Chapter 1 - PVT & Fluids

1.01 Introduction (9 min.) Sample Lesson
1.02 PVT for the first time? (5 min.)
1.03 Reservoir Fluid Classification (12 min.)
1.04 PVT Models - EOS Models (13 min.)
1.05 Black Oil PVT (15 min.)
1.06 In-place Volumes (8 min.)
1.07 Reservoir Fluid Classification - Revisited (5 min.) Quiz: 1.07 Reservoir Fluid Classification - Revisited

Chapter 2 - Bottomhole Pressure Calculations

2.01 Bottomhole Pressures (7 min.)
2.02 Well Performance 101 (8 min.) Quiz: 2.02 Well Performance 101

Chapter 3 - Multiphase FMB

3.01 Multiphase Flowing Material Balance - Theory (12 min.)
3.02 Multiphase Flowing Material Balance - Practice (11 min.) Quiz: 3.02 Multiphase Flowing Material Balance - Practice

Chapter 4 - Analytical & Numerical RTA

4.01 RTA (11 min.)
4.02 Analytical RTA (15 min.)
4.03 Numerical RTA (4 min.)
4.04 Numerical RTA - Key Concepts & Theory (22 min.)
4.05 RTA - Analytical vs. Numerical LFPs (5 min.) Quiz: 4.05 RTA - Analytical vs. Numerical LFPs

Chapter 5 - Simulation & Forecast

5.01 Numerical Model - Reservoir Simulation & Forecasting (15 min.)
5.02 Eagle Ford Workflow Example (12 min.)
5.03 Workflow in Practice (21 min.)
5.04 Sensitivities (3 min.)

Multiphase RTA in Tight Unconventionals / Chapter 1 - PVT & Fluids

Lesson 1.01 Introduction

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Transcript

01. Lesson 1.01: Introduction 02. A little bit about myself 03. I believe in a practical approach 04. Recommended Preparation 05. Role Models in Rate Transient Analysis (RTA)?06. Rate Transient Analysis (RTA) 101 07. It is better to be roughly right...08. Unconventional Reservoir Workflow

01. Lesson 1.01: Introduction

Hey, my name is Mathias Carlsen. I'm super excited about being here today to teach a course for SAGA Wisdom on Multiphase RTA and more specifically, how PVT impacts RTA in tight unconventionals specifically.
Some of you might know me from whitson, where I've been working in the last 5 - 6 years, mainly helping clients in North America on these shale-related assets. But also now the last few years, we've done work in both South America on tight unconventionals and also in the Middle East. So hopefully, I can convey some of the findings and some of the things that we've found to work very consistently in the realm of RTA and PVT, if you like, throughout this course and hopefully convince you that there's a few of these new technologies that at least we are applying now on 100s of wells across North America that you can apply and get some valuable insights from as well.

02. A little bit about myself

When it comes to the introduction to the course, I think it's natural just to start with a few key items about myself first.
So first and foremost, before I entered into the space of engineering, I was actually a soccer player back in Norway when I was in high school, but realized that I had a pretty limited potential there. So, I applied to petroleum engineering at NTNU, which is the largest university in Norway, where I also did a Fulbright type of exchange to Stanford University studying also petroleum engineering related topics. And after that, I've been mainly working for Whitson out of Houston in Texas, US on a tight unconventionals almost exclusively.

03. I believe in a practical approach

What this course will be mostly focused on is not too much theory, not too much equations, but it will be more practical. What I mean by that is that we'll not dig into all the nitty-gritty of how we derive certain equations, but will provide natural references to those equations where relevant. We're also focused much more on actually using real data and how these techniques should be applied when you have real data available. And when I talk about real data here, I'm talking about daily pressures, rates, and PVT if that's also relevant.

04. Recommended Preparation

Before you do this course, I would highly recommend that you tune in to this other SAGA course on just RTA in general with Dave and Hamid. It's a great course. And if you don't want to look at everything in that course, I would recommend to especially pay attention to Chapter 3. I think it's almost a prerequisite for at least capturing some of the things we will talk about in this course. So, if you haven't looked at that course before you take this one, please go back. Make sure that you at least watch Chapter 3 and then you tune me in back in this course after that. And as Dave always says, good luck with your analysis.

05. Role Models in Rate Transient Analysis (RTA)?

I also find it natural to mention just a few of the individuals that have helped both me in my career and also to shape up this course that we're going to go through here today, both in terms of its practical use and also its theory. Some of the people I've been lucky enough to meet in person, some people are very good friends of mine. Some people are also my colleagues and unfortunately, some of them are not with us here today. But I find it very natural to mention them because they have influenced what we're going to talk about here today. And by no means any of actually what we're going to talk about today has been my own invention. So it's more me kind of communicating, at least to how we've applied some of, like almost the compound result of all of these individuals into a very practical workflow.
Some of you might actually see my boss's face on this slide. His name is Curtis Hays Whitson. A lot of people know him from the PVT space mainly. What not that many people know is that his first book was actually on "Well Performance" that he wrote together with Michael Golan back in 1986. And he has through his mentor, which was actually Michael Fetkovich, done a lot of work within the space of RTA and kind of coupling PVT and RTA, which is what this entire course is really about.

06. Rate Transient Analysis (RTA) 101

So what is RTA? Well, that's a great question. In short and we'll talk much more about this throughout this course here, but in short, it's analysis that incorporates both fluid rates. So here we're going to talk about it in multiphase, so oil, gas, and water and flowing pressures, OK. So it's different from just traditional decline curve analysis from that perspective. And what it's actually used for in the different companies that at least we work with is actually a wide range of things, but typically it involves quantifying 2 key parameters, the first one being a way for us to quantify productivity, which is typically done with the so-calledlinear flow parameter or the A√k as it's also known as. We'll talk about that a little bit more in detail later. And the contacted pore volume or the pore volume that a certain well is seeing or experiencing or draining. And with these 2 key outputs from our analysis, operators are using it to compare well performance, both guide or validate forecasting or just use it for forecasting exercises directly, to evaluate completion effectiveness and frac optimization, to help with production optimization or drawdown management, that's a very, very common use. And of course, also use it as a starting point or a calibration point for more advanced simulation studies that typically requires days for the models to finish and run.

07. It is better to be roughly right...

I think this whole suite of RTA or this whole topic of RTA, what it really boils down to is this principle of "it's better to be roughly right than precisely wrong". So we try to use data that's readily available to us and workflows that we can apply maybe on a single well basis on less than 10 min at least the analysis and you would rather do 100s of wells throughout a field rather than just doing a small subset over a period of a year, for instance.

08. Unconventional Reservoir Workflow

What we're going to go back to all the way throughout this course is an unconventional reservoir workflow that has 5 key steps. We're going to investigate and we're going to deep dive into each and every one of these steps. And those 5 steps essentially being PVT and fluids being a very, very important input, especially in the realm of multiphaseRTA. Of course, flowing bottomhole pressures is a crucial input to this analysis and if we don't have measured bottomhole pressures, we need to calculate them from surface pressures. And in that work, PVT is an important input, again. Then when you have these 2 key ingredients together with the initial reservoir conditions, you can do material balance exercises. And we'll provide you with a brand new novel multiphase flowing material balance technique that has been developed by some folks at Coterra, Leslie Thompson and Barry Ruddick. And we'll show you how we can use that actively in a numerical type of workflow where we can investigate both analytical and numerical rate transient analysis here in detail, where you bring these results in to kind of close that loop into a forecasting and simulation run. For many of you, what will be very new in this course vs. how things have been done in the past is probably the multiphase flowing material balance and it's probably the numerical RTA workflow. So we'll put particular emphasis on both of those 2 topics as we progress throughout the course. And most importantly, we'll show you how you apply these techniques in practice with the real data and also industry commercially available in the software.
So that's it for this intro lesson and we'll dive straight into the first item here, which is PVT. We'll use some good time to understand what's important and why, and how we're going to apply that in Step #2, 3, 4, and 5 going forward.
Golan, M., and C. H. Whitson. "Well Performance, 442." (1986).Thompson, Leslie G., and Barry A. Ruddick. "Multiphase Flowing Material Balance Without Relative Permeability Curves." In SPE/AAPG/SEG Unconventional Resources Technology Conference. OnePetro, 2022.