OPTIMIZATION OF PDC DRILL BITS PERFORMANCE

Optimization of PDC Drill Bits Performance

Abstract

The rising application and utilisation of Polycrystalline Diamond Compact (PDC) drilling bits in recent past has increased the demand for a simulator tool which enables the drilling engineer to simulate these operations in a pre-planning mode. The core purpose of this dissertation is to develop a method to be used in simulation of drilling operations with Positive Displacement Motors and PDC bits. Simulation of the drilling operation requires a model to predict ROP (Rate of Penetration) of PDC bits where bit wear effect on ROP (Rate of Penetration) is taken into account. Development of this model is the secondary purpose of this study. This thesis consists of five chapters. The first Chapter of the dissertation would give us a detailed version of introduction to the thesis research topic. Chapter 2 will provide us an updated literature review of the models developed to predict performance of PDC bits. This chapter also includes description of the PDM and previous works done to model its performance. Chapter 3 will present the technical work done to develop the simulation method. It consists of the derivation of the ROP (Rate of Penetration) model and torque model, PDM performance data preparation and definition of simulation method. In Chapter 4, a set of field drilling data is used to verify the method. In addition, some examples are presented to explore how the method can be implemented in drilling operation simulation and optimisation. Chapter 5 includes a summary of the study and recommendation for future works.

Table of Contents

Abstract2

CHAPTER ONE: INTRODUCTION4

CHAPTER TWO: BACKGROUND8

Positive Displacement Motor (PDM)8

PDM Geometry9

Cross Sectional Geometry9

Axial Geometry10

PDM Performance10

Drilling Optimisation with PDM18

PDM Wear18

Polycrystalline Diamond Compact (PDC) Bit19

PDC Model by Glowka21

PDC Model by Kuru and Wojtanowsicz24

PDC Model by Hareland and Rampersad26

Better than Traditional Roller Cone Bits27

CHAPTER THREE: TECHNICAL APPROACH30

PDC Bit Performance Modeling30

Single Cutter Performance Modeling31

New Bit ROP (Rate of Penetration) Modeling40

Worn Bit ROP Modeling43

Wear Function Definition44

Bit Wear Growth Modeling46

PDC Bit Torque Modeling47

Laboratory Data Calibration of PDC Bit Model49

Confinement Effect on Rock Strength50

IADC Bit Wear Grade53

PDM Performance Data Preparation53

Method Definition56

CHAPTER FOUR: TECHNICAL RESULTS61

Method Verification61

ROP Model Verification61

Torque Model Verification65

Method Application67

Example 1: PDM Performance Study68

Example 2: Drilling Operational Parameters Optimisation70

CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS88

References91

Appendix One: Cutting Area Calculation95

Optimization of PDC Drill Bits Performance

CHAPTER ONE: INTRODUCTION

Drilling cost is a major part of oil well developing expenses. It mainly consists of the rig costs, bit costs and service costs. The rig cost can be the essential part of the drilling cost. It is a direct function of drilling time and increases linearly by it. Drilling time spends to rotate the bit, connect the pipes and move up and down the drill string to change the bit. The connecting time is usually fixed for a normal drilling operation of a specific interval. An optimum drilling plan can reduce the rotating time by increasing rate of penetration (ROP) and decreasing trip time.

Nowadays, drilling simulators have gained a leading position in the well planning and the follow up ...