away from the area you work with, i.e. the formation flowing into the wellbore. And your senses are a little bit limited here because you can't see it, you can't hear it, and you can't touch it and you really don't want to smell or taste it. So what have you left? This is the time when you want to form a mental image of what is happening downhole and try to get an idea of how do I prove it out or disprove it? And then, how bad is this situation? Is it worth the economics of a workover? The quiz here is really not that hard to solve.

05. Quiz Comment

The suggestion that I would give you is that you take every bit of information that you can get from as much experience as you can latch on to by talking to other people and learning from both their successes and their mistakes. What you need to try to find is what is causing the problem? The problem may be obvious, but what is causing it? That may be something else. And that's what needs to be solved before you get into the workover itself. Take the time and run a few tests. You may have to actually run welltests because laboratory tests, as good as they might be, are really not in the same conditions that you will find downhole. Now, if you see the problem mentally here, prove it out before you get too deep into the workover planning. And this may take, as I said, a couple of different tests. We'll cover a little bit of those as we go through this.

06. Introduction to Workovers

Now, let's put this on a little 4 position grid here. #1) what's the problem? Is it loss of production? Well, was it a quick loss? Loss over time? Did the fluid type change? And then you need to confirm what you think is the problem identity.
Then you look for what is causing the problem and this is a little bit more diagnostics. Some of this information is available in the well file if you just really go through it and think about it and compare it to other wells. Other information can come from logging runs or maybe going in with a slickline operation and determining if they're fill in the well, something of this nature.
So after you figure out what is the problem, then try to figure out what's the method to correct the problem. In other words, you've got to find the cause and then you've got to figure out a way to prevent that cause from causing more problems down the road.
Then you get to the final part that you think is fixing the problem. What are the methods? What are the skills? What are the options? What's the economics? Can you get on the pad? Is there enough room for all the equipment? What is the weather like? What's the success rate of a particular workover? All of these are important and you want to understand and learn from these what to do and of course, what not to do.

07. Steps in a Workover

And this rotates on around and it's just a feedback loop into how to design a better well.

08. Timing - Asset Value Opportunity

Now, changing things in production may have a benefit and may not. But let's look at what you are getting for the money you're spending. Simple plot here: on the y-axis, you have an opportunity to maximize the value that you're putting into this. On the x-axis, it's the impact areas. In the design, if you get that design perfect the first time, then you've had great impact by design. But at the development point, that ends and you're trying to produce that well and suddenly you're finding that it's not producing the way we thought it would or you're looking at across the fence at another operator in the field and seeing that their wells are a lot better than ours with similar reservoirs. At this point, what you're going to do or what you need to do here is look at what will fix the well.

09. Timing - Asset Value Opportunity - 2

And then, recognize it very quickly and that way you can really kick this back into the impact by design because you're modifying it at an early point in the well's production. If you let that well go for a long period of time, you haven't recovered much, but your pressure has dropped, you're losing a lot of money that way. So you need to do a workover early on. And I'll give you a clue here. Your best wells often make your best candidates for the workovers. This won't be all the time so you need to look for the problem and then look for the cause.

10. Expenditures in Successful Well Work Program

Economics does have a big impact on what we're doing here. And so successful work programs need all these required actions that you are talking about in the design and in the application. But look at the expenses that you're putting in.Normally, and this is out of an SPE paper that looked at a lot of different cost structures in the workovers, surveillance is around 13%. That means you're going in after data. Check the well integrity because that is an important part, especially if you're dealing with old wells and you think that you want to review or maybe even refracture some of these wells. Make sure that well will tolerate the fracturing pressures, the rates, and the erosion that will take place. The repair itself, that may be only a small part of the total expenditure here. So, if you're going to try to get more production, understand what you're going to spend.Leste O. Aihevba, "Well Intervention Management in Oman Fields", IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition, Kuala Lumpur, Malaysia, Sept. 2004

11. Field-Specific Scorpion Plot

Now, let's look at a couple of pie shaped distributions here of highly economic to uneconomic. Now, this is a paper from BP. And what they did is they took an area "look back" at the economics. And the economics has to be the money you spent and the production that was generated. That's what you're comparing. Look at those and this is going to give you a pretty good clue as to what will work in almost any field.
Look at the highly economic. What's the biggest impact of a workover there? It's artificial lift improvement. Now, optimization of artificial lift is one of the first things you need to look at. Any time you get into a situation where you think that well isn't producing right, look at the lift first. Then, look at the other components. Are there obstructions in the well? Are there obstructions in the formation? Do you have enough access from the formation to the wellbore itself? All of these have to enter into this.
Look down at the uneconomic; and we're jumping through this a little fast, but if you look at the uneconomical one, what was the most uneconomic workover that was typical in this area? And it's trying to control the water.Water influx is very difficult to control without losing oil production.

12. Scorpion Plot – Production Gain vs. Cost

Now, we're going to take a shortcut on all of these things and actually look at what's called a scorpion plot. Again, paper from BP on this one. And if you look at the highly economic jobs, you're not going to be spending much money, but you're getting a very good production increase. The y-axis is what you're spending. The x-axis is cumulative production gain, OK. Now, as you move out, you'll see that the uneconomic jobs are falling in a part of the graph. Go to the top right-hand corner of that graph and here is a less well (uneconomic) job, all right. Look at that one and in some cases, they were spending a lot of money and getting nothing in return or the production was actually dropping. And that's one of the things you have to consider with a workover, is that you could actually damage the well. So plan it out carefully here. And when that curve curls back, hence the name Scorpion plot, that's where you get stung.

13. Grouping Common Well Work

Now, grouping common wellwork together. And this is just some of the common things that you'll see in wellwork. And we're going to cover these and many more subjects going through this training progresses. But I've put some red flags in here, as mentioned in that first slide. This is where you can see problems coming or there's been a lot of mistakes in this area, one of which is water control. You have to understand how this works. We'll look at more of this when we get into conformance. But you can group some of these processes or jobs together. Maybe you're doing a well clean out. You want to do a re-perforating, maybe an acidization, you can group these together, you cut mobilization costs and in many cases you can get a break on pricing as well. Now, if you have a whole group of wells in the same field that need this type of a workover and it's economic to do so, you might launch a workover campaign based on a certain set of workovers that you're going to do and the processes that go into that. So keep in mind here, there's a lot of ways to save money on doing workovers.

14. Quick Quiz

Now, let me ask a quick little question here. Which is a better workover candidate? A low productivity well, maybe 10 bbls / day with a skin of 100, tremendous skin. Or a high productivity well that is producing 1,000 bbls / day, but has a skin of 4, a very low skin. But when you really look at this thing and put it through the equations to calculate production, when there's a skin factor involved, you're going to find out that you're going to get a lot more production out of that high productivity well. And this leads back to your best wells are typically your best workover candidates. Make sure that you've gotten those skins down as low as you can get because, at this point, you could probably (if you could get this down near 0 or, maybe 1 or even negative) you could get anywhere from a 30 or 40% increase in this to almost a doubling of this in terms of production. So keep that in mind as you work your way through.

15. Quick Quiz - Which is a better workover candidate?

This is an old graph that came from sand control, but it's a range of skin factors that they were seeing and how that affected the productivity factor. Now, if you look at that skin of 4 in there and then you can reduce that to maybe 1 or even to 0, you're talking about, in the 1,000 bbl / day well, you're talking about a 35 - 45% increase. You'll never get that out of that old well, even if you could remove all of the skin from there, it just isn't possible. So keep that in mind.

16. Obstacles to a Successful Workover?

Now, what are your obstacles? Well, one is lack of information. You can't go into a well operation like a workover blindly and say, well, we'll do an acid job just to see if it works. There's been papers on this that say only 30% of the acid jobs done meet the expectations for increasing production.Acidizing is a decent improvement when you have an obstruction near the wellbore and it's acid soluble. Now, in other cases, it's not going to be that good and it can actually damage both the wellbore and the formation in some cases if you don't know what you're dealing with. Learn what your reservoir will respond to and when it will respond negatively to a process. And there are formations that if you put water or acid on them, the permeability actually goes down. So know your formation.
Now is the required risk here? Is there an assessment? And is it possible to do this job with a lower risk by choosing another operation or a method of doing the workover? Balance that out.
So what are the economics? That's a big one. And you go back to how much you spent and how much production you got back? Which, of course, is going to take into account the value of the oil or gas that you're actually producing that's an incremental increase.
So, make sure your barriers are OK. We'll talk about well integrity and barriers a little bit later.
Can you bundle it with other work?
Can you access the area? And we'll have some information on this as well. But remember, you're hauling big equipment there. Are your roads weight limited or size limited? Are your bridges limited in some manner? What's the neighborhood feelings there about having all that truck traffic in the middle of a suburban area? Not too welcome in many cases, unless you prepare people for that and really explain this. Maybe you have an open house during the workover.
Now, the big one here is access to people who have the skill set and the equipment that can do this job in the best and the safest. Both those things are going to increase your value and decrease your risk. So have that really researched out before you get into the program itself?

17. How a Well Flows - What are the restrictions?

Now, how does a well flow? What are the restrictions? You can have natural flow. You can have artificial lift. And when the pressure declines in these wells, you might have some unloading problems here. So all of these qualify as workovers.

18. The Flow Equation

Now, if you look at the inflow equation, it's the height, it's the radius, it's the contact of the differential pressure. Viscosity comes into play as well. The outflow, however, once you've got it in the wellbore, is pretty well the thing that you can do something about. And the diameter of the flow path. Can you use a bigger tubing? Can you use a smaller tubing? Because you've got to unload it. Remember, artificial lift is the first thing you want to look at.

19. The Factors Controlling Flow

So with that in mind then, the factors to control flow is you increase the pressure differential between the reservoir and the sales line, that means that you're cutting out the things that serve as pressure drops. Look at your major pressure drops and try to eliminate them and then keep the velocities in each section above the critical velocity - that is, you're being able to move all the liquid out that you're producing rather than have them continuously build up a hydrostatic head and hold the back pressure on the formation.
Waddell, Kevin K. "Determining the risk in applying multilateral technology: gaining a better understanding." In SPE Hydrocarbon Economics and Evaluation Symposium. OnePetro, 1999.Leste O. Aihevba, "Well Intervention Management in Oman Fields", IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition, Kuala Lumpur, Malaysia, Sept. 2004