DEVELOPMENT OF NODAL ANALYSIS FOR PRODUCTION OPTIMIZATION: A SOFTWARE ASSISTED APPROACH

CHAPTER ONE

INTRODUCTION

Background of study

Nodal analysis also known as “system analysis” is a systematic procedure/approach applied to the enhancement or optimization of production of oil and gas wells by analyzing and evaluating the complete production system. Every component that constitutes the production system can be optimized to achieve the objective production (flow) rate most economically. The production system comprises of flow of hydrocarbon fluids from the reservoir to the surface production facilities, and including inflow performance, as well as flow across the completion, up the tubing string (including any down hole restrictions and safety valves) across the surface choke (if applicable), through horizontal flow-lines.

The production system can be relatively simple or can include many components in which energy or pressure losses occur (fig, 1-1).

Any production well is drilled and completed to move the oil or gas from its original location in the reservoir to the stock tank or sales line (for gas). Movement or transport of these fluids requires energy to overcome friction losses in the system and to lift the products to the surface.  The fluids must travel through the reservoir and the piping system and ultimately flow into a separator for gas liquid separation.The pressure drop in the total system at any time will be the static initial fluid pressure minus the final fluid pressure, PR-Psep.This pressure drop is the sum of the pressure drops occurring in all of the components of the system (fig 1.2). Since the pressure drop through any component varies with producing rate, the producing rate will be controlled by the components selected. The selection and sizing of the individual components is very important, but because of the interaction among the components, a change in the pressure drop in one may change the pressure drop behavior in all the others. This occurs because the flowing fluid is compressible, and, therefore, thepressure drop in a particular component depends not onlyonthe flow rate through the component, but also on the average pressure that exists in the component.

The final design of a production system cannot be separated into reservoir performance and piping system performance and handled independently. The amount of oil and gas flowing into the well from the reservoir depends on the pressure drop in the piping system, and the pressure drop in the piping system depends on the amount of fluid flowing through it. Therefore, the entire production system must be analyzed as a unit.

The production rate or deliverability of a wellcan often be severely restricted by the performance of only one component in the system. If the effect of each component on the total system performance can be isolated, the system performance can be optimized in the most economical way.