PRODUCTION PREDICTION AND ANALYSIS IN DEPLETED OIL RESERVOIRS

ABSTRACT

A production engineer is responsible for generating the production forecast for a well or a field. Once production drops from the peak or plateau rate, the engineer needs an estimate of decline rate. Production forecasts use risk analysis techniques to help quantify the uncertainty. History matching is the process of building one or more sets of numerical models representing a reservoir which accounts for observed and measured data. The assessment of uncertainty is always subjective; history matching should assist in creating the model of uncertainty, which is subsequently used for decision making. This study makes use of the ECLIPSE simulator in which different runs of reservoir simulations were performed. The data were obtained from well XYZ in the Niger Delta region which is currently under natural depletion and requires a measure to enhance the amount of oil to be recovered, and then predict future performance and analysis. This model is based on the physical model that emerges from data obtained from the geological, geophysical, petrophysical, and log information.

TABLE OF CONTENT

Content                                                                                                    Page

Declaration                                                                                                 i

Certification                                                                                                         ii

Dedication                                                                                                  iii

Acknowledgement                                                                                                iv

Abstract                                                                                                      v

Table of content                                                                                          vi

List of tables                                                                                               viii

List of figures                                                                                             ix

Nomenclature                                                                                             x

CHAPTER ONE: INTRODUCTION                                                      1

1.1     Background of the study                                                                            1

1.2     Drive Mechanism                                                                              1

1.2.1  Water Drive                                                                                                4

1.2.2  Gas Expansion                                                                                 5

1.2.3  Solution Gas                                                                                     6

1.2.4  Rock Drive                                                                                        6

1.2.5  Gravity Drainage                                                                              7

1.2.6  Combination Drive                                                                           7

1.2.7  Decline Curves for Drive Types                                                                  7

1.3     Statement of the problem                                                                           8

1.4     Aim and Objectives of the study                                                       9

1.5     Significant of the study                                                                     9

CHAPTER TWO: LITERATURE REVIEW                                          10

2.1     Introduction                                                                                                10

2.2     Decline Curve Analysis                                                                     15

2.3     Simulation Model Building                                                               20

CHAPTER THREE: MATERIALS AND METHODS                                    23

3.1     Reservoir Simulation                                                                        23

3.2     Research Methods                                                                                      23

3.3     Research Models                                                                               24

3.4     Description of Eclipse Model                                                            24

CHAPTER FOUR: RESULTS AND DISCUSSION                               34

CHAPTER FIVE: CONCLUSION AND RECOMMENDATION        40

5.1    Conclusion                                                                                         40

5.2    Recommendation                                                                                40

REFERENCES                                                                                         41                                           

LIST OF TABLES

Table                                                                                                                      Page     

Table 2.1: Initial rates and forecasts to production limit, Evans H unit (LaSalle)                                                                                        22

 Table 2.2: Production history for well 1, Hawkville unit, LaSalle County                                                                                          22

        Table 2.3: Models for medium without natural fractures                                         26

Table 2.4: Models parameters for medium with natural fractures 26

Table 3.1: Oil relative permeability and saturation data 32

Table 3.2: Gas relative permeability and saturation data 33

Table 3.3: PVDG (PVT properties for Dry Gas)                                            34

Table 3.4: PVTO (PVT properties of dead oil)                                               34

LIST OF FIGURES

Figures                                                                                                          Page

Figure 1.1: Typical decline curve for a well bore draining a reservoir system with a strong water drive (A) and a partial water drive (B)      6

Figure 1.2: Comparison of typical production decline curve for the different drive mechanisms                                9

Figure 2.1: Theoretical P.I versus Actual P.I.                                  13

Figure 2.2: Decline curve of a well in months                                                   14

Figure 2.3: Example project average well production history         16

Figure 2.4: Eagle Ford Shale counties                                      21

Figure 2.5 (a-d): Decline curve diagnostic ploys for well 1, STS 2 unit (LaSalle County)                                                                    22

Figure 2.6: Fracture permeability multiplier                       25

Figure 2.7: Simulation production profile and forecast for different portion of curve                                                        25

Figure 3.1:  Reservoir model (Base Case).                                                        31

Figure 4.1: Well oil production cumulative total                                              34

Figure 4.2: Well bottom hole pressure                                35

Figure 4.3: Effect of rate change on production                                                36

Figure 4.4: Effect of rate change on bottom hole pressure                 37

Figure 4.5: Effect of porosity change on bottom hole pressure  38

Figure 4.6: Re-modeled reservoir model                                                           39

                                                ABBREVIATIONS

b                                     Decline exponent

DCA                               Decline Curve analysis

Di                                   Initial decline rates

FEM                               Finite Element Method

K                                    Permeability

MSCF/D                         One thousand cubic feet per day

P.I                                  Production Index

Pnc                                  Net confining pressure